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{{#Wiki_filter:The Dec ine of Fisheries, Resources in ew Engl and
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The Decline of Fisheries Resources in New England Evaluating the Impact of Overfishing, Contamination, and Habitat Degradation Edited by Robert Buchsbaum Massachusetts Audubon Society Judith Pederson Massachusetts Institute of Technology William E. Robinson University of Massachusetts, Boston MIT Sea Grant College Program Massachusetts Institute of Technology Cambridge, Massachusetts
Published by the MIT Sea Grant College Program 292 Main Street, E38-300 Cambridge, Massachusetts 02139 http://web.iiit.edu/seagrant Acknowledgment: Sponsor, Massachusetts Bays National Estuary Program Publication of this volume is supported by the National Oceanic and Atmospheric Association contract no.: NA86RGO074. Copyright ©2005 by the Massachusetts Institute of Technology. All rights reserved. This publication may not be reproduced, stored in a retrieval system or transmitted in any form or by any means: electronic, electrostatic, magnetic tape, mechanical, photocopying, recording or otherwise without written permission of the holder. In order to photocopy any work fi'om this publication legally, you need to obtain permission from the Massachusetts Institute of Technology lor the copyright clearance of this publication. Design and production by Gayle Sherman Cover photo credits: firont cover, background, rocky coast: Judith Pederson alewifes: Robert Buchsbaum lobster: Robert Steneck harvested scallops, fishing net, and back cover, fishing boats: Madeleine Hall-Arber The Decline of Fisheries Resources in New England: Evaluating the Impact of Overfishing, Contamination, and Habitat Degradation Edited by Robert Buchsbaum, Judith Pederson, and William E. Robinson MIT Sea Grant College Program Publication No. 05-5
We dedicate this book to our colleague,John Alforing, who was a fireless advocate.fbr the health of our fisheries in the marine environment.
Acknowledgments We appreciate the encouragement and the financial support provided by the Massachusetts Bays Program (MBP). part of the National Estuary Program of the United States Environmental Protection Agency. This work was sponsored by a MBP grant, and the original concept came from their Technical Advisory Committee. In particular, we thank Jan P. Smith, Director of the MBP. for helping Its to develop the vision for this project and 1or supporting Lis as the project unfolded. We also sincerely thank the many reviewers who volunteered their time and energy to critique each of the chapters of the book at various stages and for their valuable suggestions and advice. These include Peter Auster, Mark Chandlei, Michael Dadswell, Ellie Dorsey, Michael Fogarty, David Franz, Madeleine Hall-Arber, Gareth Harding, Boyd Kynard, Sandra Macfarlane, Jack Pearce, Jack Schwartz, Jail Snmith, Peter Wells, Christine Werme, Robert Whitlatch, and several anonymous reviewers. We especially thank our authors for each of their contributions, and, in addition, for their patience as we moved the process of publishing this book along. Finally, the publication of this work at MIT Sea Grant would not have been possible without the dedication and persistence of Gayle Sherman., who transformed all the raw manuscripts into a professional publication.
Contents Preface iv I. Contamination. Habitat Degradation. Overfishing - An "Either-Or" Debate? William E. Robinson and. Iclilh Pederson I1. The New England Groundfish Resource: A History of Population Change in Relation to Harvesting I1 Steven A. Muracnski III Recent Trends in Anadromous Fishes 25 John */foring IV. Pollutant Effects upon Cod, Haddock, Pollock, and Flounder of the Inshore Fisheries of Massachusetts andCape Cod Bays 43 FrederickP Thurber* and Edith Gould V. The Effect of Habitat Loss and Degradation on Fisheries 67 Linda ,4. Deeg"n and Rohert Bnchsbauun VI. Effects of Natural Mortality and Harvesting on Inshore Bivalve Population Trends 97 Diane . Brousseau VII. Biological Effects of Contaminants on Marine Shellfish and Implications for Monitoring Population Impacts 119 Judith E. McDowell VIII. Are We Overfishing the American Lobster? Some Biological Perspectives 131 Robert S. Steneck IX. The Role of Overfishing, Pollution, and Habitat Degradation on Marine Fish and Shellfish Populations of New England: Summary and Conclusions 149 Robert Buchsbaum X. Management Implications: Looking Ahead 163 Judith Pederson and William E. Robinson
iv approach to managing fisheries and addresses Preface management needs into the future. Each of the authors was asked to review the latest scientific information on either overfishing, First Preface (2001) pollution, habitat degradation, or the relationship This book emerged from one of several issue among all three variables, on fish, lobsters, or papers sponsored by the Technical Advisory shellfish, particularly as it relates to the Committee of the Massachusetts Bays Program, Massachutsetts Bays region. Authors were encour-one of tile National Estuary Programs funded by aged to think broadly and to give some sense of the the Environmental Protection Agency. When we relative impacts oil fisheries of the factors they started this project, the crisis in New England examined in detail compared to those attributable groundfish populations was not nearly as much in to other causes. They were also asked to identify. the public consciousness as it is now. There was a data gaps and to suggest needed research. fair amount of conjecture within the fishing industry, M~anagemnent implications were then addressed in due in part to uncertainty that exists in stock the final chapter. assessment, concern about pollution and habitat impacts, and anecdotal descriptions of improved Robert Buchsbaum fish catch that seemed at odds with agency predic- Judith Pederson tions as to the root cause of the problem. We William E. Robinson thought it useful to put together a volume that *J,niar~tv 2-001 examined the scientific evidence for effects of three major factors overfishing, pollution,. and habitat degradation on northeast finfish, lobsters, and shellfish populations. This approach omits the socio-econoinic drivers which infIluence fisheries management decisions and the industry's perception of the ecosystem. We acknowledge the importance Second lPreqjice (2004). of these factors in the broader scope of the issue. however without a sound scientific knowledge, Since we first assembled the draft contributions achieving sustainability in fisheries will falter. of our authors into this volumne and penned the above Preface in early 2001. high profile lawsuits During the intervening years since we began have changed implementation of fisheries manage-the project, the public became increasingly aware inent. Significant changes in fisheries stocks and of the seriousness of the crisis through numerous fisheries management have influenced our overall newspaper articles, scientific publications, public approach to using and managing our marine envi-forums, and political activities. The closure of large ronment. Some trends in fish population recovery parts of Georges Bank to groundfishing, and the appear favorable, whereas others are not quite so recent passage by the New England Fishery optimistic. Management Council of measures to further reduce fishing mortality focused much attention on the While not universal, a number of 'improve-effect that overfishing may have on marine ecosys- ments have been documented in various fishery tems and the fishing communities that depend on stocks. Probably the most notable change is in the those ecosystems. The cause of fish population northeast ground fishery, where several species pop-declines,-the rate and extent of recovery, and ulations have increased as a result of the drastic approach to management are still debated. The use- measures implemented to reduce fishing pressure fulness of examining the declines in certain species (e. g. closure areas, severe restrictions in the number of commercially important fish,.Iobsters, and shell- of days a fisherman can fish). The National fish by taking multiple factors into consideration is Oceanic and Atmospheric Administration's compelling because it represents a holistic (NOAA's) annual reports to Congress on the
- 'Status of the Fisheries of the U.S." have indicated to save the endangered Atlantic salmon in eight an overall improvement in groundlish stocks, as Maine rivers. But the loss of habitat, uncertainty in evidenced by the stock assessment data collected in the primary cause of mortality, and small wild pop-2000, 2001, 2002, and 2003. When we started this ulations may limit a successful comeback to a work, over 70% of New England groundfish were thriving fishery.
classified by the National Marine Fisheries Service (NMFS) as overfished (NOAA, 1995). Status of the The story with lobsters is mixed. Lobster popu-Fisheries Resources off the Northeastern United lations have drastically fallen in southern New States for 1994. NOAA Tech. Memorandum England, with a concern that the same trend may NMFS-NE-108. National Marine Fisheries Service., be about to happen throughout the region. An arti-Woods Hole, MA. 140 pp.). The percentage now is cle in the December 2004 Commercial Fisheries about 30% (NMFS, 2001. Report to Congress. News reported that Maine's lobster landings have Status of Fisheries of the United States. NMFS, remained "relatively high" (yet down from 2002), NOAA, Silver Spring, MD. 127 p.). An exception- although landings have fallen precipitously in other ally good cod spawn in the Gulf of Maine in 1998, states. A recent Cape Cod Times editorial (28 June combined with restricted fishing effort, has led to 2003) reported that 91% of the lobsters taken from the recent surge in the numbers of legal size fish Cape Cod Bay north to the New Hampshire border that have been caught (although cod quotas have were barely of legal size, a trend that highlights sometimes prevented the landing and sale of these growth overfishing and does not bode well for sus-fish). Nevertheless, groundfish stocks, while taining this fishery. Nevetlheless, questions continue increasing as a result of less overfishing, are still to be raised as to whether the lobster decline is due nowhere near their historic high numbers and some to pollution, habitat degradation, or disease, rather would argue they are not sustainable. In NOAA's than simply to overfishing. The declines in the most recent status report (16 June 2004), the southern part of New England are further compli-Northeast groundfishery was still considered the cated by two different types of diseases, one of national fishery in the most trouble. TIwelve stocks which may be related to rising temperatures. Some were still listed as "overfished" (i.e. overall attribute the lack of collapse in Maine waters to biomass below a set level), and eight stocks were community management of the fishery, but recog-still subjected to "overfishing" (i.e. toomany fish nize that increases in landings are due to other fac-taken). tors (Deitz, 2003. Science 302:1907-1912). A remarkable recovery has occurred in North Fluctuations and trends in bivalve stocks con-Atlantic Swordfish stocks. While the fishery is still tinue to be difficult to assess. Recent advances in at approximately 65% of maximum sustainable high resolution video surveying of scallop popula-yield, stocks have rebounded in an incredibly short tions (Stokesbury, 2002. Trans. Am. Fish. Soc. .131: time, due primarily to the restrictive international 1081-1092) have led to a proposal for rolling open-quotas and minimum sizes imposed by the ings of different areas of offshore scallop grounds. International Commission for the Conservation of It remains to be seen whether the rolling opening Atlantic Tunas in 1997, the imposition of approach will lead to a sustainable fishery as fish-Individual Transferable Quotas (ITQs) by Spain in ermen put pressure on management to open any 1999, and the closure of critical nursery areas to productive area left unfished. Outside influences longline fishing by the U.S. in 2000 (NOAA, 2002. may further complicate analysis of success. The http://www.publicaffairs.noaa.gov/releases2002/oct recent presence of an aggressive sea squirt, 02/noaa0213 l.html; Garza-Gil et al., 2003. Mar. Dideinnum sp. that covers 80% of approximately Policy 27:31-37). 75 km 2 of prime scallop beds on Georges Bank adds another dimension to habitat degradation and Debate continues over Maine's native salmon is one for which we have little experience or populations, even while their numbers remain per- knowledge. ilously low. In June 2004, the draft Federal plan was released by the Atlantic Salmon Commission Shellfish are also at risk. An outbreak of disease
vi (i.e. a parasitic infection Quahog Parasite 26 April order, and replaced it with the compromise Unknown or QPX) in southern New England qua- settlement that had been worked out by the parties hogs has recently decimated quahog populations in in the case.. This action did not end the courts Wellfleet Massachusetts, as it did in Provincetown involvement in Northeast ground fisheries manage-Massachusetts in 1995. It is not known whether ment, however. Just after Amendment 13 to the pollution, habitat degradation or even climate Northeast Multispecies Fishery Management Plan change has led to physiological stress that weakens went into effect on I May 2004, suits were filed in .animals enough to allow parasitic infection to take U.S. District Court by both fisherman and conser-hold. vation groups. The Trawlers Survival Fund, a fish-erman's group from Fairhaven, alleged that NMFS Fisheries management debates in the northeast made illegal changes to the final rule implementing have remained as contentious as ever, and possibly Amendment 13 that would be detrimental to fisher-more so! The passage of the federal Sustainable men. On the other side, the Conservation Law Fisheries Act (SFA) in 1996. with its mandated call Foundation and the National Resources Defense for revised definitions' of what "overfished" means Fund filed briefs alleging that Amendment 13 will and its attention to essential fish habitat, led to a not stop overfishing, and Oceana filed two lawsuits great deal of debate (and little initial action) as to alleging that Amendment 13 ignores essential fish how to incorporate these mandates into the habitat. region's groundfisheries management plans. The perceived slow federal action led the Conservation All of these contentious legal battles and drastic Law Foundation, National Audubon Society and reductions in both the areas where fishermen are the National Defense Council to file a lawsuit in allowed to fish and in the number of days that they May 2000 against the Commerce Department and are allowed to fish occurred against the backdrop its agencies, NOAA and the National Marine of the recovering groundfish stock. Throughout Fisheries Service, ftor not doing enough to prevent this time period, fishermen repeatedly questioned overfishing of Northeast groundfish stocks or to why.additional harsh measures have to be imple-reduce bycatch mortality when it approved mented when the overall trends are improving. Framework Adjustment 33 to the Northeast They argue that mandating a particular stock Multispecies Fishery Management Plan. The suit recovery in a five year time span is both unrealistic alleged that the Adjustment did not comply with and economically disastrous to the fishing industry. the SFA because it based its recom inendations on To make matters even worse, in September 2002 the Amendment 7 building plan rather than the NMFS acknowledged that otter trawl lines on the more stringent Amendment 9 plan, and that even R/V Albatross IV that had inadvertently been mis-Amendment 9 failed to reduce bycatch. On 28 matched in length since February 2000 may have December 2001, District Court Judge Gladys led to mistakes in assessing groundfish populations Kessler ruled in favor of the three conservation off of New England. While they later provided evi-groups, and asked both the plaintiffs and defen- dence to show that this mismatch did not lead to dants to propose remedies for her consideration. any significant changes in the stock assessments, While each side opposed the other's plan, the two fishermen nevertheless maintained that the stock groups forged a negotiated settlement and sent it to numbers were underestimated and therefore unreli-the court on 22 April 2002. Four days later, Judge able for use in management decisions. The per-Kessler rejected the compromise plan, and instead spective of the New England fishermen and man-handed down a stunning "remedial order" that agement is in contrast to the Northwest fisheries included area closures and drastic reductions in where scientific advice and stringent measures are allowable days at sea. What followed was a more readily accepted. What seems clear today, is tremendous outcry by fishermen, their political that overfishing has been reduced, yet a number of representatives and several of the parties to the stocks are still considered overfished. In addition, case, all of whom asked the Judge to reconsider stock abundances, while increasing, have yet to her decision. On 23 May 2002, Judge Kessler reach their historically, high numbers. There are granted the motions to reconsider, vacated her three issues that are hurdles for broad support of
VII stringent management options. First. uncertainty is AgriculttIre Organization (FAO), the European a strong Component of stock assessment, which Union, and the National Research Council confounds projections of stock biomass. Secondly, (NRC). The National Marine Fisheries Service the past approach to managing single stocks has (NMFS)'s 5-year Strategic Plan for Fisheries failed to sustain some stocks, but currently there Research (December 2001) placed ecosystem are no acceptable models for managers to imple- considerations as a priority in its "new genera-ment. NOAA and other agencies are focusing on tion'" stock assessments. ecosystem management, but this science is in its infancy and without higher levels of certainty, fish- " The Ocean Studies Board of the National eries management approaches will not be readily Research Council of the National Academy, of accepted by the industry. Sciences released their report Effects of Trawling and Dredging oii Seafloor Habitat in The original premises that we based this book May 2002. which concluded that negative on - that overfishing. habitat degradation and con- effects seafloor habitat were happening'in some tamination each contribute to the health of our fish areas, and that sufficient data were available to and shellfish populations (albeit to different at least conduct preliminary assessments of degrees in each fisheries stock); that each of these trawling/dredging in other areas. three impacts has been studied independently by disciplinary scientists, in isolation from each other; " Some scientists have advocated against basing that we need to consider each of these three fisheries management on Maximum Sustainable impacts together, in an interdisciplinary holistic Yield (MSY). Richard Zabel and colleagues, for approach, in order to understand the total stress on example, have suggested that we now address commercially important fish stocks; that we need what he has termed ~Ecologically Sustainable to place more reliance on a precautionary approach. Yield" (2003. Am. Scient. 91: 150-157). This adaptive management efforts and ecosvstem--based concept recognizes that single species cannot management in order to manage our fisheries popu- adequately be managed in isolation, but.must be lations in a sustainable manner - have been reem- managed as an ecosystem. phasized many times .over the intervening years. Many of the specific points.that we made in 2001 " The importance of climate change on long-term have independently been raised since then: fisheries trends has now been recognized. Range shifts of New England. marine fish in response " In a recent paper by Giulio Pontecorvo (2003. to ongoing warmer seawater temperatures had Marine Policy 27: 69-73), the "'insularity of sci- already been documented (Murawski, 1993. entific disciplines" was identified as a signifi- Trans Amer. Fisheries Soc. 122: 657-658), and cant impediment to fishery management. this trend will continue, perhaps in a more accel-erated rate, in the future for species like cod " There is an increasing awareness that current (Scavia et al., 2002. Estuaries 25: 149-164). The fisheries practices worldwide are not sustainable failure of the Canadian cod stocks to rebound (e.g. Myers and Worm, 2003. Nature 423: 280- after their collapse in the late 19940s, even 283; Pauly et al., 2002. Nature 418: 689-695). though fishing pressure, has been eliminated, Approximately 30% of worldwide fish stocks may be of a changing climate. Scavia et al. also are depleted, overfished or slowly recovering predict changes in phytoplankton-zooplankton and 44% are currently being fished at or near dynamics that could alter the food sources for their sustainable yields (National Research fish. Based on mesocosm experiments and Cotincil. 1999. Sustaining Marine Fisheries. examination of short term temperature varia-National Academy Press, Washington D.C.). tions, the US Global Climate Change Research Program predicts that global warming will be
- Ecosystem-based management (EBM) and the detrimental to populations of winter flounder in use of Adaptive Management have been southern New England (New England Regional endorsed by the United Nations Food and Assessment Group, 2001. Preparing for a
viii Changing Climate: the Potential Consequences our authors have summarized and reviewed clearly of Climate Variabilitv and Changie. New demonstrates that each of these three impacts can England Regional Overview. U.S. Global be significant, although the data are not yet avail-Change Research Program, Univ. of New able in most cases to estimate the degree to which Htampshire. 96 pp.) Although its impact has yet each of the three operates. to be specifically documented, the spread of lob-ster shell disease and the quahog parasitic infec- We thank the Massachusetts Bays Program for tion QPX northward may be linked to gYlobal cli- providing the initial funding for this project. We mate change. also thank otIr authors for sharing ouIr vision, and for their patience as we worked to bring this book
- In January 2005, EPA will release its National to publication. We also thank the many reviewers Coastal Conditions Report, in which it desig- who read the chapters and whose thoughtful
/ nates the Northeast as "one of nations dirtiest insights strengthened this work. (They are regions." acknowledged in each chapter.) Given the per-ceived restricted audience that this volume Would Finally, both of the two major, recent and long- likely attract, publishers proved illusive. We sin-awaited, reports on the state of our oceans and cerely thank MIT Sea Grant for taking up our cause marine environment, the Pew Ocean and publishing this work. Weare all the more Commissions America's Living Oceans. grateful in that MIT Sea Grant agreed to publishing Charting a Course of Sea Change (May 2003) it "'onthe web", making its distribution and hope-and the U.S. Commission on Ocean Policy's An fully its impact much more widespread and easily Ocean Blueprint for the 2 1st Century (Sept accessible. Finally, we would like to thank you, our 2004) highlighted overfishing. contamination readers, who will have the ultimate vote on and habitat alterations (direct impacts such as by whether our work proves useful in advancing the.
trawling and loss of nursery areas. and indirect ongoing debate on fisheries management.
.impacts due to eutrophication, invasive species, to name a few) as all being important contribu- Robert Buchsbaum tors to our marine resource declines,.and called Judith Pederson for an ecosystem-based management approach. William E. Robinson Both reports can be summed up in the words of December 2004 the Chairman of the U.S. Commission on Ocean Policy:
The oceans and the coasts are in trouble, and we need to change the way we man-age them.
- Janes D. Watkins, 2004 We are pleased that our original premises for this book have now been more broadly accepted by the scientific community. When we initiated this project, many voiced skepticism that overfishing, habitat degradation and contamination could each have a role to play in the health of otIr many fish-ery stocks, and. even if they did, whether we could make useful comparisons of the impact of overfish-ing, habitat degradation and contamination on fish-eries stocks. We believe that the information that
CON 1.0 1 f.NA I I(IN, HA 111FAI D1_(iR A D A I ION, O\ ERHS I I I NG D FIBA I-F Chapter I Contamination, Habitat Degradation, Overfishing - An "Either-Or" Debate? WILI.IAM E. ROBINSON UniiversiO"of Kassachusells Boston Delpartment of Envirornineental,Eart/h and Ocean Sciences (EEOS) 100 Morrissey Blvc. Boston. 1/1 02125 US.4
.1UDII PvIMLRSON
!I'iassoch/iiie.s his.liftcl' q TeLchnology Sea Grant College Prograin 292 Main Street. E38-300 Cambridge, MA 02139 USA Fish are good for the heart, but such 2000). With recent stringent management measures, knowlectke will soon he of/itllte use if/we some stocks appear to be showing signs of recovery.
cut the heart out oj/lhe ocean. but they are still nowhere near their former levels
-Derrick Z Jackson, Columnist of abundance (NEFSC, 2000). This decline Boston Globe, 14 Jan 1998 notwithstanding, groundfishing has remained an important contributor to the overall northwest Atlanlic (-Northeast) fishery (Figure 1.2), accounting lor an average of 121.000 metric tons of landings and approximately $179,000,000 in ex-vessel value INIIROI)UCIION .for the years 1993-97 (NOAA, 1998). When con-A great number of nearshore and offshore fish- sidering.finfish landings alone for this period of ery stocks have deteriorated throughout the time, the groundfishery provided approximately Northeast over the past 30 years. The most visible 24% of the total finfish catch in the Northeast, yet example of this decline was the precipitous drop in accounted for 55% of the ex-vessel value for the populations of groundfish (benthic-feeding fish total landed finfish (NOAA 1998).
such as Atlantic cod (Gadus mohrua), yellowtail The recent crisis in the groundfishery, which flounder (Pleuronectesferrroginetus)and haddock has been steadily unfolding since the enactment of (A/elanogrannnus aegle/inius)) (NOAA, 1998; the Magnuson Act in 1976, was highlighted in NEFSC, 2000). These stocks were severely over- Massachusetts with the publication of the fished by foreign fishing fleets in the 1960s and Assessment at Mid-Decade (MA DMF, 1985). early 1970s, and then partially recovered in the Warnings have been issued repeatedly ever since mid-1970s, coincidentally with the implementation (OGTF, 1990; NEFMC, 1991, 1994, 1996, 1999, of the Magnuson Fishery Conservation and 2000; Doeringer and Terkla, 1995; Murawski et al., Management Act (Magnuson Act) of 1976. The 2000). Stocks had plummeted to such a point by overall decline of most of these groundfish species 1991 that the Conservation Law Foundation and eventually resumed, and has continued up to the the Massachusetts Audubon Society filed a lawsuit present time (Figure 1.1; NOAA, 1998; NEFSC, against the New England Fishery Management
R O'lBINS(ON & PI-RSON
.50..........................l'... ""t"":'f+'+l """flu+[ ,.' , A. B.
Principal Grund fish anlindroiunous Hm'cllhratc,
& Fiour~de.'s 60 cioIinaic jill peai 2170
[ - Abundance (r dfish1 030 Landings 1211 40 131 HI H) C. D. Vý' CO
.30 - 98 -0 ýdo 'it 38(1 46 20 200 10 100 121 glun l h A.
- 0. r---r-v--- H. . rT- 0 Figure 1.2. Mean Northeast fishery landings (thousand 60 6-3 66 69 72 75 78 81 184 37 90 93 96
)ear metric tons; A, C) and ex-vessel value (millions of dol-lars; B, D) for the years 1993 - 97. A and B include fin-Figure I.]. Trends in abundance and commercial land- fish, shellfish and other invertebrates; C and D include ings (U.S. and foreign fleets) of principal groundfish only finfish. All data firom NOAA (1998).
from the noitheastern United States. (Figure from NOAA, 1998). 1981 (NOAA, 1998). Stock biomass fell far beloxv Council (NEFMC) for failure to prevent overfishing. densities needed to maintain maximum sustainable This resulted in the promulgation of Amendment V yield (MSY) (e.g., only 21% of MSY in 1997; to the Northeast Multispecies Fishery Management NOAA, 1998): The 1999 Atlantic bluefin tuna Plan and an emergency closure of parts of Georges (Thunnus thynnus) spawning stock biomass was Bank in 1994 (NEFMC, 1994). Since stocks did approximately 16% of the 1975 level, and only not rebound as anticipated, additional amendments 3 1% of the level needed to achieve MSY (NMFS, and framework adjustments were issued, closing 1999). There are indications that soft-shell clam large areas to fishing and severely curtailing the (A ya arenaria) and quahog (lf'er'enarict nerc'enar-number of allowable days-at-sea (NEFMC, 1996; ia) populations have declined in some locales 2000). The reauthorizatibn of the Magnuson Act, (Alber, 1987; Matthiessen, 1992; MacKenzie and the Sustainable Fisheries Act (SFA) of 1996, McLaughlin, 2000) and several anadromous fish imposed new requirements, including: (I) regular (alewife, Alosa pseudoharengus;blueback herring reporting of the status of individual fish stocks, (2) Alosa aestihalis;Atlantic salnon, Salno salar; and revised overfishing definitions, and (3) recovery American shad, Alosa sapidissima)are exhibiting plans for overfished stocks that included delineating all-time low population numbers (NOAA, 1998). and conserving essential fish habitat. These restric- The situation became so serious for the wild stock tive measures are having an inordinate impact on of Atlantic salmon that the Gulf of Maine popula-the economic and social well-being of our fishing tion was proposed for protection by the Endangered communities. Species Act (Fed. Reg., 1999). Finally, there is fear While groundfisheries have received the most that the lobster (Hoinarus americanus)spawning public attention, other commercially important fish biomass may also be declining even though lob-and shellfish species have also dwindled in num- sters have been harvested in record numbers for bers. Bluefish (Pomatomnus salatrix) stock biomass almost a decade (NOAA, 1998; McBride and has shown a downturn over the past nineteen years Hoopes, 2000). Fisheries managers are concerned following a peak in total east coast landings in that if environmental conditions become unfavorable,
CONTAMINAI [ON. 11ABIFAT DEGKADAMIN, OVERFISHING D1711AH7 the lobster population will not be able to sustain overfishing, contamination, and habitat current catch efforts. alteration---is examined and discussed as to their Not all species of fish and shellfish are exhibit- relative importance to selected fish and shellfish ing an unequivocal decline in numbers. Sea scal- stocks. lops ([lacopecten magellanic'us), while considered by National Marine Fisheries Service to be overex-OVERFISHING ploited, exhibit "'boom and bust" years, dictated by inconsistent and unpredictable cycles of recruitment The cod has symbolized fisheries in and fishing pressure (NOAA, 1998; Taylor, 1998). Massachusetts and New England since the time of Striped bass (Morone saxatilis) suffered from over- the Basque fishermen who startedbringing New fishing and poor recruitment, but have rebounded England salted cod back to Europe as early as the following Northeast cooperative fishing bans initi- 1400s. Initial reports of explorers and European ated in 1982 (NOAA, 1998). Species, such as colonists describe an unlimited abundance of cod mackerel (Scomber scombrus) and Atlantic herring and other fish in New England waters. Impressive (C'upea harengus), that are not sought after inten- catches were recorded throughout the 19th century: sively by the fishing industry, have increased in numbers over the past decade (NOAA, 1998). The Northeast fisheries are not unique. While The bankers, particulaHy if the fishing the unrestricted exploitation of Georges Bank fish w,as good, would have to row back to the stocks by foreign fishing vessels in the 1960s and schooner with a dorifild of zup to. 1800 1970s resulted in the passage of the 1976 pounds five or six times to finish with a Magnuson Act, U.S. vessels quickly entered the single trawl, hollering 'Dory!" as.they fishery to resume the same trend of overexploita- bumped pq)alongside, bringing skiplper tion. This regional decline in fish populations is and cook running to the i-ail. similar to what is occurring in many other regions Joseph E. Garland. 1983 of the United States and throughout the world (FAO, 1997; Pauly et al., 1998; Christen, 1999). The reductions, however, are particularly evident The first indication to the public that something and well-documented, here in the Northeast. was seriously awry with New England fisheries was probably in the 1980s when fish prices rose PUBLIC PERCEP'IONS and newspapers began to report the plight of fisher-men no longer able to make a living catching fish. What has put us in the situation where two-thirds of the Northeast commercial fish stocks are Appearances can be deceiving. now designated as overexploited and 59% of these
- (Anon. proverb) stocks are categorized as having "low abudance" (Table 1.1; NOAA, 1998; NEFSC, 2000)? Over the past 100 years, the fishing industry has undergone What is the major anthropogenic cause of the major changes-from fishing in wooden boats stock declines in the Northeast fisheries-overfish- under sail, to steam engines, to diesel-powered ing, introduction of contaminants, or habitat degra- steel-hull trawlers, and even to factory ships that dation? The public is regularly barraged with process seafood at sea. Improved methods of locat-alarming news reports on the collapse of ourt fishing ing and catching large concentrations. of fish have industry, coastal and marine habitat degradation, increased the efficiency of fish harvesting bacterial contamination of our inshore shellfish (although catch-per-unit-effort has now decreased species, and toxic chemicals in the marine environ- due to the declining biomass of targeted species).
ment. Can declines in fish stocks be attributed For years, fisheries scientists carrying out stock largely to one of these factors or is it their interac- assessments have warned that unregulated fishing tions that are of the greatest consequence? In this would eventually lead to stock declines: work each of the human-induced impacts-
4 I{O[I Ný(N &ý N'FIES0N. Excessive.fishing has lec lo significantly that overfishing has reduced our stocks of ground-reduced resource abundance, snmaller and fish to levels that cannot support sustainable yields less fish cad shel/Jish being landed in our at current landings. A number of fishermen agree ports, adcl economic harc/'hil).foi the that overfishing is a cause of groundfish stock st/ate's. fishging ihchIstso. depletion, but also cite habitat degradation, poilu-
- MlA DMiF 1985 tion and natural weather events as important ifactors (Dorsey and Pederson, 1998; Pederson and Hall-Arber, 1999). Sea scallops and lobsters are also There is a general consensus among fisheries listed by NMFS as overexploited, but nearshore managers that the effects caused by overfishing shellfish and anadromous fish are not as easily have far outweighed the adverse impacts caused by characterized. As discussed more fully in the fol-contaminants and habitat loss, at least with respect lowing chapters, the real or perceived importance to recent groundfish declines (Werme and Breteler, of overfishing depends to a large extent on the 1983: Cohen and Langton, 1992: Serchuk et al., 1994; species, its various subpopulations (if any), the Myers et al., 1995). Simply stated, their position is subregion in question, and the availability of data.
Table 1.1. Stock abundance and level of exploitation for 51 Northeast finfish and invertebrate fisheries. Percentages refer to the total number of stocks in each category. Data taken from NOAA, 1998. SNE = Southern New England; GB = Georges Bank: I.S = Long Island Sound: GM = Gulf of Maine, S. - Southern: N. = Northern. Level of Underexploited Fully Exploited Overexploited Abundance (10% of all stocks) (24% of all stocks) (66% of all stocks) Atlantic herring Am lobster - GM I-Iigh Striped bass Atlantic mackerel Spiny dogfish (10%) (4%) (2%) (4%) Summer flounder Longfin inshore squid Am. lobster - GB+S, SNE-LIS Atlantic surfclamn Ocean quahog N. Silver hake M~ediumn Butterfish Northern shortfin squid Yellowtail flounder-Cape Cod (3 1%) N. Red hake Skates Am. Plaice (6%) N. Windowpane flounder Winter flounder - GB (10%) Northern shrimp (15%) Scup, Black Sea Bass, Sea scallop Cod-GB, GM Witch, Cusk, Tilefish, Haddock-GB Wolffish, Goosefish, Bluefish Yellowtail flounder-SNE White hake, Ocean pout Redfish Yellowtail flounder - Mid-Atlantic Low (0%) Pollock River herring (59%) American Shad Haddock - GM Yellowtail flounder - GB S. Silver hake, S. Red hake (12%) Atl. Sturgeon, Shortnose Sturgeon S. Windowpane, AtI. Salmon Winter flounder - SNE-MA, GM (47%)
('ONFANIINAIlON, HFABITAT*\[I RAI)ATION, O\'ERHISillNG [)EB.\TE CONTAMNINATION neurological and carcinogenic impacts, and resulted in the issuance of a public health advisory that is Another factor that is often identified as a cul- still in effect today (MA DPH 1988). In addition, prit responsible for declining fish populations is the the widespread distribution of mercury in the impact of chemical contaminants-those chemicals northeast from minid-western coal-fired power plants that enter the environninent from land-based, human and incinerators has resulted in the bioaccumula-activities. Are these chemicals having an impact on tion of methyl-mercury in the aquatic food webs fish populations? The answer is far from simple. (Pilgrini et al., 2000). H-umminan health advisories Numerous studies have documented the pres- have been issued. owing to mercury's neurotoxic ence of a wide range of chemical toxicants (Dow effects, particularly in developing children. While and Braasch, 1996; Jones et al., 1997; most of this concern has focused on mercury bioac-NOAA/NS&T, 2000), including those listed as cumulation in freshwater fish caught by recreation- _priority pollutants" by the U.S. Environmental al anglers, a variety ofestuarine fish and shellfish Protection Agency (EPA, 1991), in waters, sediments that are commonly used for human consumption and the tissues of our fishery resources. have also been found to contain elevated nmethyl-Nevertheless, few of these priority pollutants, and mercury levels (Burger et al., 1998; Kawaguchi et almost none of the approximately 65.000 to 75+000 al., 1999; GilhnoLIr and Riedel, 2000). substances in commercial use today, have been rou- Although the most widely publicized contami-tinely monitored in commercial species. Based on nation concerns address human health issues, a studies of contaminants in marine sediments and number of studies have directly examined the nIarine Mussels (Buchholtz ten Brink et al., 1996; effects of contaminants on the health of marine Jones et al., 1997), a number of urban harbors in organisms. While the linkage between contaminants the Northeast (Boston, Salem and New Bedford and the health of marine populations is difficult to Harbors in Massachusetts; Hudson-Raritan Bay in establish conclusively, pollution has been implicated New York/New Jersey; western Long Island Sound as a factor in several fishery declines (Goodyear, in Connecticut; Portsmouth NH Naval Shipyard) 1985; Barnthouse et al., 1990) and even in large-have been identified as containinant "hot spots". In scale ecological perturbations (Sarokin and general., organisms more distant from these hot Schulkin 1992). Many more studies that integrate spots (e.g. offshore organisms) contain lower levels chemical concentrations in water, sediment and tis-of contaminants than animals more immediately sues Wvith adverse physiological effects, and that exposed (McDowell, 1996). ultimately document the effects of contaminants on Our concern over chemical contaminants often populations, are clearly needed. As is evident in the focuses on human health. Reports of elevated con- chapters reviewing effects of contaminants on fin-centrations of contaminants in commercial fish or fish and shellfish, the investigation of contaminant shellfish almost always raise questions of human impacts on populations is one of the most pressing health impacts. For example, Murchelano and needs for future research, particularly for stressed Wolke (1985) described tumors in winter flounder populations. (Pseudoplewronectes amnericanus) collected in 1984-85 from areas in Boston Harbor MA, includ-ing an area near a sewage outfall on Deer Island HABI'rAr DEGRADATrION Flats. While raising awareness of contaminant Degradation of marine and estuarine habitats is effects on individual organisms, their study also perceived as harmful to marine resources. This invoked concerns by the news media of a possible degradation may take many forms, over and above link to human cancer. Similarly, the U.S. the effects caused by human related chemical con-Environmental Protection Agency's Quincy Bay, MA study (EPA, 1988; Cooper et al., 1991) brought tamination. Habitat degradation may be caused by physical changes, such as increased suspended sed-attention to high levels of polychlorinated iment loading, overshadowing from new piers and biphenyls (PCBs) and polycyclic aromatic hydro-wharves, filling coastal wetlands, and trawling and carbons (PAHs) in lobsters, soft-shell clams, and dragging for fish and shellfish. Although often winter flounder. This raised fears of human
6ROIUNS(ON & I'I)FI(ISON ignored as a habitat alteration, increased nUtrients Till.: "ErIrttil-AtOlt" 1)ERAT E' froni wastewatei, fertilizers, and atmospheric inputs also degrade habitats, especially those nearshore. The resulting accelerated eutrophication may cause Thefiurst step in science is the step).fi'om unwanted algal blooms. low dissolved oxygen and qualititivc i,)l/IssioC55 /0n q !iantitative altered community composition. Natural dInviron-mneasurenment. The occasional difjiculty of mental phenomena (e.g. weather, climate) must this task does not lessen its importance. also be considered in conjunction with these habitat
- i.A. Gates, 1978 changes (Werme and Breteler, 1983; Serchuk et al.,
1994; Hofmann and Powell, 1998). Regardless of whether a habitat alteration is Given that there are at least three disparate due to natural or anthropogenic causes, it can have types of impacts on fisheries stocks, the impact of a long-term impact on community structure. For each of these factors is sometimes viewed as an example, the extensive die-off of eelgrass beds ::either - or" question-- "Is a particular fishery (Zoslera marina) caused by a disease which struck decline due to overfishing, or to contamination, or the East Coast during the 1930s. markedly changed to habitat degradation?" Scientists are partly to the vacated habitat and the structure of the benMhic blame for perpetrating this situation, since they food chain, and lead to'sharp declines in bay scallop have generally avoided investigating these factors populations (Orth and Moore, 1983; Short et al., simiultaneously. Instead, separate groups of inde-1986, Buchsbaum, 1992). Some of these changes pendently-trained scientists tend to focus on each are still evident today. Otter trawling and scallop factor in isolation: fisheries scientists typically deal dredging also appear to be causing dramatic shifts with fish population assessments and gear issues; in benthic community structure due to physical dis-aquatic toxicologists with contamination issues; ruption of the bottom, reduction in habitat coin-and benthic and estuarine ecologists with changes plexity and direct interference with trophic transfer in habitat and community struicture. As a result, a (Langton et al., 1996; Langton and Auster, 1999). type of scientific polarization has imnintentionally At the far extreme, habitat may be completely lost arisen. as a result of coastal development, harbor dredging A number of researchers have now acknowl-and offshore mining operations. Nearshore finfish edged the interrelationship between overfishing, and lobster "nursery grounds" are particularly sus-pollution and habitat changes (Barnthouse et al., ceptible to all these types of habitat loss. 1987, 1989, 1990; Buchsbaum et al., 199 1; Understanding these effects and separating Sinderinann, 1994; Dow and Braasch, 1996). While physical changes from overfishing is a challenge they have advocated an integrative approach, much for scientists, managers and the fishing industry. of the species-specific information on overfishing, Some changes, such as building dams, armoring of contamination and habitat degradation has yet to be the shoreline and coastal development have impact-translated into comparable measures and totally ed shellfish and anadromnous fish, but these impacts integrated. For example, Barnthouse et al. (1987) are not well documented. The challenge for man-attempted to express the effects of contamination in agers in regard to habitat is similar to that for the same units as for overfishing, although they did chemical contamination---how localized are the not further expand their study by adding in habitat impacts and howv have they effected populations? degradation in the same type of common currency. In the chapter on habitats, the authors review Novel, integrative techniques need to be devel-studies that relate habitat alteration, particularly oped and applied, if the effects of overfishing, con-those related to human activities, to effects on tamination, and habitat degradation are to be com-populations. pared. In the past, fisheries nianagers have relied on age-frequency distributions collected during annual stock assessment cruises for assessment of spawning biomass and year class recruitment. Models based on classical population studies were
CONI.VONINAI([ON, HIABIIAI )F(6R.DAIH). ()\VlRFISHFIN( DiFiAIA 7 then adapted lor fisheries manag ers (see NRC. riemained relatively hiigh, but the biomass of the 1998a, b lbr descriptions and assessment of these more cornmercially-valtLable resource species had models). These used age-frequency and age-fecun- fallen. Although it now appears that there is no dity distribution patterns and formed the basis for causal connection between the decline in commer-fisheries managers to conclude that overlishing was cially important species and the increase in carti-the main factor affecting fishery stock declines laginous fish biomass (Murawski, Chapter 2), the (NOAA, 1998; NRC 1998a, b, 1999). Recently, community structure has nevertheless shifted dra-however, fisheries scientists have developed a num- matically. An ecosystem approach to fisheries man-ber of innovative models to guide fisheries man- agement clearly needs to be adapted to ensure sus-agenient decisions as they manage fishing elfort tainability (Parsons, 1992- NRC 1999). (Sissenwine and Shepherd, 1987; Fogarty et al., This is not to say that all of the information is 1992; Myers et al.. 1995). These models point out currently at hand to resolve the question of whether that factors such as environmental change and overfishing, contamination, or habitat degradation habitat loss may prevent the recovery of some is the most important factor affecting fisheries stocks, such as spring-spawning Icelandic herring declines. Data gaps are inherent in all scientific (Clupea harengus)and Pacific salmon pursuits. Habitat data and contaminant effects on (Oncoriowuchus spp.; Myers et al., 1995). populations are particularly scant. There is a real One type of model, a recruitment overfishing need to identify these gaps and to recommend model, allows managers to calculate maximum studies to fill them. fishing mortality rates which would still allow sus-tainable harvests (Sissenwine and Shepherd, 1987; Fogarty et al., 1992). It has been adapted in the TIlE NEED FOR A Homisrmc APPROACII Northeast Multispecies Fishery Management Plan (NEFMC, 1994). This model, which includes esti-mates of lishing mortality and natural mortality The whole is ccqtoa[ to the .itsmol/its parls. rates, could be modified to includecontaminant- - Euclid. 365-300 B.C. induced and habitat-associated mortality. Aside firom the capture and removal of fish and shellfish, other harvestingcrelated factors must also be considered when assessing fisheries stocks. The whole is greater than,the saut o/i/s Juvenile bycatch (pre-recruit individuals of corn- parts. mercially important species) suffer significant mor- - Gestalt Theory. A1[ Wertheimer, 1924 talities during all seasons of the year (Robinson et al., 1993; NOAA, 1998). Mortality is particularly severe when deck conditions are most extreme, Expressing the issues of overfishing, contami-such as in mid-sumler or mid-winter. This bycatch nation, and habitat degradation in "either-or" terms mortality has not yet been incorporated into fish- has hindered dialogue among fisheries managers, .eries management models. aquatic toxicologists, and benthic ecologists. The Interactions between fish species have also question must be rephrased if we are to address it received little attention. Declines in the population systematically. Rather than examine fish popula-of a fished species can have repercussions through- tions in terms of exclusive categories, the more out the community structure. On Georges Bank, for important question is "To what degree do overfish-example, the declines in cod, haddock and flatfish ing, contamination and habitat degradation each were apparently accompanied by an increase in adversely affect our fisheries resources?" We need cartilaginous fish numbers. Whereas skates (Raja to develop approaches that allow us to study the spp.) and spiny dogfish (Squalus acanthias) interactions among these three, not just examine accounted for only 25% of the NMFS survey trawl their effects individually. catch in 1963, their proportions increased to nearly Each of these factors is a form of stress on a 75% in the early 1990s, but has since declined population. Populations stressed by one factor are (NOAA, 1998). Total biomass of the system had generally mor( susceptible to additional stresses
8 ROBfINSO'N & I'FIMI~RSON caused by other factors. Goodyear (1985), for greater long-term benefits to the fishery than simply example., demonstrated that contaminant exposure redtucin g fishig mortal itv. can be more deleterious to fish populations that are also subjected to fishing-induced stress. Barnthouse OUR .RIT IN TIM DEIBATE, et al. (1990) described a significant interaction between containiniant-induced mortality and fishing Our intention with this volume is to examine mortality in Gulf of Mexico menhaden (Bi-eioo'ica existing data oin the effects of overfishing, contami- ])a/lno/7ts) and Chesapeake Bay striped bass nants, and habitat degradation on various fish (for+one saxatilis) populations. Contaminants had stocks in the Northeast. This assessment will, how-little impact on the populations when population ever, have implications for fishery stock manage-levels were high (unexploited populations) but had ment in areas far beyond those of the Northeast. measurable impacts when populations were low. Our authors offer their perspective on the degree to While-this interaction was rather modest, it demon- which overfishing, habitat degradation and contam-strated that overfishing and contaminant effects inants are affecting Northeast stocks, but are limit-' cannot be viewed as independent issues. ed by lack of studies correlating each factor with We must not overlook the importance of natural population impacts-the common currency. One environmental variability (both biotic and abiotic outcome has been to identify research areas where factors) and its impact on population and community new data are needed in order to improve our esti-structure. Often, decadal or multi-decadal cycles of mates of the importance of these factors, and to environmental change must be considered in order integrate them into a more holistic view. to umderstand population shifIts (Holmann and Four types of fisheries will be highlighted in Powell, 1998). Longer-term effects, such as climate the chapters that follow: groundfisheries, anadro-change and sea level rise, must also be factored in. nnous fisheries, inshore bivalve shellfisheries and While environmental variability is certainly of sig- the lobster fishery. Each of these fisheries has its nificance, the importance of fluctuating environ- own unique blend of the various anthropogenic fac-mental factors in comparison to anthropogenic tors that have impacted their fish populations. influences (overfishing, contamination and habitat. These types of fisheries were chosen because of the destruction) is being debated by the industry, man- availability of at least some data on overfishing, agers, and environmental groups. Nevertheless, contamination, and habitat degradation for each of holistic models must contain provisions for entering them. Moring's treatment of anadromous fish changing environmental variables. In the absence (Chapter 3) has come the closest to integrating all of data on cyclic processes, these models must, at three issues within one chapter. The mass of the very least, include stochastic functions. species-specific data on one or more of these three Consideration of essential fish habitat has issues has precluded this approach for the other recently been incorporated into fisheries manage- three fisheries. Instead, chapters will address poilu-ment plans (Stevenson 1994; NEFMC, 1999). This tion, habitat and overfishing issues separately. should result in a more holistic approach to fish- Thurberg and Gould (Chapter 4) will highlight the eries management by, in effect, including the inter- effects of contaminants on groundfish, whereas actions among overfishing, contamination, habitat McDowell (Chapter 7) will cover pollution impacts loss and natural factors in the decision-making on shellfish. Murawski (Chapter 2) will address process. The Atlantic States Marine Fishery stock assessment and overfishing issues tor the Commission (ASMFC 1992) conducted an exten- Northeast groundfishery, while Brousseau (Chapter sive analysis of habitat requirements in its Winter 6) will examine inshore bivalve populations, and Flounder Fishery Management Plan, but it was not Steneck (Chapter 8) the lobster fishery. Deegan and until the reauthorization of the Magnuson Act (i.e. Buchsbaum (Chapter 5) will discuss the importance the Sustainable Fisheries Act of 1996) that all man- of habitat loss and degradation. aged species were required to be examined for, The main goal of this work is to unite the sci-habitat needs. The ASMFC went so far as to con- entific energies of fisheries managers, aquatic toxi-clude that coastal habitat restoration could result in cologists, and marine ecologists in order to reach a
.( ON I.AMINAiio10N.fI ItIiT It DIit(;k..ili1irlt, OVE Iti'iFIttf N G DI~itrl 9 consensus as to the severity of overfishing, contain- 45-9).
Cooper. C.B.. M.IF. Dwole and K. Kipp. 1991. Risks of consum ptiOn ination, and habitat degradation on our fisheries el contatninated scaitohd: The Quincy t 3ay case study. Env' stocks. The data and background presented in Health Persp 90: 133-140. Doeiiroer. P.IB.and l).G. Tcrkla. 1995. Trouble in Fishing Waters. Chapters 2 through 8 provide the basis for the sum-Bostonia. Spring 1995: 15-21. marization and evaluation of the relative impor- Dorsey-. F.M atn(l .1. Pederson (eds.). 1998. EIfects of Fishint Gear ott tance of overfishing, habitat degradation and poi lu- the Sea Floor of New Eniland. Conservation law Fouindation, Bostont. MA. 160 pp. tion for each of these fisheries, as presented by Dow. 1. and V. IBraasch (cds. . 1996. The I ealth of the Gul fio Buchsbaum (Chapter 9). As further discussed in the Maine Fcosystem: Cumulative Itnacts of Multiple Stressors. final chapter (Pederson and Robinson), this holistic Regional Association fur Research oti the Gulf of MaItmc (RAR-GOMIh Report 06-1/330 April 1996. 181 pp. plus appendices. approach may challenge fisheries managers to IPA (Eivirotmiental Protection Agency). 1088. Analysis of Risks modify the way in which they manage each of the fronm Consunption of Quimcv 13ay Fish and Smellfish. Report pre-Northeast fisheries. It is our hope that the conclu- pared by Mctcalfand Eddy, Inc.. Boston, MA. May 1988. 69 pp. plus appendices. sions presented here can then be conveyed to the EPA (Envirotlnental Protection Agency). 1991. Water Quality Criteria general public, eliminating at least some of the Summary. UiS Environmental Protection Aecncy, Washington confusion that currently enshrouds these issues. D)C. I pp. FAO (Food and Agriculture Organization). 1997. 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#4. 50 CFR Part 651. hIplemented 27 June 1991. celgrass wasting disease at tie border of New Hampshire and NEFMC (New England Fishler' Managemnent Council). 1994. Maine. Mar Ecol. Prop. Ser. 29: 89-92.
Nortleast Multispc ics Fisher\ N'lanagetinteit P'lan. Aniendcltelt Siiderinann, C.J. 1994. Quantitative EIIcts of l'ollutioiti Oil NMaliie
#5. 50 CFR Part 651. hIplemented I March 1994. and Anadromnous Fish Populations. NOAA Technical NEFMC (New England Fishery Management Council). 1996. Memorandum NMFS-F/NEC-i04. June 1994. 22 pp.
Northeast MIhit specics Fishery Management Plan. Amendment Sissenwine, NI.P. and J.G. Shepherd. 1987 An alternative perspective
#7. 50 C:R Part 651. hIplemented I July 1996.
- on recruitment overfishitg and biological reference points. Carl.
NEFMC (New England Fi Isery Management Council). 1999. .1. Fish. AQuait Sci. 44: 913-918. Nolthcast MIhispecics IFishery Mlnaglienitt Plann.Amendment Stevenson. I.K. 1904, Inlcorporation of htibitat intorinatioll in U.S.
#11. 50 CFR liart 651. Implemented 21 April 1999. Fisheries Managemlient Plans:.Ali Atlantic coast perspective In:
NEFMC (New England Fishery Management Council). 2000. Gulf of Maine HabitaL: Workshop Proceedinas. RARGOM Framework Adiustment .33 to the Northeast Multispecies Fishery Report number 94-2. D. Stevenson and E. Braasch (eds.) Pp 51 - Management Plan. 3 February 2000. 63. http :1/\wv\. lie bitc.org/i idesx. hitit Taylor, I,. 1998. Another approach to scallop production, habitat con-NEFSC (Northeast Fisheries Science Center). 2000. 30th Northeast cerns, and biodiversity. In: Effects of Fishing Gear on the Sea Regional Stock Assessment Workshop (30th SAW). Stock Floor of New England. F.M. Dorsey and J. Pederson (eds.). Assessment Review Committee (SARC) Consensus Summary of Conservation Law Foundation. Boston, MA. Pp. 111-1 14. Asscssltents. National Marine Fisheries Service, Northeast Weri-te, C.J. and R... Breteler i983. Esiuarite Fisheries of tile North isherics Scieince Centcir Rfclcrcnee Doatitletit 00-0)3. 477 pp. and M id-Atlantic: lHypotheses for Declintes. Prepared tor the NMFS (National Marine Fisheries Service). 1999. Final Fishery National Oceanographic and Atmospheric Administration, Office Management Plan for Atlantic Tunta, Swordfish, and Sharks. of Pollution Assessment. 55 pp. lttp://\vww.nm fs.gov/sfa/hms/iial FM11.1tinl. April 1999. NOAA (National Oceanographic and Atmospheric Administration). 1998. Status of the Flishery Resources o1ffthe Northeastern United States for 1998. NOAA Technical Memorandum NMFS-NE- 115. National Marine Fisheries Service, Woods Hole MA. 149 PP. NOAA/NS&T (National Oceanographic and Atmospheric Administration/National Status & Trends Program). 2000. NOAA's National Status and Trends web page (July 2000). http://I%'www.orca.nios. noaa.,gov/proiccts/ttsandt/lttnl. NRC (National Research Council). 1998a. Improving Fish Stock Assessments. National Academy Press, Washington, D.C. 1998. 177 pp. NRC (National Research Council). 1998b. Review of Northeast Fishery Stock Assessments. National Academy Press, Washington D.C. 136 pp. NRC (National Research Council). 1999. Sistaining Marine Fisheries. National Academy Press, Washington, D.C. 1999. 164 pp. OGTF (Offshore Groundfish Task Force). 1990. New England Groundfish in Crisis - Again. Office of the Comin., Dept. Fisheries, Wildlife and Environ. Law Enforcement, Boston, MA. Orth, R.J. and K.A. Moore. 1983. Chesapeake Bay: An unprecedented
I: W ITiNG 1, R o i N i ! FI S I 1 1?1 R( F Chapter 11 The New EtguIad GroundLFish Resource: A History of Population Change in Relation to Harvesting STEVEN A. MURAWSKI A:ational .'IiL'[ariM Fisheuijs Servtice ANortheasi Fisheries Science Cenler H1`)ods Hole. il'!02543 USA INTIWIDt ( ON investigations, leading to (6) missed opportunities to establish sustainable fisheries or avoid major The fishing industry of New England has, for declines in production. This paper examines the over 4100 years, been identified both economically exploitation history lor important groundfish and culturally with groundtishing (German, 1987; resources off New England, and the role of fishing 1-lennemuth and Rockwell, 1987). A mixture of bot-and other factors influencing stock abundance and tom-dwelling fishes Including cod, haddock, redfish recruitment. Research and mnanagement challenwyes and flounders and allied bottoin-dwelling species (2onsti ttie thee rotnd fish resourwce (Table2-v in achieving stable and productive fisheries for these stocks are discussed. Many of the groundfish resources off New England are now recovering from record low stock sizes and landings observed in the early 1990s (Clark, IIISIOIR ICAI., PI;;IRSIr(71nI f: 1998). Management measures have only recently resulted in demonstrable reductions in groundfish mortality rates to levels low enoug1h to allow stock DuVE'utCo'ŽrLYNT orF 0t-ru M1O1-11FrSH-ERY rehuilding (Northern Demersal Workineg Group. 2000). These recent reductions in fishing pressure In. the late 19th and early 20th centuries large required unprecedented regulation of a fishery that fleets of vessels sailed from Gloucester, Boston and historically was allowed to operate virtually uncon- other New England ports to fish local and distant strained (Anthony, 1990, 1993; Fogarty and offshore banks as far away as the Grand Banks off Murawski. 1998). Newfoundland and Labrador (German, 1987: Important historical themes in these fisheries Kurlansky, 1997; Murawski et al., 1997). Catches were: (I) almost continuous change since the turn of salt cod supported nearly 400 schooners in each of the 20th century, owing to ecological, political of these main ports, and a multitude of shore-side and market trends, (2) gear sectors in competition businesses including salt mining, ice harvesting in for grounds, labor and fish,. (3) an eastward move- fresh-water ponds, and a boat building industry that ment of the fleet to the Scotian Shelf and made the shipyards on the Essex River, north of Newfoundland, followed by a westward contraction Boston, among the busiest and best known in the owing to changing markets and regulations, (4) world. The fish landed in New England and the "writing-off' of collapsed 'stocks, as effort expanded, Maritimes eventually supported the infanmous "tri-and fisheries diversified, (5) failure to effectively angle trade' with Caribbean and west Afiican coun-deal with conservation problems in a timely fashion tries and colonies (salt cod, molasses, and slaves; and to implement recommendations of scientific Kurlansky, 1997).
I1 tll, ,, S K ! lable 2.1. Species and stocks comprising the New England groundfish rCsoNrcc. Included in Comnmon Name I "Scientific Name Manaemnent Stocks IMulti-species F.N/P? F7 Alnico ad. r/aSou th GulfofMý.!,lInC Gcorges Bank yes Atlantic cod Georges Bank ves H-laddock [llcianotgrao'mno' lin G of Maine Gulf Okan yes e Acadian Redfish Sebatses fasciatus Gulf of Maine yes Pollock Pollachus virens Gulf of Maine yes White Hake LUrophysis lenuis Gulf of Maine yes Red I lake Ut-oplihySg Chi.Ss Gulf of Nlaine/N. Georges Bank yes S. Georges Bank/Middle Atlantic yes Silver I-lake Ak/1c~cius hiluinans Gulf of MaincN. Georgcs Bank yes S. Georges Bank/Middle Atlantic yes
)Ocea) Pont A,\.fr11'o- o CE 1:'& J cs Gulfofl'vlaine,'S. New Encland I s Atlantic Halibut Hippoglossus hippoglossus Gulf of Maine/Georges Bank Yes Geories Bank yes Winter Flounder P'hwrooectI's am'uric"'CinnS Gulf of Maine yes S. New England yes W\itch F lounder Gl7.nosossus Gulf of Maine yes i Georces Bank yes S. New En-land e
'Yelowtail Flounder [Li, /, S. Ne "nvanl es Cape Cod Yes Middle Atlantic yes American Plaice Hiippog/ossoidespi'aiessoides Gulf of Maine yes Windowpane SsGulf of &taineiN. Georgcs Bank yes Flounder S. Georges Bank/S. New, England yes Cusk 13rosme brosme Gulf of Maine no \koIFlrishI4narchichoxvý loit..C Gulf of Maine no Spiny Dogfish Squahts acanihias NE USA and Canada 110io Skates seven species Gulf of Maine/Middle Atlantic no Gulf of Maine/N. Georges Bank no Goose fish Lophins anmericals' S. Georges Bank/Middle Atlantic no A. B. 41
,,g* ,, ! . 1 . ,a.. ,, ,,,
.. ------------ 45 -
...s.. , B-4 ,,
Figure 2. 1. (A) Aieas closed to fshing in 1994 and the U.S./Canada boundary decided hy the Xorld Court (B) New England shore areas and fishing grounds. Year-round fishery closures for the protection of groundfish are'shaded.
\1 V.
%F " I( ,1\ ",;, ( ý ý , x F 1D
- 1 ý R I: ý, ,i ý rF The New E.'ngland roundfiSh i(LIstry\ changed sien ilhcantlV around the turn of the century. Dur1 g *n this period, there were major shifts in how fish A were cauLiht, hand led. processed, distributed and
,sold (Herrinuton. 1932.- Hennemnuth and RockwellI 1987: Scrchuk and Wig'ey. 1992). Once dominated. by artisanal, commI Lnity-based fishermen, the resource was subiected to increasing levels of. industrialization, first by company-based fleets of long-liners and gillnetters. At the turn of the century', steam-powered trawl vessels were specially-built to harvest flounders and haddock along the smooth bottomed areas along the continental shelf south and east of New England (Fig. 2.1 and 2.2; AnonynIOuIs 1906; Alexander et al., 1915). The introduction of the steam-powered trawler based oni desi gus from England (Anonymous, 1906) funda- Figure 2.2. Otter trawl fishing vessels at Boston Fish uPier, ca. 193 1. The vessel at the end of the pier is the mnl cSpray. Built in 1905 it was the first steam trawler rapidly replaced the schooner fleets. While it was introduced into the U.S. groundfish fleet. apparent that some stocks were depleted by the schooner fleetste..', halibut onl Gcorges Bank Stif- Year fered significant declines in productivity by the 1900 1920 1940 1960 . 1980 2000 I 850). overfishing of various resources and other 60 - ................. issties of fisheries management became more prob- 50 Atlantic Cod leinatic with the introduction of trawlinr 40) (Alexander et al.. 1915.- Herrington, 1932).3 20it D (:vMi:*sTic O ve RFIS HnN G: 4o{ . By 1930 there were clear signs that the fleet 180 ____.. had orown too large in relation to the capacity of
- 160 140 40 Haddock the stocks to sustain growth in landings (Herrington, 1932). Haddock landings peaked in o 1929. but declined rapidly thereafter, as stocks -0 were less abundant on Georges Bank (Fig. 2.3). 60 This prompted the development of a modern stuidy ., 40 of the population dynamics of haddock, headed by 20 Dr. William Herrington (Herrington, 1932, 1947). 601 Yellowtal Flounde'r "It is oi/ly in the last ft/+ years when, the
.f'shing leet has suffered oi'a marked scarcity of haddock that the/Jolyf (heof 2(-e beliefin the inexhaustibiliot 0fnature has I0o become potent. " (-terrington, 1932). 0 ].. ...
1900 1920 1940 1960 1980 2000 Year A major focus of the program was to document Figure 2.3. Total landings of Georges Bank cod and had-harvesting practices and to determine appropriate dock and landings ofyellowtail founder from all New mitigation measures. The research by Herrington England waters, 1893-1999.
14 \'R\ .K (I1932) and Grarham (1952) confirmed the earl ier USA LANDINGS work of I'Axander et a1. (1915) demonstrating the COD, HADDOCK and YELLOWTAIL large discard Of juvenile haddock, and great poten-CID WV '.nn;e OWT 87 9 tial wasie oftile resource. At this time catches of very small fish were common, with a large fraction of Iish beigL under 17 inches ill leng th (43 cm). It was readily apparent to researchers and some inem-bers of the industiry that the yield potential of fish
'.3 was not being realized since they were being '.3-caught at a relatively young age, before achieving most of their growth potential (e.g. "growth over-fishing"). More troubling was the tremendous nur-bers of discarded baby" haddock, that were below commercially useful size (Herrington. 1932: 60' 63 66 56 72' 5-8 8 -8 687'9
(.iraham, 1952). Comments by one Clarence Figure 2.4. Total USA landings of Georges Bank cod.
*YEAR Birdseye confirmed industry leader's concerns for haddock and yellowtail founder, 1960-1999.
wasteful practices (see comments at the end of Herrington, 1932). Scientific investigations using DISTANT-WATrER FLEETS sea sampling showed just how destructive the trawl technologv was. In 1930 the fishery landed 37 mil- Scoutinlg vessels for the Soviet fleets first ven-lion haddock at Boston., \with another 70-90 mrillion tured into New 1.n1gland waters in 196 l juvenile haddock discarded dead at sea (I lennemtuth and Rockwell, 1987). Their target was (Herrington. 1932). The very small mesh size used Atlantic herring and their fishery took about 633,000 in the nets was judged the catuse, arnd yet mesh size metric tons that.year. In subsequent years. the fish-ery for herring expanded, and other species includ-regulationis to protect haddock were not iimplement-ed until the U.S. had the authority to do so under ing silver and red hake, and haddock were targeted the auspices of the International Commission for (Brown et al., 1976; Mayo et al., 1992; Fogarty and the Northwest Atlantic Fisheries (ICNAF), begin- Mu-rrawski, 1998). From 1960 to 1966 total ground-ning in 1953 (Graham, 1952). Interestingly, a simi- fish landings increased from about 200,000 metric lr sttudy published in 1915 (Alexander et al., 1915) tons, to about 760.000 metric tons. Landings of also used sea sampling to document the high rates haddock reached an all-time record of 154,000 in of hladdock discard by the otter trawl fisherv. 1965. arid declined rapidly thereafter (Fig. 2.3). Prior to WW-ll the fleet was large in size. but Between 1964-1967 total groturidlrsh landings were profitability was low (Dewar, 1983). The war years comprised primarily of silver hake, haddock, red were again prosperous for the industry as produc- hake, flounders and cod. -lerring landings peaked tion was boosted, and protein demands and in 1968 at 439,000 metric tons, and declined rapidly rationinlg necessitated higher fish consumption. The with the collapse of the Georges Bank herring fleet was reduced at this time, as many of the stock (Anthony and Waring. 1980). The intensive largest trawlers were requisitioned for war duty as mackerel fishery occurred in the early 1970s, with mine sweepers. The return of these vessels from landings peaking in 1972 at 387,000 metric tons war, along with reduced demand resulted again in (Anderson and Paciorkowski, 1980). low profitability to the fleets (Dewar, 1983). Effort exerted by tlhe distant-water fleets thus Development of new markets such as selling ocean shifted frliom one abundant target stock to the next, perch in the midwest as a substitute for Great in a typical pattern of sequential resource depletion Lakes yellow perch sustained the offshore fleet. (I-lennemuth and Rockwell, 1987). Restrictive man-Many government subsidy programs were launched agement actions, enacted beginning in the early after the war (Dewar, 1983). 1970s severely limited catches, and distant water fleet effort declined accordingly (Hlennenmuth and Rockwell, 1987; Mayo et al., 1992). Total standard-ized fishing effort had increased four-fold on
E ý%,17N f; I D C 1) jfS I 1 0 1ýK t 11S eflictively monitored using data solely from fish-cries. A new program was developed usinIg, statisti-callv rig!orous stratified random sampling designs. Beginning wvith the delivery of the NOAA Albatross IV (Fig. 2.5) .in 1962, the Northeast Fisheries Science Center initiated Mihat has become the. longest con-tinLiously operating survey of its scope in the wvorld (Grosslein. 1969: Azarovitz el al.. 1997). The sur-vey has proved to be an invaluable tool to monitor specific stocks and species assemblages independ-ent of biases and data quality considerations inher-ent in fishery-dependent dala (Brown et al., 1976: Hiure 2.5. NOAA RiV Albatross IV, launched in U. Clark, 1981; Clark and Brown, 1977). and responsible for most standardized bottom trawl Abundance, as measured by the Northeast survey cruises betwecn 1963 and 2000. F~isheries Science Center research vessel surveys, declined rapidly as various components of the Georges Bank between 1960 and 1972 (May'o et demnersal and pelagic systems were pulse-fished by al.. 1992). Under these high eflbrt levels, fishing the distant-water fleets (Fig. 2.6; Brown et al., mortality rates increased to unprecedented levels, 1976: Clark, 1981). The Georges Bank haddock and landings and stock sizes declined (Fig. 2.4). resource collapsed under the pressure from distant The Bureau of Commercial Fisheries instituted water fisheries, failing to produce any thing but an innovative program to gain fishery independent
.poor year classes between 1964 and 1974 data on fish abundance off the Northeast USA (Northern Demersal Working Group 2000). Other (Grosslein, 1969, Smith, 2000) beginning in 1962 stock collapses in.cluded silver and red hakes, Although standardized research vessel surveys had Atlantic mackerel arid the Georges Bank herring beguLn il the late 194i0s. iioust Ii~hery resecarch stock (Fogarty and Murawski, 1998).
conducted on the northeast shelf consisted of sin-Beginning in 1973, quota-based management gle- species studies of fisheries involving data pri-was instituted under the auspices of the marily derived from commercial fishing operations International Commission for the Northw est (Smith. 2000). Commercial fisheries data have Atlantic Fisheries (ICNAF; Hennemuth and. obvious biases due to the concentration of fisheries Rockwell., 1987; Fig. 2.4). Quotas for each species in known areas of high density, and io-commer-were allocated by country, with the sum of each cial components of the ecosystem could not be species equal to the total recommended removals. Additionally, 'second-tier' quotas, less than the sttm of a country's species allocations, were intend-ed to mitigate the effects of non-targeted bycatch, R:EL:AT:i: ::A,:NAN i*:*=:*IV:::::i,. 0 'NOR:THWES so that species quotas would not be exceeded. The JATLAN:.*
- I *' ....... Ci I S GftOOS-I 6.3-, quota system under ICNAF effectively ended directed distant-water fisheries on New England
;jj5;,
grotundfish resources, as these resources were
" :: 5 "0,,:5 . 5i 5..... >,:: ... determined to have little capacity to support fish-eries beyond the levels that would be taken by the Figue 2..abndane Reativ offourfinfsh pece United States and Canada. Quotas were progres-grous fom fshew~idepeidet suvey (sratiiedmea cthtwi n kzo from@:3 NMF boto =:: traw S"333yS) 196=
3 -99 sively lowered on mackerel, herring, squids and cath/twNFSi kgfi'm otom raw suvey), 96399 other species, as these resources declined as well. 200-MILE LIMIT The clamor for the U.S. to assert control over waters out to 200 miles was great. The U.S. Congress
16 enacted the Mailuson lFisherv C(onsc'r\ithor and Relatively strong year classes of cod, haddock Management Act of 1976, takim,- control o the and some other groundfish stocks produced in 1975 exclusive economic zone (EiZ). and setting uP a and later resulted in improved Cresotirce conditions, system of reguIlation of the domestic industry. and increased giomimdhi.h abundamice and effort in Fueled by great expectations, the U.S. fishing the late 1970s and early 1980s (Fig. 214, 216 and industry expanded i apidly i ordham, 1996). ' lhe 2.7). Between 1976 and 1984 USA otter trawl fish-fleet, once dominated by wooden side-trawlers, ing effori doubled (Mayo et al.. 1992: Anthony, was repliaced virtually overnight by steel stern- 1993: Fogarty and Murawski. 1998), withl many trawlers which were equipped with modern tech- new fishing vessels entering the fishe ry (Dewar, nology lor locating, catching and handling fish. 1983). These newer vessels were more technologi-Quota-based regulations, a hold-over friom the last cally advanced, safer, and more capable of fishing days of international restrictions, were an anathema in foul weather than the vessels they replaced. As a to the growth of the revitalized U.S. groundfish result, their fishing power was substaniially higher fleet. Catch quotas were abandoned, in favor of than those in the fleet prior to 1976. ineffective measures to control the size of meshes Groundfish abundance again peaked in the in the nets, and the minimum length of fish landed early 1980s, primarily as a result of improving 2,1 jlignjljony, 1993). resource conditions for cod and haddock (Fig. 2.6 and 2.7). However, in the face of rapidly expand-ing fishing effort, abundance of the groundfish one o Akeimv exactly how -maniynew- complex declined precipitouisly (Fig. 2.6 and 2.7). coImiers iole a'ivc/ urehtr,' flhe /r'!if.our Il tile G(ul'Cf Maine. high relative catch rates were monlhs Of 1977 biut accordhlig 0oone supported in the late 1970s and early 1980s by red-rFcnort. aeli boots entce/e !he w fishem; at fish. haddock. cod (Serchuk et al., 1994) and 117f./oI/I? rote of oh'oulf onu everl, mixed flounders. From 1970'onward the cod
,lovs ,(D .w:!/
90,83). resource became the imainstav of the New England groundfish catch, as haddock and then yellowtail flounder resources collapsed (Fig 2.4). Tihe Canadians had extended their territorial jurisdiction YEAR 200 miles seaward. exclu~ding U.S. vessels which
;9,C f975 0390 795 "'M0 :995 2,00 had fished off the Scotian Shelf and the southern Grand Banks for generations. With the return of Georges Bank 20] CodL
_R the redfish fleet from the Scotian Shelf. as Canada extended its jurisdiction, the residual Gulf of Maine SSB I-a-S 00 redfish resource was quickly depleted (Clark, 1998). Georges Bank Haddock 0 * . SSB 0.0 Overlapping territorial claims in the Georges Bank Lu 0.2 region between the U.S. and Canada resulted in high-level diplomatic negotiations. In 1979 a draft ER C 0.0 0 treaty on reciprocal fishing rights was agreed to at Georges Bai~kYellowail! S 04 0 the ministerial level. The treaty recognized histori-
-09
'2,
-- 00 U] cal fisheries by the U.S. off Canada, and vice-25 0,2 versa. However, with the change in administrations ER 00 -00 in 1980, and opposition from some segments of the Georges Bank-. -
WinteKFt-ader -
- 08 U.S. fishing industry, the draft treaty was not rati-fied by the U.S. government. Ultimately, the
.. 02 boundary between the U.S. and Canada was settled S! ,1)0 in the World Court (Fig. 2.1). Americans were 1970 1975 1980 1985 1990 f995 2000 YEAR barred from fishing areas off Canada, and areas in Figure 2.7. Changes in spawning stock biomass (SSB, the northern part of Georges Bank, where so mudh 000s of metric tons) and exploitation rate (ER) for four of the haddock landings of the 1920s- 1950s had New England groundfish stocks, 1973-1999. been taken.
f) F! II R s;: lý( !:'ý 17 On Gcor-es Bank, stock sizes of haddock, cod of Maine (fig. 2.1), trip limits on some species and and yellowtail flounder, which had improved in the increases in mesh size were also instituted as part late 1970s-earl 1I 9 80s again declined as spawning of later plan amendments. biomasses and recruitment dinminished (Fig. 27). The strong 1987 y;ear class of Southern New England yellok tail lourider, was quickly lished out Rli:*( 1v: xN l>:t i (Northern Demersal Working Group, 2000). Owiig to the decrease in lishimng e'lhrt (days As a result of the ~failure of indirect controls to fished), primarily by offshore trawlers, and the prevent overfishing (NEFSC, 1987), environmental implementation of other measures including closed groups sued the Department of Commerce in 1991 areas, exploitation rates for some stocks have (Fordham, 1996). The court settlement of the law decreased substantially in recent years (Fig. 2.7). In suit required the New England Fishery particular, exploitation rates of Georges Bank yel-Management Council to develop a fishery manage- lowtail fHounder, haddock, and to a lesser extent ment plan to end overfishing and rebuild depleted cod. declined to less than 10% per year, from lev-stocks, the result of which was Amendment 45 to els, in the case of vellowtail flounder, of up to 80% the Northeast Multispecies (groulldfish) I'MP, (Fig. 2.7; Northern Demersal Working Group, imp.lemented in 1994. This plan required a reduc- 2000). The reduction in fishing mortality has had a tion in groundfish effort by 50% over 5-7 years, significant impact on the age distribution of the increased mesh sizes, expanded closed areas, a stocks, especially for haddock and yellowtail floun-mnoratorium on new effort in most fleet sectors, and der, where older ages/larger sizes are 1ore abun-iandatory reporting (logbooks.. dant than in recent years when exploitation rates Amendment #5 was implemented in May 1994. were excessive (Northern Deinersal Working However. in June of that ,ear. new fishery stock Group? 2000). Increased sUortiVotship of older age assessments indicated thatthe resource condition grotups is thouight to be important in groundfish had deteriorated to the point that scientists warned: stocks. owimig to improved hatechingi rates and larval survival due to maternal spawning experience and size effects (Trippel et al., 1997: Murawski et al.,
"Failure to lake strong manageleni 1999). In the case of some New England ground-aclions nowii t ) /ves e the limiled fishes. spawning had become increasingly reliant sp1awning hiomass finr Georges Bunk cod on first-time spawners in years prior to 1995
,mav have severe and potentiallv long-(Wig le, 1999).
lasting conisecquencesior both ihe stock Improved survival of older age groups is the andL.ishel);' -N-'C.1994 primary reason for modest increases in spawning stock biomass (SSB) for Georges Bank cod (Northern Demersal Working Group, 2000); In response, scientists reconmmnded "...substantial., recruitment of the Georges Bank cod stock remains immediate reductions in groundfish fishing mortali- poor. In contrast, improved recruitment combined ty on Georges Bank", and that "...fishing mortality with higher adult survivorship has increased yel-for cod and yellowtail flounder be reduced to as lowtail flounder SSB to the highest level observed low a level as possible, approaching zero" in the analytical stock assessment time series (e.., (NEFSC, 1994). In response to the poorer progno- since 1973: Fig. 2.7). Haddock recruitment sis for groundfish stocks, particularly on Georges remains well below the historic (1931-1999) aver-Bank, the Secretary of Commerce instituted a age, but the 1998 year class is the largest since series of measures under his emergency authority. 1978. and is projected to continue expansion of Chief among the measures instituted was the clo- SSB when recruited to the spawning poptilation sure in December of about 17,000 kim-2 to ground-. (e.g., 2001). fish fishing on Georges Bank and in southern New Although landings of Georges Bank groundfish England (Fig. 2.1). The areas have remained closed stocks have remained stable since 1995, the species to grourldfishing since then. Other measures, composition of landings reflects modest increase in including the closure of additional areas in the Gulf
I8
$ B~a~o;s~zs G~ El cases. howcver. thie level of harvest resulted in COD HADDO~'( edd YELL QWTAffl non-sustainable harvest rates, and populations (par-I ticularly of mature animals) declined (Clark. 1998:
[Lao et al., 1999). Fishery mnanagement plans for both stocks were developed and are now imple-. inented to reduce fIshing mortality and rebuild tile stocks to BMSY, Tihe dramatic decline in ground fish abundance in the late 1980s was accompanied by a variety of changes in other fish components of the ecosystem (Fig. 2.6). In particular, there were rapid and sig-nificant increases in principal pelagics (Atlantic herring and Atlantic mackerel, as well as the sniall elasmobranchs (spiny dogfish and skates). The abundance of mackerel and herring declined to Figure 2.8. Spawning stock biomasses (thousands of very low levels in the late 1970s. but has since metric tons) for Georg4es Bank cod., haddock and yellow-tail flounder. 1978-1999 (Northern Demersal Wbrking rebounded to historic proportions (Clark, 1998). Group 2000j. Iishing mortality of ierring and mackerel remains very low, as compared with sustainable harvest rates, and those observed when the distant-water diversity ainong cod, haddock and yellowtiil. Hleefs targeted them. Most of the increase in elas-flounder (Fig. 2.4). Spawning biomass increases mobranch abundance was due to the increase in among the species better reflect the increasing dogfish, partictilarly since 1980 (Rago et al., 1999), diversity (Northern Demersal Working Group, 2000: The abundance of mat ure dogfish has declined sub-Fig. 2.8). as landings have been seriotisly con- stantially in recent years, and the dearth of nature strained. Aggregate spawning bioniass for the three females in the population has produced very poor Georges Bank stocks is now higher than any time recruitment. Managers have severely curtailed since 1983, and will increase in the next few years directed fishing for dogfish in order to be able to (Northern Demersal Working Group, 2000). eventually restore the biomass of mature dogfish to Other gronndlfish stocks (Table 2. 1), have that necessary to produce MSY. showed variable trends in exploitation rate and Skate resources on the northeast shelf are coin-stock biomass (Clark. 1998; Northern Demersal prised of seven species (NEFSC. 2000). The large-Working Group, 2000). In general, stocks on bodied species (winter, skate. barndoor skate and Georges Bank have lower exploitation rates and thorny skate) have showed significant signs of are further along in rebuilding to long-term bio- overfishing, due to their vulnerability to harvest mass targets than are stocks in the Gulf of Maine and (in the case of winter and thorny skate) directed region. In particula, Gulf of Maine cod and white overfishing. Barndoor skate abundance declined hake resources, concentrated in the Gulf of Maine, significantly prior to 1970, and has only recently have biomass <40% of the biomass that would pro- made a miodest increase in the past several years duce maxiiun tm sustainable yield (BMsy), and are (NEFSC, 2000). Winter skate abundance on exploited at rates above rebuilding targets. Georges Bank peaked in the mid-1980s and As traditional target stocks declined, the New declined substantially thereafter. Thorny skate England groundfish fishery re-targeted to exploit abundance has declined throutghout the past 30 other available resources, including goosefish years. The small-bodied skates (smooth. rosette. (rfionkfish), spiny dogfish, skates, white hake, and little), have shown stable or increasing trends northern shrimp and other stocks. Two important in recent years (NEFSC, 2000). species to which effort was refocused were goose- As a group, groundfish resources have under-fish (monkfish) and spiny dogfish. Landings of gone episodes of overfishing, in the usual scenario both species increased substantially in the early of discovery, build-up of directed harvest, overfish-1990s, reflecting increased directed fishing. In both ing and stock collapse. In several cases (haddock,
ilA~ ~
\\LP\BI(if CiK~ ý1ý.,11 Vs_ý ()
yellowtail flounder) there were a iulnber of such YEAR CLASS episodes durino the 19th and 20th centuries, while
- 1995 2000 1970 IS975 1980 1985 1990 in others (redfish, Atlantic halibut. barndoor skate).
the population dynamics of extreme K-selected species has precluded such c(clic response. For those stocks %%here fishing has been reduced to low levels hallowxing'a s toclk decline, in virtually all cases, a substantial recovery of' biomass and recruitment has ensued. Atlantic herring on Georges Bank were virtually etirpated in the mid-I-970s, but now appear to be at historic high levels. 0 Likewise, mackerel recovered from overfishing to
- 0. GeogesBt cO m unprecedented high stock abundances. Numerous (0 groundfish stocks including redfish, haddock, yel- 01i lowtail flounder, witch flounder and others have increased substantially followiting relaxation of 20 1" ýti- .oth exploitation. There are a few exceptions. however.
Red and silver hake populations in the Middle Atlantic Bight have'failed to recover following significant overexploitation by the distant water fleets (Clark. 1998). Gulf of Maime stocks of the 1970 1975 1980 1985 1990 3995 2000 same species have fared much better, deepening YEAR CLASS the mystery of the lack of recovery of these popu-lations. Several theories as to the kick of recovery Figure 2.9. Changes in recruitment survival (measures as of the two southern h1ke stocks include habitat recruits at age I per kg of spainine stock bioniasst for destruction by demersal fishing gear. changes in four New England groundfish stocks, 1973-1998. the trophic composition of the system increasing Horizontal lines are LOWESS smooths, assumini a predation pressure on juveniles, continued over- tension value of 0.5. fishing of the stock (and in particular catch and bycatch Of juveniles) and changes in oceanographic does it appear that the combinations of harvest conditions necessary for effective reproduction. rates (exploitation rates below -25%), and selec-These two stocks apart. the dominant factor con- tion characteristics of the gear extant in the fisheries trolling the population abundance of northeast result in near-optimum yield per recruit for some groundfish stocks has been fishing. stocks (Northern Demersal Working Group. 2000). There is ample evidence for significant recruit-ment overfishing of many of New England's fishery TIlE RoLEts OF OVERFISIIING ANI) ENIRONMENTIA L VAlIXTION resources throughout most of the 1980s and early 1990s (Sinclair and Mtmrawski, 1997). Recruitment Herrington (1 932) and Graham (1952) clearly overfishing occurs when the reproductive capacity demonstrated growth overfishing (excessive har- of the stock is decreased by fishing, so that the vest preventing maximum yield from a given num- level of recruitment, on average, is substantially ber of young fish over their life span) and incredi- lower than when the spawning stock is larger-ble waste of the Georges Bank haddock resource, more mommies, more babies. Haddock are a good owing to the very young age at selection and high example of a stock substantially recruitment over-discards by the fishery. Growth overfishing was a fished during various times during the 20th century serious problem for most of the period before (Overholtz et al., 1986; Overholtz et al., 1999). 1994, even with increases in minimum mesh size Although there is a great deal of variation in had-to 5-1/2 in. for the directed groundfish fishery, dock stock and recruitment data, it is nonetheless owing to the mis-match with minimum legal fish apparent that at stock sizes below about 80,000 sizes (NEFSC, 1987). Only in the last several years metric tons, the probability that year classes >25
20 20 iiR.\WS KI million fish will be produced is greatly diminished. 220 Georges Bank Cod By keeping the stock below the 80,000 metric ton 200 level (e.g. since the late 1980s). the population has 180 had insufficient reproductive capability (numbers 160 Simulated, F=020 of eggs spawned) to generate year classes in excess of125 million fish, except in years of unusually 8o74 high survival of age I fish (e.g. 1975; Fig. 2.9). That the 1978 year class was good, and the product M.16020 of the high spawning biomass of the 1975 year ca C 40 class (at age 3) and not unusually high survival rate 80 (Fig. 2.9) is an important demonstration of the role Co of spawning biomass in determining year class 1977 7980 1983 1986 1989 1992 1995 7998 strength. During the I 930s through early I960s, the Year" Georges Bank haddock produced year classes in Figure 2.10. Observed and simulated spawning stock excess of 25 million fish regularly, and very good biomass of Georges Bank cod. 1978-1997. Simulated year classes (>50 million fish) in about halfof the SSB assumed that the stock was fished at F-0.2 (,16% years (Overholtz et al., 1999). The 1998 year class exploitation rate) for years 1978-1997. Recruitment was assumOed to be that observed at age I. appears to be in excess of 25 million fish, and, if conserved, should increase the SSB to over 80,000 metric tons in 2002 or 2003 (Northern Demersal haddock in the late 1970s, but again declined in the ,Working Group, 2000). Analysis of the historical 1980s. Since 1990, recruitment survival has record indicates that recruitment prospects for improved for numerous groundfish stocks (Fig. 2.9). Georges Bank haddock should continue to improve. The relationship between natural variation in recruitment survival and effects of fishing were Most northeast groundfish stocks exhibit sig-nificant, albeit noisy, stock-recruitment relation- evaluated in asimple simulation model (Fig. 2.10). Beginning i 1978 the calculated numbers of cod at ships (Brodziak et al., 2000). Given the substantial- age was subjected to various fishing mortality rate ly greater likelihood of good recruitment at SSB's scenarios. Two simple assumptions of cod recruit-higher than the median, there is convincing evi-dence that maintaining high spawning stock will ment were used: (I) the annual numbers of recruits produce benefits in higher and more regular (age I) varied as observed in the fishery stock recruitment and yields to the fisheries. assessment (Northern Demersal Working Group. 2000), and (2) the observed pattern of recruitment Natural environmental variation is a substantial survival (RiSSB), was mutltiplied by the simulated contributing factor to the strength of individual SSB to derive total recruitment. The importance of groundfishl year classes, and, if not properly fishing to the overall level of SSB and the trend is accounted for, can exacerbate recruitment declines given in Fig. 2.9. In this case, the only difference due to overfishing (Werner et al.,_ 1999; Fogarty et between the scenarios was the fishing mortality rate al., 1996). The survival of young fish (expressed as (Fig. 2.4 and 2.9). When the stock was fished at a a ratio of the number of age I produced per kilo- low level (fishing mortality rate=F=0.2), the SSB gram of SSB) exhibits important patterns of varia- peaked at over 200,000 mt in 1989, nearly three tion, as illustrated by some New England ground- times the observed level. Although SSB declined fish resources (Werner et al., 1999; Fig. 2.9). from 1989 to 1997, the absolute level of SSB at the Recruitment survival was generally good for had- end of the simulation was over twice as high when dock in the early 1960s, but declined in the late F was low. The overall yield obtained in the low-F 1960s and early 1970s (Werner et al. 1999). This case was about equal to that assuming higher es, .pattern was generally similar for haddock on but was less variable from year to year. In the last Georges. Bank and on Browns Bank off Southwest few years of the simulation, the low-F scenario Nova Scotia, suggesting some level of geographic produced substantially higher landings. This simu-coherence, perhaps due to regional-scale environ-mental factors. Recruitment survival improved for lation assumed annual recruitments as calculated
- IIýV 1:N(i I k 1ý1ý (i.11,ý1 ý, 1)1:1S If P 17,
ý: Ii i,*( 1:S ? I fi'oiu the. actual high-I. scenario. In all likelilhood, Gieores Bank was virtually extirpated in the these hi-her simulated SSBs would have generated 1970s, but has returned to relatively high abun-even hiherl recruitme nts. thereby producing still dance, and is now occupying historically important hi'her SSBs and landings. When the simulation spawning areas. The Atlantic mackerel stock has, was run with observed R/SSB values and simulated as well, increased in abundance following intensive SSBs, the landings and stock sizes under the low-F overfishing in the early 1970s.
scenario were substantia lyI greatei yet. This simple Groundfish, however, did not fare well under example shows the importance of maintaining domestic management following adoption of the proper exploitation rates during periods of both Magnuson Fishery Conservation and Management good and poor recruitmenl survival. When recruit- Act (F'ordham. 1996). Most stocks oftgroundfish ment survival was good (early-mid 1980s), SSBs declined to near record low levels of abundance by and likely absolute recruitment would have been the early 1990s, precipitating intervention in the much greater than that observed. In periods of poor management of the resources by the federal courts. recruitment survival, maintaining low Fs (or even Fishing practices during much of this period reducing Fs when recruitment survival was poor) reduced the inherent resilience of the populations woulcd have resulted in smaller declines in SSB, by removing many of the older (breeding) fish and and perhaps set the stage for a quicker turn around resulting in the fisheries depending almost com-in SSB and yields once conditions for recruitment pletely on the strength of incoming year classes survival improved. Thus, rather than being an alter- "recruitment fisheries"; Murawski et al., 1999). At native explanation for observed patterns of stock lower exploitation rates, the population would be variation, natural lluctuations in the survivo'rship Of comprised of a greater diversity of age groups, and young fish may have exacerbated declines occur- thus, if recruitment of the incoming cohort is low, ring due to overfishing. An important empirical the fishery could concentrate for a while on the observation (at least lor northeast groundtish) is accumulated stock of older animals. In the case of that a conservative approach to exploitation rates. New England groundlish. however, high rates of perhaps including' adaptive reductions in F when exploitation obviated this option. The dependence survivorship is poor, will produce greater long- on the recruitment of young fish resulted in great term benefits and more stable catches than the economic incentives to target animals at or near opposite pattern of fishing mortality *ratcheting up' legal sizes. Retention and discard of juveniles eventually leading to stock decline, typical of open became more problematic. access fisheries (Ludwig et al., 1993). The experi- Improvements in some resources followed ence in the northeast groundfish fisheries is a con- implementation of direct effort controls (prescrib-vincing case history o01recruitment overfishing and ing a 50% reduction in days at sea), along with the the "ratchet effect"--a case that need not be first ever moratorium on new vessel entrants into repeated (Ludwig et al., 1993; Sinclair and the New England groundfish fishery, closure of. Murawski, 1997). large blocks of productive fishing area, and other measures (Fogarty and M.urawski, 1998; Murawski et al.. 2000). The role of marine protected areas, CONCLUSIMNS such as the Georges Bank closures, in long-term Groundfish resources in the offshore New conservation of resotrces and ecosystems is acL'r-England region have varied considerably in abun- rent subject of intense speculation and study. dance and landings during the last 10 decades, pri- Closed areas on Georges Bank are important nurs-manly due to their exploitation history. Dramatic ery areas for a variety of grounldfish and other reductions in most offshore stocks occurred as a species (Muraxvski et al., 2000). Given the poten-result of systemic recruitment overfishing by the tial for habitat destruction by heavy towed gears distant water fleets, who sequentially depleted the such as otter trawls and scallop dredges, it is possi-wide array of species available. Subsequent to the ble that improved recruitment may result from per-end of distant-water fleet. fishing, some stocks manent protection of nursery areas providing high rebounded to very high levels, only to be over- quality feeding opportunities and cover from pre-fished once again. The Atlantic herring stock on dation. At this point, such mechanisms have not
11-. been Verified through scienltiic investigation, I toxxever, it is tlhis variation that has allowed col-although some studies have been instituted (Collie lapsed stocks to rebuild froml extremely low popu-et al.. 1997). Clearly. managers have found an ade- lation sizes. For example, unusually high recrtuit-quate combination of measures that has allowed ment survival of haddock in 1975 and yellowtail stock rebuilding to occur on Georges Bank flounder in 1987 (Fio. 2.9) resulted in significant (N'lurawski et al., 2000; Northern Demeisal but temporary stock rebuilding. as these year class-Working Group. 2000). Some resources such as es were ,,apidly Fished out. In the past. these urnusu-Georges Bank vello~wtail flounder are approaching al events oh hih recruitmlent survival at loxw target biomass levels, and could be harvested at spawning stock sizes had been interpreted as evi-I increased rates. while others Will requnire addition-al dence that environmental variation was the defin-protection to achieve long term rebuilding ing factor in year class strength, and that spawning (Applegate et al., 1998). The challenges for the stocks could be fished to very low levels without next several years will be to manage the resource threatening the productive capacity of species. in a way that will allow less productive resources More complete consideration of the relationships to meet their biomass and yield potentials while between SSB and recruitment, however., has estab-considering additional fishing opportunities for lished that for most grouildfish resources there is a more productive stocks. Biomass goals have been higher probability of good recruitment at spawning established for all Of the significant resource biomasses above the median, and that good year species, but these targets have been calculated fr-om classes are the product of good recruitment sur-information collected from stocks that have been vival combined with sufficient spawning stock. exploited at or above thein optiminurn rates for all of Thus, tile appropriateness of inanlaging for high the recorded history. It is possible that yield poten- and stable spawning stocks as a necessary element tials for some stocks max be much greater than the of fishery management goals for the New England maxinlmu landings recorded in the fishery. owing ground fish resource is firCi1ly established (Brodziak to growth or recruitment overhishir-g. Thus, an et al.. 2000: Overholtz et al., 1987, 1999). adaptive approach to malaging recovering 'he suite ofi anageinteu measures currentlxy in resources to assure that the lull productive poten- place has been sufficient to allow recovery of some tialof the resources is realized is an appropriate components of the resource. The challenge for goal for future research and management. In the managers in the future is to extend rebuilding to future, consideration of the potential ecological other, less productive components of the resource. constraints to the simultaneous optimization of bio- Given the complex biological and technical inter-masses and yields of the array of resources species actions among various resource species, extension will become more important (IMurawski 2000), but of single-species concepts into an overall ecosys-there is considerable empirical evidence that at cur- tern perspective should allow consideration of the rent levels of abundance, predation and competi- inevitable trade-offs between species. In the long tion are not significant impediments to stock run. conservative mainagement of fishing capacity rebuilding for New England groundfish resources. for vessels capable of switching target species, The history of exploitation of New England's combined with appropriate uses ot marine protect-groundfish resource has produced a repeated record ed areas to preserve ecosystem function and nurs-of failure to address identified conservation prob- eries for resource species, and improved gear lems followed by inevitable stock collapse and designs are undoubtedly the basic elemnents of a economic dislocation. The dominance of fishing as sustainable fishing strategy for the New England the primary factor indetermining the abundance of groundfish resource-a strategy that has yet to be resource species, and in fact, the structure of the fully realized. fish component of the New England offshore ecosystem has been established. Environmental AC KNOWivu. DGNI ENTS variation, working to increase or decrease recruit-ment survival, has exacerbated the effects of over- This paper is dedicated to several individuals fishing in some instances of stock collapse. whose collective vision and determined hard work
forever chianoed the scientitic view of fisheries on lhe SiUrcLliC Of l1r1W e -,-pa S i'.sh.' -. S Oil(r. OF CS Bank. Fcol Ap. 8, Supplement: Si-$i22 the northeast shelf, and put into place data collec- Ioiarti, NI.J.IR.K. MIaso, L O'(rien, F.INM. Serchuk, and A.A. tion schlemes and proerams of suifticient rigor that Roscnbergr. 1996, Asssin' -,.cerai-itv i isk -i exploited and they have stood the test of time: William lIlariIC pOpulalions RcIia.U Svt Salv 4' 183-194 ,.
- Fordham, S.V, 1996ý New Engilaid rIundi 'ish: Ft oio'i to eriel.
.-lerrinnton, William Royce, Herbert Grahain. Centeril forh-r c Cinseration, Waishci -c. D.F. 96pp. Robert Edwards, Richard Hennem udh and Miarvin German, A.W. I 9)8T Ilisiiy of, the early fishcries,c 1720- 1930. pages Grosslein. Generations of scientists to come will 409-4'l4 ii R Riackus jed.] Geoes fiank Massa-hus-us Institute ociihnobos Piess. Cabrinidge, MNassachusCtts. USA. forever be in their debt. I also dedicate this review Grahlail. I I.W. 1952. Mesh regu1h:tionls to ldel ofd!ieh Irrcs to the memory of Ellie Dorsey, a tireless worker Georges Bank haddock fishiery pp. 23-33 In Intetrnational Commission t'Or Lile North,,Aest Atlantic Flshcr icý Annual.1 Rep~ort for improved conservation of the region's fishery
- 2. IartmioilIth Nova Scotia resources. Grosslein, M.D. 1969. Giiiitiidl'ish survey program ut BCF Woods ilole . NIti Ish. Rev. 31:22-30.
Hi-nctiiciiiuli. R.C , and S Rockwell. 1987.- listori ofi fisheries ianil-4 LITfIRATUIREI CITED agement and conservation. pages 30-446 in. R Backus led.], Geores Bank. Massachusetts lnistiittc ofl I-chnology Press, Alexander, A.B. II.F NMooir and W C Kindall 1915 Otter-tra\sl Cambridge. Mlassachusetts, USA l'ishery. ApIpeniN VI. Repoit oe-'h !-nitcd Stats, Fishery Hccriincton. -W.C.19132 CoIisci'iVla n ."
-i -ilL itc I 1_[i in otter irawlsr Commission 1914. Washigton. 1) C "Trans.Am. Fish. Soc 62: 7-63 Anderson. Fl.D3.and/\ J Pacioilovsi, 1980 A rt.5 cvcx 'the north- I lcrrington, W.C( 1947. The 101Cei" intrisp-'ciic co'petition aid west Atlnitic mackerel fishery. Rapp P.-v. Ruin. C0 ns. nLt. otheir Iactors in determining eilh population level oIa major Explo. Mer. 177:175-2 11. marine species. Ecol. Monor. 1T3 17-323 Anonymous. 1906. The otter trawler Splay. Fishin" Ga7ette, 23(3l. Kurlanskv, NM.1997. Cod: A biography o: tile fish that changed the Anthony, V.C. 1990, The New Englan'd gloUndtish fishery aftcr I0 world. WAalker and Company, New Yoik 294 pp.
Scars utnder tile *-ainlsicion erv I a, 10 s-s xion I d ID, I).i, Rii nd Ci W'- 5. I i9 tI -Ii*ie
. t lbllai itO :i',,'ý resur;Mce Management Act. N. Am. J. f-isherv Niana. IW 17' 5184. exploitation and Conservationi IessOIs I Iistor, hOil, Science Anthony. V.C, 1993. The state oH groutindish resources ofIthe '60: 17, 36.
Northeastern Uniied States Fisheries 1 12- 17. Miaco. RK., M. It":.,gast, and -IMS'CetchK. 1992. A rc-ate ' fish Anthony, V.C.. and (.T. Warini . 19801 ihe assessment and maniliagc- 0io11ass and production on iciogcs Banik 1116- 1Q87 I. NW ieint of tile ,t "es Hunk herrr'"in, 5'hrv. Rapp. P.-v. teun. A1th1n. Fish. Sot. 14:5)-7'. C ons, ]o. I. xplo. MeIr-. 177 : - i11 Nitirawski. S.A., J.-. Maiure. R.K1.MIasi., and FNic SerlccIu . !997 Appl A., S. Cudrl. J.I igate, C -N-tooIC. S. MI iaw i[id L. nitwIIIg UrIound'ish,stocks -nd the Iishing iidcsi, pp. 27-7-'D Ili: .I Pikitch. 1998. Evaluation 01of existici" oVCrlisIhg defin'itjions and Boreman. t S. Nakaslhiiia .1.A. lso and R I Ki.endall (edi-recommendations Cotrnietw overfishing definitions to comply with tors) Northwecst Atlantic oocIndfish: Perspectives on a fisherx the Sustainable Fisheries Act. New England i isheries collapse. Amceiican Fisheries Society. Bethesda. 242 pp1 MantagemienCIt Council. Newtburyport_ "MA. 79 pi. Iurasiski, S.A.X P.J. lago,a d I_ A. Iripp.i99- p a9ti of'demo-Azaroviiz. F., S. Chlak, ., Despes and C Byrne. 1997 lihe graphic variation 'Ii spawning success on rIcli.rence points for, Northeast Fisheries Science Center bottom trawl suIre'y programn. f'ishery ninagemernt Pp. 77-85 In: V. Rstrepo 'iedl Proceedings ICI-S CM. I 997/Y: 3 22 pp. of the Fifllh National NMFS Stock Assessment Wkocrkshop, Brodziak, I., \V OvcIIIOloz, and 1'.tRago 2000. Does spawnhiln stock Febrmars 24-2,1, 1998, Kes Iiargo- Floridia, NOAA Techlical ai~e c - -me-i'C\eFlncn " ')- * ,_'¢1Id 111,11,Na IalNamlc M:cniioraiiidltfl NNIF S'-FI S --ft, PII
)
Fisheries Service, unpublished ma nuscript, Woods Hole Murawski, S.A., R. Biowsn, I.-L. Ia. PiJ. Rage and L. IHendrickson. Laboratory, Woods Hole, MA 2000. Large-scale closed areas as a fishery-matnagemenit tool: Brown, B.1.0., J.A. Brennan, I.1G. lleyerdahl MND. Grosslein and R.C. The Georges Bank eiperience Bull. Mar. Sci. 66h1-24 Ilenneiuth. 1976 Tlihe efiect offishing oii the mar'ic fiish Northeast Fisheries Science Center I NFlSC)1 1987 Status ui'fmixed biomass of the Northwest, Atlantic fioim tle G(,ulf ofI Maine to species demcrsal finfish resources i New Enhilcd and scientific Cape Hatteras. International Commission for the Northiest basis 'fLirmanaigemeit. National Mai ine Fisleries Service, Woods Atlantie Fisheries Research BullCtin 12 49-68. Hiole Laborators' Rcleremce. Docuitent 87-08, Woods I ole, MA. Clark, SH. 1981. Use of trawl suirey data Iii assessments. I'p. 82-92 Northeast Fisheries Science Center (NIIFSC). 1994. Report of the In: W.G. Douibleday and 0. Risvird feds.] Bottom Trawl Suirveys. I 8th Northeast Regional Stock Assessment WNorkshop 118th Canadian Special Publication oi tisheries and Aquatic Sciences SAW). Thie Plenary. National MNrine Fishieries Service, Northeast
- 58. Fisheries Science Center Rel'crncl e Document r 4-23, Woods Clark, S. 1. (editor) 1998. Status ol i'shcrv resources off the H-ole, NIA.
Northeastern tUnited States tor 1998. NOAA Technical Northeast Fisheries Science Center (NEFSC). 2000. 30th Noutheast Mernoranduin NMFS-NE- 115 149 pp Regional Stock Assesstlent \Voikshop (30th SAW). Stock Clark. SI-H. and O.E. Brown. 1977. Chanies in bioniass of fint'ish and Assessment Revicei Committee (SARC) Consensus Summary Oif squids from the Gulf of Maine to Cape Hatteras. 1963-1974. as. Assessments. National marine Fisheries Servicc Northeast determined from research vessel survey data. Fish. Bull. 75:1-21. Fisheries Science Center Reference Documen.it 00-03, 477 pp. Collie, I.S., GA. Lscaneio, and P.C. Valentine. 1997. Lflects of bot- Northern Demersal Working Group. 2000. Asscssitent oh' I I torn fishing on benthic megafauna of Georges Bank. Mar Ecol. Northeast grouindfish stocks thrcoiugh 1999. Northeast Fisheries Pro. Ser. 155: 159-172. Science Center Reference Document 00-05. 175 pp. Woods -lole, Dewar, NI. 1983. Industry Ii trouble: The Federal governient and the MA. New England fisheries. Tenple University Press,. Philadelphia. Overholtz, W.J., MNl. Sissenwine, and S.1. Clark. 1986. Recruitment Fogarty, M. J. and S.A. Murawski. 1998. Large-scale disturbance and variabilits and its implications for managing and rebuilding the
4 V! KI Gcor-ec, Mlinkihlddock i Ic! i .. , a ,.
.u;;
, x1 AFisii,\
it xSc _ 52: 1044 - 1Q57, Overhotz, WJ., S.A. NMirawski. P.J. Rago, .'1.Gabriel, M. lerceiro and JK.T. I3rodziak. 1999. ile n-ycar proieclinns of laodiiies. spannino stock bioniass, and recruliteniti lbr iVe New I-ngland groundi'ish stocks. National Marine Fisheries Service. Northeast Fisheries Sctince Center Reiferene Documeit 99-05 7- pp, Iaego. 1..I.- K A. Sosebxc, I.K. . Brodziak_ S.A. \iirawxski and 1.D. Anderson 1Q08. Implications of recent increases in catches on tile dxilntmcs of Nortllwcst Atlantic spiny dogfish (Squaihis aOclin-dthilts Fishi Res I,,\nistcrdim!, 30,6 1oI1, Screhuk, F. anid S.'. Wigley. 1992. Assessment and management ol the iicoiges Bank cod Oishry:an historical ix, vic d cLalin-tion. J1 NW Atdin. Fish Sci. 1325-52 Sercrlxtk, FNM., M.D. Grossl.in RG. Lough. and L. O'Bricn. 1994. Fishey and environmental factors affecgtii trends and fluctua-tions x Georgcs Bank aid G(ilf of Maine cod stocks: Ail overview. ICES Marine Science Svmposia 198:77-109. Sinclairi A. IF and S A. NIuraiski. 1()(9t7Why have goroundfish stok declined? pp. i 1-93 I IJ. Boreman, B. S. Nakash ima, .1. A. Wilson and R. L. Keidl IcIi edior isNorthwest Atlaintic groindfish: Perspectives on a fishery collapse. Amiericali hisherics Sociely, Bethesda. 242 pp Sni ith, TD. 2000 A talt otitWo grooiundfish trawl suirCys. CotxtribUted Paper ICES Siyixxpostinm "100 Years of Science in Under ICES", IHelsinkiIFinland, August 1-4. 2000 Trippel, F.A, O.S K esbu, and P. Solemdal. 1997. EIffects ol'adult ac adt in zeCSir itUrc oil rcproductiV Oe oIpott it ix1,1 inieC 'ishxcs. pp. 31-62 In R.C. Chambers and E.A. Trippel [cds.] Early life hlistory axd recrUitmextli in fish populations. Chapman and Itlail, Next York. i W\erner, F. NMiurawski, and K. Brander leds. . 1999. Report of the wiorks: t oii oeean cl ixisc of die NW Atlantic duringlxte 1i960,s arndI iT7Os 'and consequences lrt gadoid poplati ons. ICES (3onipe ii.e Rlsctch cieport 234. C,,pei hagenx I lexiark.8 I pp. Wialex 5. S.. 1999 IfIccts oft first-time spaw/ners oix saick--rei uit-ment reiationships for two groundfish species. J. NW Atlant. Fish. Sei. 25215-218.
Chapmer 1.11 Recent Trends in Anadromouis Fishes
.lOHiN M(ORIN\i Unitel Slutes Geological illaine Coolperalive /iTsh
& Wildlfe Rescae/ch Unit Universi, of M'aine Orono. ME 04469 1.)A The beauyo/ this, Kennebec /is'he/ " s V1' harvest pressures at sea. they encounter dams, pol-thacrt ,/i'es'h/nlei"at Sold NaIIl'cc"r'fish Lept Ilution, urbanization impacts, and habitat chanoes in compair Thanks to the lir/es running up freshwater.
as far ets /obr miles, there were two uni- It is impossible to conclude how much anadro-verses of fish at evervYfainlns foot. ihere mous fish habitat has been lost because we are i/see! to be legions q/1sbrilkedi bass. uncertain of the origiinal historical distribution of f-Capiain C&eorige7/W'imouth saw great these species. However, the construction of dams salmonn jcrnip/rrr out of the river Mhere beginning in 1798 denied access for Atlantic Bath noi ,slands.Am' there were slitr- salmon (So/mo salor), American shad (Alosa geons longer than a mai. Sometimes they sapidissi/na), alewives (A. pseildoharengns),blue-Camernight ubocad the canioes where meni back herring (A. aestivalis).Atlantic stungeon were spearing them by torchlight,and (Acipenser oxyrhynchus), and shortnose sturgeon upset the bout! (A. brevirostrumn), in particular, to most of their
-Roberi P. 7)'islarri Co//in. /937 original habitat. Kimball and Stolte (1978) estimated that, by 1950, less than 2% of the original fireshwa-ter habitat was still accessible to Atlantic salmon in New England. With improvements inrfish passage and dam removal, that percentage has risento over tNTRODUCTION 64% of the original habitat (USFWS and NMFS, Anadromous fishes are born in freshwater, sub- 1995).
sequently move into saltwater to grow, then return The National Marine Fisheries Service (NMFS) to freshwater to spawn. Because these fishes are has concluded that, "Atlantic anadromous stocks dependent on diverse environments during different have been heavily influenced by nonfishing human portions of their life cycle, they can be especially activities in the coastal zone. Damming of rivers vulnerable to a variety of environmental changes. preventing occupation of former spawning grounds During their early life stages, these fishes are sensi- was a major factor in the decline of Atlantic salmon, tive to deleterious alterations in freshwater. Later, sturgeons, river herrings, and shad. Environmental when they pass through estuaries and into the contamination is implicated in the declines of sev-marine environment, coastal pollution can affect eral species" (NMFS, 1992). As a consequence, survival. At maturity, habitat alterations, pollution, successful restoration and rehabilitation of most and commercial harvest can have profound impacts species of anadromous fishes will rely on improv-on spawning grounds. Therefore, not only are ing the freshwater and estuarine environments anadromous fishes subject to environmental and through reduction of pollution, improvement of fish passage, and rehabilitation or protection of nursery Note: Author is deceased. and spawning habitats.
Y6 2 6-IN' (; Table 3. I.A a.ldro0Ious .Iish species ofIthe Massachusetts Bay Recgion`, their relative ahubtdance, ntul Iers of streams. and aspects of freshwater residence- Further life history information can be found in Bigelow and Schroeder (1963). MNIurawski et aL. (1980), Danie et al. (1984). Mullen et al. (1986), Weiss-Glanz et al. (1986), and Jury et al. (1994). Species Relative abundlance Riiir inbr Freshwater residence Ofistr~eamns Rare: extirpated: restora- Upper portions of river; two years freshwater Atlatntic salmon tion on Merrimack River residence by juveniles
ýSeasonally present in
,coastal waters and lower Enter Merrimack and Parker rivers from April
!Striped bass rivers in summer; Bay to October; no spawning fish are from Hudson River and other areats ItSeasonallv common in Enter coastal tributiaries in sprin4: eiLZs iRaibow ssmelt spring: also landlocked I deposited m in lower sections of streams: juve-populations in.lakes niles abundant in estuaries
'Rare, isolated Unknowrn AMove between lower sections of streams and Sea-run brook trout Uestuaries populations Uncommon. few Exotic fish introduced to a few streams and fSea-ru n brown trout ]locati ons Unknown esftuaries: little information Merrimack and Charles rivers are principal iVery common II rtuns: enter frestwater to spawn in late spring Alew keife
,where there is access to lakes: adults return to sea: juveniles in freshwater until October B11lueback herring ? *Similar to alewife, btut do not migrate far Colmlinon upstream Merrimack River is principal run: enter fresh-water to spawn in spring: use ipper portions of!
,A'erican shad iComtnon 4,watershed where not blocked; young in fresh-
- water during summer Merrimack River: instream movements; spawn iShortnose sturgeon Rare near some urban areas ilIven1iles enter Merrimack River in summer;
[Atlantic sturgeon Uncolmmon I -adults and sub-adults in Bay': no river spawn-ing, although fish once spawned tip River [ .]200 km [.............. Exotic; previous introductions in New iPacific salnon species Rare Strays Hanipshire now largely gone; sonic remnant chinook salmon Sea lamprey Common -'Unknown Enter coastal streams for spawning, notably SN-lerrimack River
'The Massachusetts Bay Region is here broadly defined as the area from the mouth of the Merrimack River sotIth to Marshfield, Massachusetts (see USFWS, 1980). The minimum number of streams is the known nuImber of streams of any size.
N Ih' I>. hN,."t.V 1VI!lh 9 I Itthis Chapter. 1 wilt discuss ihe Status of cv revi , of ithe reg ion'S atit1fOl]tuu iisheries. I w 1il anadromous ftsh species in the Mlassachusetts Bay identify the principal constraints to and opportuni-and the larger Gulf of Maine region and identify: ties for restoration and rehabilitation of these the causes of declines where known. These atte unique fish populations. summarized in Tables 3. 1-3.2. After a historical Table 3.2. Summary of the status of anadromous fish stocks of the Niassachuseus Bay./North Shore region, in comparison to historical levels, and the principal factors affecting declines. Species Long-term trendf Short-term trend Factors involved Atlantic salmon Extirpated: iidergoing restoration I ow returns Diams, pollution, overIrshing Native population extir- b Habitat destruction, dais,pollution, over pated; declining numbers Increasing numbers of Striped bass of migratory fish from migratory fish fishing, now harvest reduction and non-Bay sources Variable, runs generally Stream blockage, siltation, possibly Rainbow simelt Declining high in 1989 and 1994, po1lution-decreased substrate quality, depressed other years predation by aquatic bids ISea-inn brook trout. Declining renknoat ipaos Urban development, habitat destruction
- remnant populations Increased stock in- and Sea-tin brown trout Introduced exotic species harvest Unknowi, Alewife Increasing after general Declines in 1993-1994 Habitat destruction dams, unknown decline factors Blueback hen'ing Increasing Declines in 1993-1994 Habitat destruction dams, unknown factors Declines in early 1990s; Ilabitat destruction dams, unknown slight rebound factors in 1995 Declining; Endangered R Overfishing, dams, pollution: now harvest Shortno11se sturgeon Remnant populations .
Species List restrictions Atlantic sturgeon Unknown Stable or increasing Overfishing, dams, pollution; now harvest restrictions Introduced non-native Declining. stockin- now Pacific salmon species species, strays to terminated; adults will Unknown factors affecting survival at sea Massachusetts decline Sea lamprey Declining Unknown Dams aSince 1980
23 Tible 3.3. Status of U.S. AtUlitic salmon populations by river (Table firoin NFNIS. 1998). River System Population Status I lousatonic River Extirpated' u)innipiac River f Extirpated( t lammonassett River i Extirpated Connecticut River _ Extirpated Thalmes River Extirpated 'PawXcatuck River [Extirpated Pawuxet River Extirpated River "ackstone Extirpated NVierimack River Extirpated l amprev River Extirpated 'Cocheco River _ Extirpated ISainon Falls River j Extirpated NIConsatnt River Extirpated ,Kennebunk River _ Extirpated Saco River Extirpated ,Presumpscot River Extirpated RRoyal River - Extirpated Figure 3. 1. Form er range o 'Atlantic sal on in the rivers iindroscoggin Rivet- Extirpated of New England. Rivers in bold type probably had iKennebec River Candidate Species active salmon runs at the time the first European settlers Slicepseot River Unique Stock 2 arrived. Rivers highlighted with the widest line are cur-IPerniaquidRiver Extirpated rently undergoing restoration. (Map troin International
\Medonak River Extirpated Atlantic SaImon Foundationi. 19791.
ýSt. Georges River Extirpated [U --i*-i-(Te .................
,iT~ie Duclktrap Rivet - ...... ..............
..... Unique ; {*
Stock. .... ILittle River Extirpated Pass aassawaukeag River IExtirpated Penobscot River , Candidate Species i O*land River Extirpated Union River I Extirpaled ITunk Streamn Candidate Species Narragaugus River Unique Stock Pleasant River Unique Stock Indian River ........ .. Extirpated
;Chandler River C!]
'n*'
s!eerr...... ................... ............ .....
!i?*...
Extirpated * ... Nachias Rivert Unique Stock East IMachias River Unique Stock
'Orange Extirpated Hobart Stream Extirpated iPn'__
Dennys River !:* ...................... k.........
-Unique S ............
~
Stock ..... TPennamaquan I Extirpated IBoyden Stream Extirpated IISt CroixRi ver f Candidate Species Extirpated status could result from complete blockage of the river or Figure 3.2. The aboriginal distribution of Atlantic a small population size. both of which indicate that long term salmon in North America (map fiomn Watt, 1988). The persistence is unlikely. solid black area represents habitat where the salmon have been extirpated by about 1870. The Atlantic salmon stocks in the rivers flowing into Lake Ontario and Lake Champlain were probably largely landlocked.
ŽI!yý' R;D
! FT N .\'!\.A! 0?NM:
TiV ISFTTTS -)t Table 3.4. 1listoric and currently accessible Atlantic Jersey, but the major populations were ntntld it the salmon habitat listed froom south to north. One Connecticut and Merrinmack watersheds of southern habitat/production unit- 100 in12 . (Table from NtMIFS. New England. and the Penobscot and Kennebec 1998). drainages of Maine. No one knows for sure how many salmon were present when the colonists first Accessible I arrived, but the best guess based on available habi-New En gland Rivers I lbitt HabitatHabitat IHistoric Unis tat is 100.000 adult salmon in New Ena la nd Units i waters, including 30.000 in the Merrimack (Sto!te,
- a. Laree Production Rivers (>10,006 production units) 1981). The causes of the decline and extirpation of stocks have been well documented and talttibttied (Connecticut River 89.2501 262.500: 1o dams arid pollution (Table 3.4). As the species Mklerrimack River 83600ý declined; commercial fishing accelerated the extir-Saco River1i.,........ 12,540 pation. The species was familiar to the first
............ .......)..................30.......692
...... colonists (Stolte. 1981., 1994) and stocks have been
\ndroscM oin River 717 1,060i exploited for three-and-a-hal l centuries. A 1ter a Kennebec 'River i*ci~
- ,{; ................... .................... ii 71.0031 Te*:7i- 7 ........
114,700.
. long period of fish absence., restoration progranis I cnolm~ot River 1017441 ~ 1W680. began in earnest in the I 960s, after the construc-Union River 8.3601 11,2021 tion of fish passage facilities and the enactment of o...Rivej .. .7............. 4 several water quality laws.
Restoration success in the Connecticut and
- b. Small Production Rivers (<I 0,000 production units) Merrimack rivers has been only marginal, while that in Maine rivers has been somewhat better.
Pawcatuck River 167 1 8,7 78 Despite decades of stocking in the Merrimack Keepnetuk River 84 River. restoration of Atlantic salmon cannot yet be Ie-psc-- t-Riv-e;7 .... considered successfiul (Table 3.5). A peak run of 1.672: 5851 332 adult salmon was achieved in 1991., but riuns Duck trap River only ranged from 23 to 248 in the previous decade. Passagassawaukeag Rivet 1671 418. and dropped to just 61 fish in 1993 (Stolte, 1994), Narragaugus River 585i 21 in 1994, 34 in 1995, 76 in 1996, and 71 in 1997 Pleasant River 5.7689 - 768! (New England Salmon Association, 1995, 1996:
\N'lachias River 269 502[ United States Fish and Wildlife Service IIUSFWS]
trap records). Returns in recent years.(1 23 in 1998 .Tunl, ]g i~i nTi:* ~e;................7 *-i
*,t*:ia Stie- 6,9399
.................... 69.939
- i i~i.. . . . . . : .................... and 192 in 1999) are still disappointing. Despite Last Miachias Rie 2,174 2,174; the stocking of large numbers of fry (e.g., 3.1 mil-1Hobart Stream 841 84: lion in 1994), the chances of full restoration seem Dennys River 2,090 2,090: quite distant. Less than 0.0007% of the fry that are iBoyden Stream 841 84' stocked return as adults.
The situation is only slightly better on the Connecticut River. Several hundred thousand smolts are stocked each year, along with several SPECIES S'IAI'US million fry (4 million in 1993, 6 million in 1994). Yet, the total returns for the past 10 years have been just over 2,500 salmon. That reflects an annu-ATL.ANTIC SA.vMoN al return rate of only 0.0004 to 0.4% from stocked smolts and 0.003 to 0.02% from stocked fry Alnost all runs of sea-run Atlantic salmon (Meyers, pers. comm.). Only 188 adult salmon (Sanao salar)were eliminated in New England by returned in 1995, 260 in 1996, 199 in 1997, and the twentieth century, especially in southern New 300 in 1998 despite the expenditure of more than England (Table 3.3 and Figures 3.1-3.2). Salmon $70 million on the program in the past three runs may once have extended as far south as New decades (Freeman, 1995; New England Salmon
30( Fable 3.5. Esrimated retunns of Atlaitic salmon to the Merrimack River, 1867-1999, based on trap counts. Data are taken from Stolte (1981 ) RideoLt and Stolte ( 1988), the New England Salmon Association (1996) and trap records of the U.S. Fish and Wildlife Service. Estimated number of Estimated number of Cea r returning grilse, 2-se'l- Yea r returning grilse, 2-sea-year, and 3-sea-year fish (continued) yearr, and 3-sea-year fish Hi storical rI n size 17,880( 9 9..1 .... ... 1991 (range of 8,940 to 26,820) 1199.2 199 I99 1 61 hSir. OltenI~)s atl re.s1toralioOl 11994 12 _199_5 34 '1867-1875 1882 -7 166 1996 76 188 54 11997 71
.............. i 1884 [i 33(0 1998 i12i 760 1999 . .............. 192
. ... ... . . ........... . 588 8...........8..
... .. ...... ...... [..............
1886 '1887 1,500 Recent returns 1.927
,1993 . .61
!1889 1,141 1994 2,1
'1890 1,796 1995 34 11891 1,653 7) 1996 189 2 i_9..................... ..... ....................
3,062 ... I 8918 3.600 1894 929 Association. 1995). 1895 1.776 Returns of adult salmon to waters in Rhode 1896 1,034 Island and New Hampshire have been minimal. 11897 ' 241, Farther to the north, there has been more success in 1898 .. ..... i ............. .......... ............ ............................ 16
.... restoring Atlantic salmon to the Penobscot River, Maine. Yet. despite a peak run of 4.125 in 1986, Second alteil/)ts at IresloIlCuion recent numbers of adults returning to the river have shown declines (1,578 in 1991, 1,650 in 1993, 197581977 0 1,342 in 1995, 2,052 in 1996, 1,342 in 1997 and 1.2 10. in 1998. Only 969 adult salmon returned to 1979 33 the Penobscot River in 1999., and the total run for 1980 5 all Maine rivers was only 1,164 (trap records, I1981 125 Maine Atlantic Salmon Authority). Similar declines 1982 23 have been evident on many rivers, including those in eastern Canada and the runs in wild riv'ers of 1983 114 Downeast Maine. Clearly, some unknown factors 1984 115 are affecting survival of salmon.
il985 213 The database for documenting returns of 11986 103
.... ......................... ... .............................. .... ....................................................... .................... ............ ........................ Atlantic salmon is good, but the causes of the low 11987 139 numbers of returning adults in recent years are not 11988 65 known. Many experts suspect factors in the marine 11989 . 84 enVironment are dictating return survival, possibly 1990 248 ocean wanning along southern portions of oceanic
1ý 1IN I N 1)1, 1,', 0 \1 ýý!,ýS F I ý I II zý habitat or cven ocean coolingnnear Greenland ArIi7RiCAN SHxD (Friedland et al., 1993). But there are two other obvious factors that likely play a role in restoration Commercial landings olfAmerican shad (Alosa success ill southern New England waters. First, .supij;.s.sima) peaked in 1970( when about 3.000 mt even though upstream fish passage facilities exist wei'e taken in northwestern Atlantic waters. But at the lower dams of the Connecticut and recent harvests have only been one-third of that Merrimack rivers, and downstreami passage is level (NMFS. 1992). Statistics specific to New plannedlfor the lower dams, mov ing up or down England are unreliable through the 18th and 19th past any darn involves some level of mortality. centuries: however, landing records for the entire e.Cen with itie most C licient passag Ge iciitis. Atlanfic coast suggest that 1896 wvas a peak year Thus, despite fish passage improvements, survival with catch figures about six times what the\y were of Atlantic sanirion iil New Fmwland streams contin- in 1960. Historically, runs declined dICe to poil-ues to be low compared to waters in eastern tion and inadequate fish passage, but some of Canada, where there are generally fewer dams and these declines likely were masked by the natural higher fish populations. Second, the salmon brood cyclical nature of year classes. stock used to initiate restoration was taken from Except for the most recent rui years. there the progeiiy of fish returning to thic Penobscot have been modest success storieCs in southern New River, Maine, a source quite distant.from the England, such as runs.on the Connecticut River, Massachusetts locations where the native stocks but most populations in other rivers have been were extirpated and the habitat altered. The depressed, especially during l 993-1994. Most runs Penobscot strain, in turn. is a hybrid, derived tiom in Maine. for example. were eliminated due to a combination of non-extirpated fish returnirlito impassable dams and pollution and are only now Downcast rivers of Maine and fish returning to shimwing some successes in restoration in a few Canadian rivers--becauws the nalive Pen1obscot riveis, primarily due to stocked. transplanted fish. strain was also extirpated. Thus, restoration efforts Those shad that survive spawning, along with in southern New England relyfoii a hybridized fish immature adults, generally migrate to the Bay of whose relatives were adapted for life in waters Fundy, and remnain there during the summer and much farther to the north; this is especially true for into the fall (Melvin et al.. 1992). During winter fish in the Connecticut River. months, shad from New England move into an area Because salmon in Massachusetts are in the between Long Island and the mid-Atlantic coast. soLithern Mairgin Of the historictal range of the Thus. shad are influenced not only by conditions in species. the task of restoration is especially diffi- freshwater but by conditions in several areas of the cult. Add to this the recent trends in global warm- G l- of Maine aiid soutLIw ard aswell. ing, and at least one scientist has predicted that Runs of American shad have generally "Global warming could ultimately make restora- increased in, Massachusetts waters in the 1990s, a tions on the southern edge of Atlantic salmon, the rehabilitation success story that has not been com-Merrimack and Connecticut, difficult or nearly pletely smooth. After gradually increasing until impossible" (Bielak, 1994). How native Atlantic 1993. runs on the Merrimack River declined by salmon of southern New England may have about half each year in 1993 and 1994 before responded to even subtle warming trends is a moot increasing again in 1995. Recent returns have been point, as restoration nowv involves a hybridized, impressive (22.586 in 1997, 27,891 in 1998, and non-native stock. Return rates of salmon from the 56,465 in 1998), the highest three annual runs Connecticut and Merrimack rivers average only 12 since records have been kept (USFWS trap and 27%, respectively, of those on the St. John records). Apparently, the 1993-4 decline was due to River, New Brunswick, while those of Atlantic some unknown factor at sea, as similar declines salmon from the Penobscot River, farther north, were experienced in the Connecticut River stock, average 89% of the return percentages from the St. where shad runs decreased to record lows in 1994 John River (USFWS and NMFS, 1995). and 1995 (B. Kynard, U.S. Geological Survey, Turners Falls, MA., pers. comm.). Only 300,000 shad returned to the Connecticut in 1995, less than
12 9% of the run of 1992, although returns in 1996- and other unknown factors as well (Buckley. 1998 have exceeded 600,000. 1989). No sinlee cause has been implicated. Rather, declines in individual streams are due to site-specific combinations of the above factors. AI.EWIVES AND BI[.UFACK I ERRING Runs of rainbow smelt are extremely variable, Adult alewives (Alosa pseudohareigus)and but the long-term trend indicates a decline of blueback herring- (-i1osa aesthal/;S) (ksomlenilmes coastal pop.tlatio ls in southern New England. In grouped together as "'river herring") usually return the past 15 years, only runs in 1989 and 1994 were to saltwater after spawning, and may spawn more considered good. In all other years since the early than once. Individual stocks havr been reduced due I980s, numbers of returning adults have been to pollution and danis that altered habitat and extlrelely low. particularly' in the years 1990-1993 blocked access to spawning sites (Jury et al., (B. Chase, Massachusetts Division of VMarine 1994). The National Marine Fisheries Service Fisheries. Salem, Massachusetts, pers. comm.). The (1992) considers alewife and blueback herring cause of the declines is unknown but increased pre-(river herrings) stocks as variable, dependent on dation by aquatic birds, and spawning substrate local conditions. Commercial catches for these degradation are strongly suspected. Populations of river herring peaked in the 1960s along the north- several species of coastal birds have increased dra-eastern coast, when 27,000 mt were harvested matically in recent years (Krohn et al., 1995), and annually. In recent years, the harvest has only aver- the deterioration of small coastal tributaries has aged 1.200 mt (NMFS, 1992). been shown to reduce spawning potential (S. River herring runs on the Merrimack River had Chapman, Darling Marine Center, Walpole, Maine, been steadily increasing, until 1992, but have pers. coinnm.). Surprisingly, runs have shown declined ever since. The 1999 run of 7,898 was improvem1ents in some urban rivers, tributaries to only 2% of the size of the run in 1991, but has Massachusetts Bay, While runs are decli ning in less been an improvement over the historic low return urbanized rivers with better water quality. The of just 51 fish in 1966 (USFWS trap records). The issue is unresolved, but may involve other undlocu-recent years of poor returns have not been linked to mented factors as well, such as the success of any specific cause. There does not appear to be any Chesapeake Bay and Hudson River.striped bass in-river change that could account for this decline. rehabilitation, which has led to the recent large Without a specific freshwater factor, all indicators increases in striped bass from those areas feeding point to some unknown factor at sea that is increas- in inshore waters and river mouths, particularly the ing mortality of northern Massachusetts stocks. Charles and Weymouth Fore rivers. Additional Similar declines have been noted for runs in the monitoring will be required to identify specific Connecticut River, where spawning numbers of causes of declines, as they likely are a combination 410,000 blueback herring in 1991 declined to of factors. 12,000 in just seven years, despite a Juvenile Similar declines in interior waters of Alosid Index prepared by the State of Connecticut Massachusetts have been linked to acid precipita-that predicted record runs. The actual returns were tion and a resultant decrease in pH1(B. Kynard, half and one-quarter of the predicted runs over the pers. comm.). and this may be a factor in anadro-two years, respectively (B. Kynard, pers. comm.). mnous runs of rainbow smelt as well. where low pH levels also have been recorded in coastal tributaries (Haines, 1987). Rainbow smelt do not utilize fish RAINBOW SMELT ladders and even modest amounts of woody debris in streams will block upstream passage. Thus, Although never experiencing the widespread urban development and related land use activities extirpation of runs as have other anadromous in the lower portions of coastal streams can result species, the distribution of sea-run rainbow smelt in increased instream debris and can effectively (Osmerus mordax) in coastal rivers has been affect- block upstream access. ed by natural and human-made obstructions, silta- There also has been a noticeable decline in tion, decline of substrate quality, poor water quality, substr ate quality in many coastal streams. Smelt
PFý'Eýl I ViNDý IN A\A7D;:?0V0T ýý 1:1ýýHF cggs are adhesive and naturally stick to instream obstruction of hish passage, and over-exploitation. rocks, aquatic vegetation. and submerged branches. Atlantic sturgeon were once harvested in the IHowever. in recent years, there have been notice- Merrimack River in the nineteenth century, but able declines in aquatic vegetation and increases in reproducing populations no longer exist. algal growth on instream cover (B. Chase, Atlantic sturgeon are considered quite abun-MNassachusetts Division of Marine Fisheries, dant in the Massachusetts Bay area, arriving friom Salem. Massachusetts, pers. comm.). Eggs do not Maine waters or the Fludson Rivetr (or offshore adhere to unstable substrate, such as.algae, and waters in Massachusetts Bay) in May, and remain-some reproductive potential may be lost. The wide- ing around the many islands of the Bay through the spread growIt of algae may be linke'd to changes in summer (B. Kynard, pers. conm.). Juvenile water quality and \,,ater temperature. Atlantic sturgeon enter the lower Merrimack River Even a modest increase in angler etlbrt in in summer, then ieave to go oflshore in the !ill, coastal rivers can affect rainbow smelt populations. possibly joining aduilt Atlantic sturgeon in Murawski and Cole (1978) used predictive models Massachusetts Bay. The North Shore and northern to show that populations could be severely impact- Massachusetts Bay coasts are apparently used as ed by increased angler harvest in some heavy forage areas for Atlantic sturgeon. Although NMlassachusetts rivers. MIassachusCtts has had a population estimates are unavailable. biologists modest enhancement program in the past where currently do not consider the species threatened in eggs were collected and transported to waters with the southern Gulf of Maine, as they are in the depressed smelt populations. However. the tech- northern Gulf region (Kieffer and Kynard, 1996; B. nique has been temporarily suspended because of Kynard. pers. comm.). the lack of documented success of such practices. Shortnose sturgeon are much less abundant in A Massachusetts Bay smelt monitoring program the North Shore/sotithern Gulf of Maine region introduced eg." into an unaltered stream in 1995 to than in the northern Gull' of Maine. A-reninant pop-assess the suitability of egg transfers (B. Chase, ulation of less than 100 shortnose sturgeon exists . pers. cornin.). Enihancement of stocks, throtigh in the Merrimack River, movi ng up and dows n the transportation or other means, has high public river (B. Kynard, pers. comm.). A few fish are appeal, but transfers have had only mixed success encountered in the Connecticut River. One area of in New England, partly because the extreme vari- concern is that prelerred spawning areas in the ability of year-class strength can mask the success Merrimack River are primarily in heavily urban-of rehabilitation techniques. ized sections of the river, Sticih as the concrete-lined sections in downtown I laverhill (Kieffer and Kynard, 1996). As a consequence, the areas needing ATLANTIC AND SHORTNOSE STURGEON particular protection are often the areas most sus-The shortnose sturgeon (Acipenser brevirostrtun) ceptible to impacts by hmmans. is on the Federal Endangered Species List and con-siderable research is Underway in Massachusetts on STRIPLD BASS spawning behavior and movements, and in Pennsylvania on fish culture. The species is rela-tively abundant in coastal waters of northern New England and preliminary estimates have been I mnysel/at the turn of the tdcle have seene derived for the populations in the Kennebec River, such multitudes pass out o/a [pounde that Maine (T. Squiers, Maine Department of Marine it seemed to me that one inughte go over Resources., Hallowell, Maine., pers. comm.). their backs drishod. Atlantic sturgeon (Acipenser ox -'rhvnchus) are rare -Captain John Sm ith, 1622 in northern New England (only seven were netted in the Kennebec River in 1994). but more abundant in southern New England. Both species, however, Harvested since the arrival of the first colonists have been affected by a combination of urban to New England, the striped bass (Alorone development, destruction of spawning grounds, saxatilis) was largely extirpated from most rivers
,4 f! i (
of: New Fngiland. due directly to habitat destruction, reduced pollution have recently led to i Mirked pollution, dams, and overfishing. Each has played increase in population numbers. Larval counts and a inajor role in the extirpation of native stocks, but numbers of adults have shown remarkable dams and overfishing were probably most respon- improvement in the last two years in Maryland sible Cole, 1978; V'loring, 1986; Squiers 1988).I waters, and increased nummibers o01migrating adults Such declines were not limited to New England, have been subjectively rioted in Mlasschusetts but have been present throuighout the range of' coastal regions and river mouths as well (B. striped bass. By the early 1980s. larval fish counts Kynard, pers. comm.). It is difficult to conclude in Chesapeake Bay and elsewhere were the lowest which rehabilitation technique has been responsible on record. Howeveer tihe success of' several nleas- for the recent success aInd the subsequent increased ures in the 1990s has led to a remarkable recovery numimber of' fish entering waters of coastal of lludson River and Chesapeake Bay' stocks. Massachusetts, as all techniques were initiated Unlike the restoration techniques employed for simultaneously. However, it is likely that Federal Atlantic salmon and American shad, providing fish pressutre to reduce harvest by 50% had significant passage is not the answer. Striped bass will not use in 1 tuence. fish ladders, so river systems with dams, however There are more striped bass today in the lower efficient the fish passage facilities, effectively Merrimack and Connecticuit rivers and along the block upstream distribution off striped bass. Thus, North Shore of Massachusetts than were present as long as dams remain in place on lower portions even a few years ago (former National Biological of New England rivers, full restoration of striped Service. National Marine Fisheries Service, unpub. bass to historical spawning grounds will never be records). Since there has been no direct evidence achieved. On a positive note, the removal of the of natural reproductiori in Massachusetts waters for Edwards Dam on the Kennebec River at Augusta, decades, the striped bass present along the Maine in 1999 provided striped bass and other Massachusetts Bay coastline in summer must origi-anadromous fishes access to the river upstream to nate elsewhere. Tagging studies indicate that Waterville for the first tine since the 1830s. uill Hudson River striped bass are the ones most likely restoration of the species to the lower portions of captured by sport anglers in New England, rivers also depends on remediating any water pol- although some scientists suspect that Chesapeake lution problems, which is a process that effectively Bay stripers visit the area as well. began in the 1960s. Most New England states have some level of IndiviCduals migrating in coastal waters from restoration program lor striped bass. Maine has Connecticut northward to Maine in summer are been stocking juveniles into the Kennebec River, often derived froom populations in the Hudson obtained fromn hatcheries in New York, for the past River and Chesapeake Bay (Flagg and Squiers, decade. Until recently, striped bass captured along 199 1). Although some striped bass tagged in the Maine coast in summer were the product of Canadian waters have been recaptured in New fish born elsewhere, as is the case with England (Rulifson and Dadswell, 1995), striped Massachusetts. However, there has been evidence bass generally move northward from the Hudson of natural reproduction every year since 1987 in River and Chesapeake Bay in summer, as water the Kennebec River and, most recently, in the temperatures increase. The- travel singularly or in Sheepscot River (L. Flagg, Maine Department of groups, feeding on inshore fishes and sea worms, Marine Resources, Hallowell, Maine., pers. and entering the lower portions of rivers in the comm.). Thus, some larger striped bass encoun-Massachusetts Bay region. Thus, recent increased tered in the summer from Cape Cod to Maine may numbers of adult and immature striped bass in Bay be the offspring of fish naturally produced in w aters is a reflection of restoration success else- Maine. where, not in Massachusetts, as native populations There has been no direct evidence of natural here have been extirpated. reproduction in Massachusetts waters for decades. Populations alone the east coast declined rap- Re-establishing actual spawning runs in idly in the 1980s, but restrictions on sport and Massachusetts waters will require stocking of commercial catches, habitat improvement, and spring yearling fish.
iCFECI ZEN IIF, IN AN,\RWN!011iS lFISHES 3,5 S\A-RUjN BROOK TR(OIUT P\(i FIC S\I.C N AND SEA-RUN BROWN TROUT All five species of Pacific salmon Localized populations of wild sea-run brook (Oncotivnchius spp.) have been stocked in New trOutl (N.o/l ..!sin Yfionul l di,<,) are lotilld iII coastal IEng'land waters, but ire not nativ.e here and natural streamis ot Newv Ingland and ast-ern Canada. Such spa\Vnin has enIeirally not been doc ui ncmited. populations are isolated in New England and more Three species also have been reared in coastal commoni---even abundant-northward into rivers aquaculture operations in the past twventy years of eastern Canada in areas where stream pH is not (pink salmon, 0. gOrbits-hoa; chum salmon, 0. low. Some intrirmation is available on Gulf of keto: and coho salmon. 0) kis tach). In recent years. Maine populations and at least two states New Hampshire has had a significant programn of (Massachusetts. Maine) have considered modest stocking coho and chinook salmon (0. management programs. tschawv./scha) to create coastal sportfisheries, but In all likelihood, sea-run brook trout populations stocking of coho salmon was terminated in favor of are more common than long assumed. Runs inl chinook salmon. Stocking of the latter species was eastern Maine (Ritzi, 1953). and southernH MIaine terminated in December 1993 because of lo\V (M. Dionne, Wells National Estuarine Research ieturns and encouraging, early returns from Reserve, pers. comimn/.) have survived largel]\ stocked Atlantic salmon. because of inininmal urban development and poilu- Pacific salmon are non-native species and the tion and limited angling pressure. The surviving potential for competition with native freshwater native populations are in isolated, little-developed and anadromous fishes has never been fully coastal streams. Because of the popularity of this. explored. However, numbers introduced into New anadromous form in eastern Canada, fisheries man- England waters have decreased dramatically. agers in Maine consider coastal runs to be candi- Chinook salmon stocked in 1993 will continue to dates fbr new and expanded fisheries (R. Owen, be encountered in southern Gulf of Maine waters former Commissioner, Maine Department of Inland for several years. then will disappear if natural Fisheries and Wildlife Augusta, Maine, pers. reproduction does not occur. Ocean ranching oper-comm.). Thus, increased exploitation of these wild ations in southern Maine in the early 1980s for runs is probable in the future- Remnant runs on pink salmon and chum salmon were largely unsuc-Cape Cod have co-existed with humnain populations cessful, apparently due to inadequate water temper-since colonization by the first. Europeans. atures. Expansion of the species and associated Management strategies in Massachusetts today fisheries into Massachusetts seems unlikely, partic-include slocking ol alternativ'e species, such ais ulyar with the currentcemphasis on restoration of' brown trout, Sahino trulia, to lessen fishing pres- Atlantic salnon. sure on these unique wild stocks (Bergin, 1985). The brown trout is a species introduced from SEA LAN4MPPrm Europe, and both the true sea-run form and the non sea-run form have been introduced into lower The sea lamprey (Jelrono, marints) has rivers and estuaries of New England states. Several been commercially important in the past. The fish significant coastal sport fisheries have developed, was used by Native Americans for centuries and particularly in major rivers where pollution has was taken commercially in large numbers from the been reduced. Although brown trout are exotic Merrimack and Connecticut rivers in colonial fishes, they have been established in waters of times. Runs declined rapidly due to the construction North America for over 100 years and represent an of dams, especially on the Merrimack River increasing resource opportunity. There is almost no (Bigelow and Schroeder, 1963). Currently, runs are information on sea-run brown trout after their stable, although lower than in historical times, yet release into coastal rivers except that they experi- harvest and consumption are almost non-existent. ence rapid growth in summer months ill coastal For unexplained reasons, the trap count of sea lam-estuaries. preys tripled on the Connecticut River in 1998, the
36 highest nutmIbers on record, but numbers iInOther ConnectIicuti, Merrimack, and other in ijor rivers of years have remained steady. There are. however. New England, and the heavy pollution near towns efforts underway to develop a market for lamprey and mills. The first dlain on the ( onnccticuL River skins to be marketed in Asia for the creation of Was constructed in 1798 at Turiiers Falls, purses, wallets, and other products. n uch in the M,'lassachusetts. It was 16 teet high and impassable fashion of wolffish skin and shark skin. to inigrating fish. Others soon followedl on the Connecticut, Merri1mack, Kennebec, Penobscot, and other rivers ol New England.
-lISTRinc:t. ]"RFrNDS IN NEW E>NGlAND Probably the first species to receive supple-mental stockimg to reverse the declining runs was the Anemrican.shad. Over 200 million eggs were Sahloio shad and alewives were .briner/v artiticially [latched in northeastern states during a abundant here (the Merrimack River), five-year period, 1866-1871 (Bowen, 1970). By and taken in weirs by ithe Indians, who 1866, runs of Atlantic salmon were severely tagzht this method to the whites, 15. depleted in southern New England and eggs were whom thev were used as food and brought from the Miramichi River, New mCHInrP, urntil the dam and a/fter`IVOa the Brunswick, and implanted in gravel in the CCa00! al i ,i/k4caL, c(i1/d i//.i( 1 cltoiets Merrimack River. Several states were actively putr-Lowell, put Cn end to their migrations chasino Atlantic salmon egos in the late I 860s to hitherward. though it is thought that a booster declining stocks of salmon.
few more enlep)risingshad may, still be The first salmon hatchery in the United States seen; -Henmy David Thorecbo, 1849 was at Craig Brook, near Orland, Maine: it distrib-uted tip to six million fry in the early I 870s to states as faar south as New Jersey (Bowen, 1970). Althoug-h there is some question as to tile ma- These efforts continued until the twentieth century, nitude of runs of anadromous fishes before the when the once abundant runs of Atlantic salmon in Little Ice Age (ca. 1450-1800 A.D.), particularly Maine began to suffer a similar fate to those in with Atlantic salmon (Carlson, 1988), Native Massachusetts, Connecticut, and Rhode Island. of Americans surely utilized several species Eventually, there werle iew brood stock available to anadromous fishes. Atlantic salmon were plentifnul supply eggs or fry. By the early decades of the at the time of the first European settlements in twentieth century, runs of Atlantic salmon were New England. although no one can accuratelv extirpated fi'om all the rivers of New England, assess the sizes of runs. Stolte (1986) estimated except for several smaller streams in Downeast and 300,000 adult Atlantic salmon, based on habitat central Maine (Moring et al., 1995). availability. Tie construction of a dam 160 kml In concert with the declines of Atlantic salmon, upstream fiom the mouth of the Connecticut River rainbow smelt were similarly declining due to in 1798 marked the beginning of a decades-long blocked passage, pollution. and habitat destruction extirpation process of anadromous fish runs in in lower rivers. As early as 1874, regulations were New England. Locks and canals on the Merrimack enacted to limit commercial catches (Murawski River started to appear at the end of the eighteenth and Cole, 1978). Striped bass were eliminated from century and the construction of a dam near Bristol, many rivers of New England as early as the I 830s, New Hampshire, blocked the upstreamn passage of due to dams and pollution, while runs of Amnerican fishes in 1820 (Stolte, 198 I). Whatever the specific shad, blueback herring, and sea-run alewives local situation, American shad, Atlantic salmon. declined due to fish passage problems (many runs ale'wives, blueback herring, striped bass, and rain- in northern Maine were even extirpated). boxw smelt were all declining in southern New UnreCulated commercial harvest of Atlantic stur-England by 1870 (Bowen, 1970; Moring, 1986). geon in the late nineteenth century led to depletions The causes were primarily the impassable dams and extirpations of populations that were fished located at numerous locations along the until they were no longer economically profitable.
PI-I-ENF !RENDýý IN %NADPO%1011ý HS[IFS 37
,Most restoration and rehabilitation efforts in W:Vi'ER Qt.,\sitl tile Gulf of Maine reoion have occurred since 1960. The major focus has been on tile construc- Freshwater tributaries of teie Massachusetts tion of fish passage facilities and the inmprovement Bayi/'North Shore area continue to be sources of pollitants (13ro tin.1987), L1[1t1h water \; uality is o' water quality in rivers. Once the issues of dams and water pollution were addressed in individual less ora constraint for re-establishinlg historical rivers, stocking and harvest regulation could pro- levels of anadromous Ifishes than was the case ceed with somne posibi lity of manattCwement success. decades ago. Since the passage of a number of MIany\ New England rivers still have dains and tederal and state laws in the i960s and 7i/s that pollution issues that aft'ect fish populations, so the promoted water Cluality improvenients, many rivers process ol rehabilitalion Of fish runs is ol necessity of New England have shown substantial improve-ail ongoing process. Although population levels of ment froml tile heavily polluted condition of earlier all anadromous species are well below historical times. Nevertheless, in 1995. more than half of the numlbers, American shad and blueback herritng pro- lower Charles River, between Newton and granms have shown the most success in tile Waltham. was covered wvith aquatic vegetation--
Massachusetts Bay/southern Gulf of Maine region. primarily water chestnut. Such dense vegetation caii affect wvater quality and even block fish pas-sage. The principal cause was the heavy nutrient CURRENT AN) FuIURI C(.NSTRAINTS load to the river from human sources, such as lawn fertilizers, septic tank input, and raw sewage (Allen, 1995). Sonic of this material eventually OBST'RUCTIONS ANi) FisiI PASSAGE-i reaches Massachusetts Bay and influences water quality as anadromous fishes enter coastal streams. By their very nature. anad rontoIs fishes inust Levels of PCB and Mercury continue to be accu-descend rivers, later ascend rivers and, in some mulated by fish, necessitating fish consumption cases, repeat the process more than once. health advisories for humans (see Chapter 4 by Downstream passage mortality associated with Thurberg and Gould). There is no evidence that damis varies with fish passage design, but has contaminants arc today adversely affecting the reached 62-82% for American shad and blueback health of adult anadromous fish in New England. herring on the Connecticut River (Taylor and However, there have been recent studies with Kynard, 1985) and with similar values on other freshwaterand estuaritie fishes that indicate fish northeastern waters (DuBois and Gloss. 1993). subjected to higher levels of mercury in the envi-More recent studies have estimated mtuch lower ronrent may exlhibit behavioral changes or mortalities, due to higher recapture rates and lower reduced reproductive success (Wiener and Spry, mortalities in control groups (Mathur et al., 1994). 1995; T. Haines, U.S. Geological Survey, Orono, Mortality rates for passing Atlantic salmon have Maine, pers. comm.). Specifically, avoidance of ranged from 9-23% in waters of Massachusetts, predators may be impaired and hatching success New Hampshire, and Maine (Stier and Kynard, reduced. This has been untested for anadromous 1986; Moring. 1993). species of North Aierica, but such subtle impacts Stream blockage is likely one of the causes of could result in lower survival of fish in streams the decline of rainbow.smelt in the past decade and with higher mercury content. It is likely that some has certainly led to declines in striped bass. As water quality factors continue to influence spawn-these two species do not utilize fish ladders, re- ing runs and spawning success of rainbow smell establishing historical levels of these fishes will and may affect other species as well, such as PCB require removal of some dams (such as recently problems affecting striped bass in the Hudson occurred on the Kennebec River) or refinement of River. fish lift technology.
LA..ND)tJ PRALic:'1`.S were imposed. In New Fngland, commercial fish-ing for stripers has traditionally comprised a small-Several types of land use activities can disturb er percentage of the catch than that of recreational aquatic ecosystems and potentially cal have a sig- anglers so its impact has probably been less. nificanil impact on a.adromous fish duriing their For Atlantic salmnon, Maine has long had a freshwater residence. Moring et al. ( 1994) sumInIa- recreational fishery which was finilly hanned in rized the physico-chemical and biological changes 2000. Now that the dcays of river trapping (19th that can occur when forest canopies are opened,. and early 2'0th centuries) is over, the maiJor harvest riparian vegetation is removed, stream banks are of these fish is by coinmercial fishers on the high altered, or roads are constructed. These conse- seas beyond US territorial waters. For stiurgeor. quences include increased sedimentation., excess there is currently little take these days. but previ-particulates in gravel. increased stream flow. Otis sport and commercial tIshers were responsible increased temperature, decreased dissolved oxygen, for limited harvests. decreased insect drift, decreased fish populations, More effective fisheries management plans will losses of nutrients flrom watersheds, and ecological minimize the effect of harvest on anadromouIs shifts in enerCy input and fish and macroinverte- species. particularly niumbers of spawners. Two brate species diversity.. recent management actions show how this can ben-Such disturbances occur fr-om agricultural use. efit these fishes. Federally-mandated increases in road construction, loggiug, and urban development, the minimum size limit for striped bass have appar-and can directly affect nursery and spawning habi-entlv achieved the desired effect of reducing har-tat of anadromous fishes. An extensive review of vest by 50%. Maine (the only state that always had the biological consequences of such land use prac- some level of sportfishery for Atlantic salmon, tices indicates few definitive studies in New until 1994. with catch-and-release from 1995-1999) Lugland (Moring and Finlayson. 1996), except Cor reduced the sportfishing-induced mortality from the Hubbard Brook studies in New Hampshire (e.g. 20% of the run to zero. iwo other management Likens et al., 1970) and several logging sttudies in actions just adopted will hopefully have positive northern Maine (Moring et al., 1994). There have effects on anadromous fish populations. Recent been no studies in New EnLoland that directly link negotiations wvith Canada and the buy-out (at least such land disturbance activities to losses of anadro- temporarily) of the WVest Greenland fishery for mous fishes. However, urbanization along coastal Atlantic salhon may prove fruitful in the next sev-tributaries and logging in upper watershed tributar- eral years if higher numbers of adults stirvive ies of the Merrimack River likely influence differ-ocean fisheries and return to Massachusetts waters cut stages of anadronious lishes. to spawn. A new fisheries management plan for shad and river herring has just been adopted by the EXPLOITATION Atlantic States Marine Fisheries Commission in response to declining runs of those species. Overexploitation, primarily by commercial In addition to fisheries management plans, the fishers, has contributed to the decline in striped exploitation of some anadromous species is bass, Atlantic salmon, and Atlantic sturgeon. restricted under other environmental regulations. Maryland is the major spawning area for striped The shortnose sturgeon is protected under the bass that migrate along much of the northeast coast Federal Endangered Species Act. The Atlantic and the state where the bulk of the commercial sturgeon may be listed soon. catch has been centered. In the 1960s and 1970s. the total catch of stripers by commercial and recre-ational fishers in Maryland was roughly the same, COASTAL AQIJACUI.,TURE thus both probably contributed to the collapse that In recent years, Atlantic salmon, rainbow-steel-ensued. Once the stock collapsed, however the head hybrids (Oneorhynchzis in vkiiss), and Arctic sport fishery dropped to less than 20% of the com- char (Salhelinus alpinus) have been reared in off-mercial catch while the commercial fishery contin-shore cages to meet market demands for salmon tied their harvest until drastic management measures
11F
)1 EiN1S TN '. - im~NN[
s 39E aInd trout. At present, most such activity is CiLIS- forlls ofxwi Idlife are most obvious with respect to tered around the Maine-New Brunswick border, aquatic birds. Federal protection of-double-crested although aquacLIture operations have been estab- cormorants and other species since 1916 have lished from Cape Cod northward at various times recently led to exponential increases in coastal in the past. Tihe mna jor biological concern is that Ib)reeding populations in Massachusetts (Krohn el escapees fr-om these cages are now entering U.S. al., 1995). The number of breeding pairs o" (double-rivers. A storm in fall 1994 resulted in the escape crested cormorants in Massachusetts has more than of' thoutsands of Atlantic sallmon, nianiv of"which tripled in less than 15 years, from 1.760 to 7000. were subsequently encouniered in coastal rivers of and the number of bird colonies has almost dou-eastern Maine. Generally\ 10% of caged salmon are bled durin( that time (Krohn et al.. 1995). These likely to disappear from cages durinu rearing birds are known predators of such anadromous (Moriing,- 1989). If thly originate lioon non-native species as rainbow snielt and Atlantic salmon sources, these escapees can and do hybridize with smolts. As the bird popuIlationIs have increased, native stocks, thus altering the genetic components pressure on anadrom0ous stocks also increased. A of salm1on used in restoration. Even though the recent estimate concluded that over seven percent stock ofAtlantic salmon that is used in restoration of the Atlantic salmon smolts in the Penobscot of the Merrimack River is non-native, selection is River ate consumed by cormorants in the spring as faCvoring an artificial "'site-specific" stock that does the Fish inigrate downstream (B3lackwell. 1996). It return and reproduce. Thus. genetic dilution of is difficult to reach conclusions on a New England-such fish could further reduce the possibility of regional basis as cormorant predation varies locally. restoration. Another threat is represented by the dependent upon the presence of dams and breeding recent outbreaks of two diseases in both cultured populations. and wild stocks of Atlantic salmon of eastern AlthoucLh cormoranlts have been the birds most Maine and New Brunswick. The cultured stocks studied as salmon predators, at least six other bird may be acting as reservoirs of diseases that get species are known predators on Atlantic salmon passed on to the wild stocks" smOlts in New England and eastern Canada (Moringi et al.. 1998). As cormorant populations have increased (or in some cases stabilized), other SYNERISTI( CoNSS)F [ RAH ONS birds, such as terns, have concUrrently declined. Increasing population numbers of anadromons Thus, the overall impact of bird predation on fishes is a difficult management premise because salmon and other fish species still needs to be no single species can be managed in a vaCULuim. For assessed.I example, as striped bass numbers increase, more of Links between Massachusetts anadroinous these predators will, be entering the lower portions fishes and inshore and offshore marine fishes are of New England rivers. The success of their feed- less clear. Successftil restoration of Atlantic ing in these habitats will depend, among other salmon, for example, may have been hampered in things. on the success of programs to increase runs the early 1980s by substantially increased harvests of Atlantic salmon and American shad. Survival of of capelin (Mallotus villosus) on the high seas. Atlantic salmon smolts, rainbow smelt, and This osmerid is the favorite food of Atlantic alewives, in turn will be influenced by the breeding salnion in offshore waters. success of federally-protected aquatic birds, such as double-crested cormorants (Phalacrocoraxaw-i- SUIMMARY OF ISSUES FACING ANADROMOuS FISllES liuts), the popularity of new sea-run brown trout spoil-fisheries (potential predators of smolts and prey Anadromous fishes,. by their very nature, are for striped bass), and the success of striped bass influenced by conditions in freshwater as well as at restoration programs, as well as fishing and non- sea. Stocks of all anadromous fishes in the fishing human activities. Thus, rehabilitation pro- Massachusetts Bay region have declined from his-grams must be managed fr'om a broader perspective. torical levels, principally due to dams, habitat alter-The interaction of anadromous fishes and other ations and pollution. To a lesser extent, overfishing
40 \1lý i~ . (ý on declining stocks also has played a role. levels of hiavy tetals, PCBs, and acid precipita-Initially, impassable dams blocked upstream tion still may be adversely alftecting anadrotnous passage of anldrinomous fishes. thus preventing fishes, especially through levels in sediments. fishes from reaching most spawning grounds. The When a fish stock is dlecliini, commercial or first types of' Fish ladders and lifts were quite ine- sport exploitation only axccelerates the decline of ticient, but state-of-the-art designs of today still anadrotnous fishes. It is an additive factor that can involve somre mortality in passage. Downstream sometimes become critical in the presence of other fish passa hhas lagge-cd behind concerns flor contributors to stress and moittalitv. AnLe'I s have upstream passage, yet this Is equally important. taken a portion of returning stocks, yet this source Mortal it o" dojtream-n (grathtie uvenile and has never been considered a primary factor in the adult fishes can be significant due to mortality overall declines of stocks. Commercial fisheries froom turbines and predation, but recent advances (First in freshwater, then in saltamer) have played a with bypass systems, especially with Atlantic role in the decline of striped bass, Atlantic salmon, salmon, have shown promising results. Water level and Atlantic sturgeon. With current management changes dux to competing demands for surface efforts reducing the commercial 'and sport catches waters also iayx be an important factor. but this of striped bass and Atlantic salnon, harvest activities tieeds x orestUdy. will likely have less negative influence on restoring A signirilcant portion of the habitat once utilized anadromous stocks. by anadromous fishes is no longer available. Thus, There are restoration or rehabilitation programs the reproductive and nursery carrying capacity of utnderxwav for almost.all anadromous species in the New England freshwaters is no longer as high as. it Massachusetts Bay region, 'some modest and some was in Colonial times due to blocked passage and quite extensive. The results have varied (Tables land disturbance activities, such as agriculture and 3.1-3.3). Runs of American shad have shown the lo gginge. most iinprovement, although progress with river Since the mid I S00s, pollutants have continued herring seems a distant prospect. Numbers of to influence the freshwater life cycles of anadro- striped bass along the coast have increased recent-moIts fishes Impaired Water qiuality together with ly. but not as a result of natural spawvning in blocked fish passage was a major cause of declines Massachusetts. Coastal runs of rainbow smelt and cxti tPtn or antdroIIos stocks. Mil l and appear to be declininigt over a broad -eocraphi cal tannery wastes, sewxage effluents, heaxv metals .area; returns in 1994 were high. but thistmay be an (particularly from industrial plants and paper com- anomaly. Native runs of sea-run brook trout appear panies). and sawdust and pulp from sawmills and to be stable. Atlantic salmon restoration has shown lumber companies have all entered rivers tributary -little success despite decades of heavy stocking of to the Gulf of Maine. fr'y and smolts. Drought conditions in 1995 do not The most severe pollution occurs in coastal appear to have adversely affected juvenile Atlantic waters, obviously because these areas are adjacent salmon in streams (R. Spencer, Maine Atlantic to the land-based and discharge sources of pollu- Salmon Commission, Bangor, Maine, pers. tants. Anadromous fishes can be severely impacted comm.), but witnter survival may have been by heavy metals, pesticides, hydrocarbons, and reduced as a consequence. effluents because they pass between the coastal Restoration or improvement of anadromous waters (as well as polluted rivers) in their migra- fish populations in the region seems to be a func-tions between freshwater and saltwater. In addition, tion of many factors, each of.which must be as Thurberg and Gould summarized in Chapter 4, improved in order to .show tangible results, particu-many pollutants have more pronounced effects on larly: improved fish passage, increased availability immature stages of fishes. The majority of species of appropriate habitat, improved water quality, and of anadromous fishes in New England do not travel well managed sport and commercial harvest. The far from shore; larvae and juveniles in the inshore, priority for restoration and rehabilitation of anadro-more heavily-polluted waters are faced with the mous fish runs in the Massachusetts Bay region consequences of pollution. Although pollution is and other areas of northeastern United States significantly lower in the twenty-first century, should be to provide suitable habitat for species
iZ1 11N L>I Dii Iv A -i.\ c1 z(I%1t1,SIcyct iN & > IS I f I and access to that habitat. If that is accomplished, Ilam pshire Fish and Game Department; Brad the imnpediments to restoration will argely be those Chase and Randy Fairbanks. Massachusetts of natural variability in ocean conditions. Division of Marine Fisheries; Richard Hartley, Massachusetts Division of Fish and Wildlife: Larry REsi*\IwCII NcEIws Solte, .oe IcKeon, and led lMevers, U.S. Fish and Wildlife Service; Norm Dube and Randy Despite the Iong history of exploitation of Spencer, Maine Atlantic Salmon Commission: Lew anadronmo's fishes. and the lecgthy, dcaiabase, several Flagg and Tom SqUiers, Maine Department o1" areas of research are necessary lor future manage- Marine Resources; and Boyd Kynard, U.S. ment, restoration, and rehabilitation. RLunS of Geologtical Survey,. for backgzround information alewives. blueback herrin-., and Atlantic salmon and unpublished data. are being minluenced by. some undocumented marine factors. In order to properly evaluate man-LITERATURE CITED agement and regulatory actions performed on Alleni S. 1995. Out-of-comntol vegetation choking pails of the behalf of these anadr"oinous stocks, it is necessary Charles. iRoston Globe. Boston. MA. July 3`)_I W5, to know why runs have declined despite improve- t;eir;l, 31. 19S5. MLOasschsettts Coastal trOLit management. Ill: Wild ments in water quality and fish passage. I his TroLit ll. F. RI- cicic is0n uldR.H i ilHaUIc i d..* icd. "FIly Fishers wid Trout UInlimited. Vienna. gV'irhl.-l p. 1 142. requLiirCs rcserch oIi occan warining and cooli] ag iielak, A. Iý 1994. Pollution and salmon: What's tie iroblem! in: A trends, commercial harvesting, and the dependency . Ilard Look at Some "uonoh Issues. S. Calabi and A. Stout (eds.). of these anadromous species on certain prey items, New onaaEnland Atlantic Salmon Manengecent ccnccrence. New Enigl and Salmon Assoc iation. NcburVporir MA. p. 200-212. such as capelin. Bigclow, H.B. and W.C. Schroeder. 1963, Fishe ofFtice. Guilff Another area of concern is restoration of Marci U.S. Fish and Wildlilce Service, Fish Bull. 74.1-577. striped bass stocks to southern New England and llackowel,. BF. 1996 i.coloc'v ol I)occuhle-Crested Cormorants in the is
'cnohscot Rixer ancd nao Maoin. I'h . d sertation, University elsewhere. The modest, but consistent. success of of Mane,. Oconco 141 pp.
Maine's restoration program tprovides some evidence Bowen- J.l. 1970. A history oi` fish culture as related to the develop-that important gains can be achieved with moderate M len (? l'ishcry progia s "i. Fish. Scl)c. Spec Publ. 7:71-931 tBroxcn, B. 1987. Boston Harbor and Niassachusetts Ba,.-issuces. Financial investment. Factors influencing distribuh- r icso On.cccelcic i,. (ll: lrces, and 7 C, asialzollc ,17. Pric, F'i111 tion and spawning success of striped bass need to xvnipos O)n Coastal nlid Occan Mani*-elnrit O. 1 Magoon. ii. Cinversc, r ). Miner. I..r Tobl i. 1). Clark. "tlnd G f)o-iicai ieds i. be investigated. Third, the Fragile existence of sea- Vo. 3. Act-. Soc. Civil i-ng., New' Ycrtck p , 09-3t10i. run brook trout stocks from Cape Cod northward in BuckeINy J. 198Q. Species Profiles: Icil,. Histocy and Env ironcntci l the United States needs to be identified and man- Requiruccments of Coastal Fishes and Invertebrates (Northi Atlantic): Rainbow Smelt. U.S. Fish and Wild. Serv., Biol. Rep. aged. Our knowledge of the biology. seasonal ,RN i.106)m ,i, d AcirmiyCorps o i. ihcc rsc'sR EI.-,ri -- . I I pp. movements, and habitat requirements of this Carlson, C.C. 1988. --Where's the salmon?" A reevailuation ol the role anadromous form is primarily firom waters of the .ofanadroiccous fisheries in aboriginal New England. In: Holocene Itilian Ecolocy in Northeastern North America. 13.1 Maritimes. Nicholas (cd.). PlenCum Press, New York. p. 47-80. Fourth, broader-scope investigations need to be Coffin. R.I T' 1937. Kennebec. Cradle ofAciericans. Nexw York, initiated that involve multi-species approaches. For Farrar & Rinehart. Cole, I.N. 1978. Striper: A Story of Fish and Man. Little, Brown. and example, striped bass restoration in waters contain- Company, Boston an d Toronto. 269 pp. inc, sea-run brown trout or sea-run brook trout Isanie, .S , i.G. Trial andi, J.G. Stanley. 1984. Species Profiles: Life should be conducted after studies conclude that I istory acd [cixvironniental Requiretrents of`Coastal I ishes and Invertebrates. (North Atlantic): Atlantic Salmon U.S. Fish and predator-prey influences are not self defeating. The Wild. Ser. F'S/0.S.-8i11.22 and Army Corps of Engineers TR success of one program should not be at the EL-82-4. 19 pp. DuBois, H.B.and S.P. Gloss. 1993. Mortality of juvenile American expense of another program, just because the two shad and striped bass passed throughb ( ssberer erusslox tur-are conducted by separate agencies working in the bines at a small-scale hydroelectric site. N. Am. J. Fish. M-canage. same geographic area. 13: 178-185. Flag., L.Nand T.S. Squiers, Jr. 1991. Management, enhancement. and restoration of striped bass in the State of Maine, U.S.A. In: Proceedings ol'a Workshop on Bioloigy and Cuiture oi Striped ACKNOWLEIDGMIf:NTS Bass (Jilo,-onesaxatilis). R.H. Peterson (ed.). Carl. Tech. Rep. Fish. Aquat. Sci. 1832. p. 23-28. I wish to thank Duncan Mclnnis, New 'Freeman, S. 1995. Low salmon runs worry scientists. Union-News. Spri-r'ield, MA, August 4. 1995. "
4-2 IRiN(; I:rielIcIand- K I. ).f. R dd i indIJ. F. Kocik. I9'93. NInalie Survivial Assoc. BlIt., Faill 1 pp. iii N-rthi Asic ric',o a., Erpe. . antic satimn: Eloinlcis oI" Nev,, Finglhd Sahl on -ssccition. 1906 The Nc,u En21lod Salilo growthi and environment, iCES.IJ MNr. Sci. 50:481-402, Assoc. BuIll Itall. 4 pp. lai I es. A. I987. A.ilaiiic salinon rcsiorucs IiIhc nortli eastc In NNlFS (iNatioai NMI-ie Fistrics Ser;ievi )l92 01u. I-is at United States and tile potwntial ctlccts of"acidification from Oceans V S Dep. Comuterce- Nat. Oceanic arid Alinnes. Acdmil.- aunrtsilcric dcposkia . Wa:ter. Air Soi Poll. 35:3 7--8. \N" i',2tll on. D.( 14 pp. ,l .lry, S.1 I., Jf. . Field. 5.1. Sbi,,c 1)M. Nelso, and Ni.F.N Monaco. NNFIES (Natimoia Marine iIisherics Service)e i90R, Essen.ial tlsh hahi-9194, I)iSirihitton and Auindanc ill FI' heS and hsvertchresCc in t!t t dim t inj 1,[ tr Ailalhtic S`Ldm- I i 1 % di-cl North Atlantic Estuarties 1. vl,. RcppNo, 13, Nat (.Oceanic and script prcsentcd io New, IinIihitd I-iihercs .'1amnl'-cnlont Cioincfii Anmospheric Ad ini.- Nat, Ocean Scyrv. Strategic Enviion. Rideolt. S(G and I,.W. Stolte. 1988. Rcstoration of Atlantic sahltoin
,.\s111- Div- Sflc f S M I.) 7'i pp ilC Coh-iiicticcl aid l MNeri itick ri1C-i. macS p7-S in 11..
Kiel"iýr. M.C. and I1 Kyvnard. 199t p, ing of the shortnose stur- Stroud- ed. ICesCniand lI-toire ANtlantic Saithion Nanagemll
-con it the Merrimack RiverNMas-,achtIsetts. Trans. Amil.Fish. N-ariine Rccreational Fisherice 12. Atlantiic Salmcoii Federation.
Soc t25: 179-186 lpscmich, MA andNatidmiitCal Caiitii t ioN Marine Citser,-attin. Kimhball. D.C. and I,.W Stolte. 1978. Return ofthe Atlantic Salmon. Savttilah. Geortgia Water Scturu. 8 ppI Rit/si, C.FI. 1953. iEastcrn liro k I root Polo latilons of Iwo' Nlaiilc Krohn, W.B.. 11.1. Allen- JR Morina and- A. . Hutchinson. 1995. Coastal Streams. Master of Science thesis, University of Maine. Double-crested cormorants in New England: population and Orono 101 pp management histories. Col. Waterbirds. 19 (Spec. Publ. I):99-109. Rulifsoni R A. arid N-MJ. Dadswell. 1995. Life history arid population Likens, GC- F.H. Borntann, N.iN- Johnson, D.W. Fisher anid. R.S. characteristics of striped lass in Atlantic Cainada.uirans. Ai. Pierce. 1970. EIl.ects, of" lores\ cuttinStand herbicide treatment oin Fish. Soc. 124:477-507. lliltrie it hudnets ill the H-iuhbmard BIrook ", atershed ecvssteii. Smith .1.1622 See: Sinmith, .I. and P.I-. Barhouir 1986. The Complete IEcol. MNnotior. 40 23-47 \,V5orks of Captain.lijhn Smith. 1550- 1(3 1. Uiiversits otf Nol th Nlathlir. DI R.-I3 I lcisec and. 1)D Robinsion.I 1994 l-i e-passage Ciioliml Press. aortality \fojuvenilc Atlantic shad at a low-head hydroelectric SqUiers, I S.. Jr. 1988. Kennebec River Striped Bass Restoration dam. Trans. Am Fish Soc 123 108-Ill. Prograim. Maine Dep. Mar. Resources, Auigsta. 3 pp NIclvin. G.I).. NI . Dadswccll and J-A. -IcKenz.ic. 1 L)2 Usefulness o1" Sticr. )... ard 13. Kynard. 1986. Use of radio telectetry to deterini teriistic and morphometric characters In discriminaitiilg piPtlth- thie iiorttlits cf'Alanitic salilon siiols ptassCd throuigh a 17 NINA tionis ofArierican shad (,-Iosa sapidi,,siita)(Ostreichithvcs. Kaplan turbitle at a luIv-head hydroelectric dam. Trans Am. Fish Cluperdae) inihapiting a mtarine eanvironment. Canll..1. Fish Act Soc 115:771-775, SciL 419(2': 266-28(1. Stoloe. !LW 198 1. The Foru4otten Sainon ft lhe Merrimack River. Nboring. I.K. 1'986. Stockinc anadron~ous species to testorc or U.S. Dep. SfI['lic Interior. 1U.S.(;ovt. ]rinting Office enhance fishCries. It: Fish Culture in I isherics N-namaemcit Washington, D.C. 214 pp. RIH. Stroud ted.). A-m Fish. Soc.. Bethesda. MD. p. 59-74. Stol tc. I\V. 1!986. Atlantic salmon. In: Autdubin Society Repirt. Mi\riing, .. K. 19S9. l0occumtientltnmtn10 of" tnacco*nted-ltr assesof chti- R.I.. DiSilvestrid (.cd. Nat. A;iduonli SoC.. Nev York. p. ,v(,- look salhton tf-ont saltwater canes. ['ron. Fish-Gut. 5 1: 173- 176. 713. Molring, J.R. 193 Anadromotis stocks. In: Inland Fisherics Stolte, 1.W.V19 i9. Atlantic salliicit iestoCration in tie MNerrimack Rivcr Manageinent in North Atmierica. C.C Kohler and WA. I lubert, basin. In A I lard ILook at Soille louhl Issues. S. Calabi aind A. (eds.). Am. Fishl Soc.. Bcthesda. Matad. pi 553-80. stout icds. i N.New L-gland Atlantic Salhot Nlanagemeint Moring, JR. and K. Finlaysont 1996. Relatiomship Bietwecn Land Conference New Igliand Atlantic Salmon Assoc , Newtbutryport, Use Activities kind Atlantic Salmdoion (5/no Sot/cat: A L.itetatumrc MNA.p. 22-35. Review. Nat. Council Paper Industiry fr Air, Stream Improve., Taylor, R.E. and B. Kynard. 1985 NiMortal iy of jyuvenile ANlerical Tech. Bull. 86 pp. shad and hIlueback herring passed thrtough a low-:head Kaplan Nloriitn, .. R , CG Caiiai.- .u-d .1) NI. Miiulen. 191i4. "l'.Icct-sof li- hydr,;-cilc crKi turbine l ions .I\i1A . I tshSic I 4 :3i -43 5. gins practices on fishes in streams and techniques Ror protection: Thoreaut B I) 1849 A Week on the Concord and Merrimack Rivers. a review of four studies in the United States. 1I: Rehabilitation of Republished, 1998. PCeguiin Books. Freshwater Fisheries. I.G Cowx led.) Fishing News Books, l'hurberg, F. attd F. Gould. this volumtitie. Oxtbrd, U.K p. 194-207. USFWS (U.S. Fish ainld Wildli e Service). 1980. Atlantic Coast Moring, .1,R,, J. Mtarancik. arid F. Gritl'iths 1995. Changes in stocking Ecological Inv,'entory: Bostot*n. Inventory map. strategies for Atlantic salsmlon restoration arid rehabilitation in USFWS ([U.S. Fish and Wildlile Service) arid NMNIS (National Maine, 1871-1993. Am.. Fi-sh Soc. Svntpos. 15:38-46. Marine I-isheries Service). 1995. Statits Review fcr Anadroitmos N-oring. J.R.. C. van den Ende, arid K.S. I-lockett. 1998. Predation oil Atlantic Salhon in the United States. 131 pp. Atlantic salnon smolts in New England waters. In: Smtolt Watt. W.D. 1988. M-,ajor causes artd implications ofAtlantic salhon Physiology Ecolo-y and Behavior. S. NIcCoriick and D. habitat losses. In: R.H. Strotud (cd.). Present arid Fuiture Atlantic MacKitlay (edsl. American Fisheries Society, Bethesda, MD. Salmon Management. Nicasuiring P'rourcss Toward International
- p. 127-138. Cooperation. Atlantic Sanlon Federation, Calais, ME and Mullent D.M., CW. Fay and J.R Morming. 1986. Species Profiles: National Coalition lkr NMarine Conservation. Inc., Savannah, GE.
Life -I stories arid Enlvironmental Req utireitenits of Coastal pp. 101-112. Fishes and Invertebrates (North Atlantic): Alewi fe/Blueback Weiss-Glanz, LS.- J.G: Stanley and, .I.R. N-oring. 1986. Species IHerring. U.S. Fish attd Wild[. Serv 82(l 1.56) arid Arinty Corps of profiles: Life Bistory ald Einvironmental RItlteirements of' Engineers IR EL-82-4. 2 1 pp. Coitmal Fishes and Imvertebrates (North Atlantic) Atmerican M-lnrawski, S.A and C.F. Cole 1978. Population dynamics of'anadro- Shad. 13.S. Fish and Wild. Serv. 82(1 159) and Army Corps of imoos rainbow smelt Osmerus smor-aox iii a MassachuisCtts river fEgmineers 'R EI,-82-4. 16 pp. system. Trans. Atll Fish Soc. 107:535-542 Wiener, .G. aid D.J. Spry. 1995. Toxicological significance of rner-Murawski, S.A., (_.1. Clayton, R.J. Reed arid, ClF. Cole. 1980. cury in freshwater fish. In: Interpretintg Concentrations of Movements of spawning rainbow smltelt. Osmerus mordax, in a Environmental Contaminates in Wildlife Tissues. G. IHeinz and Massachusetts estuary. Estuaries 3:308-314. N Beyer (eds.). Lewis Puiblishers, Chelsea, Michigan New England Salmon Association. 1995. The New England Salhon
I S PI)A 1;"NT I]FFE(" Chapter IV Pollutant Effects upon Cod, Haddock, Pollock, and Flounder of the Inshore Fisheries of Massachusetts and Cape Cod Bays FREDERICK P. THURBERG EDITH GOULD NrationalOcespc and,-'1tmos72hericAchninist'cration
-Vatio/?a/ ',WarineFishieries Service 212 Rogeirs Avenue Nhil/tzr/. (iT 06460 LSA Nowhere is man's ecological naivele populations due to such tactors as weather, variable more evident than in his assul/ptions predation, gradual climate change, food availability, about the capacitO of/the atmosphere. temperature. salinity, and interactions among envi-soils, rive-s. and oceans to absorb ronmental variables. Contaminants may be adding p)ohlution. additional stress to populations already stressed byi
-PaulR. Ehi-lich (&:Ane H Ehrlich. 1970 natural environmental Hluctuations, anthropogenic habitat alterations and overfishing, thereby con-tributing to declines in fish populations in some areas.
INTRODU1CT ION This chapter focuses on the effects of four major pollutant categories (metals, petroleum Of the three possible impacts being discussed hydrocarbons and PAHs. PCBs. and pesticides), in this Volume (contamination, habitat alterations each of which contain individual contaminants that and overfishing), the effects of contaminants on are listed on the Environmental Protection demersal fish populations may well be the hardest Agency's list of"priority pollutants" (Table 4.1). to document. Catastrophic impacts of contaminants Toxicological impacts are assessed on several com-(e.g. oil and hazardous waste~spills) exhibit readily mercially important Northeast groundlhsh species apparent effects, but are relatively rare and are including cod, haddock, pollock and four flounder localized. Thus, they probably have little effect on species, of which cod and flounders have been the overall fish population structure. The more impor- subject of considerable research. The European lit-tant contaminant effects are from chronic, low level erature abounds in both experimental and field exposures. As with catastrophic effects, even these work with the Atlantic cod, Gadus morhua, from chronic impacts are localized geographically. which the more relevant reports have been abstract-Contaminant impacts may be difficult to dis- ed for inclusion here with American and Canadian cern from habitat alterations and overfishing papers. In the American Northeast, the winter because the overall impact may be due to the com- floundel, Pseudopleuronectesamericanus, has also bined effect of low levels of.multiple contaminants been the focus of much experimental work, and is (acting in an additive, synergistic or antagonistic perhaps the most widely studied marine fish with manner). In addition, contaminant impacts may be respect to pollutant toxicity. It is widely distributed, masked by natural fluctuations in demersal fish is highly visible as an important commercial and
441* Table 4.1. "Thc US. Environmental Protection Agiency's recreational fish. is easy to handle iti the laboratory, Prionty Pollution list (U.S. EPA, 1984). Contamimaints and is. readily collected from contaminated coastal marked with an asterisk have been routinely nonitored ateas. -hIle nuttiiber of field and laboratory reports since 1986 in sediments, marine mussel tissue and of the effects of pollutants ot the other five species groti .tish tissues by NOACA's National Status a"rd Ithaddock. LIJIiOl "'I'lUi\mitM af/aul'u; pollock, lTrenIds Program (Bendthic Surveillance Project l//olhines vil/its: yellowtail flounder, /elt'oneclces (NOAA,,NS&T. 2000) and Mussel Watch Project: i!C/,';'i w-o zwtoi,.:\ erican plaice. bH/1',,ot,!ov.i5uc'S Lanenstein and Caimtillo, 2000). P/aessouei/s; witndowvpanie flounder. Scn.phhha/mils Metals aquostis), whether examning cause-and-efltcts,
?W, As*' B\. Cd(*. Cr*i tu*. II*. Ni*, Pb*. Sb*. Se*. TI.
circumstantial evidence, or even engtaging in iniformned speculation, is sparse. Our aint here is to sutumiarize the various types all congeners and Arochlors of toxicological effects, both lethal and sublethal, PAllIs* that have been shown to occur at the organismal, acenapthiene*. ace naphthy lene* anthracene*. tissue, cellular and subcellular levels of biological be nzo(ahailthrace lie!*, benizopur yelic, benzo(a)py rene*. organization. This review follows the progression be/z.o(b.kklHuroranlhiene, hys ie* dibenzea.h ianthracenc* of research froii the laboratory where toxicity was 1'tlnranthicne*. fluoreie*i, iCnno-p\yrene*; naplhthallue*. demonstratecd through carefully controlled laboratory phenanthrene*, pvrcne, exposures, to the field where laboratory observa-Pe:sticides tions were confirmed at contaminated field sites. aldrili*. chliordane*. DDTll. DDE)*. )DD*, dieldrin*, While much of the early laboratory work used eldosulplihans, eidriin. endrin aldehyde, heptachlor*, hep- high, often environnmentally-tunrealistic concentra-tachlor epoxide*, hcxachlorobenzene*, ltindanes iBtIC *, tions of contamiinants, these studies have neverthe-toxaphiene less been useftul in determining the initiation, pro-gression, and mechanismts involved in many Other haloe*nmed compounds bromniolnrii carbon tetrachIlride, chlorinated benzenes. adverse health effects observed in the field. chlorinated naplhlhalenes, chloroalkylethers, clihIobnenzene, Additional laboratory studies showed effects upon chlorodibromomethane, chloroforin, diclichlorobenzenes. very sensitive early life stages as well as effects dichlorobeizidine. dichhbtiethane, dichhl.rhromnmehane, upon reproductive processes. The next critical dichloroethylenes, dichlorophenol. dicliloropropaiie,. stage, linking these laboratory. field. and reproduc-dichloropiopciic., dichloropropylenc. dioxins (TCDD,. tive biology studies to population effects, has been haloethers. halometlhanes.lhexachlorobutadiene. hexachloro- attempting to demonstrate that pollutants do have a ci c lokiexailes, hachii racyc lpentadicne, hexach lotietlianei measurable effect upon fish recrutitment processes methylbromide. methylchloride, methylchlorophenol, and thus effect population structure. This has been methylenechloride. pIentaehlorolphenol, tetractilorobenzenc. a difficult and elusive effort. The multitude of tetrachloroethanes. tetrachloroethylene, tetrachlorophenol, potential stressors in the environment (i.e., temper-Itichlorinated ethaics. trichloethyene, trichlophenol- vinyl ature, season, predators., parasitism, siltation, food chloride availability, to nam e a few) in addition to the possi-Phthalates ble antagonistic and synergistic effects of multiple butylbenzylplithalate, dibutylphtlialate, diethylphthalatc, polltUtants, both organic and inorganic, found in dinethyl phithialate, die thyl hexylph liat ate. ph thalate esters contaminated habitats, clouds the determination of N itro-compounds specific effects of pollutants on fish populations as dinitrophenol, dinitrotoluene, dinitro-o-cresol, nitrobenzene, a whole. Mathematical models are being developed nitrophenols, nitrosamines. nitrosodibutylaniine. nitrosodi- to consider the interactions of these multiple factors ethylamine, nitrosodimethylamine. nitrosodiplienylamine. with contaminant effects, but the definitive answer nitrosopyirlidiae, nitrosodipropylamine is still some time away. This at least partially Other compounds explains the lack of information on direct effects of acrolein, acrylonitrile. asbestos, benzene, benzidine, cyanide pollutants on fish populations and communities. dimethylphenuol. diphenylhydrazine, ethers, ethylbenzene, isophorone, phenol, toluene
t).I'MAJ *Ni FFvlz, i5 45) Co.i'..mI'INANT DIsTIhIIlIF'IoN IN, FINIISII are, at tile very least, an indication of habitat con-tamination. Temporal changes in contaminant body burdens have been diocuimented. at least fot some locales (e.o . Canadian G inorhuo, Freeman and The ialiev / '/ssochise'ts' niarine lithe, 1984; Misra et al., 1988; Norwegian G Ur, vil(*ulC is (leIalciLel Pollut'ion is inor;ha, Skfre et al., 1985). Decreases in environ-inptclinlfish and shellfish health and me.nial eXposure 1o these contaminants are geenerallv illnacing isleries.hi; s-enderini /ish and reflected in declines in fish contaminant bioburdens s//ei/i/s!i iii somenclocaiion isinl o calUo over time. ci'eating the unu'arr/ aud pi!h/ic pekrieplion thal all seafbod shouti be shaumneJ -t114-DDAJ 1985 Higher concentrations of metals in seawater Various metals., pesticides, polychlorinated and sediments have generally, although not univer-hiphe vIyls (PCBs). polycyclic aromatic hydrocar- sally, been correlated with higher concentrations of bons (PA -Is) and other petroleum hydrocarbons metals in various fish tissues. Geographical differ-have been measured in fish taken fiomn the wild ences in concentrations of Zn, Cu. and Cd in (lable 4.2). Elevated pollutant levels in fish tissue Atlantic cod muscle,.for example, reflected local Table 4.2. Examples of contaminant bioaccuMulation in deinersal fish species from the western North Atlantic.
. .. . ... ........ ---i-i-s-----
Species of Fish Collection Site Toxicant Ileasured Reference Examined I ilanlic cod InUWIc Balhic Sea CI Cd. Zn 7 'cniitii et al.. 1982 li.-ntic cod Norway 1-ig .JulshaIm in et al.. 1982
.i niicI Atiltic cod.
Newlioundland & Labrador 1 As Kennedy, 1976 nknerican plaice livnr, usleiC i~tlantic cod Nova Scotia, New LBrunswick DDT Sins et al.. 1975 lAtlantic cod liver t" IIa(Iiad oreanoctiloriics Friemanii and Uthe, 1984
...... . -F H addock n uiscie offshore PCB Capuzzo ct al.. 1087 Winter flounder muscle NY Bight. Hudson Shelf various metals Reid et al.. 1982 Winter f]otndcr liver Long Island Sound I Cu. Mn, Zn Greig and Wenzloff. 1977
!Winter flounder liver Boston Harbor various metals MacDonald, 1991 Winter flounderi muscle, liver NY B3ight PAHl. organochlorines MacLeod et al.. 1981 Winter flounder whole body New Bedford Harbor PCB Connolly, 1991 Winter tlounder liver NY Bight PCB Reid ct al., 1982 Winter flounder onad liser Long Island Sound PCB Greig and Sennefielder, 1987 Winter flounder liver New Bedford Harbor PICB Elskus et al.. 1994
.- .-...... .-.. ..... ....................... . . . ...... . . . . . . .. . . . . .. . . . . .. . = . . . . . . . . .. . . . .
ioundera liver Long Island Sound PCB. various metals Greig et al., 1983 flounder W~indowpanet Jinder Imuscle Delaware Bay lae Gerhart. 1977 flomunder
46li I ý T; Riý , C::; I: 1 concentrations In seawater (Perttihta et al., 1982). polycyclic oriariochlorine pesticides were found ill
.i American plaice collected oft Newfoundland and livers of male American plaice sampled in the Labrador had arseic concentrations in muSCle tissue North Sea neai areas of major rive'rile input and that were similar to levels in sediments, much higher other souices of inthriopogenic pollution than those totind in Atlantic cod, redttish (Sebasics (Knickmeyeriand Steinhart, 1990). Pesticide levels narimits) and turbot (ReIinl'lcdlius hipo gllossoi(Js) were also elevated in winter flounder from a tribu-fhorn the same area, but lower than concenirations tary of BuzzaiIrds Bay MA, indicating significant
- in the local shrimp upon which they prey levels of contamination in this area (Connolly.
(Kennedy. 1976). 1991 ). The highest concentrations of pesticide con-In contrast to these two examples where metal taminants Were found in coastal harbors and indus-body burdens correlated with environmental con- trialized centers (MacLeod et al., 1981 ), whereas tamination. metal body burdens in winter flotnider offshore areas had very low levels (Connolly, did not reflect the high metal levels found in the 1991). Similarly, levels of PCB congeners in liver sediments of the more contaminated sites sampled samples of male and female Atlantic cod reflected from the New York Bight and Long Island Sound a decreasing PCB pollution gradient away from the (e.g. Christiansen Basin, and thed"Nludhole" 310 kiu motith of tlle G lonmma, Norway's largest river SSE of the Basin) (Reid et al., 1982: Carmody et (klarthinsen et al., 1991 ). Offshore haddock fish-al.. 1973). In a comparison of two sites in the west- eries had very low levels of PCBs, plresumiiably to-east pollutant gradient in Long Island Sound, reflecting the low PCB exposures as distance from Hempstead Bay (westernmost) was considered the mainland is increased (Capuzzo et al., 1987). heavily polluted comnpared to \vaters off Shoreham PCB concentrations were higher in \vinter flouinder NY (mid-Sound) based on metals in sediment data. gonad and liver samples from the more polluted yet Cti., Mn, and Zn concentrations in livers of win- sites in Long Island Sound' (Greig and Sennefelder, ter flounder were twice as great for Shorehaam as 1987). although no relation was found between For Hempstead (Greig and Wenzlof 1977). The windowpane flounder liver concentrations of PCBs absence of a correlation between metal concentra- anid a Long Island Sound pollution gradient (Greig tions in tissues and the environment was also et al., 1983). apparent in Gerhart's (1977) study of HIg in eleven Fish may obtain these organic contaminants not fish species incltiding winter flotinder from only via the soluble phase, but also throutgh ilges-Delaware Bay, and McDonald's (1991 ) review of tion of contaminants present in or bound to prey data on winter flounder fiom within Boston Harbor. items, as well as by contact or ingestion of contain-Wintei flounder is a pollution-tolerant species that inants bound to particles and sediments. The rate of migrates between shallow and deeper waters sea- uptake depends oil the lipophilicity of the coim-sonally, and therefore may not reflect contaminant pound. Winter flounder exposed to crude oil-spiked levels from a single site. sediments for 4 months accutimulated more of the low molecular weight PAHs than the more lipophilic, higher molecular weight compounds LiPOPHILIC CONTAMINANTS (1-Hellou et al., 1995). The more lipophilic the con-Lipophilic contaminants such as chlorinated taminait, tlhe more important is the ingestion route in uptake. Connolly ( 1991), for example, demon-pesticides (DDT, DDT analogs, chlordane, dieldrin, etc.). PCBs, PAHs and other petroleum-derived strated, using a food-chain model, that uptake of contaminants, have the ability to accumulate in the soluble PCBs across the gill of winter flounder was lipid-rich tissues of fish. For example, DDTs were exceeded by dietary uptake of PCBs. Contaminated measured in cod liver in quantities far exceeding prey species provided 80-95% of the PCB body the amount present in the flesh (Sims et al., 1975), burden. Assimilation efficiency of PCB declined a fact more important to the health of the fish than fromn high values for trichlorophenyl to low values to the consumer of cod flesh. for the more highly-chllorinated (more lipophilic) In general, concentrations of these lipophilic congeners (Connolly, 1991). contaminants in fish tend to correlate with contami- Some of these lipophilic contaminants are quite nant levels in the environment. Elevated levels of persistent in the environment, as reflected in
47 4 Table 4.3. Toxicological efeccts and diseases possibly associated with concentrations of toxicants ill fish. Potential correlictions made between body tissue burdens with suiblethal toxicological elfects. ocItxicant iAssiciated Mecasure of ojt Rel'erence Meiasured
.\tl tic cod ilivcr kidney., IBahlti oa cd !ýkeletal dceIoniitile, I oneL & l.)elide'cl. 198i sky Icton I Atlatic co Atani cod It live !Nort iSa io I 7Tcus~xudrni!Stork.
PC3 1983 It)t'te.~ vi I 1)8.1 - I lI...-. jAtlantic co'd iliver 1Hal htx I hrbor iassuncd. ýlnty change' in liver ctrecian tal-.. 1981a.b ml talts. oreanies 1
, allan1tic cod behavior A'tklmic IcCod 5i I c....u.. PAI I prasitic ni16o_ Ics has .... r i aii ... anl 1900...
Attatitic cod liver, testes tab exposUre IPCB 'reduced strvival & reproduction Sangatan-g et at., 198 1 [ellowtiail epidermis INY Bight iambient scmxaterifin erosion Ziskowski et at.. 1987 t flounder
. . ... ...... .. skeleton
. .. _ . . ... ........ .. . . .. . .i .. . .
iYellomtc il .... ive..r. skeleto ein i N.. i parii.- siiis. iver lesions. sk.. eta I Dcspres-tatanko et at 1982. ,fnlu,,, d .r ilatdaic ,aborm,alitics .tilichei:iiio c l..- 1986 , St1.11- .I.&
*iii ieSii*d . . lv II-look ft Itv
- . C...lc...
ii-c ih-iT, ijir l St t Coill t .. li Ii. la ts a1.*a ii cIIIli. - i tier laounder NI Wi Lnter flounder epidermis, liveri Y Bight * . or 1Dr7I imcireased livcr size, fill erosion Sherwood. 198) Witer i~lPTde/ ive,,, Bed Ioi c~t -r IC 3 iiiciesed 1w-151 protein (but to WEskus edad.. 1989 (t]a, It FN puu. . .! 'de in, FRO*t) Wiiirte r tionder gonad. larvae, ILon" Isand IPCI Ilowered iepiroductive rates: sin larvaeIINeIs-on et al.. 1991 einbrvos 'SoutnedI enbrx.nib l ibnonnii itie " Winier flonder [egs. .New led lo,*rd [- i........ allem In \ ta e 1Black c _al.. 1988 AiWinie" floundcr liver Boston I larbor IAltI liver tuinor & other liver ttiteltaitao & Vo-lke 1991: i p-a tho lo gies piiaa"iMookare !.M o r It)199 I9 *lo litCt 1 Sntloh.\
- tcal
-:iI."
__ Iliverb: T____o,, & O'Cokt or 1991.
\\inttr flounder 'epidermis, sktt New York Bight ambient seawaterifin erosion Ziskowski c tl.. 1987 "irt~. later ~i eclO rtic i It . eggsI .oit, Isilaitnd ittibiciti Sctv aiter C""
, C~tt*,t.ui1x . .ell itncctisi cli a -i c tiev C l:i.. 1991 tiSold mo'sotnc dci.irise, sl(oxer de,.
i t\Vinter floundcr liver, bloodt New t laven Cl.I metals. t.tBs liVCr lesion)s. blood cell ahnorm alt- ticrig & WcnzIoll. 197;7. I cells Lonslaid ities, liver NA dattiage. liver nea- Greig & Sennel'elder. 1987.
.. . . Sound. NY liuhb ;plasi5 (rcnluniid CLal.. 1901.
-____ under blood cells cNY ight A. NJ. ant eoncleii in rI Lotugtes & lebert. 1991:
fi-
.tmrteoun d cells coastal it- ambient seaiwateriervthiocvte mutations and !LongWell etal. 1983 flounder
_p._- __ Atlantic i microntcleiit vvinter flounder blood cell Ct Boston HIarbor. NEinambient seawaterlhigher no. immature eroflracetes Daniels & Gardner. 199
\\Winter flounder lar vae ]\\;r Narra-anseut Bt.ambient seazsater s, votlk-sac larvae: hvr rate survivalButcklev et al.. 1991 Minter liounder liver, plasita, Boston Harbor ambient serwater iedUcd: ttcpdtici pecttral lin ascorhicICarr ci at.. I991 brain, muscle, acid conc. helpatic glycogen. lip: I epidermis Iplasma glucose:
Ireimnelthrie_ brainacid
;ttitniO serotonin. to-conte otiscet 1Wi rte-r fItotdeiIliver If alifax I larbor lambient seatwateriliver: necrotienic eflects liepatocyteirTax ct al., 1991 ibasoptmitia, nmacrophageaiggrega-ution, hepatic epithelial vacuolation) t Wier Ilounder I'er Lon IsIad S0Und biet seiaers t hIo_-.1)N A a Ier. iii liver Gronhtild et at., 1991 Witter hitnder whole body Ilab expostire D)DT & dieldrin reduced stirVival of'embr-os -[Siwth & Cole. 1973 VIndoxtaolp,*e Ii. blood Long Is*a*ad SOtUndibet s.aw.ieri*inceased I-lt & hietotglobin Dawso,. 199(0 Wiitdo tpane, New Yorp Bight tambient seawvater fin erosin OConnor. 10/6 Yelloxwtail, & skeletotit \Vinter flounder 1-4 _
Windottpane eLong Isladteuntiaoien abnornIiities in eggs LongwelI et tt 1992 Ifloumnder ewtrnloi
'48 itR*:~i 4G ;
temporal monitoring of iish tissues. Most Greiczand Sennelfelder, 198/). After spawning, organochlorine compounds in livers of cod caught PCB concentrations In gonads decreased to very off the east coast of Canada ii 1980 showed no low levels (0.03-0.08 ,ttg/g). In contras,. F.lskus et change in concentrations over tile previous S yeais, al. (I1994) f1ound that the content and concentration with the exceptions of DDT and the PCB group, in of PCB congeners in winter flounder liver taken which there was a general decline between 1972 from New Bedford Harbor fish, did not correlate and 1975. with no significant change thereafter with either sex or reprod ucti ve state. H owever. they (Freeman and Ulthe. 1984). Following a 1972 DDT cautioned that the hiich tissue concentrations of ban in Norway. cod liver samples showed decreas- PCBs obtained at this extremely contaminated site ing concentrations of DDT: 10 years after the ban. may have obscured sex and reproductive condition the highest level of cod liver DDT was about one- di fferences. third of the corresponding 1972 residue level (Sk~re et al., 1985). The persistence of lipophilic contaminants in TOXICOLOGICAL E I'FEC'S OF CONIAM INANTS fish themselves is related to several factors, includ- ON FINFISI. ing the conlai inant's degree of lipophilicity, the size of the orgranism's fat stores, the organism s abilitv to metabolize the contaminant, and the 4S LI"'li'dC a wc/)Oll 'I'St117Ca IvelInc? ; organism's seasonal turnover of fat. When exposed club, the chemical barrage has been to a radiolabeled PAH (benzo(a)pyrene) and a PCB hurled ugain.t the fabric of life - a fahric congener for 24 h, for example, cod eggs and on the oie hunl delicate and cleslruclible, newly-hatched larvae accumulated both fr'om the on the other MiraeulotlsHIv lough and seawater. After being moved to uncontaminated resilient, and capable ofstriking Nack in seawater, the yolk-sac larvae showed no apparent unexp)ected ivais. eCliminatioii of the more lipophilic compound, the -Racha/ C!(arson, 1962 PCB, although there was a clear elimination of some benzo(a)pyrene (Solbakken et al., 1984). PCB levels in winter flounder liver were signifi- Bioaccumulation of contaminants does not nec-cantly correlated with body fat content, although essarily imply that the contaminants are having an fat content itself did not correlate with the contami- adverse effect on the organism. Nevertheless, there nation gradient (Reid et al., 1982). Haddock and are imumerous examples to show that both laboratory cod from aNorwegian flord had clearance rates for and field exposures to various metals, pesticides, DDI and PCB that were slower than those found PC.Bs, PAiHs and other petroleum hydrocarbons do for wolffish, sea scorpion, a European wrasse, and in fact elicit toxicity. In some cases, toxicity has lemon sole. While demonstrating interspecies dif- also been linked to elevated tissue bioburdens of ferences in contaminant metabolism, the slower'
- these contaminants (Table 4.3).
clearance of liver DDT in cod as compared to the other species examined may also be attributed to the substantially higher fat content of cod liver METAL S (Skhre et al., 1985). Each of the thirteen metals listed as EPA priority Fat stores are closely tied to the fish's seasonal pollutants (Table 4.1 ) varies in toxicological potency cycle of reproduction. PCB levels in female cod and mode of action. This differential toxicity is best also varied seasonally (levels in Sept./Oct. greater illustrated with data on winter flounder. The order than corresponding levels in June and Nov./Dec.),. of sublethal metal toxicity (2-5 mo, 10 pg/L metal) although no such effect was seen in male cod for adult winter flounder was CdCI?> HgCl> (Marthinsen et al., 1991). Similarly, work in Long AgNO3 (Calabrese et al., 1977). Metal exposure Island Sound showed concentrations of PCB in either elevated (Hg) or depressed (Cd) gill respira-winter flounder gonads to be highest (0.73 i.tg/g tion. Mercury, but not cadmium or silver, induced wet wt) in the months just before spawning, as
.statistically significant hematological responses.
compared to levels in other months (0.056-0.36 pg/tg;
r()iA..Y~flF! 49 Cadmi nut, hOWevCe, was the most potent inducer of more susceptible to toxicity than either adults or transcription of the oene for metallothionein (('han membrane-protected embryos. LC., concentrations et al., 1989 ,lessc ni-Eller and Crivello, 1998). the (the concentration of a metal that is needed to kill principal function of which appears to be the main- 50"% of a test population) are typically higher for tenance of homreostasis for the essential trace metals adult fish and non-hatched embryos (U.S. EPA. zinc and copper (Roesijadi and Robinson. 1995). 2000). Nevertheless. high concentrations of metals Exposnre ol w'inter flounder to low concentrations maiy effect hatching success. Concentrations ofSil-of Cd indluced several signilficant metabolic ver above 54 ti L in aflow-through bioassay (18 responses: . I) the ability of magnesium to promote d, 54 - 386 tu/L) produced greatly reduced percent enzyme-substrate binding in enzymes such as viable hatch in waintei Hlounder embryos aiid caused glucose-6-phosphate dehydrogenase (G6PDH) was larval mortality (K.lein-MacPhee et al.. 1984). impaired; (2) G6PDH. wasinduced in gonad, heart, Embryos exposed to 180 and 386 j~tg/L hatched and skeletal muscle; (3)) kidney tissue in particular earlier than those exposed to lower concentrations. showed an increased expenditure of energy (for and many had physical abnormalities. Mean total synthesis of enzymes to maintain homeostasis length and mean yolk-sac volume of hatched larvae under subletlal cadmin iui stress) and a loss of sei- tIro the 386 uoiL silver exposure were significantly sitivity to normal metabolic control (maCnesiuim s smaller than the lower Ag exposures. In contrast to enhancementof enzVyle-stibstrate affinities); and Klein-MacPhee's experiments, the percent viable (4) in the liver, glycolysis and shunt activity hatch of winter flounder embryos was not effected increased (Gould. 1977). These same phenomena by silver (0- 180 ui/L) but was decreased by cad-weie observed in mercury-exposed Hlounder but to miulml (1,000 jtg/L); addition of silver, however, a lesser extent, whereas silver-exposed flounder decreased the toxic elfect of cadmium on the viable showed very little effect (Calabrese et al.. 1975, hatch response (Voyer et al., 1982). 1977). Metals initiate a number of additional toxico-logical effects in fish. Acute exposures to high OiL metal concentrations as well as chronic exposures Much of the toxicological research on commer-to much lower concentrations can elicit morpholog- cial fish species was spurred on by concerns over ical changes (e.g. lesions in winter flounder and oil spills. Petroleum pollution has been shown to haddock olfactory organs followingi 18 1hexposure correlate with a variety of adverse behavioral, to 500 ,ug/L Cu, Bodam mer, 1981; abnormal physiological and morphological parameters. Cod swelling in windowpane flounder gill tissue follow- avoided'concentrations of total petroleum hydro-ing 2 mo exposure to 10 ýtg/L Hg, Pereira, 1988). carbons down to 50 ttg/L, either in solution or as Important metabolic enzymes can be inhibited (e.g. an emulsion (Bohle, 1983.). In the laboratory, detec-winter flounder Na. K-ATPase inhibition by Hg, tion thresholds for behavioral changes (snapping, organic Hg and organic As, Musch et al., 1990). darting, coughing, and restless swimming activity) Various metals can interfere with ion transport in cod upon sudden exposure to oil compounds across membranes (Hg and niethymercury can were observed at concentrations as low as 0.1-0.4 inhibit Na transport, Renfro et al., 1974; .tg/L (Hellstrom and Doving, 1983). Various fish Farmnfanrmaian et al., 198 1; Dawson, 1990; 1H1g, species, chronically exposed to the water-soluble organic Flg and organic As can inhibit K transport, fraction (WSF) of crude petroleum or to oiled sedi-Venglarik and Dawson, 1986; Musch et al., 1990). ments, exhibited reduced growth, food consumption Methhlinercurv can increase the energy expenditure and body condition, depletion of energy stores, for transepithelial electrolyte transport in winter reduced gatmetogenesis and spermiation (release of flounder gill and intestinal tissue (Schinidt-Neilson mature sperm r-om the Sertoli cells), liver hyper-et al., 1977). Ionic Hg, organic Hg and organic As trophy, splenic atrophy, impaired imImune response., diminish the absorption of some amino acids in and morphological abnormalities such as gill flounder species (e.g. leucine, Farmanfarmaian et hyperplasia, filament fusion,. increased skin pig-al., 1981; tyrosine, Musch et al., 1990). mentation, hepatic granulation, increased gall-blad-In general, early life stages of fish appear to be der size, increased numbers of mucus-producing
Rw z>!ý ~m-I 111) epithel ial cells, capillary dilation, delayed sper- sites, whereas the liver did not (P'ayne et al., 1984). natogenesis, and an increase of nielanomacrophage Nevertheless, the same research team, using oiled centers in the spleen and kidney (Khan et al., 1981: sediments under a control led laboratory exposure, Dey ct al., 1983: 131urton et al.. 1984. Khan and later found that biomarkers indicating exposure to Kiceniuk, 1984; Kiceniuk and Khan, 1987: Payne oil were (in order of decreacsing sensitivity): liver and F'ancev. 1989). Chronic exposure of cod to MFO activity, liver condition index (liver wt/total crude oils., it was concluded, results in severely dis- body wt), kidney MFO activity. spleen condition abling lesions and reproductive impairment. Yet. index, and muscle protein and water content. Liver mortality due to oil spills among large free-swim- lipid and glucose levels and condition indices for nig ic nsh has hardly ever been recorded, Bohle uLt,kidnev. testis and whole fish were not affected (1983) concluded, because they can move away at anyxexposure level (Payne et al., 1988). fron containimated areas.. Induction of these .enzmnes in the liver typically Exposure to petroleum hydrocarbons typically precedes liver damage, although both liver hyper-induces the synthesis of sevet al cellular enzymes, trophy and MFO induction may occur simultane-the Mixed Function Oxidase (MFO) enzymes, that. ouslV. The level of exposure to oil at which liver mnCtabolize Soi e ol the1.se conpounds. The most hypertrophy continues to increase while\1IF()" studied of these MFO enzymes are the group of activity begins to decrease has been called the Cvtochrome P-450 enzynmes (e.g. aryIhydrocarbon "*point of crossover." It may represent the point at hydrolase (AHIH), ethoxyresorufin 0-deethylase which the detoxication mechanism is overwhelmed (EROD)). Several genetic isoforms of P-450 (Hutt, 1985"). enzym es have been identiflied in western Atlantic As indiclaed eatrlier, early life stages are often fish (Wall and Crivello, 1998; Nelson, 2000). more susceptible to contaminants than adults. While P-450 enzymes are constituitive, elevated Yellowtail flounder eggs collected during the first levels are biosynthesized "on demand" to catalyze three days following a gasoline spill near Falmouth the breakdown of many organic pollu.tants. Cod MA had an 81% mortality rate (13 of 16 eggs died; and haddock captured close to oil platforms Griswold, 1981). Many of the cod and pollock eggs showed significantly higher levels of Al-Il in their collected shortly after the Argo Merchant oil spill livers than did fish caught in areas well away from (during the pollock spawning season) had oil oil activity (Davies et al., 1984). These data were adhering to the outer membrane and showed evi-the first to indicate that oil in sediments around oil dlence of cytological abnormality of the embryo's platforms may be bioavailable to fish in the area, cells and nuclear configurations indicative of cell probably via the food chain. Chronic exposure to death coupled with division arrest (Longwell, petroleum WSF' in the laboratory produced an oil- 1977). In the laboratory, cod eggs and larvae inducible MFO activity that was elevated 4 times exposed to WSFs, suspensions of crude oil, cuts higher in the liver and 3 times higher in the gills (oil distillation fr'actions), and some low-boiling than in control fish (4 mo, 300-600 bIg/L; Payne aromatics exhibited increased mortality, reduced and Fancev. 1982). Winter flounder, exposed for 4 growth, and several morphological abnormalities: mo to oil-contaminated sediment that was weath- delay and ir:egtlarities in cleavage and develop-ered for a year had levels of hepatic Cytochrome P- ment, poor differentiation of the head region, mal-450 that were seven times greater than unexposed formed upper jaw, protruding eye lenses, abnormally controls; fish exposed to freshly oiled sediment (I bent notochord, and various levels of inhibition of liter oil in 45 kg sand) exhibited a thirteen-fold P- hatching and assimilation of yolk (Lonning, 1977). 450 induction rate (Payne and Fancey, 1982). Both survival and feeding were further impaired However, examination of winter flounder collected following photodegradation of crude oil compo-firom the site of an oil spill in 1984, and from a ref- nents (Solberg et al., 1982a). Kfihnhold (1974) erence site showed that reliance on the measure- found through laboratory exposures that cod eggs ment of liver MFO parameters alone could lead to were most sensitive to crude oil during the first few false negatives in biological monitoring programs. hours post-fertilization. Oil retarded development, The kidney provided statistical differences in ele- delayed or prevented hatch, and induced significant ments of the MFO system between control and oil mortality by 10 h post-exposure. Those larvae that
pm I ;,.Ir I 51ft~r; did hatch showed a high level of abnormal devel- feeding ability within 24 h of transner to clean opment or abnormal swininning movements, and water (Tilseth et al., 1984). Cod larvae less than 20 died within a tew days. mm are the size most hatlried by exposure to a 50 + Further work with early life stages confirmed 20 utg/L W SF of oil (Foyn and Serigstad, 1988). the variety of adverse morphological changes. The effect of a I- to 2-h exposure of cod egos to Developing cod embryos exposed to Ihexane the WSF is not acute but instead long-term, leading extracts of sCa-suriface linicrolayer from 5 marinas to starvation of the cod larvae. [lhere is no recovery located in the North and Baltic Seas sho\wed signif- from tile effects of exposure to the oil WSF when icant embryo mortality as well as severe deforni- cod eggs or larvae are placed in clean seawater ties in live hatched lartae at two of the sites (f'loyn and erigstad, 1988). (Kocan et al., 1987). Other Studies noted a signifi- Goksoyr et al. ( 1991 ) exposed cod eggs, larvae cant decrease in growth rate (Tilseth et al., 1981) and juvenile cod to a WSF of-North Sea crude oil and a toxicant concentration-dependent reduction (1-6 wk., 40-300 ttg/L_) and examined them for in feeding (Solberg et al.. !982a.b.c). Such oil- induction of Cytochrome P-450 enzymes. Althouglh induced disturbance of physiological and behavioral the exposure began durino the egg stage, induction patterns would redticeleeding ctpalbi litV at thle onset response was delayed until aftt hatchittg. I he P-of feeding, with consequent high mortality in the 450 induction response wvas dose-dcpendent, and field. Morphological disturbances that result in the recovery in clean water resulted in normalization of ultimate death of the larvae, may in turn lead to P-450 levels (Goksoyr et al., 1991). 1mlmuno-serious effects on the fish population in the polluted chemical response (i.e. induction of the specific area. Cytochronie P-450 I C as deternined by intinuto-Exposure of cod eggs to the water-soluble frac- chemistry) in the liver of juvenile cod and in tion (WSF) of crude oils (50-150 ttg/L) did not, hlonlogenates of whole larvae was dose-dependent. however, significantlv affect surface membrane Larvae and juveniles that were allowed to recover permeability, nor was osmnoregulatory ability of the in clean seawater showed a P-450 decline toward embryo affected by these ecologically realicstic con- control levels within a few days (Goksoyr et al., centrations.(Mangor-Jenseni and Fyhn, 1985). The 1988). Laboratory exposure of juvenile cod to WSF of North Sea crude oil (50 pgiL ) had no crude oil and oil dispersant produced significant effect on oxygen uptake of the ,._os. vet stronoly' changes in physiological parameters (heart rate, suppressed oxygen consumption by cod larvae at respiration, gill ventilation rate and amplitude) that the time of final yolk absorption (5-7 d post-hatch), did lot occur until pollutant concentrations were when the larvae begin to feed (Serigstad and Adoff, close to lethal levels (Johnstone and Hawkins, 1980). 1985). Crude oil extracts can also affect the ener- Because oil dispersants are often toxic to early getic processes of cod eggs and larvae in addition life stages of fish, they are often studied together to causing structural and developmental damage. with oil as contaminants. The higher the aromatic One such .extract (8 mng/L total dissolved hy'drocar- content of an oil dispersant, the greater its toxicity bons and dispersed oil) had no significant effect to unfed haddock larvae (Wilson, 1977), Larvae Upon oxygen uptake in late-stage cod embryos and were more susceptible to a dispersarit's toxic larvae with functional yolk sacs. Early embryos effects immediately subsequent to first feeding. and starved larvae however showed reduced Oxvygenl Numerous dispersants have been developed, how-consumption when placed in the extract, and the ever, that are 2 to 3 orders of magnitude less toxic starved larvae became narcotized (Davenport et al., than the kerosene-based dispersants available earlier. 1979). A number of behavioral effects were also docu-miented. Larval cod exposed to sublethal amounts PA H s of the WSF of crude oil exhibited reduced growvth, One component of petroleum hydrocarbons, lower specific weight (neutral buoyancy), reduced the PAHs, has received additional attention because feeding ability and swimming speed, and a serious of its known ability to induce various MFO disturbance of the swimming pattern. Larvae enzymes (Solbakken et al., 1980; Foureman et al, exposed to 4. I mg/L or higher did not recover their 1983; Stegeman et al., 1987). In male and female
5 -) C! {: winter flounder collected over a 2-yr period fromn a irom environmental chemicaIs takel tiP by tile fish. relatively non-polluted area in Nova Scotia waters, but are not sufficient to identitfv the causal agent. sCeasonal variation (about ten told) in hydrocarbon- The breakdown products of several PAI Is are inducible P-450 activity was less than that caused often more toxic than the parent Coiiipounds. PAIH by environmentally realistic levels of pollutants metabolites have been detected in adult cod (Addison et al., 1985 Edwards et al.: 1988). Liver (Davies et al., 1984). In parallel field and tank P-450 activity in this species, therefore. might be studies, fish exposed to nominal levels (50 ue/L) of used to indicate environniental contamination. benzo(a I C)pyrene in the wvter showed liver A HH However. inducible P-450 activity in American values 5-40 tines that of the control. These plaice livers was low and did not vary signi'ficantly inetabolites :an be accumulated by predators vid over a presumed organic pollution gradient in New their prey (McElroy and Sisson, 1989). Risk Brunswick (Addison et al., 1991). The inference assessilnlts for predators IIIust therefbore take into was that organic pollution was low anrd uniformly account metabolites produced by prey as well as distributed in this estuarine-river system. Si ilarlvy the parent compound. hepatic P-450 IA activity was highly variable in n1u lvichogs (P macithi/ns hi~; uc/ l,) ui sampled from salt marshes in Massachusetts, and did not correlate with gradients from relatively clean to Chlorinated pesticides are known to elicit neu-highly contaminated (Moore et al., 1995). rological effects on organisns, primarily by inter-Nonetheless, liver toxicity is thought to be fIering with acetylIcholiine/acelylcholinesterase func-linked to Cytochroine P-450 activity. High levels of tiol. Laiboratory exposuIr of 3-yr old cod to low PAfs have been found in Boston Harbor sediments levels of DDT produced tachycardia (rapid heart-(Malins et al., 1985) and are thought to induce win- beat), a decrease in the fiequency of respiration, ter flounder liver toxicity. Various pathologies seen and disruption of the central nervous system's reg-in liver tissue excised frlom winter flounder collect- ulation of miLuscle contraction in stomach and gut. ed friom Boston Harbor were attributed to PAI I- Upon removal of the toxicant, however, normal induced g1enetic mutations leading to tumor forma- functions returned after 6-7 d (Shparkovskii, 1982). tion (McMahon et al., 1988a.b; Figure 4.1). From Other modes of toxicity are also possible, although the late 1980s to tile present, however, tumor g'enlerally -it high or1aoch lorie concentrations. prevalence in winter flounder from Boston Harbor For example, chlordane inlhigh doses induced (Deer.Island Flats) has decreased from a high severe liver damage, and at subacute doses pro-around 12% to 0% , even though PAI-I concentra- cduced macrophage aggregation and a persistence of tions in the sediments have not changed signifi- necrogenic effects in the liver (Moore, 1991). cantly (Mitchell et al., 1998). Thus, PAH may not Hydropic vacuolation, regarded as a precursor of be the causative agent for inducing hepatic tumors liver neoplasia, appears to be correlated with envi-in winter flounder. Experimental work implied that rolniental levels of chlorinated hydrocarbons the MFO system is involved in tumor formation. (Mitchell et al:, 1998). Cytochrorne P-450 enzymes (EROD and Al-IlH) Cod larvae are far more sensitive to the chlori-were induced in winter flouLnder in the laboratory nated pesticide DDT and its breakdown product by injection of the PAH N-naphthoflavone DDE than are the Iiellbrane-protected emibryos. (Stegeman et al., 1987). Immunohistochemical Percentages of malformed and dead emlbryos and treatment of liver tissue firom winter fIounder fur- larvae increased with increasing concentrations of ther revealed evidence of liver histopathology DDT, which was overall more toxic than DDE (Smolowitz et al., 1989). Winter flounder fed chlor- (Dethlefsen, 1976). Chlorinated pesticides also dane- and benzo(a)pyrene-contaminated food exhibit toxicities to winter flounder eggs and adults. developed proliferative lesions similar to cholan- Abnornial gastrulation and a high incidence (39%) giocellular carcinomas in winter flounder taken of vertebral deformities were seen in developing from Deer Island Flats in Boston Harbor (Moore, eggs from adult winter flounder experimentally 1991). These studies show that P-450 could play a exposed to very low, sublethal concentrations of role in the production of a mutagenic metabolite DDT(I-2 lug!L; Smith and Cole, 1973; Figure 4.1).
53 N&~t N 4 Vt
- NAN Stir NA
/ N, A-I 4 N
I, ~Ž~' D V A-2 2 ~ NAt
>3/4A .*AFA>*?< ~
c< N h'-, A A
'N
* , <S
<A/A ~tt~L~ A E
B c( Figure 4. 1. Some examples of abnormalities in winter founder, Pseudopleuronec'tesamericcanns,associated with con-taminated environments. Similar abnormalities have been reported for other marine fish species. A. Normal vertebral column (A. I) and fusion and compression of groups of individual vertebrae (A.2) as described in Ziskowski et al. (1987); B. Finrot disease (fin erosion) as described in Ziskowski et al. (1987); C. Abnormal skeletal development in larval flounder as described in Nelson et al. (1991); D. Gill bifurcations associated with contaminated sediments as described in Pereira (1988) and Pereira et al. (1992); E. Red blood cell micronucleii (arrow) as described in Hughes and Herbert (1991); and F. Liver tumors (neoplasia) as described in Murchelano and Wolke (1991).
-54 No such elfects were seen in eggs from flounder EROD activity and immunologically quantitied P-similarly exposed to dieldrin, nor were residues of 45()0E concentrations, apparently due to a hormonal either insecticide detected in the milt of exposed or effect acting primarily to suppress induction of P-control male winter flounder. 450E, the activation catalyst for EROD (F0rlin and Hansson, 1982).
Different PCB mixtures produce different PCBs effects in marine fish. Feedina Aroclor 1254 to ToxicitV has been attributed to PCB exposu re iuvenile cod to produce liver concentrations of ca. in both the. field and the laboratory. Cod having 900 pg/g wet wt had variable effects on the UIlcus syndrome (epidermal lesions thought to be Cytochrome P-450 enzyme system. The P-450 due to an imbalance in corticosteroid metabolism) enzyme ethoxycoumarin o-de-ethylase (ECOD) had significantly higher PCB residue concentra- was induced 30-fold, but Aroclor 1254 had no tions in liver tissue than did cod without'the syn- effect on ethoxyresorufin o-de-ethylase (EROD) drome (Stoi;k, 1983). In heavily urbanized areas of activity. Feeding Aroclor 1016 to juvenile cod Long Island Sound having higher PCBs in the sedi- induced no increase in P-450 enzyme activity inents (New HIaven, Hempstead, Norwalk), winter (Hansen et al., 1983). flounder tended to have lower rel)roductive suc-cess, when spawned in the laboratory, than did OTHER CONTAMINANTS flounder from less urbanized sites (Nelson et al., I991) . In that same study coin pari ng several differ- Recent studies have focused on a group of ent sites in the Sound', winter flounder embryos chemicals, the "-endocrine disruptors", that interfere firom the New Haven site had the most abnormali- with fish (and by implication, human) endocrine ties and the lowest percent viable hatch. Nelson et systems when present at extremely low environ-al. (1991) also fotund that floun.der with hilh liver menital concentrations. In plasma of sexually concentrations of PCB (Boston) had small larvae. mature male winter flounder exposed to crude oil, Black et al. (1988) reported that eggs of winter for example, total concentrations of the sex hor-flounder from New Bedford Harbor (MA) were mone androgen (both free and conjugated) were significantly higher in PCB content (39.6 pbtg/g dry statistically lower than controls (Truscott et al., wt) than those [roin Fox Island (a relatively clean 1983). During early maturation of the gonads, how-area in Narragansett Bay, RI), and larvae hatched ever, oil exposure had no effect on total plasmatic from these New Bedford eggs were significantly androgens and estradiol in either female or male smaller in length and weight. There was a signifi- flounder. cant inverse relationship between PCB content of One subset of these endocrine disruptors, the the eggs and length or weight at hatch. "environmental hormones", include chemicals that PCB concentrations in winter flounder liver may mimic the function of the sex hormones sampled froom 3 southern New England areas with androgen and estrogen. A broad range of chemicals differing degrees of PCB and PA\H contamination are known to be estrogenic, including several PCB (New Bedford Harbor, NBH; Gaspee Point, GP; congeners, dieldrin. DDT, phthalates, and alkylphe-and Fox Island. Fl) reflected the varying degrees of nols, as well as synthetic steroids (estradiol, PCB-contaminated liver, with NBH> GP> Fl. Liver ethynylestradiol, etc.). While their individual estro-EROD activity was the same at all three sites, but genic potencies differ, all are potentially present in P-450 concentration (measured immunologically sewage discharges. Alarm over these chemicals with an antibody against vertebrate P-450 .1A l) was raised in the early 1990s when excessively was significantly higher in the NBI-H fish (Elskus et high concentrations of vitellogenin were measured al., 1989). The data suggest that P-450's catalytic in male rainbow trout caged in the effluent of activity (for EROD) is being competitively inhibit- sewage treatment plants along English rivers ed at NBH, (even though P-450 levels are elevated) (Harries et al., 1996, 1997). Ordinarily, vitel-possibly by some congeners of PCB (Gooch et al., logenin, a yolk precursor protein, is only produced 1988; Elskus et al., 1989). In contrast, sexually in the livers of mature female fish, when signaled mature female winter flounder showed lowered by estradiol in the blood. Recent studies have
shown that this phhenomenon is not restricted to range of contamni nant mixtures in fish (Broderitis et freshwater fish. Male flounder. Platichih~vsfilesus, al., 1995; Logan and Wilson, 1995: Pape-collected fi om live EngI'llish estuaries and froii the Lindstrom and Lydy. 1997). Threshold concentra-southern North Sea also displayed elevated vitel- tions of additive toxic metal mixtures need not be logenin levels (L.e et al.. 1999; Allen et al.. 1999). high to produce toxic effects (e.g. cod exposed to Investigations are now underwvay to look lor envi- Cn plus ZIi Swedmark and Granmo. 1981). ronmental hor'monles in Chesapeake Bay., Long Limited water circulation in Cstuarine and coastal Island Sound and Boston Harbor. waters would be most likely to produce examples of such toxic effects in young fish that use these ntursery areas. MIXED CONTAMJINANTS A drawback to the TEF approach is that it only Fish are never exposed to single contaminants considers additive responses. A number of studies on fish species have demonstrated the importance in nature, but to complex mixtures of organic and of antagonistic and synergistic interactions of con-inorganic substances of varying potency. taminants. For example. several lipophilic contami-Comparisons of fish sampled from relatively clean iants interact synerOistical iv to modulate the levels and polluted sites have documented a variely oF of two important detoxification components in the adverse impacts, including slower reaction times. liver of English sole (PlIeuronecles i'etulus; skeletal abnormalities, higher prevalences of Nishimoto et al., 1995). Different metals often degenerating hepatic parenchymal cells, and compete for the same binding sites within cells. decreases in such biochemical parameters as hepat-ic and pectoral fin ascorbic acid concentrations, Because of this, metals such as Ca can protect hepatic glycogen and lipid levels, plasma glucose against Cd toxicity, as shown in the mumMichog, Funduluts heleroclitus (Gill and Epple, 1992). concentrations, brain serotonin and norepinephrine The interactions between metals and organic concentrations and the concentration ratio of vari-otis free amino acids in muscle tissue (Olofsson contaminants have received particular attention. and Lindhal, 1979; Despres-Patanjo et al., 1982; Winter flounder exposed to a PCB (24 h, I mg/L) in the presence of added cadmium (200 ug/L), Carr et al., 1991). Planktonic stages have been accunmtlated significantly less PCB in their liver shown to exhibit cytotoxicity and decreased sur-and gills than did those dosed with PCB alone vival rates. mitotic abnor'malities, chromosome (Carr and Neff, 1988). Additional studies have damage, slower developmental rates, cell necrosis, shown that cadmium arid benzo(a)pyrene interact and smaller yolk reserves (Perry et al., 1991: to alter the biotransformation pathways in the liver Gronlund et al.. 1991: Buckley et al., 1991, Nelson et al., 1991; Longwell et al., 1992). A variety of of the munilnclihogs (van der Hurl et al., 1998). other toxicological responses have been demon- Zinc and phenanthrene interact to effect the toxicity in sheepshead minnows, Cvprinodon variegatus strated in fish sampled from heavily polluted liar-(Moreau et al., 1999). It is therefore clear that bors (e.g. Halifax, Tay et al.., 199 1; Salem and much more work needs to be done in order to bet-Boston, Zdanowicz et al., 1986, Moore et al, 1995, ter understand the ilipacts of contaminant mixtures Wall et al.. 1998; New Haven CT, Wolke et al., on fish populations. 1985. Gronlund et al., 1991; various harbors in the Northeast, Johnson et al.. 1992), and fi-om sites adjacent to sewage effluents (Weis et al., 1992). THE CBR APPROACit However, it is generally not possible to attribute the adverse effect to a specific contaminant. The additivity of some contaminants was rec-ognized early on for the various PCB, congeners, As bioaccumulation iste/n//obr predic'ting and led to the development of Toxic Equivalency impacts? The answer is, infact, thiree-Factors (TEF) that are specific for fish (Newsted et fiold: 'no', )'es' and 'maybe'. No, it vwill al., 1995). Additional models are now being devel- not be useJul for some containinants oped and tested to deal with the effects of a broader either now or in the fidure. Yes, it
56 a!)peas to be useid nou;ii .one con- accumulated in blood and gill tissues ill a Close-laIninants.... Lid a mae in thei ItInce it dependent manner, yet there was no statistically wJ/I hl l c', .i so/ l . ha/ /)1/ t/i1 l coa - signiticant accui'nul tioil of( d under the experi-ta/ tina/tl7S. anctlntlot)" all otilisttas. mental conditions employed. Ihe CBR approach
-le' ',ti I:\l.0C~;m.1997 has only been directly tested for fish in a few labo-ratory studies (e.g. Niimi and Kissoon, 1994).
Nevertheless, it is clear that this approach holds It is important to point Outt that nuoSt of the much promise Imr assessing the potential of adverse studies of toxicological efflects of containinants responses to pollutants in field collected fish. reported in the literature have related containinant Additional work will furlher refine and validate the exposure (i.e. concentrations-in the surrounding approach in the years to come. water) with the toxicological eff'ect. This is typical-ly the approach that has been taken in toxicity test-POLLUTION-IANKEI) [ISTOPATIIOLOGY AND ing. where lD01 s are computed for exposure con-centrations. M cCarty and Mackay (1993) have recently advocated correlating toxicity with the concentration of a contaminant that accumulates in the tissues of an orgaanism rather than the concen- .lhhcic, p*)lihitio/ has b'en implicaled in tration of contaminant in the surrounding water. the high prevalence of lesions in eastern This is referred to as the "Critical Body Residue ,Norlh AtIlantic hollom fish, Conclusive (013R)" approach to aissessing toxicltv. Sinlce toxic- Clause andd cf2fc'l 1clalionsh/is /r1cnain toj ity should more directly correlate with the concen- be established. tration of a toxicant at the site of action in the cells -R.A. stwJrehelano, L. Despres-Paltanjo or tissues rather tham the exposure concentration, 01d0. Ziskowski. 1986 this CBR. approach should allow us to better assess toxicological effects by pinpointing a potential causative agent among a suite of multiple exposed Fish that are collected from contaminated sites contaminants, and should allow us to predict sub- often exhibit a broad range L" of
/
- histopathologies and lethal toxicity from existing bioburden monitoring diseases, in addition to the lesions and morphologi-data. cal effects mentioned earlier. Four examples are To support this CBR approach, existing pub- presented below, as well as a discussion of the lished data have been reexamined to identify those interactions between parasites and pollution effects.
instances where body burdens were measured Investigators have often pointed out the apparent along with toxicological responses (Jarvinen and correlation between pollution and these adverse Ankley, 1998). For example, cod fr'om the Baltic effects, although causation has only been suggested. Sea that were found to have elevated levels of cad- In only a few cases have laboratory studies been mium in liver and kidney tissue also had externally done to investigate possible causative factors. visible skeletal deformities (coinpressiols of the A variety of liver pathologies have been identi-spine and deformities of the jaw; Lang and fied in cod, yellowtail and winter flounder collect-Dethlefsen, 1987; e.g. Figure 4. I). For the com- ed from the field (Despres-Patanjo et al., 1982; inercially important Northeast species, less than 30 Freeman et al., 198 Ia, b, 1983; Murchelano et al., such studies have been identified (Table 4.3). 1986; Murchelano and Wolke. 1991; Turgeon and While a direct relationship between contaminant O'Connor, 1991). Of 100 live cod collected from body burdens and the degree ofltoxicity would be Halifax Harbor, 73 had histopathological lesions in expected, establishing this relationship is often elu- their livers (Freeman et al., 1983). Histopathological sive, particularly when studies were not specifically analysis of livers from winter flounder revealed designed as CBR investigations: As described one liver neoplasm in a fish friom the western end previously, both Cd and Hg induced adverse effects of Long Island Sound and none in fish from the in long-term laboratory studies on winter flounder eastern end of that west-to-east pollution gradient (Calabrese et al., 1975, 1977). Hg was readily (Turgeon and O'Connor, 1991). High prevalences
HIOIMŽTi-AN F I 1F: of liver lesions, blood cell abnormalities, liver Block Island Sound, and twice those iound iii DNA damage, liver neoplasms, concentrations of Georoes Bank and Long Island Sound flounder organic chemicals and. trace. metals., and high le\Cls (I-InOlies and I lebert, 9 1.). Inshore New Jersey of PCBs in gonads in winter flounder from New and Viirginia fish had significantly higher MN fre-
-laven have been found (GreitLand \Veizloffl 197 Iucies than thosne !rn, the GullFof Maine and Greig and Sennefelder. 1987: Gronlund et al., Block Island Sound. Ihere were higher frequencies 1991).1'Fattv change." a degenerative process in of MN in flounder ftiom Hempstead and Shoreham.
the liver, has been attributed to exposure to organic N.Y. as compared to most other sites in the Sound. contaminants or trace metals (Freeman et al., Erythrocyte MN were consisteltly higher (Hughes 198 1ab). Considered with other pathological sig- and Hebert. 199 1) in flounder from Ihe more highly nals, exceptional accumulation of liver lipid and contaminated stations examined, New York Bight increases in liver size have been linked to body Apex and Hempstead, which are contaminated with burdens of PCB, pesticides, and other organic toxi- metals arid PAH (Carmody et al., 1973; MacLeod cants (Sherwood, 1982; Freeman et al., 1983'). et al., 1981 ; U.S. EPA. 1984). Winter flounder col-Pathological changes in liver seem to become pro- lected from the coastal mid-Atlantic had statistically gir.ssihcv), greater with inicreasi ng size 0f t[ie fish higher evcryiiocvyc nautation feclucncies than those (Freeman et al.,, 1983; Murchelaimo and \Volke. 1991). froom more offshore waters (Longwell et al.. 1983). In a Boston Harbor field study, for example. Winter and wvindowpane flounder from western tumors were not found in Fish smaller than 32 cm Long Island Sound had significantly higher fre-in length (Murchelano and Wolke. 1991). The same quencies of micronticlei than those firom the New study revealed a pattern in liver pataoloy: pro- York Bight, wiith ilh froin both these areas having gression from necrotic lesions to neoplasia (Figure signiticantly higher mutation firequencies than
- 4. 1), and suggested pollutants as the likely inducers flounder sampled elsewhere (Longwell et al.,
of the lesions (Murchelano and Wolke 199 ). 1983). The higher incidences suggest a link with Investigators have attempted to induce liver environmental pollution. tumors in the laboratory. but with limited success. Several diseases also appear to correlate with Payne and Fancey ( 1989) reported that liker hyper- pollution. A high incidence of fiu-rot disease was trophy in winter flounder increased with increasing observed in windowpane, winter, and yellowtail oil exposure for 4 months to varying concentrations flounders exposed to materials Cdlimped in the New of crude oil in sediments although the number of York Bight (O'Connor, 1976; e.g. Figure 4. 1), win-melanomacrophage centers in livers was reduced. ter flounder having the highest incidence. The Boston Harbor sediment extract, injected peri- highest rate of fin-rot in yellowtail and winter toneally, was acutely toxic to Winter flounder; flounder was seen in fish collected from the inner perivascular edema was observed after 10 d in stir- New York Bight when compared to either offshore vivors (Moore, 1991). Gardner and Yevich (1988) waters of the outer New York Bight or inshore reported that fish exposed for 90-120 d to sediment within Massachusetts Bay (Ziskowski et al., 1987). fi'om Black Rock Harbor (Bridgeport CT) devel- PCB concentrations in muscle, liver and brain tis-oped neoplastic or proliferative lesions in the kid- sues were higher in winter flounder with. fin-rot ney, olfactory and lateral line sensory tissues, gas- frorn contamiinated sites (primarily winter flounder) tro-intestinal tract, and buccal (cheek) epithelium than in fish from reference sites (Sherwood, 1982). but not in the liver; cytopathology and cell necrosis The erosion pattern of the fins arid the association were also detected in the pituitary. In the field, win- of higher prevalences of fin erosion with greater ter flounder collected from Black Rock Harbor and degrees of sediment contamination suggest that fin-New Bedford Harbor (MA) had similar lesions. sediment contact in an area where toxic contami-A second well-studied example of histopatho- nants have accumulated on the bottom is an impor-logical impact is the increase in the incidence of tant factor in development of the disease. small inclusions (micronuclei, MN) in fish red Lymphocytosis (elevated mean blood lympho-blood cells (Figure 4.1). MN were elevated sixfold cyte counts) is a second example of a potentially in flounder from the New York Bight Apex as com- pollution-related disease. High lymphocyte counts pared to fish friom the inshore Gulf of Maine and in winter flounder were correlated with liver
58 1'[I-t i i I necrosis and suspected levels ofsediment chemical POIui.rI.AIO l() EI I: IK-CTS contamination; winter flounder collected f'rom As described above. there is ample evidence to Boston HIarbor had higher nLutimbers of in mature show that commercially important species bioaccu-erythrocytes than 'did those fiom less urbanized muulate~contam i nants and exhibit toxicological envirotnments (Daniels and Gardner, 1989). responses to contaminants that they are exposed to. Disturbances in the distribution of blood cells and These effects are generally restricted to heavily alterations in lymphocyte counts were related to polluted coastal sites. Although the impacts on neoplastic lesions and indicative of chemical con-ld ividual fsh may: be of interest to toxicologists, it tarnination in sediments. is the possible adverse impacts on fish populations The interactions between fish parasites and that are of interest to fisheries managers and envi-coontaminant impacts are complex. On the one ronmental regulators. Assessing the impact of con-hand, parasitic infections may make fish more taininants at the population level of biological orga-prone to the additional stress caused by pollution. nization has proven to be difficult, but is currently In a laboratory exposure., hemoprotozoan-infected one of the most active areas of toxicological cod reacted more sensitively to petroleum hydro-research. Two aventIes are beil*g pursin d: () rising carbons than did non-infected fish (Khan, 1987), as biomarkers: and (2) incorporating contaminant measured by poor body condition, excessive nItic us impacts into currently used population dynamic secretion by the aills, retarded gonadal develop-models. ment, and greater mortality. Similarly, juvenile and Biomarkers are biochemical, cellular, physio-adult winter flounder, some infected with the blood logical or behavioral changes that can be measured parasite 7iJvuaiwnsoinainu*inta*ensis., were exposed in tissues and provide evidence of contaminant to sediment contaminated with crude oil (6 wk, exposure and/or toxicological effects (Depledge et 2.6-3.2 rng/g) or to clean sediment (Khan, 1987)..
.uve- al., 1995). Investigators have attempted to correlate Mortality was significantly higher (89% for one or more bioinarkers with adverse impacts on niles, 49% for adults) in infected, oil-exposed fish tish populations (,Johnson et al., 1992: Stein et al.;.
than in fish with either condition alone. On the 1992; Wall et al.. 1998). For example, the induction other hand, the stress caused by pollution may and expression of Cytochriome P-450 enzymes make fish more susceptible to parasitic infection. In have been proposed as biomnarkers of organic con-the field, parasitic infections accompanied by low-tam inant exposure (Stein et al., 1992; Moore et al.. ered host resistance were found to be more preva-1995). However, in some highly polluted environ-lent in cod after chronic exposure to petroleuin ments (e.g. New Bedford Harbor). EROD activity hydrocarbons (Khan, 1990). Likewise, exposure to in winter flounder was depressed even though P-oil in the laboratory, increased the incidence of 450 gene induction was evident (Elskus et al., Thypanosoma infection and death (Khan, 1987, 1989). In another polluted locale (Newark Bay), 1991). Interestingly, parasites may in some cases be both adult and larval mummichogs failed to exhibit more susceptible to pollutants than the fish host. As P-450 induction at all, sriggesting adaptation to pol-a result, fewer parasites might be fouind in fish lution stress (Elskus et al., 1999). These examples exposed to contaminants. For example, Khan and demonstrate that biomarkers must be asssessed Kiceniuk (1983) observed that there are fewer par-carefully, and the use of a single biomarker is asites in fish exposed to oil, and suggested that the unwise. Biomarkers cannot, at present, be used to lowered parasitism might be attributed to toxicity predict impacts on future population structure. induced by water-soluble fractions of crude oil Investigators have also attempted to incorpo-and/or modification of the gut environment. The rate toxicity data into fisheries models. Initially, intensity and prevalence of parasitic infections modelers simply modified the mortality term in were more pronounced in fish exposed to water-population or recruitment models to include a com-soluble extracts than in those exposed to oil-con-ponent which they attributed to contaminant toxici-taminated sediment (Kahn and Kiceniuk, 1983). ty (Waller et al., 1971; Wallis, 1975). However. these authors provided no rigororis jistification for their contaminant-induced mortality terms. Another
'(ILTIANT59 approach applied multiple linear relression to fish as age-specilic fecundity in their analysis. Because stock data to assess the signiific.ance of hvdrological of differences in life histori, menhaden and striped factors and contaminant impacts I (e.g.
In sewage load
, seag load- bass had different capacities to sustain the same ing, dissolved oxygen concentrations, biological level of containiant-indUced mortality. Menhaden oxygen deniand) on the historical time series data were better able to tolerate pollution. The model (Summers and Rose. 1987). This modeling indicat- also showed that fish populations that have been ed that hydrological factors were far more impor- reduced in numbers by overfishing were much tant than contaminant effects for striped bass stocks more susceptible to the increased mortalitv and in the Potomac, Delaware and [ludson Rivers, reduced fecundity caused by contaminants.
whereas pollution was of more significance for Current models used by fisheries scientists to American shad. While this approach can explain predict long-term effects of exploitation on fish historical data, it is not useful for forecasting populations are quite imprecise. Adding in the (Summers and Rose, 1987). A third approach con- effects of contaminants., with its own order-of-mag-bined toxicological data with physical occano- nitude confidence in the extrapolation from acute graphic data in a risk-assessment model (Spailding toxicity test data adds another layer of uncertainty. et al., 1983. 1985) in order to assess the probable Barnthouse et al. ( 1990). for example, cautioned eftects of an oil spill on cod populations. This that the tmcertainty in estimating Iong-term effects assessment provided useful predictions: (1) most of on fish .populations using their model was generallV the hydrocarbon impact on cod would occur within greater than the range of responses to contami-the first 60 d after a spill; (2) 41.5% of the nants, since the largest source of this uncertainty is spawvned cod would be adversely aflected by oil attributed to the inherent uncertai ntv of curre lTyIN concentrations in excess of 50 ltg/L; (3) cumulative used fisheries models. Nevertheless, modeling is loss to the population would peak at 23.9% in the already providing considerable insights as to the 7th year a fter the spill: and (4) of the four seasons. interactions between contaminants and overfishing winter and spring spills would have the greatest on various fish poptilations. With further rofine-impact. ments, more holistic models should be able to Recently, investigators at Oak Ridge National examine a Multitude of forcing factors, incliding Laboratory have further advanced the methodology fishing pressure, habitat alteration, contaminant needed to incorporate toxicity data into fisheries effects and natural environmental variability. models. Two of the most critical steps in this pro-cess are the application of acute toxicity test data SNIxMMAiln' AND DISCuSSION (e.g. 96 h LC, 0 data) to predict thresholds for chronic lethal and sublethal effects, and the extrap- The highest concentrations of chemical con-olation of data from one tested species to another taminants are to be found in coastal, industrialized (Suter et al., 1987; Suter and Rosen, 1988; or heavily urbanized, and waste-disposal areas. Barnthouse et al., 1987, 1989). Not only survival, Such estuarine, coastal habitats are also the spawn-but also sublethal effects, including reductions in ing and nursery areas for many important comlmner-fecundity, can then be calculated (along with confi- cial fishes. These early life stages are most stiscep-dence limits) and applied to fisheries models. tible to toxicants, the larvae more so than the eggs, Initial work indicated that fecundity is the most as the latter have the protection of a membrane sensitive toxicological factor that needs to be incor- (Dethlefsen, 1976; Mangor-Jensen and Fyhn, 1985; porated into population models, and has a greater Foyn and Serigstad, 1988). long-term impact than reductions in survival of In some fish species, tissue concentrations of young-of-the-year fish (Stiter et al., 1987; pollutants do not necessarily reflect sediment con-Barnthouse et al., 1989). Barnthotise et al. (1990) centrations of those pollutants, whether metals or then predicted long-term changes in Gulf of organics (Greig and Wenzloff, 1977; Greig et al., Mexico menhaden and Chesapeake Bay striped 1983; MacDonald, 1991 ). The work of Marthinsen bass populations using a Leslie.Matrix-type life et al. (1991) illustrates the difference in this respect cycle model. They included natural, contaminant between fish species: they found that PCB levels in and fishing-induced age-specific mortality, as well Atlantic cod reflected a decreasing PCB pollutant
60 tcmn outh of Norway's larget river, gradtient h-o01 the lfemiale but not inl male fish (Marthinsen et al.,. whereas PCB levels in tile European flounder did 1991 ). The fattier the liver, the slower the clearance not. In wintCr fltonder. PCB body burdens were rates of these fat-soluble toxicants (Skgire et al.. accumulated from prey species in the sediments,. 1985). rather tha horom tb water column or flont sedi- Induction of Cvtoch om.e P-450 enzymes is ment contact (Connolly, 1991). associated with liver pathology in fish, a circum-Circumsiantial evidence linking disease and stance that could play a role in the production of abnormalities in various fish species to polluted cancer-producing agents from environmental chem-habitats is abundant. Proliferative lesions in icals by generating breakdown products more toxic endocrine, exocrine, respiratory, sensory. excretory than the parent compound (Sinolowitz et al., 1989). and digestive organs, alteration of plasma protein Ulcer-like lesions are considered to be a result of and ion concentrations, and interferences in hormonal imbalance caused by PCB assimilation metabolic pathways were found to be characteristic (Stork, 1983). Chronic exposure of adult cod to of species such as winter flounder that spend much crude oils produces severely disabling lesions and of their lives in some moderate to highly contarni- reproductive impairment (Khan and Kiceniuk, nated inshore areas. Liver disease was found to be 1984; Kiceni ik and Khan, 1987). absent in populations frorn uncontaminated off- In the case of metal-organic interactions, cad-shore areas. 'fihe degree of sediment-chemical con- nmium strongly depresses several detoxifting tamination and disease suggest a causal interrela- enzyme systems (George, 1989), and appears to tionship (Gardner et al.- 1989). depress PCB uptake in winter flounder (Carr and More immediately associated with p0lthiant Nefi, 1988). In contrast, the European flounder,, exposure, abnormally high levels of detoxifying P- Platichth-Vsflesus, when exposed to diesel oil 450 enzymes may signal (for a short time) expo- showed no increase in detoxifying activity"when sure to organic contaminants such as PAlIs, PCBs copper was. added to the oil (Addison and Edwards, and chlorinated pesticides (Addison and Edwards. 1988). Overloads in marine animals of even essen-1988). This response varies with sex and gonadal tial trace metals (notably copper) can interfere with maturation (Spies et al., 1988a,b; George, 1989). normal intracellular metal regulation, with conse-Similarly, induction of metal-binding proteins may quently lower fish health and often reproductive signal (tor a short time) exposure to heavy metals failure. These phenomena have been observed most (Fowler and Gould, 1988; George, 1989; Roesijadi clearly in a Gulf of Maine marine bivalve, the sea and Robinson, 1995). scallop (Gould et al., 1988; Fowler and Gould, Unlike PAHs and chlorinated pesticides; differ- 1988). ent IPCB congeners sometimes elicit conflicting From the foregoing review, it is clear that pol-effects (Hansen et al., 1983), with some congeners lutants can alter the normal health and physiology inhibiting others (Gooch et al., 1988). A hormonal of Northeast fishes. When these fish are exposed to suppression by one PCB congener of the detoxica- pollutants in the laboratory. a variety of adverse tion of another PCB. for example, has been effects have been clearly demonstrated. When fish observed in sexually mature female winter flounder are collected from contaminated environments, pol-(Forlin and 1Hansson, 1982). Black et al. (1988) lutants are measured in the tissues of these fish found a significant inverse relationship between and associated harmful physiological and biochem-PCB content of eggs and length and weight of lar- ical effects can be observed (Table 4.3). The exact vae at hatch. Goksoyr et al. (1991) have shown that contaminant responsible for the effect is often elu-in the early life stages of a fish, the normal protec- sive (Wolfe et al., 1982) because multiple pollu-tive production of enzymes that break down organ- tants are usually found in a contaminanted environ-ic toxicants for elimination is delayed until after ment and the pollutant effect may be due to the hatching. combined action (additive, synergistic or antagonis-Tissue concentrations of organic contaminants tic) of a mixture of pollutants. such as PAHs, PCBs, and pesticides are significant- The major factor that remains unclear is the ly correlated with body-fat content (Reid et al., link between these observations and the effect that 1982); PCB body burdens vary with season in pollutants might have on the population structure
"MA, I ii/XlýHC'ia 6 of the varioUS fish stocks. O)ur flailuri to make rea- Iant/Ithousc. I _W (iVW. xtr ti. A I.. I sc n and ... / uc IatIp, 19 is7. tint vesonscs . t"stI ppais t ic 'on/int-sonable quantitative estimates of these effects at the o ~~
nants, F,nviron, ~ A"l,\xieo I Che ~ ~ hn 6 S8II-824 isirn 1 to/ IOI MCIcolll.i population level may be a result of our inaIbility to BalnitOse. L.W.. G.\ . Su'icII idnAI Rosen. 19S9. lltn tirin u pop-ulation-lt vel signifiicance fiott indi idual-level el/cc/s At-n separate clearly effects of pollutant stress from cxtrapnlati n iroin fitshee science to /xceolo lit Aouatic other encVironeinettal stresses. Overl.shin', c limate -iixicolo', and itot',it H il I.e VAl. I . I. ILcooitsd (3iW" changLes, food availability, habitat alteration, and Suter it eds. Si'P 1007 Aimirican S ciet,' for -lestni and tc Materials, Philadelphia PA Ppo289-31)6 predation are amnonf the other factoi's that after fish Bartthouse. L.W.. GW. SUtcr II and A'. Rosen. 1990. Risks of toxic population levels an onbscure any possible effects Con]taminant]s l[e'po iid Ii polpulaijtwlsý h{ el c o:, [iJ'e his-tory' data uclertaints aid exploitation intensity. tviron. iToxicol of a degraded habitat (Cohen et al.. 199 1 Checot. 9: 29'71 I Sindermann. 1994). Black, D.E., D.K. Phelps and R.L . apan. 1988. rTe effect oi' inherit-Sindermann (1994) perhaps best sums up the ed contamination oniegg and larval Winter flounder. present state of' this dilemma: 'si pl;'*,tiitio cl nittyiric auto. aNI. il.'viron.
/iRes 25 45-62.
Bodammet. J.E 198 I."lie Cytopathological Effects of Copper on the 1Ofactors Organs of Larval Fishi (! seudoti)leuonecies ariericcinus anid He 1a;ttg'ixtntinusii egllJfiu ittist IC ES CM-19 SllE 4 6 ( Biol.) It seenis. withi the evidence /7rCeseiiilY Bohle, B. 1983, Avoidance o1fpetroleum hidrocarbons by the cod i(,o'adhi 'situ Irisu, 10. Dirý Ski r .ldcui. Kv, I ? cntw(t/a~/alc:, 1/h/~.1o'chIu/ 0117,1"I/hi 7 /)O[tl-IIodterius SJ.I NI.I) Kahi and M.I. Itoclund, 0995. Use of ioiit ure ovetridiing iii delter-'niini*ugi/s 1ion toxic response Lo define tile primary iode oftoxic action fbr a ac/oce. bit/ uie hick sq/liciewi qualiii- diverse itducs/tritl or"'ani che iciv sx Ini/irr
!5;91-1605.
"foxi ol Chctiy 14:
(olive dalo to iuake I)ositive sltaemensl BLIckley, L..I. A.S. Smigielski T1A IlIalavik E MI Caldaronei BR.
/2o0/I cause and e*ltela rettionsthp.s,of Bucri/s and GCC ILaurctnc 19901, Winter fl*oind er i'.~c'tt~f jici'he,,
i ti.* i.Cv'i clffclac/t a /)o11/1110iion.
/cii i.
location variabtlity in size and survival of larvae reared in the-Co . A.nolln -
-CJ Si'ndcrnanim, 1994 laboratory. Mar Icol Pro- S-i. 74: 117-124, BuIcrotoi , ., M. I1. crtct itd 0 K cIdlei. 1984. ipidermal condition ii post-spawned winter foliuicc, Ps-eu'dop/iettsonieces ameri/t 'anits fWaldbacirn), mai/aincdin helai /Hd i exposure to Der Ile further suggests that implementation of new crude ptiolctmi JI Fish Bic/i 25 503-606 poll uition mon intort ng and assessment programiis, Calabrese, A., F.I. AIicrherg. 'viA i,)Dawson and I) R. Wenzto'f 1975.
Sublethal phi siol giai- stress illduceyd.b1 cadvnium mid inercusr' critical findings from laboratory and field studies, in tie wintei flounder, Pset'iioplettro, cices antericamii, In: better and longer-term data sets, as well as the Sublethal Effects of' loxic Chemicals on Aquatic Animals.111 development of new simulation models, may pro-. Koetnan and J.J.' \V.A. Strnk eds ). isevier Scientific Publishing House Amstvrdam. Pp 15-2 1 vide answers to this vexing problem of listiinguish- :aliihresc, A., F.P TIhurbcrvg and F Giouldc i97 7,iF/ic/s if cadMicum, ing pollution effects from. overfishing, habitat mercury and silver n/inmarine animals. Nar. Fish. Res 3) : 5-Il. 9 degradation and other environmental factors, and Carson. R. 1962, Silent Sin . Houghtan Mi/lini Publ., Ioston/i. MA 368 pp allow us to assign a quantitative estimate of the Capctzzo, J.M.. A. Mvcmiroy and G. Wallace. 1)87. Fish and Shellfish impacts of pollutants upon fish stocks. Contamination ii New England Waters: an Evaluation and Review of Available Data on the Distribution of Chemical Contaminants. Report to Ccoast Alliance, Washington D.C 59 pp. plus appendices. LIfERATURE. CITEI) Carmody, D.J., I.B. Pearce and WE. Yasso. 1973. Trace metals in Addison, R.I. and AJ. Edwards. 1988. Hlepatic microsomal mono- sediments of New York Bight. Mar. Poll. Bull. 4: 132-1 I35. oxy..einase activits in llounder Plhiilcht'.s /lesus fron polluited Cari-. R.S., KI'. Hilhman and J M. Neff. 1901. Field assessment of sites i I.angesunId ord and romrn mesocosms experimentally biomarkers tor winter tocunder. Mar. Poll BuOc122 61-67 dosed with diesel oil and copper Mar. Ecol Prog. Ser 406: 51-54 Carr, RS. and I.M. Neff 1988. lInhienye oflprior exposure to xenohi-Addison, R.IF,- A. Idwards and K. Renton. 1985. lepa/ic mixed func- oties on the metabolism and distribution o' poychloriated tion oxidascs in winter tlounder (l'seutioplettiout*c es biplienyls and phenantihrene in winter flouinder, aoiericanus): Seasonal variation and response to PCB fceding. l'seudlopleurotectes americoiust Mar.IFnviron. Res. 24i 73-78. Mar Environ. Res. 17: i50-151. Chan, K.M.. W.S. Davidson, C.L. I tew & G(L. Fltcher. 1989. Addison. RT., PD. Hansen and E.C. Wright. 1991. Hepatic Mono- Molecular cloning of metallothioneiti ctDNA and analysis of rnet-oxygenase Activities in American Plaice (lippo"/ossoi/s plates- allothionein gene expression ii wintei flounder /issues. Can. J soides) from the Miramichi Esiuar\'. N.B. Can. "ech. Rep. Fish. Zool. 67: 2520-2527. Aquat Sci.. No. 1800. 18 pp; Chapman, INPI. 1997. Is bioaccuImulation useful for predicting Allen, Y., ATP. Scott, P. Matthiesen, S. iIla,,orth. J.E. Thain and S. i/pacts? Mar. Poll. Bull. 34: 282-283. Feist. 1999. Survey of estrogenic activity in United Kingdom Cohen, E., D.G. Mouitain aid R. O'Boyle. 1991 . lcocal-scale verscus estuarine and coastal waters and its efldets on gonadal develop- large-scale factors affecting recruit/tent. Can. J. Fish. Aquat. Sci ment of the Ilouider PlauicithysJlesus.Environ. Toxicol. Chem. 48: 1003-1006. 18: 1791-1800. Connolly, J.T. 1991. Application of a food chain model to polychlori-
itacd hilliclyl[ cotilao inatiol o t" [lie iob-ter nd*il mwr ic loinctel oneud -xposoii -o ci niinult rio.r -o r. NIar ll. 97, H ficod clhiams in Nesw Bedibrd Harbor. I-nviron. Sei Terlinl 25: I"tvni, LI.and 1 Serigssad. 19," . Oil I.x lortiort in N,e',t: ()ihohre 760-770.* Fields Fish ILarvae as the Critical omiponelt in tie Asscsslit DaLiels- T.G. and G.R, Gai doCr. 1989. A coIlpaiaiivc sttdV o the dll- 01 Potculial tonsetluenCes IIr thie ish RCSItuihcS. IC28 (N'I-ferential blood cell counts of winter I ounder 19885/E:! ('seydosielit/inec'es oii riitnic) collected in News England. Frceinaii. I.C . BB.tungilaio ( n}irl' c MNI NCInenix.1(1 l81a. NIand Malr lFii5 roill e.,. 2,58: 5-1 Tiuc ill ro 17i liol-Ls l' 'v i -Iictli- c lh\tri,)phthalaei lDehpi I a venport.I . S. I ,oniing a;nd I .J. Sacthre. 1979. T1he et cicts i 1 i n the Atla-tvc Cod ir(ridies tiirhita) tCl S C- 1981/liE:5 F'kofisk oil extract upon oxygen Uptake in eggs and larvae ol the Fleeimant: l IC- I.F. UIthe. G Il1.Sanualani and I.TI Garsidc 198 1b. cod. Gadus miorhiui L. Astarie. 12: 31 -'4. Contaonlnant'liver I listopathology in Canadian Atlantic Cod Oi~ases.. .M .. .1. i C I. lullin. 1h J, A- 5\ isol thes rI.p 1(i-LHv-,,i u I IU S C 'M-1iS ii l! levels of hepatic arvI hydrocarbon hydroxyl ase in iIh catight F~recman. II.C 13,San alann J.I.. ithel FT1 (;arside and PGi chisc to0and di-iUnit hr!el North Sen oil licUds NIi Eviron h,
- tta,: 1 x N,\i~is,l ,,ivtu ealmihin iulk ai';icd asusa!.-us, lr p -
14: 23-45. chlorinated lhdrocarhon lit. inshore Atlantic cod (l,6alicis Dawson, M.A. 1990. Blood chemistry of the window, pane fliounder lm/oniu). Arch. tI viron Contain. Toxicol 12: 627-632 Scophalihnus aquosts in I.o0n .Islanad 'SoLind eograFlhical sei- I-iceli'it). II.C. and .I . Uthe. 1984. iPolychiornated bip eliiyls, sonal and experimental variations. Fish. Bull. 88 429-437. organochlorine pesticides and chlorobenzenes content of livers Depledgc. MH.. !A.Aagaard and P. Gyorkos. 1995.-Assessment of from Atlanhtic cod (Gthcis morhmuna) catught off -lalithx Environ. trlace octal IOxiCitv LiSiiig iiioiccUlar, phlsiological und bchavioral 1-4 Assc ss. 4:389-3941 Ilouilitoini bioinarkers. Mar. Poltu Bull. 31. 19-27. Gardner, GR.. R.J. Prucll and L.C. Folnar. 1989. A comparison of Dcsmre.-'iiinc I. -I, .1 Ziviowsvl and 1,>.\ Nlirlxc!ain,,, F0 2. both n*i-iasiic aiid ut- o-i-nopt:sic disoiders hi , i-tci Pounder Distribtiiioii of lishllDisecaces Monitored on Stock Assessmenl ~/e, S/'.'&'ihlld iliili*{'.'ues o {lli'micTiius) I'rot'ii eimihil Icas, in Ne\, Cruises ill the WCestern North Atlantic. ICi:S 3M-l9823( uul'uiuland Nlar I .viriui Ices 28,393-3')7 l M"I i.)). Galciuter. (".1R.lurd P.1)Ycvich. 1988. CouniParative histopaitho,.gical Oethlefsen, V. 1976. The inlluence of DD'I and DDE oil the enibryo- eltLe is of chemitcally cottaitinated sediment oni marine oran-geneisis and the mortality of larvae of cod (Gadus moirhua L.) iss. NMarEnviron. Res 24: 311-316. Mccrl'orschung. 25: 115-148 George, S.G 1989. Cairn ilm efthcits on plaice liver hebobiotic and Ictll[i dcui\.vati-t n -.teCiiL:t;Iicse-respciise AC.*ulat 'l \-vo I -. IChleh :rcu, V )1.9,6 Fibh h1 the pollillte North Sea tcntm. S: i09-I_ 303-3 1IH, De-, A C.- IW. Kiceniuk. 11P Williami. R. I'.A. Khan and J.F. aI'lie Glcrhart, I 1, 1977, Pes-icicides in fish. wvildit iand estuaies- Pestic. 1983. Long-term exposure of marine fish to urnde pctrolcunt I.
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10ra 631 (innlndW.I), S.1.. cha lt. McCain, (.CCClark, ir, M1. ruttiiicni i i parasiles r xtwo secs o(iai ine Iis .. Wid'd NIyers J.E. Stcin. I) 'W [ioxn. J.T. landahl MMN Kli hanand I, l)isciaes 19:253-258 ararinasi. 1001. Multidisciplinary asscssmenw oi pollution it t*ree Khan, R.A. and .1.Kiceniuk 1084 Illistopatlhlogical ellects of'crudc sitls in Long Island SoundiC.L'Stiuarics. 14: 2-99-305, oil On ktlaillc cCodtnloinOxi chrome CxposaLe. Can O 02.
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;tll\ill' K a.doxl*'i iand w vale:r I il Klcin..NacF'icc. 0...I ,,\. Cardhli and W..1 l3erry. 1,84 Il'liicts ,Isilvcr "loxiecol. Chent 15 1993-2002 on eags and larvae of the xvinter iloundei. Airier 1rans I2isi. Soc n . ;n.nhl .nn P>N tth . 1 Nci l I, .
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66 ~iOV Vover. R.AA-.. A. Cardi.F III I I an 1982 lvCIshc and CGI. llh Viability of embrvos of the wmiter IHounder. f.Veudopl~eInrooeMes nlercicoi"is. esposed to ixntI-cs of :admnitl and silver it comtt-bmituiOn wit" sClCCtCd 1ixcdse1aiinliCS. Aqiatic loxicol. 2: 223-233. Wall. K.L. and J. Crivello. 1998. Chlorzotazonc metabolism 1w sein-
!ii cxis\cticc ol' .a LCIiloLutIder liver IIIcroFo ! I-i i% tin.ieCC CYI'21E -like isoitrm inn elcl ts. "osicol. Aprl. Ilharnacol. I Il 98-04.
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=iIcs (NIA) a3 fishillmoniots Btull. Lnviron. Contai . loxicol. 35:
222-2-271 Zdaiowicz. V.S . DIF. Gadbiis -id 'IV.W. Newman. 1986. I-cvels of Oiiac and inorganic Contamiiants in Sediments and Fish Tissues and Prevalencis o' Patliolouical Disorders in Winter Flounder from Estuaries of the Northeast United States. 1984. 1EE Oceans '86 Conference Proccedings. Washintitont. D.C.Septeatber 23-25, 1986. Pp. 578-585. Ziskowski. J J, L. Desprcs-Patanino, R.A. Murchelano, A.B. Howe. D. Ralph and S.. Atran. I Q87. Disease iII commercially valuable fish stocks in the northwest Atlantic. Mar. [toll. Bull. 18: 496-504.
iiAviTAT [.OSý I-ND D1,:iiRA'-1 %!"[ON 6-17 Chapter V The Effect of Habitat Loss and Degradation on Fisheries LINDA A. DETGAN The Ecos ,stem Cer/er lfaiuine Biological Laboratory W4oods Hole. MA 02453 ROBERT BIJCHSBAUM A'lassac/oSCII,i in A taiuoo SociCetly 3460;ioperioc Rood ffl'nc,n,, V4t 01984 The importance to the Uniied States 0/ have changed the suite of species that can survive the fisheries on its coasts con scarely be in a given area. We can make reasonable predic-exagugerated, whether we coasicler the lions about which species will occupy certain habi-amount lood which i!"whoilesome lhYV lat types under certain management regimes - for yied, thepccior' I, va/e o/ their iprod- example., how the returnl of lbrests to much of New
/c'ts. the number ofmenet and boys o,-)r England as farms were abandoned has influenced whom they fitrnish profitable occupl*ati.o, the distiribution of such species as black bear, the stimults to ship and boot building white-tailed deer, and moose. For a variety of rea-which they sufpljy anid, not the least of sons, our understanding of the relationship between all, their service as a school fbr 'Secten. marine fish and their habitats is, by comparison, at froin which the merchant-marine, as well a primitive state, and our predictive capabilities are as the totvvy ofthe countr3y, derive their minimal. The purpose of this chapter is to review most important recruits. -Baird, 1873 human impacts on marine fish habitats and address the question of how such impacts might be affect-ing fish populations superimposed on fishing itself and natural environmental variation.
INTRODUCTION INStlORE AND OI;FFSIIORE FisH HABFIATS The notion that the abundance of an organism is to a large measure a function of the quality and Much of the information that relates the quantity of suitable habitat available to it has been impacts of habitat alterations by humans to fish an integral part of the science of ecology since that populations will be taken from studies of nearshore field of endeavor came into existence in the 20th and estuarine fish, since a number of major studies Century. Perhaps because the habitats beneath the have been carried out there. It has been recognized sea are hidden from direct view, the connection since the early I 800s that nearshore marine habi-between fisheries and habitats has only recently tats, particularly coastal embayments and estuaries, received much attention from scientists and fisheries are important for the survival of some species of managers. In the terrestrial realm, we know a great fishes and shelifishes. In some parts of the country, deal about how human alterations of the landscape coastal species are the major component of
68 conmmercial and recreational fisheries. Even where Table 5. 1. Major categories of hunIaii impact on coastal the direct harvesting of estuarine and coastal aquatic habitats. species is not nILiericallV or economically signifii-cant, estuaries and coastal embayinents may still be -,,;V'EG()RN" iEXAM PLIL Physical habatat loss draimae, shoreIne dredeii, spoihl essential for fisheries because tiey%;Srv as nurs- P disposal Cries f'or the juvenile stages of species harvested offshore or for the prey of commifercially important Hydrology changes. Ifreshwater diversion or withdraw-x II al. tidal constriction due to cause-species. twrays or culVCets, hdVdi0clecti); The high productivity of bays and estuaries. planits particularýly those with salt marshes and other vege-tated habitats, may help support offshore food webs Litrophictinon ertilizers, sewage, runoft, septic i VsstCeis, land use (Odurn, 1980; Deegan, 1993). Thus.nearshore arid offshore habitats are linked ecologically. What we cSediment delivery increased due to soil erosion, can learn from tihe impacts of habitat alterations on chan-'es decreased due to upstream dams nearshore fish will be relevant to habitats further ni hlitroc(luCCdl pS species Phtroewmili',. Lieen crabs otfshore, such as the hshingirounds of Georges Bank. Because it is a popular place to live, visit, Fishi nicthoc.s-
-j -irawls, clamn rakes, scallop recreate, and conduct business, the coast has been physical impacts dredges measurably altered and degraded by a variety of F
humlan activities: (I ) urbanization, (2) agriculture, Colo-ilinii I'll) iais 'heavy metals, hy drocarbons, (3) alteration of water flows by roads, railroads, organics., waste dumping/debris and dredging, (4) diversion of: f'reshwater flows for hikvher wvater temperatures, alternate uises (5) overharvest of biological IchaniLes illC;sea-level increased sorim eveils. !loodinr resources, and (6) pollution from point and non- G jof marshes, declines ill point souirCes (Table 5. I). There is also an under- 1productivity standing of the physical disturbance of berithic habitats by mobile fishing gear. Because this type of disturbance is so widespread and intense both to maturity" covers a species' full life cycle inshore and offshore, many scientists and managers (Federal Register. 1997). are concerined that it could be impacting fish popu- \Ve have chosen. to define habitat broadly lor lations, perhaps inhibiting recovery of overfished this paper. Habitat is that part of the environment stocks. on which organisins depend directly or indirectly to carry out their life processes. For fish, this includes spawning grounds, nursery areas, feeding areas, DEFINITION OF HABITAT and migration routes. The definition of what is a Essential fish habitat (EFH) means those habitat for a particular species will vary according. waters and substrate necessary to fish for spawn- to the number and extent of life processes used by ing, breeding, feeding, or growth to maturity. For an ecologist to delineate a habitat. In this chapter, the purpose of interpreting the definition of essen- we will consider habitat as those parts of the envi-tial fish habitat: Waters include aquatic areas and ronment that together make a place for organisms their associated physical, chemical. and biological to survive and prosper. This includes the physical properties that are used by fish and may include environment (such as structure provided by plants, aquatic areas historically used by fish where appro- sediments or temperature), the chemical environ-priate; substrate includes sediment, hard bottom, ment (such as salinity arid dissolved oxygen), and structures underlying thewaters, and associated the many organisms (such as plants and inverte-biological communities; necessary means the habi- brates) that comprise a food web (Cronin and tat required to support a sustainable fishery and the Mansuerti. 1971; Peters and Cross, 1991; 1-loss and managed species' contribution to a healthy ecosys- Thayer, 1993). tern; and "spawning, breeding, feeding, or growth Defining and describing what habitats are
ii A rll A i ij INý ýI\ol) DI Fý;NA IA' 1, 69 essential to a species is comphcated. Difterent life think of hunian impacts to marine habitats as fitting history Stages May require a different habitat, or an into three categories: organlisIn may use a variety ot habitats during each I. permanent loss (e.g.. fillino of a coastal wet-of its life stages. For example, menhaden require at land). leist four di cfierct habitats (Deegan. 1093). Hey 2. degradation (e.g.. eutrophicarton ',and spawn offshore (I), then depend on tidal currents 3. periodic disturbance (e.g. mobile gear). set up by river discharge (2) to bring larvae into The first results in a loss of habitat quantity, the estuaries whvlere they use salt marshes (3) for feed- other two in a loss of qUality. All three may reduce ing and protection from predators. As juveniles, the ability of a region to support fish, however they they use open bay areas (4) to grow to a size where differ in that the first is irreversible, the second they can move offshore (back to 1). A number of may or may not be reversible, and the third is gen-common species in the Massachusetts region have erally reversible once the source of disturbance is populations that make regular. seasonal migrations removed. Recovery times for the second category between estuaries and nearshore coastal waters. depend on the nature of the agent causing the These include winter flounder, summer flounder, degradation (e.g., very slow for PCBs vs. relatively three-spined stickleback. DlLieSiih, Striped bass, short for nutrients once the source of contan iination Atlantic silversides and a variety ofdiadromous has been removed) and the physical characteristics species (Table 5.2). of the region (sediment type, hydrodynamics, etc.). Physical structure is the most visible aspect of Recovery times for the third category will vary a habitat and is therefore the basis for most habitat depending on the intensity and periodicity of the classifications. Kelp beds, seagrass meadows, inter- disturbance (e.g.. how frequently trawled) and the tidal marshes, intertidal and subtidal mud and sand nature of the habitat itself' Superimposed on these flats, or offshore ledges and banks provide distinct human-related alterations are natural fluctuations in physical structures that serve as habitats for fish habitats, such as storms. and long term climatic and other marine organisnis. I ess obvious struc- changes. tural components are fironts separating different water masses or plumes of turbid, low salinity HABIT-ATfl QiANTITY ANt) QuAIJrM water produced by large rivers. Structure alone is not sufficient to provide a functional habitat for an Habitat quantity is a measure of the total area organism. Habitats can be dysfunctional, even available. while habitat quality is a measure of the though the basic physical structure is present. if carrying capa-city of an existing habitat. aspects such as food webs or primary production Documenting the former is reasonably straightfor-have been altered. In addition, environimental prop- ward, particularly for some nearshore habitats, such erties such as temperature, salinity, and nutrient as salt marshes and eelgrass beds. The extent and (food) availability greatly influence the use of these rate of actual loss of coastal wetlands have been areas. well documented for parts of New England and Some habitats cannot be assigned to a specific elsewhere over the last.few decades by a number of location. The convergence of the freshwater plume researchers and agencies using aerial photography of a river and the ocean changes its location with and ground surveys (Dexter,. 1985; Hankin et al., the discharge of the river and the tidal regime. 1985; Costa, 1988; liner and Zinni, 1988; Dahl, These areas are an important pelagic habitat and 1990; Field et al.. 1991; Tiner, 1991). Maps, how-support dense populations of zooplankton that are ever, do not indicate whether a current existing critical to the survival of larval and juvenile stages coastal wetland or seagrass bed still functions as it of fishes (Townsend, 1983, Govoni et al.,.1989W had historically. Grimes and Finucane, 1991; Govoni and Grimes, Less is known about the distribution of off-1992; Doyle et al., 1993). shore habitats in New England waters than nearshore habitats and about how such habitats GENERAl.. CATEGORIES OF IMPACTS have changed as a result of human and natural fac-tors. Certainly scientists and fishermen have long From an ecological perspective, it is useful to been aware that certain underwater features, such
70 [)/:i-:; 'table 5.2. List of fish species occurring ill coastal Massachusetts waters and their relationship to estuaries. Fisherx indicates species historically or currently taken in either commercial (C) or recreational (R) Fisheries. I luman impact effects are keyed to Table 5.1. Possible impacts on each species are based on documenled cases and assessment of habitat requirements of individual species by the authors. Comnmon Name [Scientfilc Name Hhuimaii hilmpact d ,b
/u)IuI'
...l............. S...........iI.~i'
........ /.....i. . .. . , .
litaided fullitFish fu Petui B Iackusc shinni- P
\<orii ,uu~.,-/i Bliidle shiner Ot,/ri Dt/rel;namus k o 1111Mit lroul (introiuced)l lt u,-/t;, N:
C ha in pickerel [~so v luger Whit,len-etch 1w On..,tWrr/-uju/ Diadromous Alfe \ vi te
*i-*7
;;7;i-{'e
- ~
........... ....... .......... ~ A..
...... .. Iu
.... 'u psifeduhurenguis
....... ---- --. .......... ... . Pelatic x
.Amiericant eel luguinla ros/ruta CR N:
Aimierican shad l1,' sap.hiissi.no (C R x idiit0d,i {7.s]...... fii ... .............. iiS7/7777T~ i . :....................... Aliianuc S/,Iilmon " toio suri/i N: 1caic AItlantic stutn'ooii i!CConii tS( *t r . hlCiSu i l-gimtic N: N: ltiunack .,trrriu>. I/o;7 t oesi,.It.ljs C Rt X N: N: Rainbot smelt Oo-erits 5 x .or .. t'dti_'it C R/ Sea lamprey mernizonmuiis S ~irt nio.k trout 5. lj'uios;t
!ubo'b,>~i X I Re sIdent NXiJ fi ~xoidstickleback. Gustet-o~sbeos Wi/euibru U Fliourspine l*77;_ sticklebkac
~ et~ct
-----...... .Apeltes 7.oito(frbrct's
*0.2,.cN'/)/i/,ttl, 77....777
.. .............. ..... B enihic
( irithhv if7.. t'/*?tk/t!, I losehoker i rirw-wsjes fu /Ctbus t tdhic 11Luittd -Sil erSides IA rid/it li-i ,hstu Lon*horn sculpin iAxvooce/pm/tus ocuroccmio.'iz osus X N: I) Muinmiehog 1'undo/os hclco'riur ý Bv ihic Naked gob)' Qob'iosoruc; bostri ItPeBmlagic nihic N lurspine stickleb'ack Plun'itito ts gl~lium Blit uttc NoirtIiern pipefislh - ngT.ithii.rTci.s ------------- No ihe i ip ipcu r. . . Sp/tctoi'oiTdes flitatttthlttt loithi ni (iNte'. o-ad tistli Outsal"I tt Itn .... ..7 .... ... ..........
. . m--- hic Sheepsthead minniiiow. C mprirmidon varie gaivs Shor17ie
.gthorn i 7{;{c-*scu...1pi... ..... ......--------------..
....... tmAlvyocepholis scorpiiis . ... .. ...... Benthic XIX S11moothti lounder - Liopseita putnam! C I B~eIh-III C S6ickleback Gastetosleuis spp, Brithic N:XN x--
Striped kil*ifish Fudidthus maoilis __ B.*nthic B. ih{iic X i X
-hreespine stickleback Gasterosteus actleatus x-- -
Nursery Atlantic nienli*iden lrevoistia. ovranmtus C R 'Pelag'I c- i x IN :: Atlantic silversides WAenidia meidia c elag[ia xc
- x N x Atlantic tonicod £omcoc/ Benihic I x xficrogad/ms
- x Bay Anchovy :Anc'hoa milcilli I lPelaiic Nx x 1x ___
BluheFish Itoo,,atomus saltatrict C R Pelaici Cunner 17alogolbio adsperri.,' i C R B[nlhic x x x xNIN: Mlullet itug-l cep/hlus t Biienthc t N Pollock Poluchims vire,-,s I C R Pelagic x x x L_ ?/ Striped bass Striped mullet
.AiuuolI
!lorone' s(yatilis cephalus' C R CR Pelagic Benthim.X N:
x N: x N: Summer flounder IPuru-ichihys,,Ieniois- CR Benthic Nx: - j Wiautoer Iod ulo onleuss C R Benthic Ix x x W~inter flounder Ptru/opl)ettr~oectuls amoericroius- CR Benth \jN: x _______
71 common Name iScientific Namet l'isimerv' Zo/Ane Humnan Impact KI H
-tkicanplaic tiltit / lt (htr/i Atlaniti cod Atlantiic herringl Cti'ca hacir itlt' Atlanticn.iactkercl \tLnut.. ,crdclcih Atl'un1ii. Spilt l*_iiinp-Sncke1r 1t'tt Ct',o I Ctt 'II I SiS 1i70sIIts b
,\tlantii-C1-x. x o .I..S.i h1 ..............
.4iru1ci a hy' s IIR'tutlh tttt '0 tO.;
Blacir seibais Btlotched CLISk-Cel Mo'icltion 01at BLtuterfmlsh Pejn tius tri rconthios (oha Iuclotelt ntrott crittcdtir Congeru cc! I'-usk I)iubcd shatnny Lunit;ctto.s ncttccitin FOIBIOu ptI floun11der / ib(ilittC ) tr ttt s
.. .. . I . ,
(joosclish I o/ihitI arncricantns Haddock 1AI. et/l) ratnutlu ttr'glefinits I It ip hirc iiardf7h intitet et/tt Ct r icpteu t o'iimpits iackerel siad LXcapCtrS *,UC01ticIt t Not thern kiniifishi Northern scarohin l'riw intrs cuirolmit s Northern set ictt !Spitirrtcuic 1.ot ert, Ocean perch -. srires martnlis Ocean pout yaltrt)o~treeS cittericarouis Ocean sunfish Offshore hake iAler/*ucriits a/d ic/its C Pie rm it ] /'tiintoluls forctalts R-ad-iaited sliaininv Lvtli tItii t "R o hake Red ....................... l .................... il*t
... 1 iig u chItto h o a:........ ..e h. .s .. .I iI. .... C R.......
_I........ Rock gunnell ['hotanneln 1/t Scup Stenotontts chrvsop~s CR Sea raven Ietr'ntiptertto atericanits Silver hake Alerlucciris bilinearis CR Sk-ates.spp. Rioatsp... _____ . .... Smooth dlogfish AlttsfeIns rants C Smooth skc Ru/u scow C Spiny dlogfish -~ Str/r iuihrsC Striped searobin . prionontu rdoans Thorny skate Rica rucdatd o Weakfish OCinoscion re,'ais CR White hake L.rophvcit lett,it C R Whlite mnullet JAhfottll 'ittente_ -C R_ W indowvp ane- Sr'rtphthcdoitsrtnus ttaI1Sf,__ C K_ Winter skate Rariaa rrel/ri e Witch FIlounder G/ývpu'oceyphulus cinoglosstts CR Yellowt~ail flunder Limratndrt f rrtgitnea CR Physical habitat loss; Hydrology changes; Eutrophication; Sediment delivery changes; Introduced species; Fishing methods-physical impacts; Contaminants; Global climate-changes in sea-level.
-7 fI) & B 1: (
as Geor-es Bank. are a(tractive to diverse marine particularly where there are enough i atkected organisms and have had a general idea of the bot- areas nearby to compensate For the loss. The cumu-torn types in different regions through bottom sam- lative impact of many small losses over tine may, pling by trawls and dredges. The recent develop- Iioweveri. ultimately lead to a severe impact on a nIent of sidescan sonar, high ICsolution seisiic fiishery. profiling and echo sounding, and video-equipped As unimpacted habitats get smaller and more remotely operated vehicles (ROVs) and sub- fragmented, the capacity of the populations to mersibles has stimnulated nm*pping efforts in certain recover from natural catastrophic events as well as sections of GuI f of Maine, particularly the north- human-induced stress is likely reduced. The small east section of Georges Baink. Stellwagen Bank, incremental increase in a stress. such as.a increase Jeffreys Bank, and Swans Island (Valentine and iI nutrient loading from a new development, may Lougli, 1991 \,'alentine and SchiInLick, 1994; Auster be enough to turn the corner from habitat degrada-et al., 1996). tion to loss. Most environmental regulations gov-The degradation of habitat quality, such as erning developments require assessments only on a through siltation and alteration of salinity, food site-by-site basis and cumulative impacts are not webs and tiow patterns. lnay be just as devastating considered. Management of fisheries occurs at a to the biological community as a loss in quantity. regional scale, but the changes in habitats that may Siltation caLiSecd by land-based erosion may smoth- uiltiniately lead to a severe impact on a fishery are er a smelt spawning bed in a tidal river just as off- the result of cumulative impacts at much smaller shore deposition-of dredged materials may smother scales. Over a long enough period of time the SLIM of the benthic eggs of Atlantic herring. The physical all the small changes may result in a large imlpact. structure of the habitat does not need to be directly altered for negative consequences to occur. Anthropogenic alterations in the tidal flow to a Loss ovF H,\irTvr QUANTITY marsh frequently results in the invasion ofsalt marshes by /hragmiles aust*'alis, generally thougllt to be poorer as a habitat than the plants it replaces. vobodh knows how much salt marsh Habitat loss and degradation are interrelated existed along the Atlantic coast oq /Norlh because habitat loss is the ultimate end point of America before the Europeans arrived. gradual declines in habitat quality. NtO matter hoin much n'as here, the set-tiers began to change the existirg amount ahnost immediately [TIE QijES)TION OF SCALE
-7Tal and 7Tal, 1969 The effect of habitat loss on organisms depends to a large extent on the scale of the loss. A single small loss may not, in itself, cause an observable effect. However, tile cumulative impact of many
[IIt...ING AND OUTRIGHT Loss OF COASTAL. iIABITATS small losses may be quite significant at a regional scale. For example, the diverting or damming of Loss of coastal wetlands due to residential and one river, although locally important to the species industrial development has been severe in the in that river, may not have a regional impact. United States. Recent estimates-suggest that about However, if enough water is diverted from the 54% of the nation's original 915,000 kmin of wet-many rivers flowing to the Gulf of Maine,. the lands (freshwater and coastal) have been lost coastal boundary current setup by freshwater dis- (Tiner, 1984), and over half of the nation's original charge and important to the survival of many off- salt marshes and mangrove forests have been shore fish could be altered (Townsend, 1991; Doyle destroyed (Watzin and Gosselink, 1992). A particLi-et al., 1993). Similarly, the loss of one acre of salt larly intense period of loss occurred between 1950 marsh or the destruction of a small patch of cobble and 1970. habitat may not have a detectable effect on fish. Boston HLarbor is a local example of this
LV '-1 Iý 1I '7:I acreagte ot salt marshes that has occurred after the passaoe of wetlands re-ulations in Massachusetts indicate that losses vary from vitually zero in less developed parts of the Massachusetts coast to about 9% in a fourteen year period inl oe highlyv urban area (studies summarized in Buchsbaum, 1992). Of the approximately 15.500 acres of vegetated estuar-ine wetilands between PIlurn Island and Scituate. Massachusetts, about 24 acres (0. 15%) were either converted to uplands or changed to nonvegetated wetlands from 1977 throughd 1985-1986 (Foulis and Finer. 1994). Although this is a much smaller num-ber than what occurred in the 1950s and I960s, nonetheless small, incremental losses of coastal habitats still occur from public works projects that are exempt fron regulations, from illegal fillinrg froom boater activities, and firom the construction of small docks and piers. The latter often involves dredging several hundred cubic yards of material and re-arranging the shoreline to one more suitable to human use. There is less intormation on historical changes in acreages of subtidal eelgrass beds and subtidal Figure 5.1. Alteration of BIston Harbor by tF in.-1775 and intertidal sand and mud hlats than there is for to 1990 (fon MAVPC Boston Harbor Islands salt marshes. Like salt marshes, these areas provide Compiehe sive Plan). The grey patterned areas iidicate important habitats for a variety of fish and shelIfisli landfilt. species (Whitlach, 1982: Thayer et al., 1984; Hleck national trend (Figure 5. 1). From 1775 through the et al., 1989). Undoubtedly, many of these habitats 1970s, the physical shape of Boston Harbor has were filled along with vegetated wetlands as popu-been drasticallv altered by filling. The part of lation centers grew around estuaries. In addition to Boston that is now the North End and Beacon Hill filling, these shalltW, subtidal areas are affected by was originally a peninsula connected to the main- other human activities. Power boats, for example, land by a narrow strip of upland (the Boston Neck) can directly remove submerged vegetation and with extensive salt marshes. The Back Bay, a associated attached organisms (Thayer et al., 1984) densely urban neighborhood harboring some of the and resuspend sediments from tidal flats. tallest buildings in the city, was once a shallow estuary with extensive salt marshes. South Boston DREDGING SUMTI DAL BENTI'HiC HABITANS and Charlestown were also originally surrounded by tidal marshes'that are now destroyed. Filling Many New England coastal communities connected with btuilding Logan airport alone depend on dredging to maintain their harbors for amounted to 2,000 acres. recreational and commercial uses. Fioom 1960 to The wholesale loss of coastal habitats from 1981, enough material was dredged from Beverly. human activities has been halted, in large part due Chelsea, East Boston, South Boston, Gloucester, to. federal wetlands protection mandated under the New Bedford, Fairhaven and Salem, to fill a one Clean Water Act of 1972. At the state level, square mile hole 4.5 ft deep (Pierce, 1985). The act Massachusetts has one of the most stringent coastal of dredging, as well as disposal of the dredged wetlands protection programs in the country material, has an immediate affect on the benthic through its Coastal Wetland Protection Act of 1964 community. In the past, dredged materials were and the Wetlands Protection Act and Regulations, often used to fill salt marshes and tidal flats to cre-passed in the 1970s. Estimates of the change in the ate more dry land, so a number of coastal habitat
tyPCS \Vere atl'eO d be dredging Much ofthis sedi- creates a more narrow intertidal and shallow subti-ment had toxic levels of chemicals such as PCBs. dal zone. There are also cascading effects on marsh PA-s, or metals, hence the impacts go beyond just and tidal flats due to changes in sediment transport physical alteration ofthe habitat. Dredge spoils processes and long-shore currents. In the long term, have also been deposited in ofi.:shore disposal areas development ofshore'tilhes maC pree\ the normal such as the Massachusetts Bay and Cape Cod 13,1y migration of salt marshes inland as they respond to Disposal Sites. Although regulations now require rising sea levels. that such dredged material meet certain standards A recent concern has been the effects of shad-in relation to contaminants to be considered suit- ing from docks and piers on eelgrass communities. able for oitshore disposal, this practice clearly A recent study carried out in Waquoit Bay on Cape alters both the inshore dredged and offshore filled Cod indicated that eegrass plants under docks benthic comi tIn ities. were lower in a nurnbIr oi growth parameters coin-Dredging causes losses of submerged aquatic pared to otutside controls (But-dick and Short. vegetation, such as eelgrass. through both direct 1995). Shading effects froom docks is also believed and indirect causes. Dredging shallow subtidal to favor algae-dominated communities over eel-ect loss oi'Ceicrass in a aceas has resu lted in the diiC grass. Algae-dominated communities do not sup-number of areas around the coast (Costa, 1988). port the diversity and biomass of fishes that are Declining light penetration and smothering associ- typical of submerged aquatic vegetation habitats ated with the turbidity plume caused by dredging (Deegan et al., 1997). also cause indirect losses in submerged aquatic vegetation (Thayer at al.- 1984). Since they are not DECTINE IN HABITAT QUAI IIAY as well-delineated as intertidal habitats, eelgrass meadows are more likely to be inadvertently The loss of habitat quality or carrying capacity dredged even \. ith current wetlands protection 4- is more subtle than the loss of area. The term hIabi-ulations. tat qtmalitv is used to refer to the functional Dredging alters inti tidal and sutbtidal habitats attributes of an area, such as providing food or by making some areas deeper by sediment removal shelter, needed to support fish and shellfish. and others more shallow by filling. In addition to Habitat quality is altered by a variety of factors, being primary habitats for important shellfisheries, including sedimentation, nutrients, toxic chemicals, shallow subtidal and intertidal flats are important physical disturbance, and colonization by aggres-feeding areas for many flatfish, including winter. sive alien species of plants and animals. Sources of summer, and windowpane flounders (Pearcy, 1962: these impacts include urban sewer systemt.s, indtms-Tyler. 197 Ia; Berogman et al.. 1988: Saucerman, trial outfalls, ocean dump sites, individual septic 1990; Saucerinan and Deegan, 1991 - Ruiz et al., systems, storm water runoff, agriculture, fishing 1993). Dredging eliminates feeding sites for many gear, and the atmosphere. The degradation of habi-fish by' altering the species composition of the tat quality affects a range of ecological processes: invertebrate prey within the benthos (Whillatch, primary and secondary production, trophic dynam-1982). Tyler (1971 b) suggested that the loss of tidal ics, succession, and species diversity. flats in the Bay of Fundy through dredging could Boston Harbor was an example of how a multi-reduce winter flounder populations by altering food tude of impacts, including toxic organic contami-availability. nants, heavy metals, nutrient loading, and sedimen-tation, altered the benthic food web. Approximately 60% of the bottom area of Boston Harbor had a Sti.OREtANE MODIFICATION benthic invertebrate community that was either The use of sea walls and bulkheading results in moderately or severely impacted by pollution. This an alteration of intertidal habitat and associated trend has been at least partially reversed with the communities (Whitlatch, 1982). Construction of upgrade of the wastweater treatment facility in the hard surfaces along the coast transforms a soft late 1990s (Rex et al., 2002). bottom community to a hard bottom and usually
S iUTlROPitiC(-ON the excess algae and other organic matter decays. Areas that are particularly prone to hypoxia One of the Majoi causcs of habitat decline include coastal ponds, subticlal basins, and salt associated with human activities along the coast is marsh creeks. Water circulation in coastal ponds is the inc~ense in nutrient loading. esecially nltroeen, often restricted, 1andinl some ponds may be com-In general, tile effects of increased etitrophication pletely isolated from the sea tor long periods of are negative. Elevated levels of nutrients runningi time. The coastal ponds on the south shore of Cape into a bay. from lawn feirtiliZers, a'gricuiltural fields. Cod and Rhode Island are rich habitats for estuar-and sewage, stimulate primary production. result- me fish and shellfish. However, the surrounding ing in increased growth of phytoplankton and watersheds of many ponds have undergone rapid macroalgae, reduced water clarity, and alteration of growth in the past thirty years, and they now are the w\ater chemistry. The iagal species composition routinely lVpoxic in summuier (l.,ee and Olsen, 1985; changes to a dominance by species that are not D'Avanzo and Kremer, 1994). Communities sur-readily incorporated into existing trophic structures rounding these ponds often propose regular open-(Paerl, 1988). Nuisance macroalgae acumirnulate in ing of these ponds to the sea as a way offrejuve-shaIlow watcrs (I.cc and O1scn, 1985: \,Valieda et al., niating" fish and shellfish habitats. Ihe bottom 1992) and the abundance of rooted aquatic vegeta- waters in subtidal basins may be isolated from the tion declines dtie to shading b\ attached or floating well-oxygenated surface waters during periods of algae (Orth and.Moore, 1983). If the growth of stratification in the summer. For example, the dis-algae exceeds the ability of higher trophic levels to solved oxygen levels in Stellwagen Basin occasion-consume it, the excess bioinass accumulates on the ally drop below 6.0 mgiL when the waters are strat-bottom where it is decomposed by microbes. ified (Kelly, 1993). Subsequent effects may be low dissolved oxygen One approach to understanding the loss of events, changes in the species of plants and animals habitat due to low DO is to nap the amount of area present, and loss of critical habitats such as sea- in a bay that does not meet minimum DO standards grass beds. These effects are likely to affect sniall t5 mg/L according to EPA standards, 5.6 mng/L in consullmer organismls such as zooplankton and Massachusetts). Parts of the Inner Harbor in Boston amphipods, as well as the fishes that depend on frequently violate the 5 mng/L standard and the these consumers for food. Changes in the food web Charles River Basin often is completely anoxic may alter species composition at the higher trophic because of inputs from combined sewer outflows levels, from those desirable by humans as food, and altered hydrology (Rex et al., 1992.). In such as flatfish, to less desirable species such as Chesapeake Bay and western Long Island Sound, gelatinous ctenophores or sea- nettles (Purcell, extensive areas of the bottom often fails to meet 1992, Caddy, 1993). minimum DO levels required for survival of fishes and invertebrates (Welsh and Eller, 1991; Low DiSSOLVED OXYGEN Breitburg, 1992). Even short episodes Of low DO can have strong Decline and even loss of habitat clue to inade- effects on fish populations. A severe fish kill in quate dissolved oxygen (DO) is one of the most Waquoit Bay was caused by one low DO event severe problems associated with eutrophication of which lasted less than 24 hrs (D'Avanzo and coastal waters. Depletion of some (hypoxia, < 2 Kremer. 1994). Juvenile winter flounder which rag/L) or all (anoxia) of the oxygen in the water or used the I-lead of the Bay site as a nursery area the sediments causes changes in community com- were killed and washed up on the beach along with position and even death of organisms. Although shrimp, crabs, and other fish and invertebrates somec degree of oxygen depletion can occur in nat- (Figure 5.2). The juvenile winter flounder popula-ural systems, even in offshore basins, oxygen tion in the anoxic location did not recover, although depletion has been exacerbated by increased populations at other sites which did not have a low sewage and increased nutrient inputs resulting from DO event were unaffected. If the low DO event development and agriculture around estuaries. had been more widespread, it could have caused Oxygen is used up by the respiration of bacteria as the failure of an entire year-class for the population
76 LOW DO AT HEAD OF and other urban harbors inorth of Cape Cod, 0.3 BAY STATION although it can be locally important. E 0.2 lo.sORS tF .;):."RA.55 0 0.1 The alteration and loss of eclgrass habitats due to eutrophication provides a good example of the 0.0 MAY JUNE JULY AUGUST SEPT effect o0f hlalbitat degradation on fish cotttmoanities. 1989 The high diversity and abundance of invertebrates Figure5.2. Juvenile winter flounder abundance at three and fish in eelgrass ecosystems is due to: (l ) habitats in W\aquoit.Bay. This graph illustates the effect increasedl survivorship due to the physical structure of a local, 24 hr low. dissolved oxygen event on the of vascular plants that provides protection from abundance of juveniie winter flounder. Juvenile winter predation (Orth et al., 1984; Bell et al., 1987; Pohle flounder at the I-lead of the Bay site were killed by a low et. al.. 1991 ) and (2) greater supply of food (Heck dissolved oxygen event that lasted less than 24 hrs and Crowder, 1991- Deecan et al.. 1993). The fune-(D'Avanzo and Kremer, 1994). PoIplulations at other loca- tion of> eelgrass and other vegetated habitats in tions (eelgrass, sand) that did not experience a low DO shallow waters parallels that of the cobbles and event were unaffected. biogenic structures in deeper offshore waters that are now of such concern because of mobile gear of this estuary. even though it lasted less than 24 impacts (Anster and i..,angton. 1999). Thus an hours out of the entire year. examination of studies of how the alteration of the Low, but not lethal, levels of dissolved oxygen structure of eelgrass habitats has affected fish com-can also lower the growth and survivorship of fish- mtunities may provide insights for those more off-es and impact shell fish. Growth of juvenile winter shore habitats as well. liottncder held at oxygen concentrations of 6.7 mg/I Because eelgrass beds are subtidal, they require was twice that of fish held at 2.2 mgi/L (B ejda et relatively clear water so that they have enough al., 1992). Fish held under conditions of diurnally light for growth, hence (hey are sensitive to sedi-fluctuating DO also showed growth suppression ment loading and to eutrophication. In the past compared to fish held at high DO levels. Some twenty yeais, eelgrass losses related to declining behaviors of young fish such as moving uIp into the water quality have been documnented for Southern water column and increased swimming activity are Massachusetts (Costa, 1988- Short et al.. 1993: also increased Under low DO levels making them Deegan et al., 1993) and Long Island Sound more susceptible to Predation (Bejda et al., 1987). (Rozsa., 1994).1Historical records indicate that eel-Shellfish growing under low oxygen conditions are grass was once widespread in Boston Harbor, but stressed (see Brousseau. Chapter 6). now only a few limited areas (Hingham Harbor) Not all coastal waters are equally susceptible to have suitable light penetration to Support eelgrass low oxygen conditions. In general, low oxygen (Chandler et al., 1996). For most of the remainder conditions are rare in surface waters and rare in the of the New -Englandcoast, there is little docuimen-winter. Low oxygen is most likely to occur in bot- tation of overall trends in the abundance of.this tom waters at night in the summer because of habitat, although short term fluctuations have been warm temperatures, high metabolic sediment noted (Short et al., 1986). delnand and water column stratification. Areas that Increased nutrient loading causes declines in the are vertically well mixed and well flushed by the habitat quality of submerged aquatic vegetation and tides, which includes most of the New England eventually complete loss of large areas of this habi-coastal enibayinents north of Cape Cod, rarely tat (Costa 1988; Batiuk et al., 1992; Deegan et al., experience hypoxia. Estuaries in this region may 1993; Short et al., 1993). Eutrophication alters the exchange more than 50 percent of their water with physical structure of seagrass meadows by decreas-well-oxygenated seawater every day. Low DO is ing shoot density and blade stature, decreasing the not considered a widespread problem in Boston size and the depth of beds, and by stimulating the
! .1.:15 ' , IFff I ; kýA'1',. 7 I 77 excessive orowth of macroalgae (Shor t al., WAQUOIT BAY 1993). The initial response of eelgorass to low levels of nitrogcin may be positive where the eelgrass E
itself is nitrogen-linited (Short, 1987).. Macroalgae and phytoplankton, however, ere able to trInsforn Z excess nitrogen into growth more rapidly then eel- C grass. so they eventually outcom pete and smother the eel,,rass lShort et al., 1993 . 14 Another typical consequence of eutrophication within an estuaryI is a geographic shift of eelgrass habitats towards shallower higiih saline areas near 5 4-the mouth ol the estuary. lelgrass in deeper areas 3-(lie first because the plants are very sensitive to 2-reduced light levels (Dennison, 1987, Costa, 1988). 0 Beds near the head of the estuary are also highly susceptible to the effects of etitrophication because 10 of high nitrogen concentrations resulting from, lie 8-close proximity to runoff from land. 6-Eelgrass is subject tO intense natural population 4-fluctuations which may be exacerbated by eutroph- 2-ication. An epidemic of wasting disease in the early 19'0s wiped out most eelgrass along the entire east coast (Rasmtissen, 1977). Eelgrass recovered to some extent, althotigh it never recolonized some former areas. The disease has periodically recurred 8 in local embayments in more recent years (Dexter. 1985; Short.et al., 1986). Eutrophication may increase the susceptibility of the plants to the wast- 11- -E AI-I 9 C9 1AR 1989 1990 ing disease by decreasing the plants ability to resist 1988 disease and by restricting the plants distribution Figure 5.3. Fish abundance, biomass, number of species within the estuary (Buchsbaum et al., 1990; Short and dominance all are lower in low compared to medi-et al., 1993). In the past, low salinity areas of the uim quality eelgrass habitats in Waquoit Bay, MA estuary at the upper reaches of estuaries have been (Deegan ct al.. 1997). Repinhted wiih permission, a refuge fr'om the disease during outbreaks. As Estuarine Research Federation. mentioned above, however, eutrophication tends to be most severe in the low salinity, upper reaches of areas with low water quality (Figure 5.3). The estuaries. This restricts eelgrass to the more saline number of fish species that use estuaries as a nurs-areas where it is most susceptible to wasting disease. ery area or spawning location was much lower in The replacement of eelgrass by macroalgae in a areas of poor water quality compared to areas with eutrophic estuary results in a highly modified fish moderate water quality (Figure 5.4). Fish associated community even before the plants themselves have with the benthic zone were more strongly affected disappeared (Deegan et al.., 1997). In studies of than fish associated with the pelagic zone. For Waquoit Bay and Buttermilk Bay on Cape Cod, example, winter flounder, a benthic species that assessments of the relative degradation of eelgrass spawns in the estuary, was one of the first species 'habitats were based on year-round measurements of lost from eelgrass habitats under eutrophic condi-chemical and physical characteristics (e.g., algal tions. blooms, macroalgae, low DO, high nutrients, The largest impact of loss of habitat quality on dredged channels). Habitats that had moderate fish community structure was found in the late water quality had more individuals, more biomass, summer periods as a result of the cumulative more species and a higher diversity of fish than effects of habitat degradation (Figures 5.3-5.4).
[i~lI~\' & Number ot Nursery Species Table 5.3. Changes ill the fish community coln position of eelgrass habitat in WaCILoit Bay over time. Data are 0~ 0ro1mtDeejan el al., 1997 and Curley Ct al. 197 1. Number of Species % Composition L>1 Year 1967 1988 1995 1967 1988 1995 z Fishery 10 7 3 63 2 9 Forane 14 13 6 3;7 98 81 z Total 24 20 9 100 100 100 MAR DEC JAN DEC MAR 1988 1989 1990 Number of Estuarine Spawning Species 6 - 1 . . . 1I I l.I I'` l. . l I.I.I I.I. Species common in commercial and recreational Low fE fisheries, such as winter flounder, white hake and 5- -aMed pollock declined during this time period. The num-C) 4 ber of fisheries species declined from 10 to 3, and 4)g 3- the percent composition of the catch declined from 63% to 9% between 1967 and 1995. A decline in 2 - the lumber of forage species is also apparent which indicates that the loss of fisheries species is probably not due sitllplV to overfishing. The n]u[m11-z MAR DEC JAN DEC MAR ber of forage fish declined firom 14 species to 6 1988 1989 .1990 species over the same 30 year period. Some small Figure 5.4. Number of species using eelgrass habitats as lorage lish. such as sticklebacks and silversides, nursery areas and tile number of species that spawn in increased in abundance and forage fish now estuaries were lower in low compared to mediumn1 quality account for roughly 80% of the catch in eelgrass celgrass habitats in Waquoit Bay, MA\ (fiom Decean et areas. al., 1993). Direct links between loss of celgrass and loss of commercial catch have been demonstrated in Many species of fish migrate into estuaries ill the other areas of the world. Jenkins et al. (1993) spring and summer as adults to spawn and feed and demonstrated a clear connection between a 70% as juveniles to find protection and ample food loss of seagrass and a 40% loss in total commercial before returning to the open ocean as adults. By the fish catch in Western- Port Bay, Australia. The end of the summer, when the fish community has strong, parallel decline in fish catch and seagrass experienced the cumulative effects of low oxyvgen, loss occurred in species which were specifically higher mortality due to predation and disrupted adapted to life in a seagrass habitat. Species with a food webs, there were fewer species, fewer individ- reduced ecological link did not show a clear paral-uals and lower biomass in areas of high anthro- lel decline. pogenic stress compared to less disturbed areas Along the east coast of the United States. the (Deegan et al., 1997). This result is likely a combi- closest connection between eelgrass and a comner-nation of lowered fish production, higher mortality, cially important marine species is not with a fish and migration away friom degraded habitats. but is with the bay scallop. The larvae of these Declines in eelgrass habitats and commercially bivalves settle on eelgrass blades prior to their or recreationally important finfish were apparent in transformation into adults (Pohle et al., 1991; New England over a 30 year time period in Waquoit Brousseau, Chapter 6). The harvest of bay scallops Bay (Table 5.3). Comparison of the number of declined drastically during the wasting disease epi-species and the percent composition of the catch in demic of the 1930s (Thayer et al., 1984). In addi-eelgrass habitats in Waquoit Bay indicate a sharp tion to bay scallops, there is some indication that decline in the number of species and abundance of gadoids in coastal regions make use of eelgrass recreationally or commercially important species. habitats at certain life stages. Chandler et al. (1996)
":W, 79 found that two to three Year old pollock were trawlers access to rocky and cobble habitats that caught more often within eelgrass beds then in were formerly inaccessible. As a result, virtually all neighboring., unvegetated habitats in Biostoin benthic habitats are nlow potentially, sUsceptible to Harbor. Pollock also preferred vegetated substrate the effects of mobile gear. We summarize the major o\xer sand in Great South Ba,. Loiing Island (Bricgs cientic issues in toe next ftew Pa!Oai'aphs and and O'Connor, I 171 , Tupper and B utilier (1995) suOgest that the reader refer to one of the recent reported higher growth rates of age-0 Atlantic cod reviews for more details.
in celerass comrnpared to sand.y areas, cobble habi- Mobile fishing gear such as otter trawls, scal-tats, and underwater reefsin Nova Scotia. lop rakes, and clam dredges are used in a variety of Survivorship in eelgrass was lower than in. cobble nearshore and offshore habitats to harv est diemersal and underw\.ater reefs hut higher than in sandy. habi- and benthic species. These can change the physical tats. Studies of eelgrass beds alone the Danish habitat and biological structure of ecosystems and coastline in the carI,, 1900s concluded that eclgrass therefore have potentially \yide ranging impacts ott was an important habitat for juvenile cod (Peterson a number of ecological levels. Studies have already and Boysen-Jensen 1911 ; Peterson, 1918) as have documented that mobile gear reduces benthic habi-more recent studies in Nova Scotia (Tupper and tat complexity by removing or damtaging the actual Butilier, 1995). physical structure of the seafloor, and causes Most of the fish that currently use eelgrass as a changes in species composition of infauna, i.e.. habitat in New England are not directly taken in smaller invertebrates that live in the upper layers of commercial or recreational fisheries, but are forage the sediment and are prey for groundfish (Dayton fish or prey lfr species taken in lisheries (Deegaln et al., 1995; Auster and Malatesta, 1995; Auster el et al., 1997, Heck et al., 1989, 1995). Because al., 1996; Collie et al. 1997; Auster and Langton, much of the current eelgrass habitat is arguably 1999: Engel and Kvitek, 1999). Mobile gear may degraded by pollotion to some extent already, also chan'e surficial sediments and sediment establishing a direct link between declines in coin- organic matter, thereby affecting the availability of inercial or recreational iinfish fisheries and loss 61" organic matter to microbial Ibod webs (PiIskaln et eelgrass habitat in New England using existing al., 1999; Schwinghamer et al., 1999). Of major areas will be difficult. Unfortunately, information direct concern to commercial fish interests is the on fish use of eelgrass areas in New England prior potential impact that the loss of benthic structural to the 1930's is lacking, maaking it difficult to estab- complexity may have on the survival of juvenile lish if eelgrass was an important habitat for fish- groundfish. From an ecosystems perspective, the eries species prior to the onset of the wasting dis- simplification of the physical structure in repeatedly ease epidemic and habitat degradation. trawled areas would likely result in lowered overall biodiversity. The level of trawling in New England waters is intense. Auster et al. (1996) estimated that FISt!ING AC'ivIrnEs since 1976, the annual areal extent of trawling on Georges Bank has been equivalent to two to three times its entire bottom area. Some specific loca-tISHIIN(i GrEAR tions are trawled as much as 40-50 times per year (A uster and Langton, 1999). The ongoing concern about the impacts of Trawling results in a loss of habitat complexity mobile fishing gear on benthic communities in through the removal of both biogenic structures, fishing grounds has been reflected in a number of such as sponges, bryozoans, and shell aggregates recent symposia, reviews, and edited volumes (e.g., and sedimentary features. This is important to fish-Dorsey and Pederson, 1998; Auster and Langton, eries since physical structure may be critical to the 1999; Watling and Norse, 1999; NRC, 2002). The survival and growth of different fish species. Many issue is potentially very important since the level of taxa, especially juvenile fish, exhibit facultative disturbancerepresented by mobile gear is associations with microhabitat features such as bio-widespread and intense. The development of roller genic depressions, shells, burrows, sand wave gear through the 1980s and 1990s has allowed crests, and even patches of amphipod tubes in low
S r .F1 ; '2 &2R TIs~
*, n%1
\j topographic CnvironIents such as subtidal areas of Sonie habitats are 1or1 sensitive 1o the effects Massachusetts Bay (Lough et al., 1989; [.angton of fishing gear than other habitats. In a study of the and Rob nsonr 1990; A uster et al.. 199 1, I 994. physiccally stressed intertidal zone of Miinas Basin, 1995, and 1996. Malatesta et al., 1992: Walters and the impacts of otter trawling were found to be Iuanes. 19033- Tupper and Bounihier 1995). Cobble- minor (Brvlinskv et al.. 1994). These coneLfusions.
gravel over sand-mud, for example, is a primary however, cannot be assumed to be true for subtidal habitat for juvenile lobsters. This habitat may be a habitats with more diverse assemblages of benthic bottleneck for the recruitment of earlv benthic organsniss and lower levels of' natural disturbance phase lobsters, as well as other shelter seeking (Sainsbury et al., 1993). Daan (1991), on the basis species such as Jonah (Ca/ice, hore'dis) and rock of prodtiucion/biomass ratios, suggested problems (Cancer irrorausI crabs (Wahle and Steneck. mighit be most severe in heavily tished areas, sub-1991). Late juvenile silver hake, (Mferluccius Mi/in- tidal areas, or fbr long-lived org'anmisms. earls), showed a positive association with amphi- Aister and Langton (1999) presented a concep-pod tubes in flat sandy areas (Auster et al., 1994., tual model in which the impact of mobile gear on 1995). Postlarval silver hake mayk occur in patches habitat complexity increases with fishing effort, but of dense amphipoCd tube cover to avoid predators the extent of increase depends on the habitat type. and to be near preferred prey (i.e., amphipods and More complex habitats, such as piled boulders and shrimp). Similar associations have been found for cobbles with epifauna show the steepest decline in Atlantic cod (Gotceitas and Brown 1993) and yel- habitat complexity with increased fishing effort. lowtail flounder (Walsh 1991, 1992). In laboratory Their model predicts that cobbles and gravel with studies, Lindholn et al. ( 1999) found that predation no epitlAuna would show little decrease in habitat on age-0 cod was significantly lower when the bot- complexity with increased fishing effort, since the torn was covered by emergent epifauna. such as is effect of a trawl there would be to turn over struc-present in an untrawled area, compared to bare tures, bUt the pie-existing structrures would still be sand. Destruction of benthic organisms. such as present afterwards. Recently a comparative risk amphipods and worms, by trawlintg alters food assessment that integrates the size. severitv.sensi-availability and microtopography which could sub- tivity and uncerlainty of the impact of trawling on sequently affect the growth and survival of juvenile the seafloor has been developed (NRC, 2002). fishes. The impacts of mobile gear are not limited to In nearshore habitats, vegetation, such as eel- offshore habitats. Clam harvestino by raking and grass and kelp, and boulders and cobbles provide mechanical harvesting (Cclani kicking")'has a tile microtopography that provides a refuge and severe and long-lasting effect on seagrass ecosys-foraging area ibr juvenile fish and macroinverte- tems (Peterson et al., 1987). Seagrass biomass in brates. In deeper habitats, the microtopography is mechanical harvesting treatments fell by .65% created by worm and amphipod tubes, sponges, and below controls. Recovery did not begin until more other biogenic features along wvith the boulders and than 2 years had passed and seagrass biomass was cobbles. Mobile gear flattens this relief in both areas. -35% lower than controls 4 years later. This could Trawl fishing not only changes the physical have severe impacts on fish and shellfish that character of the seafloor, but also increases turbidi- depend on seagrass as settling locations or for pro-ty and resuspension of bottom sediments (Auster tection from predators. and Langton, 1999; Pilskaln et al., 1999). Sidescan The extent to which trawling, dredging, and sonar shows that physical disturbance to surficial other fishing activities have contributed to the sediments by trawling, as evidenced by abundant decline in fisheries or would impede recovery of and persistent trawl furrows, is extensive on the overfished species in New England is still an area seafloor of heavily fished areas within the Gulf of of debate among fisheries managers, the industry, Maine (Jenner et al., 1991; Valentine and Lough, and scientists. The evidence at the moment is indi-1991). Trawling generates a plume of suspended rect, in that the losses of structural feattires of the sediment which increases turbidity and may alter benthic community that are known to be important sediment composition if the finer particles are to a number of commercial fish species at some life swept away on water currents. stages have definitively been observed as a
03S ',N f) I IF V 'NR consequence of mobile fishingoear. A1011-1thou1h 1he Lag 11iiiC aftc.r Lurbainization evidence does not indicate that tile Current fisheries crisis has been caused in laige lesuIeC by. the habitat effects of mobile Lear. the ma jo concern is with how these habitat ilnipacts 11N al;'ct recov-erv. At the current low population levels of many commercial groundfish it is possible that increased predation on juvenile groundbish in habitat impact-ed by dragging could be hindering recovery. It is logical to assume that an activity carried Out over such a wide area and that impacts juvenile survival will ultimately affect fish populations at low popu- Las time before lation levels. It is clearly an area where more -Urbanization research is needed, particuarly on how trawling affects the suirvival ofjuvenile fish and on the impacts and recovery periods of different bottom types undler different intensities of trawling. Time (hrs) figLure 5.5. Alteration in volume, timing, duration and BY'CATCi-I intensity of freshwater inpuits with increased urbaniza-tion in the watershed (fIoni Dnnne andi leopold 1978). Discards of bycatch, i.e., non targeted species or undersized individuals, can also have profound effects on fisheries habitat. We cannot do justice to and DiCarlo. 1972). Relation of river r11inotf for this complex topic here, however it needs to be the production of hydropower, domestic and indus-mentioned. Many individuals discarded as bycatch trial use. and agriculture reduces the volume and do not survive after being released. In addition to alters the timning of' freshwater delivery to estuaries. the obvious direct effects on populations and The flow of the Ipswich River, for example, is marine food chains of the loss of a large number of reduced by about half due to water withdrawals for individuals, the disposal of large quantities of dead human uses (K. Mackin, lps. Riv. Watershed bycatch may alter the organic matter loading and Assoc., pers. comm.). The type of land use in a cause changes in dissolved oxygen profiles and watershed is also a strong determinant'of the quan-nutrient cycling., tity, timing, duration and chemical composition of freshwater inputs to estuaries (Hopkinson and HlYDROIOGICAL AUiERAIONS OIF ES'fIuRIES Vallino, 1995). Urbanization, for example, affects the timing and magnitude of river discharge after a rainstorm (FigLire 5.5). Urban areas have large CHIANGES IN FRiWAR INPUiS expanses of impervioLis surface, such as roads or parking lots, which causes more water to flow off Fisheri-es yields of coastal species have repeat- the land more quickly than if the land were forest edly been correlated with fireshwater inputs or field. (Aleem. 1972; Sutcliffe, 1973; Deegan et al., 1986; Such reductions and alterations of freshwater Nixon, 1992). Freshwater flow diversion, regtula- inputs affect water circulation and the chemical tion and alteration by control structures and properties of estuaries. Diversion of freshwater changes in land use have caused serious damage to increases the salinity of coastal marine ecosystems estuaries worldwide (Clark and Benson, 198 1, and can diminish the supply of sediments and Rozengurt and Hedgepeth, 1989; Hancock, 1993). nutrients to coastal systems (Boesch et al., 1994). Virtually every river flowing into Massachusetts Habitats may change in response to altered hydro-and Cape Cod Bays has an altered hydrograph due dynamics. Alteration of the natural hydroperiod can to control structures or changes in land use (Rebeck affect estuarine circulation on different time and
B1. , IIS 13.ý17'd niaginitude scales. includinlg short-term (diel) and DAMtS A.ND ROADYW.A\S 'longer term (seasonal or annual) changes. Salinity and sedneimentation rates have a marked effect on Dam construction on tidal rivers has caused the type and rate of wetland habitat present. In addi- habitat degradation within estuaries. Changes in nonn, organisms themselves often have specitic Saiin- flow, sediment delivery, salinity. and temperature itv. temrperature or habitat requirements for spawn- result in changes in estuarine cominiunity structure, ing or successful growth during juvenile stages. water chemical composition, food webs and loss of Many fish species depend on the developmem f'ershk.ater and estuarine habitats. Withdrawal or of a counter current (low set up by, freshwater dis- diversion of 40'%, of the annual runoff of the charge to enter estuaries as larvae or early juvneniles Skokomish River (Washington State) has resulted (e.g., Pearcv. 1962): lownsend and Graham. 198 I in a 6% loss of total unvegetated flats. more than Wipplehauser and McClcave, 1987; [ay et al., 40% loss of low iitertidal area, 18% loss of eel-1989). Counter current flow is the input of water at grass area and a reduction in the size of the meso-the bottom from the coastal ocean to counterbal- haline mixing zone (Jay and Simenstad, 1994). One ance the outflow of freshwater at the surface. A result was a 40% loss of optimal fish habitat high frcshwatcr discharge causes a strong saltwater between I885 and 1972 due to changes in sedirnent influx which carries many species into estuaries load and distribution (Figure 5.6). In this case, sed-(Kaartvedt and Svendson, 1990). Pearcy (1962) iment transport was the critical link between found that larval winter flounder changed their upstream alterations and the remote, downstream depth distribution between day and night and this, estuarine consequences. Dams also affect the coupled with the conitter-cUTrreit flow, concentrated migratorv paths of fishes due ditectly' to blocking them in estuaries. As freshwater inputs to estuaries (Moring, Chapter 3) and also to changes in the dis-are lessened with increased freshwater withdrawals tribution. or local extinction, of prey species or in the \wateished, longitudinal and vertical estuarine alteration of temperature and salinity regimes. habitat structure is altered and larval transport can be Many marshes are fragmented and hydrologi-disrupted (Dadswell et al., 1987). Other examples of cally isolated by roads. causeways, railroad beds, New England species likely to be affected by alter- and dikes. Restricted water circulation results in ations in counter current flow are American eel, declines in primary productivity and fish use of striped bass, white perch, Atlantic herring, blue, crabs, these habitats (Roman et al., 1984; Rozas et al., lobsters, Atlantic menhaden. cunner; toincod and 1988). rainbow smelt. MO;SQUTOttCONr ROt. Many salt marshes along the east coast of the United States are lined with mosquito control ditch-es. Their effect on fish that use salt marshes is not clear. By increasing the amount of water penetrat-
-2 ing into the vegetated surface of the marsh, such
- 4) MALLW channels may increase the use of marsh surfaces at CL high tide by foraging fish, such as mumimichogs (Rozas et al., 1988). Conversely, negative effects on salt marsh fish would occur where ditches drained salt pannes and fish habitat dried out.
POWER PLANTS Figure 5.6. Loss of optimal fish habitat due to diversion The impacts of power plants on estuaries and of freshwater and resulting alteration of sediment load fisheries has been the subject of extensive reviews and hydrology (Jay and Simenstad, 1994). Reprinled (e.g., Uziel. 1980; Larsen, 1981; Hall et al.. 1982; iw'ith permission, Estuarine Research Federation. Boynton et al., 1982; Summers 1989; Reeves and
[(.\ r i "\-i i,us ý ý,\: i ýr)t ýi,.ý, i,ýý- it ,\: S 1) Bunch, 1993)). Power plants can affect fisheries by: the last 50 years, howv ever, is not sufticient to have I ) altering water circulation patterns by water with- caused the current dramatic declines in fisheries. drInwal and changing water temperature. 2) altering estuarine production cycles through changes in ExOTtc<; water . pertre and circulation patterus. 3t increasitng death, decreasing growth and altering The introduction of exotic species may also spawning because of elevated water temperatures, have profound effects on habital quality bv aifeet-
- 4) increasiiw' mortality by direct impingemnent of ing predation and competition interactions. Carlton larvae and juveniles on intake screens, 5) increas- ( 1993) listed 13 different marine organisms that ing mortality and decreasing growth by releasing have been introduced into New England coastal contaminants such as chlorine, birom inC, copper waters since colonial times. inciudino two crabs, a and zinc, and 6) increasing mortality of fisheries bryozoan, five mollusks, four sea squirts, and one species by direct impingement of their forage red alga. Some of the exotics, such as the European species. For example. Summers ('1989) found that periwiitkle. Lu.io!r lilo'ecu'., and the green crab.
striped bass, bluefish and weakfish could experi- Carci,-ts inaemis, have been with us so long( that ence significant losses (>>25%) to total popuIlation few people realize they are not native. Many of production due to high levels of forage fish entrain- these were carried to New England waters as foul-inent by power plants. ing organisms on boats or in the ballast water. There has been interest in using the intense This is a relatively new area of research, so tides in the Bay of Fundv and other macrotidal there are little conclusive data on the ecological estuaries throughout the world as a source o0 impacts of exotics and how they might effect fish hydroelectric power. A major issue is the potential and shellfish habitat. Some of the impacts are likely affect on fish attempting to pass through the tur- to be quite profound. Green crabs, are voracious bines. Dadswell and Ruli Son (1994) estimated a predators on soft-shelled clams and newly settled mortality of 20-80% of fish, depending on the winter flounder, and interfere with -Attempts to species. passing through a low head tidal turbine on transplant eelgrass. The non-native haplotype of the Annapolis River estuary in the Bay of Fundy. Phragiilesacstralis has pushed out native species Dadswell (1996) estimated that the-annual shad of salt and brackish marsh plants and may increase spawning run on the Annapolis River has declined the rate of sedimentation in marshes, reducing the by over 50% in a fourteen year period since the amount of intertidal habilat available to marsh fish installation of the hydroelectric plant despite the (Able et al., 2003). Zebra mussels, which have col-absence of local commercial fishing. The mean onized oligohaline as well as freshwaters in the size, length of males and females, the mean and Hudson River basin (Mills et al., 1996), have had maximum age of individuals, and the percentage of strong effects on freshwater phvtoplankton and repeat spawners have all declined in the shad run zooplankton populations in that river (Caraco et al., during the same time period. 1997). SEA LEVEL RisE Two CASE- STUIIIES TIIAT CONSIDER BOTll FISiiING AND HABITAT EFFECTS Global change and the rising sea levels could have major impacts on estuarine fish populations and coastal fisheries (Kennedy, 1990; Bigford. WiNTEt FLOUNDER [N NEW' ENGLAND 1991). If sea level rises faster than the ability of' salt marsh surfaces to accrete sediment and peat, Winter flounder (Pseudopleuronectes ameri-then a greater amount of the surfaces of salt marsh- canius), is one of tile most commercially and recre-es will be regularly flooded during high tides in the ationally important fish species in the northeast and future. This would provide increased habitat for provides one of the best examples of the impor-estuarine fish if tile marsh maintains its stability. tance of habitat to fisheries yield (ASMFC, 1992). The small change in sea level that has occurred in Many populations spawn in and use estuaries as
S~ 1'4K hi, 1131L nurscry habitat (t lowe and Coates. 1975: 1lowe ct very few adult age classes (ages 1-3) contribute to al.. 1976), It has been the focus of a variety of egg, production because fishing mortality was high. CnVi ronmeital impanivct Studies Kecause of its CeCo- [his means that loss ofa single year-class because nomic value and because it shows clear responses of disruption of juvCnile habitat could lead to a to poor 001' alt.i i ii tV (Munche Ian0 and Briggs. serious population decline. The combination of 1985; Bejda et al., 1992). Flarl, life stages (eggs. habitat limitation and severe overfishing leaves the larva and jUveniles) of inshore populations are sus- stock vulnerable to collapse. The best strategy for ceptible to water withdrawal (Crecco and Howell. stock preservation is both habitat improvements 1990), toxic substances (Nelson et al., 1991 ) and and control of fishing pressure. physical loss or degradation of habitat (Briggs and These recommendations apply to inshore O'Conner. 1971 ). Habitat degradation has been stocks of winter flounder. A similar analysis for off-shown to increase juvenile mortality (Briggs and shore populations, such as those on Georges Bank. O'Conner, 1971) and decrease growth (Bejda et al,, has not been done and may or may not come to 1992: Saucermanl. 1900). Age-I and older fish are similar conclusions. also subjected to high levels of recreationa! and fishing mortality (Borenian et al.. 1993). The Fishery Management Plan for inshore TiH Nott Nrit t Wrst STit, A us'rti'AIIA stocks of winter flounder provides an analysis of Although we currently lack the data to separate the relative effects of habitat loss versus changes in fishin, mortality from habitat alteration effects in fishing mortality on fish survival (ASMFC, 1992). New England offshore fisherics, examining a simi-Based on the work described below (Boreinan et lar situation for the North West Shelft region of al., 1993), the plan concludes that a strategy of Australia is instructive. This region faced problems habitat improvements that would increase juverille similar to those of our offshore fisheries in New sLIrVivorship would result in long term benelits io England. Fish species composition was changing population success and provide a firmer basis 1or from desirable to undesirable species, and total increasingyields in the future than would a strameg,.' abundance was declino The Northt West Shelf based solely on a reduction in fishing mortality. was under intense trawling fishing pressure Boreman et al. (1993) compared the relative value (Sainsbury et al.. 19093) and its benthic habitat of increasing age-0 survival through habitat altered. The catch of epibenthic fauna (mostly restoration or decreasing fishing pressure on adult sponges, alcyoriians and gorgonians) had declined stocks as ways to reverse the trends of decreasing from 500 kg/hr to only a few kg/hr. Little was stock declines. They used the eggs-per-recruit known about the relationship between the fish (EPR) method which is a way of equating mortality stocks and the habitat provided by demersal effects on early, life stages of a fish species to sub- epibenthic organisms other than that there was a sequent loss of fishing opportunity. T1u1s the EPR strong correlation between the presence of these. method can be used to compare changes in poten- organisms and fish populations. Four research tial egg production due to loss ofjuvenile fish hypotheses were developed which either together because of habitat loss or degradation to losses in or separately could explain the changes: egg production due to harvesting of adults. As H I. environmentally induced changes independent such, it.gives managers a means to compare poten- 0f the fishery, tial effects of habitat change with changes in fish- H2. multiple independent responses by fish species ing mortality. Their analysis based on population to exploitation, characteristics of Cape Cod Bay flounder popula- H3. alteration of biological interactions due to the tions indicates that doubling juvenile survival fishery, or through habitat restoration yields the same egg pro- 1-14. indirect effects of fishing, such as habitat duction as reducing fishing mortality by 63%. This alterations. result suggests that growth in stock abundance is Each explanation had different management limited by a carrying capacity bottleneck that implications. If the main cause for the decline was occurs sometime before the fish become susceptible the loss of epibenthic habitat (hypothesis 4), or to fishing pressure. They also found, however, that trawl-induced changes in competitive/predation
&S AN D) )IAC;R \D.0\1 N'.
interactions thyhpothesis 3). then there nioght be declines in flSh populakiorIs, since Most fish POPuW scope for expansion of a trap fishery to replace lations for which there are adequate data have also trawling.. OGi tile other hand, if tile historical been heavily exploited. ().in an embayinei"t level, declines were because these stocks had intrinsically we know, for example, that loss of eelgrass reduces low prodctivcIi ity (hlypothes is 2). thei the onlyt sohu- le ab[:iit\ of the bha- to su pport hay scallops and tion xWas to cut back on all fishing. Winter flounder. These populations are also under To clarify these issues. ail adaptive nmanage- heavy fishing pressure that may have had an equal ment approach was used. Broad areas ol the NW\,S or greater impact on numbers. The combination of were regulated with 2 diff"erent mnanagenment habitat loss and degradation, overfishing, and some regimes (open to trawling and closed to trawling) natural environinental fluctuations may cause tor 5 years arid the fish populations and epibenthos 'Treater declines in a population than any of these monitored by fishery-independent trawls. Catch r.ctors alone. Some species can use alternate habi-rates in the area closed to trawling increased along tats, food sources and migration pathways. while with the epibenthos, while fish catches and epihen- others cannot. In addition, different populations of thos abundance continued to decline in the areas the same species may hive different habitat open to trawling. A second area which had initially requLirements. l or exa lp1c, [lie Georges Bank pop-0i been open to trawlino was closed to trawling 2 ulation of Winter flounder never comes 'Into any years into the study and catch rates in this area also estuary. while other populations are specific to cer-began to recover. tain estuaries (Howe et al., 1976). T'hese results show a good correlation between With those caveats in mind. there are several the catch rate and the abundance oftepibenthic predictions one might make i'Ihabitat losses and organisms, however, it was possible that both the degradation were major factors in fisheries epibenthic organisms and the fish were responding declines. Although the discussion of these predic-separately to the effects of trawling. To test 1or this. tions poits to the difficulty of'separating habitat alternate resource dynamic models were developed. frioin other factors as causirng most fisheries Comubining the historical catch and effort data with declinies, we hirln1 it is still instructive. the experimental results indicated that abundance of the major fish species is limited by the amount TIli I MOiST ,,I \,"IctjS IOI ((.OSE of suitable habitat. (epibenthic fauna). The analysis SPEiCIES W\VtlOSF HAi\ITAT HixIA, t31lEN rTIIE MOST carried out on the NWS illustrates the scope for use DEiRF \DED. VARIA
\ QUAlti\
I'\tt NS IN H1,,il-\.iii,IiTA ANI) of the "adaptive" mianagement approach to evaluat-EXTENT SHOUItD BE REFI.ECTED IN FL.UCTUATIONS IN ing seemingly contradictory explanations to large THEI1FISHI=.I7?0' and complex problems. Anadronious fish are the clearest example of a strong relationship between habitat degradation and WiCit NoirriiLAsT' FIstH SPECIES HAVE BEEN population declines (Moring. Chapter 3). Dams. AIiFEcTI;) BY HA rI'AT Loss OR DEC RADATION? culverts. and cranberry bogs have all been impedi-Because of the complex relationships of indi- inents to their passage to spawning areas (Rebeck vidual species to habitats and the myriad causes of and DiCarlo, 1972) and erosion due to poor land habitat degradation it is difficult to unambiguously use practices and euitrophication have degraded establish cause and elffect between habitat declines their spawning areas. and fisheries declines. The above example of Inshore stocks of winter flounder also show a nearshore populations of winter flounder provides loss of fisheries yield because of habitat alteration, one illustration of a particular population where although the causes vary from estuary to estuary habitat degradation has affected a fishery. Except (ASMFC., 1992). Land derived pollhtants tend to for anadromous fish (see Moring, Chapter 3) and decrease in a gradient with distance from shore the decline in bay scallops during the eelgrass (Figure 5.7). In sorte estuaries, the loss has been wasting disease epidemic in the 1930s (Thayer et attributed to euItrophication and anoxia; in others, al., 1984), there are little data allowing us to toxic contaminants. The previously cited example unambiguously link habitat changes with regional of the relationship between bay scallops and eelgrass
86 [)LFG \ I( S[I ;). Clostridium peeringens (Normalized to % 4Fines) Deegan et al. (1 997) on Cape Cod underscore the vs. Distance from Deer Island Point particular importance of eelgrass habitats in the Si 51. ... . 020 40 km Northeast to coastal fish and macroinvertebrates in
,wga, . rie..;, I ' .. 40L terms of supporting a larger measurable diversity of species than other estuarine habitats. Nonetheless, the impact on linfish fisheries from the eelgrass decline of the 1930s and other, more recent I , IS declines has not been demonstrated. This is in part because we lack historical data both on the extent.
of these habitats and on abundance of fish within 19942 6913 1994 1995 i896 1997 M99a 1999 2900 these habitats and because currently few fish
.1 1., Yea species of commercial importance use these habi-(a) tats (Heck et al., 1989; Deegan et al., 1997).
10-W 70'10-\\ 70'?0 \\ Since the present decline in commercial fish 42 40" species in New England is occurring both near and offshore, nearshore habitat loss is obviously not the only explanation for the decline. The commercial fishery of New England is less dependent on 4010 species with a clear ecological dependence on 42)30' coastal areas than other parts of the country (Nixon, 1980). For example, of the top five impor-tant commercial species of finfish in New England 42120' (Atlantic cod, haddock, yellowtail flounder, American plaice and winter flounder), only winter flounder uses estuaries extensively, and even within 42°10" this species, not all populations use estuaries (ASMFC, 1992). As stressed earlier in this chapter; 7. the most widespread habitat alteration in offshore fishery has been the use of mobile gear. Since all these offshore species are currently at low popula-tion levels due to intensive fishing (Murawski, Chapter 2), any effects of habitat changes from _ J fishing gear have been strongly confounded by fishing mortality. (b) Broad scale environmental changes have Figure 5.7. Distribution of land derived (a) Clostridium occurred on Georges Bank and other offshore (MWRA, 2003) and (b) Dissolved inorganic nitrogen regions, but the evidende that they are the primary (Libby et al., 2000) from Boston Harbor into cause of recent fisheries declines is not compelling. Massachusetts Bay. Such environmental changes include recent increases in seawater temperature and the impacts also provides an example of a response of a fish- of mobile fishing gear described earlier. If these eries species to habitat degradation and loss. factors were having a major impact on offshore Recent declines in the bay scallop fishery on Long fisheries populations, then one would, at the very Island have been attributed to the loss of eelgrass least, expect a decline in the survivorship ofjuve-as a result of smothering by the brown tide organism niles relative to the size of the spawning stock. (Dennison, 1987). Species, such as bay scallops, Such a decline in this ratio could also be caused by that are not flexible and that have very specific other factors, such as survivorship of eggs and 0 requirements for spawning, feeding or migration year fish prior to recruitment or increases in pathways are most at risk from habitat change. predator populations, so this is not a conclusive Recent surveys by Heck et al. (1989, 1995) and indication, but it should nonetheless occur. Based
-%1ý11A` L! ý ., f. i(11:
AN:rý fýFi;N MIA ý -,7 on tire ratio of new recruits to the biomass of- he fish declines, then there should have been a larger spawning stock'that spawned the new recruits. decline in coastal fish populationsdduring 1950-there is no evidence 101 Irduced juile SulrViVOr- 1970 than in recent ycars when wetlands protection ship in cod, haddock, and yellowtail flounder efforts have been stepped tip. (MaCmwsk i. Chapter 2). These species are at his- There are several reasons wVlhv relationships toric population lows in our region, and it is likely between wetlands loss and declines in fisheries that the magnitude of overfishing in the offshore have been difficult to document even in those fisheries overwhelms any effect of habitat alter- regions of the country where the fisheries are com-ation in New England at this time. prised of species that have clear ecological links to coastal wetland habilats. First, we often do not have good documentation on the fishing eflort or LENIHIC P:i5. SHOULD SI IOW GR"A[IR DECLINES landing of inshore fishes most likely to have been THAN WHOLLY PELAGIC SPI'ECIES affected by these coastal alterations during a rele-Because most habitat alterations have their vant time period such as during the period of most greatest impact either directly or indirectly on the intensive wetland filling ( 1950- 1970). For example, benthos, another prediction is that benthic species we have only sporadici niformation on Anierican are more likely to be affected by habitat degrada- shad. striped bass and winter flounder landings tion than pelagic species (Caddy, 1993; Deegan et prior to 1965 (Figule 5.8). Another difficulty is that al., 1997). L.ow dissolved oxygen in bottom waters, in the past most estuarine fisheries were not fully alteration of benthic substrata, and concentrations exploited, thus, any loss in the total population due of pollutants all should disproportionately impact to loss of habitat could be made rip in the iisheiy benthic species. by increasing effort (Houde and Rutherford. 1993; The recent declines in fisheries have, in fact, NOAA, 1995). On a national level, most (but not affected many demersal species dramatically. all) estuarine-dependent fisheries in the Uniied However some pelagic fish. Atlantic Bluefin Tuna, States have declined sharply or collapsed, in con-Atlantic Swordfish. and a number of shark species, trast to relatively stable catches of estuarine-depen-are all overexploited and at low population levels dent species on a global scale (I loude and along the east coast at present (NMFS. 2001). Rutherford, 1993). Houde and Ruitherford (1993) These are not known to have any benthic stages. attribute overfishing as the major cause of the Atlantic herring and mackerel, two pelagic species decline of estuarine fish, with some impacts from that are not heavily fished now, are presently rela- habitat alteration and "the vaguely documented but tively abundant and classified by NMFS as under- probably real consequences of pollutants and con-exploited (NMFS, 2001). Atlantic herring have taminants." In sum, the "timing hypothesis" is hard demersal eggs and may be subjected to impacts on to test since there are too many confounding vari-the benthic comnmunity by mobile fishing gear ables-in particular, estuarine fish stocks were (Valentine and Lough, 1991), yet they seem to be overfished at the same time severe habitat alter-doing well. ations were occtirring. When the composition of fish comnmunities in coastal areas are considered over long periods of THE TIMING OF THE DECLINE IN FISHERIES SHOULD BE time (> 20 yr) some changes become apparent. In RE'LATED TO TIHE TI MING OF HIAB I[AT LOSSES Waquoit Bay, for example, some fish species were AND DEGRADATION 10 to 60 times less abundant in 1967 compared to 1987 while some increased in abundance (Figure It may be possible to test this hypothesis with 5.9). The differences in the fish cominunity, nearshore fish that use coastal wetlands and estuar- described earlier in this paper between existing ies because the periods of some habitat losses are moderate and low quality eelgrass habitats in well defined. As described earlier, the filling of Waquoit Bay, while consistent and significant, were coastal wetlands was most intense in the northeast small compared to such changes seen over a thirty between 1950 and 1970. One would predict that if year period in the entire bay (Table 5.3, Deegan et the loss of coastal wetlands was a major factor in al., 1990). Species common in commercial and
6-4- " AMERICAN SHAD - FISH ABUNDANCE 1967 VS 1987 Cunner 1t940 1950 1960 1970 1980 1990 Pollock Grubby STRIPED BASS T. Silverside White Hake 0 4' Winter flounder Mummichog N. Pipefish U3 O0 ... ".-- A. Tomcod 1940 1950 1960 1970 1920 1990 Oyster Toadfish 20-f ------- A. Silversides 15 WINTER FLOUNDER A Striped Killifish 3 Stickleback 10] 5 "_ Black. Stickleback Bluefish 0' Blue. Herring 1940 1950 1960 1970 1980 1990 Rain. Killifish YEAR
-60 -40 -20 U LU 40 60 FiOure 5.8. Landing statistics for three species, American LOSS GAIN shad, striped bass and winter flounder, that have a strong ecological co1eCt6i1o tO estuaries and that are Aso11 ilpor- Fieurre 5.9. Changes in fish Conmunitty coiipos ition and tant in corninercial and recreational fisheries (fhorn Houde abundance in Waquoit Bay' over a twenty year period and Rutherford. 1993). Note that the landing inltorliation (Deegan et al., 1990). Many important commercial and for these species prior to the mid-1960s is very sparse. recreationally important species, such as winter flounder, declined in relative abundance, while small forage fish.
r- 1'u1m17. 1*.'edi*bi1e / h I cri, on, Rc.e-i h such as rainwater killitish, have increased in relative tbUd Mice. recreational fisheries, such as winter flounder. white hake and pollock declined during this time 20 YEAR CHANGE IN FISH ABUNDANCE period, while some small forage Fish. such as stick- 20-lebacks and silversides. increased in abundance. The 10-7 number of species that declined in abundance exceeded the number of species that increased in 0 ot o 0 abundance across all life-history patterns over the _10f -7 twenty year period (Figure 5. 10). Species that use the estuary as a nursery area were particularly affect- 20- -20 ed with 84% of the species declining in abundance. RESIDENT NURSERY ANADCATAD MARINE ADVENTIOUS TOTAL It is difficult to attribute changes over 20 years LIFE HISTORY STRATEGY in Waquoit Bay to any single cause because many Figure 5.10. The number of species in each life hisiory changes occurred simultaneously: land use in the category which either declined or gained in abundance watershed chanred from natural to suburban, nutri- from 1967 to 1987 in Waquoit Bay, MA (Deegan, ent loading increased, the open bay' was dredged, unpublished data). Negative nutmbers indicate the uimn-and its hvdrology was altered by freshwater control ber of species that declined in abundance, while positive structures and dredging. The decline of eelgrass numbers indicate the number of species that gained in area to less than 20% of historical levels and the abundance. reduced carrying capacity of the remaining habitat as a restlt of these alterations were probably is possible that despite the past losses of habitat, important factors in the change in the fish commu- enough suitable estuarine habitat still remains to nity. In addition to these local factors, regional fish- sustain populations of estuarine species. In addi-ing pressure has changed the populations of preda- tion, certain essential components of the marsh tory fish, such as bluefish, cod, striped bass, and comrnmunity, such as the mumninichog, Fmndidush. summer flounder, that migrate into estuaries along heteroclitis, are sufficiently flexible in their own the coast for part of their life history. habitat requirements and tolerant of habitat degra-T]here are other reasons why there has been no dation that they can still provide the key links umambiguous "signal" reflected in nearshore fish between estuaries and offshore fisheries despite stocks firomn coastal wetland loss and degradation. It human activities in coastal areas.
"A" L:0ýý AND I! I. iiKALI ý`!-N S9 Au unwitin ' experivient curently Lmdervav low and the fish typically mature at an early age.
that might test these speculations is related to the Populations levels of K-selected species are con-tremendous loss ol coastal wetlands in the stinied by a relatively stable enivironmetital carrvilng Mississippi River delta due to land subsidence. In capacity. K-selected species produce fewer young, .thits arca. containing roughly one quarter o0i he butt hi her juveille survi vorship than r-selected country's coastal wetlands, about 57,00( acres of species and are slower to reach reproductive age. coastal wetlands were replaced by open water Irom The relative imloiance of juvenile vCerstis 1974-1983 along with an even grealer amount 01 adult mortality should be related to features of fi'eshwater alluvial wetlands (Tiner, 1991 )..The reproductive or life history strategy. Juvenile mor-land in fhe delta is undergoing submergence tality is generally related to an aspect of the habitat because the heavily channelized Mississippi River while adult mortality is often controlled by fishing and its tributaries no longer provide the sediment effort. that has historically enabled these wetlands to keep Schaaf et al. (1993) used life history informa-pace with rising sea level (Turner and Rao, 1990). tion for 12 stocks of fish from the mid Atlantic The loss of wetland acreage has not had an inimme- region to compare the effects of destroying IuveniilC diate impact on such estuarine dependent coirmnier- and adult habitat through pollution on stock size. cial species as brown shrimp, but there is slpecula- They used estimates of aoe-specific mortality and tion that the long term consequences could be dis- fecundity in single species computer simulation astrous. once the submerged wetlands remnants models to compare the effects on stock size of an completely break tip (B3oesch et al., 1994). increase in mortality at the juvenile stage, such as Because increased fishing pressure and habitat might be caused by pollution, verstIs increased alterations often occur almost simultaneously, it adult mortality. For example, they found that will always be difficult to completely separate their destroyingt 2% of the estuarine habitat of jivenile effects both spatially and ternporally on fisheries. Atlantic menhladen could result in a 58% decline in This becomes even more problematic when one population levels after 10 years. Destroying, the source of habitat alteration is the gear used in the same amount of oceanic adult habitat resulted in fishery. Overfishing and habitat alteration may also only an 8% decline. Variability in juvenile sur-act synergistically in contributing to the decline of vivorship appears to be quite significant for some fisheries. One likely interaction is that overfishing stocks, while other stocks were more susceptible to causes the initial collapse of the population and changes in adult mortality. habitat alterations prevent the recovery of the fish- The analysis of Schaaf et al. (1993) which pre-erv even after fishing pressure is reduced. dicted a large decline in long-term harvest of men-haden from a small alteration in juvenile habitat also emphasizes the cumulative impact of small VARIATIONS IN LIFE AMONG DIFFERENT SPECIES changes in habitat on populations. Their analysis HISTORIES (I.E., R- VERSUtS K-SELE"CTED) SHOULD also showed that a severe pollution event (and pre-AFFECf[HE DEGREE TO WHICH THE'SE SPECIETS ARE sumably other forms of habitat degradation) could IMPACTED BY HABIIAT AILTERAIMONS have a devastating effect if it occurred when the fish were concentrated in their spawning areas. It One might look at life history characteristics of would be interesting to expand this modeling to fish to see if any factors inherent in the fish make their populations more or less susceptible to the include fishing mortality and loss ofjuveniles to impacts of fishing or habitat alterations. Some traits bycatch. Most exploited fish species in the northeast are that may be significant include ntumber of young produced, age-specific survival, age at first repro- intermediate between r- and K- species and contain duction, age-specific fecundity, longevity, and num- elements of both. Groundfish, for example are rela-ber of different habitats required over a lifespan. tively uniform in their life histories, generally maturing between 2 to 3 (gadids) or 3 to 4.(floun-Some species, termed r-selected, produce an abun-dance-of young to compensate for fluctuating and ders) years. Their reproductive and.mortality terms unpredictable environments. Juvenile survival is vary from stock to stock. Compared to terrestrial vertebrates, almost all species of fish (and shellfish)
g0 f)BE(iAN & 11CISI(iDfAWON in the northeast produce tremnendous numbers of parts of the country? young and have extremely high juvenile mortality rates and large year to year variations in reproduc- I'4h1aai' trhe spalial and ltenporalscales of the tive success. On the other hand age to first repro- criticalecologicalprocesses? Must we consider duction differs substantially (2-3 years in Atlantic processes on the scale of a single salt marsh cod, 7 years in lobsters, 8-10 years in Atlantic within an estuary, several salt marshes within a bluefin tuna), as does adult survivorship. We pre- single estuary or a series of estuaries? Is it suf-dict that populations of rapidly maturing and short- ficient to understand year-to-year variation or er-lived species are less likely to be influenced by are there longer-term, perhaps decadal trends in anthropogenic habitat alterations than those that are weather or river discharge. that we must more K-selected, since rapid growth and maturity account for ill oIr management plans? should be advantageous in a changing, disturbed environment. In addition, the populations of r- Are there life history bottlenecks? selected species should recover more rapidly fiom. Understanding the sequence of life-history habitat alterations and overfishing, at least in the stages that control populations in the absence short term. The analysis remains to be done. of harvesting is critical to population manage-ment. Wahle and Steneck (1 991) suggest that cobble habitat is essential for the settling of IN THFE FUTURE juvenile lobsters and may be fostering a demo-It is clear fiom the above discussions that the graphic bottleneck. Ilow many other species of links between habitat alteration and loss of fish- fish have such a critical relationship with a par-eries production can be subtle, diverse and operate ticular habitat type that may be limiting their on many scales from site-specific to regional. The populations? differences among species in the nature of the rela-tionship between fish and their habitats underscores WI4hat taclors influence the carryingcapaciti of/ the difficulty of determining the cause and effect habitats? For examnple, what role do physical relationships between habitat loss and degradation. structure and the production of food play in and loss of fisheries. It should not be surprising determining how many individuals or species that we can find no unambiguous correlation will be found in an area? between a single type of habitat alteration and the loss of a fishery since many habitat alterations have 1 What lands'capefiactors control the productivitv occurred simultaneously. Isolating the impacts of anddistributiono/habitats? Understanding habitat alterations is also confounded by fishing why habitats are not uniformly distributed nor activity and other constraints on fish populations. uniformly productive among locations would lead to a better understanding of the landscape features that must be preserved to maintain IMPORTANT RESEARCH QUESTIONS fisheries. For example, are seagrass beds adja-cent to marshes more productive than those in What are the criticalecological processes and open embayments or those occupying small habitats that sustainfisheries? For example, coves between rocky headlands.? Are offshore are upwellings important in the New England biogenic habitats of uniform density more pro-region? What environmental "cues" do fish use ductive for fish than those that are patchy and to determine migration pathways and spawning scattered? locations? How important is regional hydrolo-gy in distributing larvae friom "sources" areas? What are the impacts of eutrophication,.con-In estuaries, how important are inputs firom taminants, andfishing methods on critical eco-uplands compared to in situ production within logicalprocesses and habitats (i.e. assess the estuary? Are salt marshes and seagrasses ecosystem and habitat integrity)? We need to critical nursery habitats for fish and shellfish in understand not only how natural ecosystems northern New England as they are in other and populations function, but also how human
HAIT.AT\ [LOSSAN\D f)E7ik.D.AIION 9)1 intervention changes the way ecosystems func- proposed dredge and fill operation or where a tion. Although changes in water quality as a specific type of fishing gear is used. result of anthropogenic eutrophication are well documented, we know much less about the fWill a system of marine reserves be a useJliti indirect effects of eutrophication on biological tool in sustuining/ishp,,pulations? If'so, what communities. For example., what are the conse- are the key characteristicsof the habitat that quences to fish of the frequent disturbance of should be protected? A number of scientists the benthic community by mobile fishing gear? have suggested setting tip nonextractive marine reserves as a conservation tool to insure sus-Wf/hat are the separateeipcts of ovetfishing tainable fisheries (see articles in Shackell and and habitat degradationon populations and Willison 1995). Which species will benefit by ecosystems? Removal of an animal population having refugia [Vrom direct fishing mortality by fishing and loss of the ability of a habitat to and friom the indirect effects of fishing gear? support certain species may have very different implications for the structure and function of What are the habitat characteristicsoIf'reatest ecosystems and the future viability and man- importance to managedfish antd shellfish and agement of fisheries. Fish that are the targets of to the integrity of the mainne ecosystem? I--ow fisheries may control important ecosystem pro- will such reserves be manaoed and integ~rated cesses by their predation on other animals., into fisheries management plans? How large do behavioral activities such as burrowing, or by they need to be to be viable? How many differ-providing physical struiture as by-products of ent habitat types should each conlain? H-ow their life-history (see Witman and Sebens should each be linked to other reserves to make
.1992). Removal of key species can cause the a viable system?
indirect decline of other species. Altering the habitat directly can cause a general decline in WVhat are the trends in various habitats? Is the the abundance of organisms as well as cause habitat stable or is it degrading? What natural species shifts. or anthropogenic factors are responsible for any changes inthe habitat? What type of habi-tat monitoring program is needed to aid in IMPORTANT MANAGEMENT QUESTIONs REI.-ATIED TO maintaining sustainable fisheries resources? THiF RESEARCH QUEiSTIONS What are the acceptable levels of change in What are the most important areas of habitat to habitat variables?What are the boundaries of protect? The Magnuson-Stevens Fisheries acceptable change? For example, how much Conservation and Management Act (MSFC-MA) of 1996 requires that fisheries managers water can be harvested for offstream use and delineate, protect, and conserve essential fish how much can the seasonality of flow regimes habitat (EFH). Baseline ecological data must be altered without major impacts on fish com-munities. How often can a benthic conm.unity be collected on existing habitats and their asso-ciated fish communities so that managers can be trawled before it begins to degrade? determine which habitats should be considered What are the quantitative relationships between essential to fish, what threats these habitats habitat change and watershed activity? It is face, and what level of protection they need. important to establish the linkages between The MSFCMA provides the opportunity to des-watershed activities and fish habitat. ignate a subset of EFH as habitat areas of par-ticular concern (HAPC). These "HAPC's" ate Quantitative relationships will have to be estab-lished. For example, what land use practices especially critical to some species of fish, vul-contribute to sediment runoff and how can land nerable to human impacts, and therefore in use practices be modified to reduce sediment need of high levels of protection. This may be important if there are multiple choices for a contribution to an acceptable limit?
- 97) t FjC:
D1 .' & ý11CI.:IRI.,% 17\1 What are the habitat rehabilitationoptions? In nearshore areas are probably responsible for certain circumstances management actions to past and onIgoing declines in some nearshore rehabilitate degraded habitat may be both desir- fisheries. able and practical. Managers need data on spe- e. The most critical habitat question relating to cific rehabilitation requirements. For example., commercial fish in New England at the it may be possible to replant salt marshes, but moment is how habitat alterations in offshore managers need to know what are the hydrologic, regions are affecting fish currently at low pop-geomorphologica, and production characteris- ulation numbers after years of overfishing. The tics that will make salt marshes productive fish impacts of widespread and intense disturbance habitats? Cost is another obvious consideration. of offishore benthic communities by mobile gear on fish survivorship, particularly juvenile groundfish arid demersal eggs of pelagic species,
SUMMARY
AND CONCLUSIONS are potentially significant. Its affect on fish
- a. Over time, the problem for coastal habitats has population numbers has not been quantified changed from outright destruction to more sub- yet. Such alterations on offshore habitats have tie degradation, such as e utrophication. In off not been as significant as overfishing in shore habitats, the recent expansion of mobile explaining the current fisheries decline, however, gear to habitats that were formerly immune to existing data on the impacts of mobile gear dragging and bottom dredging has exacerbated suggest that the rate of recovery will be impeded the impact of fishing activities on habitats and without habitat conservation and managiement.
the fisheries they support. The impacts on fish- f. A number of modeling studies suggest that eries will likely depend on the type and extent even within the context of overfishing, habitat of the habitat alteration, the frequency of the degradation can still have an impact on fish disturbance compared to natural changes, the populations. characteristics of the habitat, and the life histo-ry characteristics of the species involved. AcKNOVNLELDGI ENTS
- b. Habitat degradation can drastically alter fish communities. Eutrophication and alteration of We thank our colleagues for stimulating and freshwater inflows are currently the two most challenging conversations on the relative impor-prevalent problems in nearshore habitats. tance of human versus natural factors controlling Offshore, substantial changes in the physical populations. Reviews by Peter Auster, Mark and biological structure of habitats as a result Chandler, and William Robinson contributed greatly of the widespread use of mobile gear have been to this manuscript. This work was supported in part documented. How these perturbations impact by the Jessie B. Cox Charitable Trust, The National fisheries and the marine food web is still under Science Foundation (NSF-OCE 9726921, NSF-investigation. DEB 9726862), the Mellon Foundation, the
- c. Winter flounder provides one case where habi- Environmental Protection Agency (R825757 1),
tat degradation is believed to impact certain and the Massachusetts Bays Program. coastal populations measurably. Toxic pollu-tion, water withdrawals and other forms of LITERATURE CITED habitat degradation reduce the viability of eggs and juveniles. The extent of these impacts Able, K.W., S.M. Hagan, and S.A. Browyn. 2003. Mechanisms of marsh habitat alteration due to Phragmites: Response of young of varies from place to place. the year mumotichog (Fundulus heteroclitus)to treatment for
- d. Loss and degradation of coastal habitats are Phragmnites removal. Estuarie 26:484-494.
Aleem, A. A. 1972. Effects of river outflow management on marine probably not the major cause of recent declines life. Mar,.io. 15: 200-208. in most commercial fish stocks in New England. ASMFC. 1992. Fishery management plan lor inshore stocks of winter This is because most of the currently important flounder. Fisheries Management Report No. 21 of the Atlantic States Marine Fisheries Commission, ASMFC, Washington, DC. fisheries are based on offshore populations 138pp. with no direct ecological connection to Auster, P. J. and R.W. Langton. 1999. The effects of fishing on fish nearshore habitats. Habitat alterations in habitat. In : L. Benaka (ed.). Fish Habitat: Essential Fish Habitat
iitýPrtilt ti-oss !\\t. rii:,;R.\DTI:.s)i:i 93 iVFH)and Rehabi I itation. American Fisheries Society, B3ethesda, tats in Mainc: An ecosystem appiroach to habitats. Part I: Benthic
-Maryhand. habitats. Maine Natural Areas Programt Dept. of Fconomic and Auster. I' .1.and R. .1. Malatesta. 1995. Assessing the role of non- Co.omunity Development. Augusta. ME. 51 pp. + appendix.
extractive reserves for enhancing harvested populations in ten- Bry insky. N1, J. Gibson and D. C. Gordon Jr. 1994. Impacts of floutn-perate and boreal marine ecosystems. In: N. Shackell and J. I-1. der trawls ott the intertidal habitat and community of the Minas M. Williams (eds.). Marine Protected Areas and Sustainable Basri- Buy of Fundv. Can .1. Fish. Aquat. Sci. 51. Fisheries: Science and Managemlent of Protected Areas Buchlsbatttt R.N. led.) 19920 Tiuntit the tide: Toward a livable coast. Association. Wolfville, N.S. pp.82-89. in Massachusetts. Massachusetts Audubon Society, Litncoln, MA. Auster, 1..J.. J..t.Malatesta and C. 1_I)onaldson. 1994. Small-scale 12 ! 1 habitat variability and the distribution of postlarval silver hake. PIuchsba'um RN.. F. 1. Short and D. 1. Cheney. 1990. Phenolic-
,krhlccius bilineoris. Proceedings of the G( f lot Maine I labhit nitirogen interactions in eelgrass. Zostera iriinwo L._ Possible Workshop. RARGOM Report Number 94-2:82-86. implications for wasting disease. Auat. But. 37:291-297.
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Factors inrllucneing distribution of jrvenlIC velloiw'- Short FT., D. NI. Burdick, .. S. Woll'and G. F. Jones. 1993. Fekrass tail flounder (Limandafrtferigineo) oi thie Grand Bank of in estuarine research reserves alon' the East Coast ITS A Part 1: Newfoundland. Neill. J. Sea Res. 29: 191-203. Declines from pollution and disease. and Part I1: Management ot 'Watling, L. and F. A. Norse (eds.) 1999. Special section Effects of celerass meadows. NOAA-Coastal Ocean Program Publ. 107 pp. mobile fishing gear ott marine benthos. Conserv. Bio. 12:1178-Sntith. E. M. and P. T. Howell. 1987. The effeicts of bottom trawling 1240. on American lobsters, Hloirerus aniericanus, in Long Island Watzin, M. C. and J. G. Gosselink. 1992. The fragile flinue Coastal Sound. Fish. Bull. 85:737-744. wetlands of, the continental United States. Louisiana Sea Grant Sutmmers. J.K. 1989. Simulating the effects of power plaint entrain- College Program. I..S.U. Baton Rouge, IA US Fish and inent losses on estuarine systems. F;col. Model. 49:31-47. Wildlife Service, Washington DC; and National Oceanic and Strtcliffe, W. It, Jr. 1973. Correlations between seasonal river dis- Atmospheric Admin.. Rockville MI). charge and local landings of american lobster and Atlantic halibut Walters, C. J. and ti..hanes. 1993. Recruitment limitation as a cotise-in the Gulf of St. Lawrence. J. Fish. Res, Board Can. 30:856-859. quence of natural selection for Use of restricted feeding habitats Teal., J. and M. Teal. 1969. Life and Death of the Salt Marsh, and predation risk taking by Juvenile fishes. Can. J Fish Aquat. Ballantine Books, NY Sci. 50:2058-1070. Thayer, G., W. Kenworthy and M. Fonseca. 1984. The ecology ofeel- Welsh, B. L..and F. C. Filer. 1991. Mechaniisfs controlling summer-grass meadows of the Atlantic Coast: A community' profile. U.S. time oxygen depletion in Western Long Island Sound. Estuaries. Fish Wildl. Ser. FWS/OBS-84/02. 147 pp. 14:265.278 Tiner. R. W. 1984. Wetlands of'the United States: Current status and Whitlatch, R. 1982. The Ecology of New Entland Tidal Flats. recent trends. U.S. Dept. of Interior, USFWS, National Wetlands FWS/OBS-8 1/01. U.S. Dept. of the Interior. Washington, DC. Inventory Project. 59 pp. 125 pp. Tiner, R. W. 1991. Recent changes in estuarine wetlands of' the coter- Wippelhauser, G. S., and J. D. McCleave. 1987. Precision of behavior minous United States. Coastal Wetlands, Coastal Zone 91 Conf. ofnmigrating juvenile American eels (Anguilla rostrata)utilizintg ASCE, Long Beach, California: p. 100-109. selective tidal stream transport. .. Cotns. Ciem. 44:80-89. Tiner, R. W. and W. Ziini, Jr. 1988. Recent wetland trends ii south- Witman, J. 1. and K. P. Sebens. 1992. Regional variation in fish pre-eastern Massachusetts. Prepared for USACOE. U.S. Dept. of dation intensity: A historical perspective in the Gulf of Maine. Interior, USFWS, National Wetlands Inventory Project. 8 pp. Oceolocia 90:305.315. Townsend, D. W. 1983. The relations between larval Fishes and zoo-plankton in two inshore areas of the Gull' of Maine. J. Plankton Res, 5:145.173. Townsend, D. W. 1991. Influences of oceanographic processes on the biological productivity of the Gulf of Maine. Rev. Aquat, Sci. 5:211.230. Townsend, D. W., and J. J. Graham. 1981. Growth and age structure of larval Atlantic herring, Clupea harengus harengntr, in the
INS[ IOR F [I V~A VE NIOI{AIAI.Y AN\ID I I A R\ E IN( 97 Chapter VI Effects of Natural Mortality and Harvesting on Inshore Bivalve Population Trends DIANE J. BROUSSEAU FairfieldUniversity Biology Department Fairfield,CT 06430 USA INTRODUCTION (1982-1998) Massachusetts has been the leader nationwide in the production of bay scallops and in
.most years is second only to Maine in the produc-The future ofthe qcuahaung industry of tion of soft-shell clams. Combined, the annual Massachusetts lies in the hands of her cit- landings of quahogs, soft-shell clams and bay scal-izens, since only through public sentiment lops in Massachusetts have ranged between 3-5 can suitable laws be obtainedfor its million pounds between 1982 and 1993, valued at preservalion. between eleven and twenty-one million dollars, ex-
-David L. Belding, 1912 vessel price (NOAA, 1999). Commercial landings (in Belding, 1930b) and average value of the quahog, soft-shell clam and bay scallop fisheries in the U.S. from 1982-1998 are shown in Figure 6.1. Since ex-vessel The inshore bivalve fishery of New England is prices do not reflect costs associated with manag-focused on three commercial species: the soft-shell ing the fishery, such as enforcement, operation of clam (= soft clam; Mya arenaria),the quahog depuration facilities, etc., these values may overes-(= quahaug, hard-shell clam, or hard clam; timate the realized economic value of the Mercenariamercenaria)and the bay scallop resources.
(Argopecten irradians).The soft-shell clam inhab- Although no complete map of productive shell-its intertidal mudflats throughout the region but the fish beds exists, the Massachusetts Geographic primary fishery for this species is centered along Information System (MASS GIS) program in col-the coast of Maine, the North Shore of laboration with the Department of Marine Fisheries Massachusetts and in Boston Harbor. The quahog, (DMF) is currently mapping locations of potentially which inhabits intertidal and shallow subtidal flats, productive beds and their public health classifica-and the bay scallop, which is associated with eel- tions along the Massachusetts coastline. The map-grass beds (Zostera marina), are predominantly ping of shellfish management areas and sampling distributed in southern New England (South Shore stations has been finished (data available from T. of Massachusetts including Cape Cod and the Hoopes, DMF). The completed project will provide Islands, Rhode Island and Connecticut). needed baseline information against which future Since all three species are harvested in assessments of shellfish growing habitat can be Massachusetts, and since Massachusetts fisheries compared. Such information will also be useful to data, albeit limited, are available on each of them, managers interested in selecting seeding sites for this state will be highlighted throughout this chapter. juvenile shellfish (Parker et al., 1998). Historically, Massachusetts has been a major shell- There is a growing concern among scientists fish producer. During the past fifteen years, and managers that the shellfish resources in many
98 areas of New England are declining (Rice, 1996). In fact, as early as 1905, reports were issued indi-cated that a decline in shellfish resources was already underway (Kellog, 1905; Belding, 1930a). (, This decline is reflected in the U.S. commercial landing statistics (Figure 6. 1), especially for soft-ol,2 UI il S 40 H shell clam and bay scallop resources, the bulk of which are harvested in New England. Annual catch statistics compiled by Matthiessen (1992) suggest that the landings of quahogs in Massachusetts have steadily declined fr'om the 1950s to the 1990s (Figure 6.2a). Statewide landings of soft-shell clam have remained fairly stable (Figure 6.2b), but land-Year ings from Buzzards Bay (Alber, 1987) during the period 1955-1985 have steadily decreased. Bay 30- scallop landings from the 1950s to the 1990s show Soft-shell clam considerable variability, with years of high produc-tion followed by several years of decline (Figure 6.2c), making it difficult to detect a definite trend. 20 A downward trend in these stocks may simply be 0 masked by natural variability. There are a number of possible reasons for declines in landings of bivalve shellfish along the New England coast. One may simply be reduced fishing effort - fewer shellfishermen working coastal areas. This possibiity seems unlikely, how-ever, since on Cape Cod alone, the number of 20-Year recreational clam permits issued each year has roughly doubled between 1970 and 1990
"_-" 10-(Matthiessen, 1992). More likely, the reduced land-20O ings are the result of reduced availability of the Bay scallop resource due to increased contamination, habitat degradation or loss, and 'overfishing'. The degree to which any or all of these factors contribute to shell-0P Ie 1"" ' -lc fish decline, however, remains to be assessed. The
¢- V potential role of contamination are addressed by McDowell (Chapter 7), whereas habitat issues are discussed by Deegan and Buchsbaum (Chapter 5).
It is the purpose of this chapter to focus on the role of natural and fishing mortality in the apparent decline of inshore shellfisheries resources in New England, using Massachusetts as the primary Year example. Figure 6.1. U.S. commercial quahog, soft-shell clam and bay scallop landings in millions of pounds of shucked LIFE HISTORY INFORMATION - FACTORS meats and landed value (millions of dollars), 1982-1998, AFFECTING NATURAL MORTALITY as reported by the U. S. Dept. of Commerce, NOAA, Fishery Statistics of the United States, http://www.st.nmfs.gov- The effective management of any fishery pls/webpls/MF_ANNU AL_LANDINGS.RESULTS. depends on availability of reliable biological infor-(black bar =landings; grey bar = value). mation for the species in question. First, an
INSIlORE BIVA\LVE MORTAIITY AND IIARVFSTING 99 understanding of the causes of natural mortality in 3 I Quahog populations is necessary in order to assess the degree to which overall mortality is due to harvest-ing. Secondly, knowledge of life history informa-Ut tion is essential if harvesting strategies are to be CD z_ 0 developed and fishery impacts are to be assessed z through the use of mathematical models. Among the first accounts of the natural history I I i,i~ I huh of the commercially-important inshore bivalves of Massachusetts are the reports of Belding (1930ab,c) published by the Massachusetts 1.
- 0) Division of Fisheries and Game in the early 1900s
ýý 1ý5ýý , 0 05 and reprinted in 1930 [and again in 2004]. These Year reports give detailed information on soft-shell clam, quahog and bay scallop life histories and fisheries. Since the publication of those early reports, a considerable body of literature has devel-oped, much of which is of importance in assessing V) z I and managing these three species. In some areas, however, critical information is still lacking.
Z 2! n SOFT-SHELL CLAM (A'fya arenaria) Mva arenariareaches sexual maturity in its second year of life (Coe and Turner, 1938; Porter, 1974; Brousseau, 1978, 1987). Gamete production rate varies from year to year and from population to population for reasons yet to be determined (Brousseau and Baglivo, 1988). The time and fre-quency of spawning varies widely in geographically separated populations (Table 6.1). The traditional view of fixed patterns of spawning based on latitu-dinal range is inadequate; habitat-specific exoge-z nous factors such as local water temperature and Z food supply must be considered as well. z a Settlement of recently-metamorphosed larvae from the plankton, approximately two weeks after fertilization, is the major source of recruitment into the population (since post-larval transport of spat is probably limited). Large fluctuations in yearly recruitment are characteristic of marine organisms Year with planktotrophic larvae. Larval recruitment, Figure 6.2. Commercial quahog (a), soft-shell clam (b) when it occurs, may represent a large proportion of and bay scallop (c) landings (millions of pounds of the population, and that year-class may dominate shucked meats) in Massachusetts, 195 1-1993. Solid bar the population for many years to come ("year-class = landings as modified from Matthiessen, 1992; gray phenomenon"). Recruitment fluctuations from year bar = landings as reported by NMFS, Fisheries Statistics to year are largely the result of differential mortali-Division (http://www.st.nmfs.gov/ow- ties which can occur during three critical phases: 1) commercial/gcrunc-cgi.sh?SELECTIONSTATE=Mas fertilization, 2) the free-swimming planktonic stage sachusetts&qyear I = 1982&qyear2= 1999).
100 BRoUSSE.., Table 6.1. Duration of the spawning season of MyIva arenariaalong the Atlantic coast reported in the literature. (Modified from Brousseau, 1987). STUDY SITE MONTI-H REFERENCE J F M A M J J A S 0 N D Malpeque Bay, Canada Stafford, 1912 Sullivan, 1948 St. Andrews, Canada Stafford, 1912 Battle, 1932 Eastern Maine Ropes and Stickney, 1965 Boothbay Harbor, ME Ropes and Stickney, 1965 Robinhood Cove, MA 1951 Welch, 1953 1952 Welch, 1953 Gloucester, MA 1973 Brousseau, 1978 1974 Brousseau, 1978 1975 Brousseau, 1978 Plum Island Sound, MA Ropes and Stickney, 1965 N. of Cape Cod Belding, 1907 N. of Boston Belding, 1930a Ipswich, MA Stevenson, 1907 Plymouth, MA Stevenson, 1907 Southern Cape Cod Belding, 1907 Belding, 1907 Chatham, MA Stevenson, 1907 Martha's Vineyard Deevey, 1948 Woods Hole, MA Bumpus, 1898 Rhode Island Mead and Barnes, 1904 Wickford, RI 1950 Landers, 1954 1951 Landers, 1954 1952 Landers, 1954 Stonington, CT 1983 Brousseau, 1987 1984 Brousseau, 1987 1985 Brousseau, 1987 New Haven, CT Coe and Turner, 1938 Westport, CT 1984 Brousseau, 1987 1985 Brousseau, 1987 New Jersey Belding, 1930a New Jersey Nelson and Perkins, 1931 Chesapeake Bay Rogers, 1959 Chesapeake Bay 1956 Pfitzenmeyer, 1962 1957 Pfitzenmeyer, 1962 1958 Pfitzenmeyer, 1962 1959 Pfitzenmeyer, 1962
INSIORE FBVALVE MORTALITY AND IIARVESTING 10 I (a) Bain Island, Stoniigton. CT (b) Jordan Cove, \Vaterlord, CT (c) Long Wharif New I laven, CT E 04 0( Size Class (ame) sloe Class (mm) Slhe Class (mem) (d) Oyster River, Wesi Haven. CT (f) Milford Point. Milford, CT S 0 Si.. Cl..s (040) Size Class (mm) (g) Old Mill Beach, Westport, CT (hl Saugatuck River, Westport, CT (i) Cove Beach, Stamford, CT E E-Slze Class (0am) Size Class (00) sl Closs (ra) .Figure 6.3. Size frequency distributions of Mya arenaria(soft-shell clam) during the late summer, 1988 for nine pop-ulations in Long Island Sound, (a) Barn Island; Stonington, CT; (b) Jordan Cove, Waterford, CT; (c) Long Wharf, New Haven, CT; (d) Oyster River, West Haven, CT; (e) Gulf Pond, Milford,/CT; (f) Milford Point, Milford, CT; (g) Old Mill Beach, Westport, CT; (h) Saugatuck River, Westport, CT; and (i) Cove Beach, Stamford, CT. and 3) the early post-settlement larval attachment may result from a number of abiotic factors includ-phase. ing anoxic conditions, unfavorable temperatures, The extent of this early life stage mortality can low salinities and the effects of contamination (see range from 40 to 100% (Muus, 1973; Gledhill, McDowell, Chapter 7). Biotic factors such as inter-1980; Brousseau et al., 1982; Brousseau and specific competition (Bradley and Cooke, 1959; Baglivo, 1988; MacKenzie, 1994). As with other Sanders et al., 1962; Moller and Rosenberg, 1983; newly settled invertebrates (Hunt and Scheibling, Andre and Rosenberg, 1991), predation (Kelso, 1997), catastrophic post-settlement mortalities of 1979; Wiltse, 1980; Ambrose, 1984; Smith, 1952; newly-recruited M arenariaare not unusual Guenther, 1992) and biological disturbance (Dunn (Brousseau, unpubl.) and appear to be characteris- et al., 1999) may also contribute significantly to tic of some environments. High mortality of spat post-settlement mortalities in M arenaria.The
102 BROUSSF.-\I degree to which these various causes of mortality to increased risk of predation (Ambrose et al:, 1998). are responsible for recruitment fluctuations is still Biotic factors such as competition, predation, largely unknown. disease and parasitism are probably more signifi-In addition to temporal variations, newly-settled cant contributors to natural mortality than abiotic
- 1 arenlrwia also show marked spatial variation in ones, but again the severity of the effect may vary recruitment, both within and between populations depending on the size (age) of the individual. The or population subunits (Snelgrove et al., 1999; failure of the soft-shell clam fishery of New Vassiliev et al., 1999). Patterns of recruitment in England during the early 1950s was attributed to nine populations/subpopulations of M. arenaria predation from the green crab (Glude, 1954), but from Long Island Sound during the 1988 late sum- this effect was most likely operating on juvenile mer spawning period are shown in Figure 6.3. clams. Mva arenariareach a refuge from predation Spatial variation in spatfall may occur in a wide once they attain a certain size or have the ability to range of circumstances and depend on such factors burrow to depths beyond the range of the predator as hydrodynamics (Emerson and Grant, 1991), suit- (Edwards and Huebner, 1977; Commito, 1983; ability of settling substrate and differential survival Smith et al., 1999). Nonetheless, field experiments of post-settlement juveniles. have demonstrated that one deep-burrowing Natural mortality rates, although high for lar- nemertean, Cerebratuluslacteus, is an important vae and spat, tend to decrease at close to an expo- predator of adult soft-shell clams (Rowell and Woo, nential rate with increasing size and age in M. are- 1990). Competition for food or space is most likely naria.(BrOusseau, 1978; Brousseau and Baglivo, a substantial cause of mortality only in the small, 1988). Survivorship schedules fbllow the type Ill surface-dwelling clams. On the other hand, para-survivorship curve of Deevey (1947) - extremely sites have been reported in both juvenile and adult heavy mortality early in life followed by low. M. arenaria (Uzmann, 1952; McLaughlin and roughly constant, mortality rates thereafter. Faisel, 1997) and two types of neoplasms have Quantitative inter-populational differences in age- been identified. It has been shown that gonadal specific survival rates are measurable (Brousseau neoplasms inhibit normal oogenesis and spawning and Baglivo, 1988), suggesting that within the (Barber, 1996), whereas hematopoietic neoplasia, a framework of a general life history strategy, a proliferative disorder characterized by increased response to the biotic and abiotic components of numbers of "leukemia-like" cells in tissues and the immediate environment is possible. organs (Farley, 1969) has been shown to be a major The environmental factors with the greatest source of mortality in field populations (Brousseau effect on the survival of estuarine bivalves, especially and Baglivo, 1991; Weinberg et al., 1997). '
the surface-dwelling juveniles, are temperature, The lifespan of M. arenariahas been estimated salinity, dissolved oxygen, substrate, water move- at 10-12 years in Massachusetts populations ment, sediment transport and food availability. (Belding, 1930a) and the oldest individual found in Adult M. arenaria,however, typically inhabit the a study of age/growth in Long Island Sound was 11 intertidal zone and are adapted to a wide range of years of age (Brousseau and Baglivo, 1987). An fluctuations in water temperature and salinity inverse relationship between growth rate and age (Belding, 1930a; Chanley, 1957; Pfitzenmeyer and has been described for M. arenariaand a general Drobeck, 1963; Castagna and Chanley, 1973; Shaw trend of increased growth rates with decreasing and Hammons, 1974). In addition, sediment depth latitude exists (Table 6.2), however, geographical tends to buffer temperature and salinity variations considerations alone are poor predictors of growth (Sanders et al., 1965; Johnson, 1965, 1967), proba- patterns (Belding, 1930a; Newcombe, 1935; Swan, bly minimizing.the effects of these factors on sur- 1952; Smith et al., 1955; Newell, 1982; Brousseau vival of adult clams. The physical disturbance of and Baglivo, 1987) or mean life expectancies. clams brought about by activities such as harvest-ing is also a possible factor causing mortalities. Studies have shown that commercial baitworn dig- QUAHOG (Mercenariamercenaria) ging negatively affects the survival of M arenaria The youngest age at sexual maturity reported by directly damaging shells and by exposing clams
INNSIORE BI VAL\IX NI:MOKI.\LTTY AN DI) I A RN\ESH NG; I03) Table 6.2. The time needed for Mwva arenariato reach harvestable size (51 mm) as reported in the literature (Adapted fiom Brousseau and Baglivo, 1987). Site Latitude Age at Reference 51 mm (yrs) Prince Wi-liam Sound, AL 60'34'N 6-7 Feder and Paul. 1974 Roskilde Fiord, Denmark 55'34'N 6-7 Munch-Petersen, 1973 Lynher River, England 50'23'N 3-4 Warwick and Price, 1975 Econiomy Pt., Nova Scolia 45 20'N 5-6 Newcombe, 1935 (8 ft. above chart datum) St. Andrews, New Brunswick 45 10'N 5 Newcombe, 1935 (8 ft. above chart datum) Clam Cove, New Brunswick 44 45'N 7 Newcombe, 1935 (16 ft. above chart datum) Clam Cove, New Brunswick 44 45'N 5-6 Newcombe, 1935 (8 ft. above chart datum) Sissiboo River, Nova Scotia 44'30'N 5-6 Newcombe, 1935 (8 ft. above chart datum) Bedroom Cove (Georgetown Is.), 43 35'N 5-6 Spear and Glude, 1957 ME Sagadahoc Bay (Georgetown Is.), 43 35'N 3-4 Spear and Glude, 1957 ME Rowley, MA 42 26'N 2-3 Belding, 1930a Quincy, MA 42'09'N 2-3 Turner, 1949 Gloucester, MA 41'39'N 2-3 BrousseaIu, 1979 Monomoy Pt., MA 41°30'N 2 Belding, 1930a West Falmouth, MA 41 30'N 2 Kellogg, 1905 Narragansett Bay, RI 41 24'N 1-2 Mead and Barnes, 1903 Stonington, CT 4 1'20'N 1.5 Brousseau, 1987 Old Mill Bch., Westport, CT 4l°07'N 1.5 Brousseau, 1987 Saugatuck R., Westport, CT 41 06'N 3 Brousseau, 1987 for M. mercenariais one year of age (Loosanoff, totrophic larvae, and like the soft-shell clam, 1937a; Eversole et al., 1980; Bricelj and Malouf, recruitment of the quahog is sporadic. Unlike the 1980). The spawning time of quahog populations soft-shell clam. (Belding, 1930b; Molter and varies with latitude, and the length of the spawning Rosenberg, 1983), however, there are no reports in period increases with decreasing latitude (Table the literature of the settlement of extremely large 6.3). Local conditions play an important role in the concentrations of spat. Quahogs are seldom found reproduction of this species. Appropriate tempera- in high enough densities to allow commercial seed ture and food supply is necessary to condition qua- harvesting'(Kraeuter and Castagna, 1989). The lar-hogs to spawn in the laboratory (Loosanoff and vae lead a precarious existence at the mercy of both Davis, 1950, 1963; Castagna and Kraeuter, 1981). natural enemies and adverse physical conditions. Gametogenesis.coincides well with phytoplankton Work to date suggests that predation by organ-abundance (Loosanoff, 1937b; Ansell and isms such as crabs, carnivorous snails, demersal Loosmore, 1963) and Kassner and Malouf (1982) fish and birds is the dominant factor controlling have suggested that food availability influences the quahog abundance in naturally-occurring sets timing of spawning. Whether or not food or certain (Hibbert, 1977; Kraeuter and Castagna, 1985; chemical constitutents within their food act as a MacKenzie, 1977; Virnstein, 1977; Bricelj, 1993; stimulus to trigger spawning in natural populations Micheli, 1997), but the role of established infauna remains to bedetermined. in limiting M. mercenariarecruitment remains The major source of M mercenariarecruits unclear. In spite of a growing number of studies into the population is from the settlement of plank- which have demonstrated that established benthos
104 0o,*ss*.S Table 6.3. Spawning period for populations of .\Iercencariamercenarca along the east coast of North America based on evidence of gamete maturity and release. (Modified from Eversole, 1989). STUDY SITE TEMP (-C) MONTI-H REFERENCE J F M A M J J A S 0 N D Wellfleet, MA 24 Belding, 1930b Milford, CT 23-25 Loosanoff, 1937b Long Island, NY 20 Kassner and Malouf, 1982 Long Island, NY 20 Delaware Bay, DE 25-27 Keck et al., 1975 Core Sound, NC 27-30 Porter, 1964 N. Santee Bay, SC 20 Manzi et al., 1985 Clark Sound, SC 20-23 Eversole et al., 1980 Wassaw.Sound, GA 22-26 ------------------------------------ Pline, 1984 Alligator HIbr., FL 16-20 Dalton and Menzel, 1983 Indian R., FL <30 ---------------------------------------------- Lesselman et al., 1989 can adversely affect the early recruitment of benth- magnitude o4 the impact of natural sources of mor-ic animals (Williams, 1980; Luckenbach, 1984; tality on larval/juvenile survival. The only pub-Andre and Rosenberg, 1991), a study by Ahn et al. lished account is a study of post-settlement survival (1993) has shown that dense Gemma gemma popuI- in a New Jersey population in which a natural mor-lations do not reduce the survival of newly-settled tality rate of 75% was reported during the first six quahogs in a sandy substrate even when food is months of life (Connel et al., 1981). limited. Similarly, laboratory studies by Zobrist and Life expectancy of adult quahog isnmarkedly Coull (1994) have shown that growth and survivor- higher than that of juveniles (Hibbert, 1977; ship of juvenile clams is not significantly reduced Connel et al., 1981), and survivorship probably by the presence of meiofauna. Rice et al. (1989) also follows the type III survivorship curve of have shown that intensive shellfishing enhances Deevey (1947). The adult quahog has few natural settlement and/or survival of juvenile quahogs, but enemies, few parasites and few pathogens that Whether this is dueto removal of competing adults cause catastrophic mortalities. The occurrence of or to the disturbance of the sediment itself is not gonadal neoplasia in M mercenaria has been docu-known. There is surprisingly little in the way of mented but is rare (Bert et al., 1993), and, in fact, empirical data available, however, to assess the the quahog has been reported to possess an anti-
I N S 1 (0lR AL AN) 13VALVIE %0OIRrA LITY IIAR':1ST1 N 105 tumor substance called "niercenene" which may 12 to 18 months (Barber and Blake, 1983). Adult protect the species from cancer (Schmeer. 1964). bay scallops experience a period of mass mortality The recent appearance of QPX, a protistan disease during their second winter and before the start of reported to occur in quahogs from Prince Edward the second spawning cycle. Belding (1930c) esti-Island (Whyte et al., 1994) and Massachusetts mated that under natural conditions only 20% of (Smolowitz et al., 1998), may represent a signifi- the A. irradiansreach the two-year mark. The cant threat to survival in juvenile and young adult cause of the mortality has been attributed to senes-clams. cence (Belding, 1930c, Bricelj et al., 1987), but the Mortality within natural populations of Alf. mer- adult bay scallop also has natural enemies. Sea cenaria has been attributed to low salinity by stars and the oyster drill (Urosalpinx cinerea) both Haven et al. (1975). A mininum salinity tolerance prey on adult bay scallops, but their damage is of 10 to 13 PSU was suggested by Castagna and believed to be minimal. Chanley (1973) and salinity tolerance tests indicate Gamete maturation in A. irradiansis dependent that salinities below 10 PSU would likely result in upon food supply and a certain minimum tempera-death during a 10-day exposure period (Winn and ture (Sastry, 1968), but spawning is not restricted to Knott, 1992). On the other hand, quahogs appear to a particular period in the year or to a critical tem-be quite tolerant of low temperatures and low lev- perature (Sastry, 1963). As with soft-shell clams els of dissolved oxygen (Winn and Knott, 1992). and quahogs, there is considerable geographic dif-Mercenariamercenaria is one of the longest ferences in spawning season, with spawning occur-lived inshore bivalves of New England. Belding ring later in the year in more southerly populations (1930b) estimated that quahogs live at least 20 to (Belding, 1930c; Sastry, 1966; Barber and Blake, 25 years but Jones et al. (1989) reported two speci- 1983; Bricelj et al., 1987; Peterson et al., 1989; mens from Narragansett Bay that were 40 years of Tammi et al., 1997; Tettelback.et al., 1999). Bay age upon capture. This long lifespan is probably scallops in Massachusetts commence spawning due in part to the clam's hard shell and its ability to with increasing temperatures (Belding, 1930c) close up completely for extended periods of time, while those further south spawn with decreasing excluding all but the most persistent of predators. fall temperatures (Gutsell, 1930; Sastry, 1963). Bay scallop recruitment clearly shows a high degree of variability from year to year (Peterson BAY SCALLOP (Argopecten irradians) and Summerson, 1992) which may in large mea-Unlike the two other bivalves discussed above, sure be due to variable larval mortality. The initial Argopecten irradiansis a hermaphroditic bivalve free-swimming stage is followed by settlement (i.e. possessing both a testes and an ovary when onto elevated surfaces, primarily eelgrass blades sexually mature). However, only.one type of sex (Zostera marina), to which they attach by means of product is usually given off at any one time byssal threads. Once settlement occurs, bay scal-(Belding, 1930c). It is hypothesized that this non- lops are vulnerable to predation due to their thin simultaneous release of gametes helps prevent self- shells, epifaunal habit and inability to maintain pro-fertilization by individuals within the population. longed valve closure. In spite of the fact that eel-grass has been shown to be an effective spatial Self fertilization, however, could play a role in the persistence of populations at very low densities. refuge from some crustacean predators (Pohle et Most scallops only spawn once, during their al., 1991), high predatory risk still exists for first year of a two-year lifespan. Such a short life unattached scallops prior to attainment of a partial size refuge (ca. 40 mm) from most predators. span is unusual among marine bivalves. A life expectancy of 20-30 months has been reported for Periodic losses of eelgrass, such as that due to a "wasting disease" in the 1930s, have been disas-bay scallops from Massachusetts (Belding, 1930c). trous for the bay scallop industry (Thayer et al., The maximum life expectancy of Long Island bay scallops is 22-23 months (Bricelj et al., 1987). In 1984). The occurrence of unusual algal blooms North Carolina, most scallops live only 14 to 18 (Aureococcus anophagefferens) has been linked to recruitment failure of bay scallops in LongIsland months (Gutsell, 1930), while in Florida, they live waters (Siddall and Nelson, 1986; Cosper et al.,
106 BROUSSEAU 1987; Tettelbach and Wenczel, 1993). The larvae Table 6.4. Comparison of the shellfish landings (quahog either starved to death (Gallagher et al., 1989) or and soft-shell clam) as reported for the years 1990 - encountered suboptimal temperatures for survival 1992 to the Massachusetts Division of Marine Fisheries due to delayed spawning of the adults brought by shellfishermen and constables. Landings statistics are about by the presence of the algae (Tettelbach and reported as number of bushels landed. Rhodes, 198 1). An outbreak of the red tide Landings dinoflagellate, Plvchodiscus brevis, has also been linked to the recruitment failure of the bay scallop Shellfishermen Constables in North Carolina waters (Summerson and Soft-shell clams Peterson, 1990). Town: Gloucester 1990 203 2,000 STOCK ASSESSMENT 1991 953 3,000 1992 1,231 4,000 A large part of the difficulty in assessing the role of overfishing on inshore bivalve stocks is the Town: Rowley lack of dependable stock assessment data. In 1990 285 Massachusetts, a statewide survey of marine 1991 281 resources, including shellfish, was conducted about 1992 462 3,800 30 years ago by the Division of Marine Fisheries Town: Newbury and published between 1965 and 1973 as a mono-1990 2,857 6,000 graph series (Jerome et al., 1965, 1966, 1967, 1968, 1969; Fiske et al., 1966, 1967,1968; Curley 1991 3,584 6,772 et al., 1970. 1972, 1974. 1975; Chesmore et al., 1992 5,180 7,879 1971, 1972, 1973; Iwanowicz et al., 1973, 1974). Town: Essex No follow-up survey was ever done, however, so 1990 1,352 5,000 those studies are not useful in assessing trends. 1991 1,742 5,000 The commercial landings statistics cited in the Introduction (Figure 6.1) are simply the annual 1992 1,603 compilation of the landings statistics reported to the U. S. Department of Commerce by the states. Quahogs They are of limited use in assessing trends in abun- Town: Dartmouth dance since they are biased by the level of fishing 1990 7,610 13,564 effort and, in the case of sedentary bivalves, the 1991 6,393 18,951 acreage of shellfish beds open to harvest, both of 1992 2,461 21,884 which can vary from year to year. Measures of landings per unit effort (LPUE) are more instruc- Town: New Bedford tive than landings statistics alone for assessing 1990 1,822 2,235 abundance, and to some degree fishing pressure, 1991 85 940 since decreases in LPUE with increased fishing 1992 225 465 effort suggest a population in decline from over-Town:, Fairhaven fishing (Gulland, 1974). In order to calculate LPUE, annual estimates of 1990 153 16,400 landings as well as a measure of fishing effort are 1991 440 8,100 needed. In Massachusetts, landings records (both 1992 234 44,200 reports from individual shellfishernen, and consta-ble reports) and licensing information from each town are compiled by the State's Division of Marine fishermen, however, may be underestimated. A Fisheries. These data are currently the only means comparison of the shellfish landings reported by available to monitor annual changes in shellfish shellfishermen and those reported by constables for abundance. Reports of yearly catch by individual seven Massachusetts towns selected at random for
INSIIORE BIVALVE MORTALITr AND HIARVFSTING 107 eooo t Soo (b)Newb"ury t (a) Rowley 0 0 600 4-t 400 CL
- 0. 100.
Cn S5 0 Year Year ZO-(c) Quincy * * (d) Gloucester CL 200.e 0 V) wO 40-40 U C 20 M0 _j Yea r* Year Year Figure 6.4. Landings per unit effort estimates calculated from soft-shell clam landings for four municipalities, a) Rowley, MA, 1972-1993. No data available for the years 1979, 1980, 1986, 1991 and 1992; b) Newbury, MA, 1972-1993; c) Quincy, MA, 1978-1993. No data available for 1981; d) Gloucester, MA, 1972-1993. No data available for 1975, 1982, and 1989. the years 1990 - 1992 supports this contention. In spot checks of catch by the local warden. There are each town, the size of the .catch reported by the still other towns where the constable simply bases fishermen was consistently lower than that of the landings estimates on the number of permits issued warden, in most cases by at least 50% (Table 6.4). and the quota allowed, assuming that every As a result, shellfish landings estimates fisherman has caught his quota on every day in submitted by town constables are generally con- which fishing can take place. sidered more reliable, but the reliability of these Another difficulty in determining LPUE from estimates too, can vary from town to town. First, Massachusetts landings reports lies with the the method of estimation is not standardized among method of reporting the number of licenses issued. municipalities. In some cases, constable reports are The state requires that only the total numnber of based on the number of diggers, ability of the dig- shellfish harvesting permits issued by the town be ger, and a production rate estimate for each flat reported. In some towns more than one species dug. Such an assessment requires that the constable may be fished commercially. For example, many of have an intimate knowledge of the harvesters and the towns in Buzzards Bay harvest both quahogs the resource harvested and has time allocated to and bay scallops. Therefore, it is impossible in monitor both. In others, the towns rely on a written most cases to determine the actual number of shell-report from the commercial fisherman coupled with fishermen harvesting each resource.
108 BROUISSEAS U Given the shortcomings outlined above, the 300 (a) Quincy usefulness of LPUE estimates calculated from o Massachusetts DMF shellfish landings reports is limited. However, in the absence of independent stock assessment data, it provides the only source 200 of information currently available to assess trends mi g I CL in abundance of nearshore bivalve stocks. With am these serious limitations in mind, the following assessment was made for the soft-shell clam (A 100-a* resource in Massachusetts. CD a U Estimates of landings per unit effort based on M constable "catch" statistics (bushels per year) and 0 60 80 100 120 140 16 0 the number of commercial shellfish permits issued were calculated for soft-shell clam stocks from the Ucenses following cities/towns: Rowley, Newbury, Quincy and Gloucester (Figure 6.4). These towns were chosen for three reasons. First, soft-shell clams represent the only commercial bivalve resource in 120 0 a a (b) Gloucester these areas and hence it could be assumed that all reported fishing effort was on this resource. t 100' 0 a Secondly, it could be assumed that the acreage 80-open to shellfish harvesting has remained .E a a unchanged. In fact, increases in the amount of 60" acreage closed to shellfishing on the North Shore were negligible during the 1980s, probably because 40
- a this area of the coast has not experienced the rapid Cn a a U 0
increase in development and population compared ,aI to other parts of Massachusetts during this time
- 5 C
20-a
'I period (Buchsbaum, 1992). Thirdly, the number of _j 0 6 100 200 300 commercial licenses issued provides a fair estimate of the actual fishing effort applied in any year. Licenses Even though the number of recreational permits issued far exceeds commercial ones in many towns, Figure 6.5. Relationship between landings per unit effort "mess" diggers account for less than 20% of the for soft-shell clam landings and the number of commer-cial licenses issued for two municipalities, a) Quincy, total catch reported.
MA, 1978-1993; b) Gloucester, MA, 1972-1993. The absence of any clear trend in the annual landings per unit effort values suggests that soft-shell clam stocks have fluctuated dramatically in Of the four data sets, however, the information abundance during the period of analysis, especially from Quincy is probably the most reliable (Figure in the towns of Gloucester, Newbury and Rowley 6.4c). All clams taken legally from Quincy flats (Figures 6.4 a,b,d). In Gloucester, peak periods of must be depurated before being sold. The landings.. abundance occurred during the early 1970s and data reported by Quincy are the actual number of around 1980, with periods of rapid decline follow- bushels taken from Quincy flats which passed ing. These periods of clam abundance were proba- through the depuration plant in Newburyport. bly due to an unusually good spatfall which sus- Unless some clams were reaching market illegally, tained the fishery for a few years (R. Knowles, these production figures should account for all the pers. comm.). In Newbury peaks of abundance clams taken from the flats in those years. Except occurred.in the late 1970s and late 1980s whereas for two years of high abundance (1983 and 1992) in Rowley soft-shell clam abundance peaked in the the reported soft-shell clam production per digger mid to late 1970s. hovered around 75 bushels per year. Again, there is
I NSH(ORE IBIVALVE MORTALIT\Y AND HA RVESFrING o09 no clear indication from these data that LPUE has conducted transect surveys to determine soft-shell shown a decline over the years studied. clam densities in areas of Salem Sound which have The relationship between LPUE and the number been closed to shellfishing for over 30 years (B. of commercial licenses issued for thecities of Chase, pers. comm.). Sites in Salem Sound, Gloucester and Quincy is shown in Figure 6.5. Massachusetts, sampled as part of the DMF's While any plot of landings per unit effort against marine resources study in the 1960s (Jerome et al., effort must be treated with some reserve, decline in 1967) have been resampled and may provide some LPUE as fishing effort increases is usually regard- interesting comparative data. However, these ed as an indication that a stock is overfished efforts are largely local and small in scale. More (Gulland, 1974). The scatter of points for resources should be made available to municipali-Gloucester data and the steady clam production ties so that this type of approach can be extended to from Quincy flats does not support thle contention all areas in the State which support shellfishing that resources in these areas are overfished. To activity. A program similar to the Massachusetts some extent this is a self-regulating fishery. Unlike Coastal Commercial Lobster Trap Sampling offshore fishermen who must maintain a boat and Program (Estrella and Cadrin, 1992), is needed for crew, the capital investment to dig inshore bivalves inshore bivalve resources so that more accurate is small and the diggers will probably choose other trends assessment is possible. employment in years when the resource is not abundant enough to justify the effort. FISIERIES ASSESSMENT In the absence of truly reliable stock assess-mlent data it can only be said that the available information does not support the belief that soft-shell clam resources of the North Shore are We have left indcone those things which overexploited. The inability to make even these we ought to have done: And we have crude assessments for either the quahog or the bay done those things which we ought not to scallop; however, only emphasizes the critical need have done... for more reliable stockassessment information for -Book of Common Prayer all commercially fished inshore bivalves. Most (Anon, 1928) importantly, there is a need for accurate landings information. A system that. allows management per-sonnel to determine the volume of shellfish landed "Overfishing". as it relates to marine resources, on a daily basis should be the goal. Secondly, better can be defined in three ways: (I) as the removal of ways of estimating fishing effort are needed. A so many animals from a biological community that measure of effort such as "hours dug" would pro- ecologically related or dependent species are nega-vide a more instructive measure of the actual dig- tively affected; (2) as the removal of so many ani-ging pressure on a population. In a study done by mals from the population that over time the aver-Creaser and Packard (1993) information on age size of harvested individuals is reduced dra-catch/effort and landings was recorded during all matically (growth overfishing); or (3) as a fishing tides fished from a population of soft-shell clam in effort so intense that the number of animals har-Machiasport, Maine that had recently been opened vested over time declines as a result of lowered for depuration digging. This study could serve as a reproductive output in the harvested population model to managers from other locales interested in (recruitment overfishing). The latter definition is generating reliable catch statistics for their fishery. operative in much of the finfisheries literature The city of Gloucester is presently attempting (Gulland, 1974; Beverton and Holt, 1957; Ricker, to generate more accurate landings information for 1975) and is probably relevant to invertebrate clamflats within the city (R. Knowles and D. stocks as well. Nevertheless, efforts to predict fish-Sargent, pers. comm.)ý Lack of adequate personnel, ing intensities at which this effect will be felt in however, has limited this effort to flats designated shellfish stocks have lagged far behind similar as "management areas". In nearby Salem, a citizen efforts for finfish populations. Over the past few volunteer group (Salem Sound Coastwatch) decades, however, there has been some progress in
11 0 rOIUSSE[ the knowledge of the dynamics of invertebrate models are deterministic. Consequently, they are stocks and a resultant interest in the development not entirely appropriate either for shellfish or other of methods of assessing and managing these marine species in which recruitment ofjuveniles is resources. As these approaches have become more highly variable from year to year and controlled refined, an understanding of the life history, envi7 largely by environmental parameters not yet fully ronment and ecological interactions of the organism understood. Many extensions to early models of has taken on increasing importance. population growth have been developed, including viewing some of the life history parameters as ran-dorm variables and incorporating the effects of har-APPLICATION OF FISHERIES MODEI-S vesting into the model (Beddington and Taylor, Mathematical models have been used by fish- 1973, Rorres and Fair, 1975). The next step is to ery scientists in attempts to understand the mecha- develop generalized optimal harvesting strategy nisms driving population dynamics in species. The models for the stochastic case. value of such models to the manager is that they Limited attempts to incorporate more realistic provide a framework in which to study the conse- treatments of recruitment variability into modelling quences of possible management actions. The three efforts aimed at assessing management strategies types of models most commonly used in fisheries have been made.- In a study of yield. sustainability assessment are: (1) surplus production and yield- under constant-catch policy and stochastic recruit-per-recruit models (Beverton and Holt, 1957), (2) ment for the Atlantic surf clam, Slpisula solidissima, stock-recruitment models (Ricker, 1975) and (3) Murawski and Idoine (1989) assumed a binary pat-matrix population models (Leslie; 1945; 1948). tern of recruitment in which year-class strength is Structural models such as surplus production and uniformly poor except during relatively infrequent yield-per-recruit (Y/R) models can be used to pre- years when exceptionally strong cohorts are dict changes in yield or Y/R with variations in fish- recruited. Ripley and Caswell (1996) introduced ing intensity. Stock-recruitment models may be stochastic recruitment (log normally distributed) to used to predict recruitment levels for a given a stage-structured matrix model of clam popula-spawning stock size. Matrix populations models are tions. In a preliminary study of the soft-shell clam, often used to predict changes in population size Mva arenaria,using comnputer simulations to esti-based on fixed schedules of vital rates (age or size- mate the mean and range of population size pro-specific birth and death rates), i.e. life tables, for jected over many decades, yearly larval settlement the population under study. The success of these rates were varied randomly while all other vital models as predictors, however, lies in the degree to rates were held fixed (Brousseau et al., unpubl.). which their assumptions are met. While all three The study .found that an adaptive harvesting strate-types of models have been applied to bivalve popu- gy (harvesting intensity is adjusted according to the lations, the use of more holistic models that inte- settlement rates during the recent past) gave rea-grate factors such as natural environmental vari- sonable yields while protecting the standing stock. ability, contamination, habitat impacts, and fishing The major limitation of all these studies, however, pressure have yet to be attempted. is the inability to verify the range of input parame-Matrix population models have been used ters used. Consequently, it is uncertain whether or extensively for analyzing life history tactics in a not the conclusions reached are directly applicable variety of species (Hartshorn, 1975; Longstaff, to populations in the fieldU 1977; Caswell and Werner, 1978; Enright and Better empirical information is needed con-Ogden, 1979; Pinero et al., 1984; Levin et al., cerning the distribution pattern of settlement rates 1987), and the Leslie matrix model (Leslie, 1945; in shellfish populations. Sensitivity analysis of pop-1948) in particular, has long been used to estimate ulation growth rate to changes in the life history population size. These models, however, rely on parameters of several species of commercially the availability of age (size) - specific schedules of important shellfish has shown that population births and deaths (life tables), information that is growth rate is more sensitive to changes in larval not yet available for all the species of bivalves dis- survival/early recruitment than to changes in other cussed here. Additionally, in their usual form, these life history parameters such as fecundity and adult
INS 1; ORE BITVAIVI- MORTALIT TV AND IIAIR\ IUTIN(I I I survivorship (Bronsseau and Baglivo, 1984; Recent developments in molecular techniques Malinowski and Whitlatch, 1988). Tile importance have made several types of genetic markers (mito-of this early fluctuating stage in the life history of chondrial DNA, ntclear DNA and allozymes) these species predicates the need to focus more available for assessing population-level structuring attention on understanding the relationship between on local and regional geographic scales. These stock density and recruitment rates, the long-term techniques have been widely used in finfisheries pattern of recruitment events and the role of hydro- research to. estimate intraspecific genetic variation dynamics in the settlement process in order to as well as population allocation to mixed-stock improve the usefulness of population models in fisheries for a number of commercial species applications to marine species. Intensive field work including cod (Pogson et al., 1995), bluefin tuna focusing on bivalve larval biology in natural sys- (Grewe et al., 1997), salmon (Scribner et al., 1998) tems must be done in spite of its high cost and and red mullet (Mamuris et al., 1998). Such stock labor-intensive nature. identification has become a major focus of research efforts aimed at assisting in the formulation of marine finfishery management decisions. SUSTAINABILIrY Or TmE BIvALvE FISHiERIES Molecular techniques have been used less widely in efforts to delineate shellfish stocks. Defining 'overfishing' as that activity which Information is beginning to emerge for such directly leads to declining stocks over time is related to an important finfisheries concept known as max- exploited molluscan species as abalone (Shepherd imum sustainable yield (MSY). As fishing pressure and Brown, 1993), deep-sea scallops (Wilding et al., 1998) and limpets (Weber et al., 1998) as well increases more individuals of progressively smaller as for soft-shell clams (Morgan et al., 1978; size are harvested until the decreasing size of the Caporale et al., 1997), quahogs (Dillon and Manzi, animals results in decreases in total catch size 1992; Juste, 1992) and bay scallops (Bricelj and (weight) despite the increased numbers harvested Krause, 1992; Wilbur et al., 1999). Large-scale (growth overfishing). The MSY for a commercial finfish species is estimated based on records of research efforts aimed at defining the stock bound-commercial catch, size and age of harvested aries for such widely-distributed species such as M. species and annual recruitment variability. mercenariaand M. arenariaare needed, however, if effective management of the resource is the goal. Structural models, such as surplus production and yield-per-recruit models developed initially for fin- For sedentary species, such as bivalves, the dif-ficulty associated with defining the population unit fish, have been applied to invertebrates in isolated greatly complicates stock assessment calculations. cases (Caddy, 1980), but in general have been of limited usefulness in estimating yields in exploited The concept of the metapopulation has been used molluscan stocks. One problem with such models by population biologists to describe the dynamics is their dependence on adequate information on the of spatially fragmented subunits of species which are linked together by dispersal stages (Hanski and intensity of the fishing effort (see discusssion above). Gilpin, 1991 ). Such analysis could have application Another problem central to the difficulty in in the management d economically important species such as scallops and clams whose stock maintaining sustainable shellfisheries is the inabili-ty to define the management unit. The term biolog- units may occupy as large an area as a sea, gulf or ical "stock" has often been used to describe a dis- estuary or as small an area as a single shellfish bed. Decisions regarding management of such resources crete, self-perpetuating population of organisms that share a common gene pool and can be man- depend in large part on an understanding of the rel-ative importance of local (demographic) versus aged (Larkin, 1972). The biological stock is now viewed by many in the fisheries community as the regional (recruitment and/or emigration) processes in the overall maintenance of the population unit. management unit. Understanding the genetic struc-In order to assess the relative importance of these ture of an exploited species is the first step in factors, however, a clear understanding of stock devising management strategies that ensure the long-term survival of a fishery. structure is needed. Related to the difficulty of defining the "unit
I I -) BROU;SFIAI stock" is the difficulty in establishing an overall shoreline armament, increased siltation caused by stock-recruit relationship for sedentary molluscan altered land-use practices, and conflicts brought populations. Stock-recruitment models have been about by the increased use of the nearshore envi-used to predict recruitment levels for a given ronment for recreational activities (Deegan and spawning stock size in various finfish populations Buchsbaum, Chapter 5; McDowvell, Chapter 7). (Ricker, 1975). Hancock (1973) reported, however, Eutrophication of estuaries may accompany land-that there is little evidence to indicate a direct rela- based development (Menzie-Cura, 1996) and may tionship between spawning stock size and recruit- impact shellfish beds by altering the food supply ment in an exploited population of cockle (sometimes increasing shellfish productivity). More (Cardiurn edule). He concluded that "heavy spatfall often than not however, increased primary produc-may occur in a whole range of circumnstances, tion results in more frequent periods of low dis-including (1) when adult stocks are high or low, (2) solved oxygen through increased respiration of the when predation has been reduced or (3) when con- primary producers and associated community, par-ditions for larval survival and settlement are espe- ticularly during warmer weather and overcast days. cially good, or any combination of the three." Data Sediments may become hypoxic or anoxic, and on stock and recruitment for most species he dis- even shellfish that can survive prolonged periods of cusses are so limited, however, that to generalize low dissolved oxygen (M arenaria,M. for species other than the cockle is unwise. (This mercenaria)can become stressed (Newell and difficulty is also described for lobsters by Steneck, Hidu, 1986). Juveniles are particularly susceptible Chapter 8). It may simply be that stock-recruitment and may die if dissolved oxygen levels persist for relationships are masked by the difficulties associ- prolonged periods. The presence of increased algal ated with defining the stock "unit" as discussed mats or degraded sediments may also interfere with above. It is too early to conclude that the size
- spat settlement.
and/or demographics of the parent stock has little The majority of the contaminant and habitat influence on reproductive success or failure in degradation impacts listed above (and described in invertebrate stocks. more detail by Deegan and Buchsbaum in Chapter 5 and by McDowell in Chapter 7) are rather local-ized, and do not impact the entire metapopulations CONTAMINANTS AND HABITAT DEGRADATION of soft-shell clams, quahogs and bay scallops uni-Increased population pressures during the past form ly. Thus the impacts of contaminants, habitat twenty-five years leading to overdeveloped shore- degradation, and overfishing are difficult to assess line areas and increased threat of bacterial contami- not only at the metapopulation level, but also at the nation have been well documented, especially for local population level because of the broad disper-the South Shore of Massachusetts (Buchsbaum, sive abilities of the planktonic larvae. The analysis 1992; MBP, 1996). This has led to the largest rate presented in this chapter indicates that we are of increase in regional shellfish closures in the' unable to measure and document any significant State due to contamination by fecal coliform bacte- impacts from the combined stresses of fishing, con-ria. The North Shore experienced lower closure tam ination and habitat destruction. There is no rates than other regions during this period only clear evidence of overfishing, at least not for the because of its long history of shellfish closures due Massachusetts soft-shell clam fishery. While it is to fecal contamination. As the number of shellfish likely that both contaminants and habitat alterations closures rise, harvesting pressure on remaining contribute to larval mortality and reduced recruit-beds becomes more intense, increasing chances that ment, the importance of these additional stresses overfishing will occur. cannot be measured at the present time, especially Increased development brings other changes against the backdrop of extreme interannual vari-that influence shellfish habitat and productivity, ability in recruitment that would be observed in the such as the addition of nutrients and toxicants to absence of these anthropogenic stressors. estuaries and embayments, alteration or restriction of tidal flow due to roads, bridges, piers and
INStHORE" BIVAL\ESMORTALITY ANDI).-ARV\ESTING I 13 CONCLUSIONS recruitment failure during some breeding cycles. It has been suggested (Hancock, 1973) that the rela-tionship between stock and recruitment in such species is so tenuous that the occurrence of a heavy In view of its importance both to the pub-spatfall is equally likely whether adult stocks are lic health and to an industry qofsuch mag-high or low, raising a question concerning the nitude I earnestly recommend that a benefits of managing or protecting exploited stocks. commission he appointedand an appro-The perceived absence of a stock-recruitment priation made to cover a thorough inves-relationship for invertebrates, however, is more tigation of the entire sub/ecl o] the pollu-likely the result of a failure to view local clam flats tion of our clam flats... or scallop beds as spatially fragmented subpopula-
-ZA. Howes, 1930 tions of a larger unit, the dynamics of which can be (in Belding, 1930a) understood only if all of the subpopulations are considered together. Viewing resource units as part of a series of local subunits which in part, owe This chapter assessed the impact of natural their persistence to the dynamics of other local sub-mortality and harvesting pressure on inshore populations, may provide important insights into bivalve resources, using data from Massachusetts the management and protection of these areas.
as the primary example. Based on this review, the It seems undeniable that active harvesting, only fair conclusion to be drawn is that information which removes adults from a population, will ulti-currently available for assessment is inadequate to mately affect reproductive output and overall inor-determine whether or not a statewide decline in tality levels in a population. Whether or not such these commercial stocks has occurred. The LPUE alterations lead to reduced productivity over time, statistics calculated for the soft-shell clam do not however, is less easily determined. No data are support the view that stocks have declined over the available to assess the impact of harvesting fori past 25 years in the four North Shore communities either the quahog or the bay scallop. Analysis of studied, but that conclusion is based on very limit-LPUE versus fishing effort for soft-shell clams ed data. Lack of appropriate data to make even the indicates that this species is not overfished, but the crudest assessments for quahogs and bay scallops data on which this analysis is based are question-makes it nearly impossible to comment on the sta-able at best. The absence of reliable statistics for tus of those species in the state. The other the assessment of long-term population trends Northeast states have equally poor data sets or lack makes it impossible to determine the extent to critical data entirely on these three species, making which reported declines in-these resources are the defensible stock assessments all but impossible. result of overfishing and not simply the result of Added to the difficulty of documenting stock natural fluctuations in species abundance. trends is the inherent problem of identifying and assessing natural versus man-made sources of mor-tality. In addition to the various anthropogenic LITERATURE CITED causes of mortality (pollution, habitat destruction, Ahn, l-Y, G. Lopez and R. Malouof 1993. Effects of the gem clam and overharvesting), natural mortality from an Gemma gem-ma on early post-settlement emigration, growth and survival of the hard clam Mercenariamercenaria. Mar. Ecol. adverse environment, predation, competition and Pro". Ser. 99:61-70. disease also contributes to fluctuations in species Alber, M. 1987. Shellfish in Buzzards Bay: A resource assessment. abundance. The relative importance of each of Buzzards Bay Project (BBP- 88-02), U. S. EPA, Boston, Mass. these factors in the overall picture is far from 75 p. Ambrose, W. G. Jr. 1984. Influences of predatory polychaetes and understood, but almost certainly, no one cause is epibenthic predators on the structure of a soft-bottom community responsible, nor are the same cause/causes respon- in a Maine estuary. J. Exp. Mar. Biol. Ecol. 81: 1 15-145. Ambrose, W. G. Jr., M. Dawson, C. Gailey, P. Ledkovsky, S. Leary, B. sible for all the species discussed. Tassinari, H. Vogel and C. Wilson. 1998. Effects of baitworm In clams and scallops, which have vulnerable digging on the soft-shell clam, Mya arenaria,Maine: Shell dam-planktotrophic larval stages, natural mortality is age and exposure on the sediment surface. J. Shel*f Res. 7:1043-1049. extremely high early in life, resulting in complete Andre, C. and R. Rosenberg. 199 1. Adult-larval interactions in the
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(ONTO I;NAlION IFIF(I5.C AND MIONITOR IN(;1 NIF\lRIN E S1111II.Ilfn I 19 Chapter VU Biological Effects of Contaminants on Marine Shellfish and Implications for Monitoring Population Impacts JUDITH E. McDOWELL l4'bods Hole Oceanographic Institution Department of Biology l'Toods Hole. A44A 02543 USA INTRODUCTION molluscs is still lacking. Natural biogeochemical processes that ultimately control contaminant bioavailability and uptake by bivalve molluscs must also be examined when evaluating the poten-The integrity of the worl's coastal tial of bivalve molluscs as indicators of chemical waters is jeopardized by the deliberate contamination. These biogeochemical processes and inadvertent entries of societ,'s dis-influence contaminant persistence and bioavailabil-cards. Mla[any substances itilroduced by, ity, ultimately controlling the fate and effects of
,nankind are toxic to marine organisms, these contaminants in coastal marine environments.
thus impinging upon the health of ocean The purpose of this chapter is to evaluate the communities or restrictingthe human effects of contaminants on molluscan shellfish from cons umption offish and shellfish. the New England area, and to place these effects in
-Edward D. Goldhera 1980 context against the impacts caused by habitat degradation and overfishing. Much of the bivalve monitoring data that has been collected in the The use of a sentinel species as an indicator of region can be used to augment findings from labora-chemical contamination has been widely used in tory and field studies, and help us to assess the monitoring programs in the marine environment impacts of contaminants on populations and (Bayne et al., 1988; Jones et al., 1995). This individuals.
approach has led to greater insights on the spatial and temporal distribution of contaminants and CONIAMINANT DISTRIBUTIONS IN SEDIMENTS AND associated effects on sentinel species (Butler, 1973; SIELFISII NRC, 1980; Farrington et al., 1983; Bayne et al., 1988). Bivalve molluscs, including several species Regional studies in the Gulf of Maine have of mussels, oysters and clams, have been the most documented the spatial distribution of several commonly used sentinel species in Mussel Watch classes of contaminants including trace metals, monitoring programs. chlorinated pesticides, polychlorinated biphenyls Although our knowledge of the distribution of (PCBs), and polycyclic aromatic hydrocarbons specific compounds and groups of compounds (PAlIs) in sediments and biota (Larsen, 1992; continues to increase, our understanding of cause Kennicutt et al., 1994). These studies have been and effect relationships between classes of contam- reviewed in detail elsewhere (McDowell, 1995, inants and specific biological effects in bivalve .1997). The relationship between contaminant
I 20} X:OW I inputs and the distribution of contaminants in sedi- The use of chlorinated pesticides in agricultural ments and biota largely reflect a gradient, with practices has declined since the early 1970s but nearshore areas, especially urban and industrialized traces of pesticide residues have been reported at areas, having the highest levels of contamination., locations within the Gulf of Maine subjected to and offshore areas having significantly lower con- inputs from agricultural runoff(Hauge, 1988; centrations. Larsen. 1992; Kennicutt et al., 1994). NOAA's The first U.S. Mussel Watch program (1976- National Status and Trends Mussel Watch Program 1978) provided a regional assessment of contaminant also noted elevated concentrations of aromatic distribution in bivalve samples from New England hydrocarbons, chlorinated pesticides and other waters (Farrincton et al., 1983- Goldberg et al.. chlorinated hydrocarbons in bivalve samples, espe-1983). Data collected in this program documented cially in urban harbors and industrialized areas the strong urban influence on contaminant distribu- (NOAA, 1989; Jones et al., 1995; O'Connor, 1998). tion in mussel samples for both trace metal and Trophic transfer of contaminants to higher level organic contaminants. A recent review of a decade predators and the human consumer are generally of data collected in the Mussel Watch component most significant for lipophilic contaminants such as of National Oceanic and Atmospheric chlorinated hydrocarbons, and other persistent Administration's (NOAA) National Status and organic pollutants (POPS). Shellfish closures and Trends Prograin (in id-1980s to mid-1990s) con- advisories based on chemical contamination are cludes that the concentrations of contaminants in relatively few but include some examples from the bivalve samples are declining for many classes of New England coast, notably PCB contamination in contaminants (O'Connor, 1998). Exceptions to this New Bedford Harbor and dioxin contamination in general conclusion are reflected in the data for Maine (McDowell, 1997). organic contaminants and lead, particularly at sta-tions in urban areas such as Boston Harbor. To a large extent contaminant distribution in TOxICOI.oIGCAL EFFECTS OF CONTAMINANTS ON sediments and biota reflect not only contemporary SiicA.Tisu inputs but also a history of industrial activity. For example, chromium contamination in certain loca-tions within the Gulf of Maine ecosystem - Great The relationship of disease and environ-Bay Estuary (NI-t), Saco River (ME), and Salem mental stress is becoming increasingly Harbor (MA) - reflect a history of inputs from the w,ell established u'ith time. Hunan activi-once thriving tanning industry (Capuzzo and ties - particularlythose that result in Anderson, 1973; Armstrong et al., 1976; Mayer and chemical additions to the coastal/estuar-Fink, 1980; NOAA, 1991). Concentrations of other ine environmnent - have increasedthe trace metals are elevated at other locations - potential stresses on fish and shellfish Boothbay Harbor, Boston Harbor and Quincy Bay - inhabitingthose areas. Circumstantial and reflect a pattern of wastewater input and other evidence for associationsof pollutants industrial sources of contaminants to shallow water with certainfish and shellfish diseases embayments (NOAA, 1989, 1991; Sowles et al., and abnormalitiesis accumulating. 1992; Jones et al., 1995). Hydrocarbon inputs may -CarlJ. Sindermann, 1979 also vary spatially and temporally as a result of chronic municipal discharges, agricultural prac-tices, oil spills and other point and non-point The effects of chemical contaminants on sources. In the Gulf of Maine there are numerous marine bivalve molluscs have been examined locations that have received inputs of petroleum extensively during the past two decades. The hydrocarbons from both chronic discharges and majority of the studies have been conducted on the accidental spills [Boston Harbor (MA), Casco Bay blue mussel Mvtilus edulis (e.g., Bayne et al., 1985, (ME), and Penobscot Bay (ME)] (Johnson et al., 1988) with an effort to integrate responses over 1985; Larsen et al., 1986; MacDonald, 1991; several levels of biological hierarchy (Table 7.1) Menzie-Cura & Associates, 1991; NOAA, 1991). and to examine responses linked to specific classes
ION *['\,\IINA I ION EFFE( I ý; .\N D MONITOR IN(; OF \L\V IN F. ý' I IF LLF I SH 1211 Table 7. I. Response levels of marine organisms to sediment geochem istry research have increased our chemical contaminants; adapted from Capuzzo ( 198 1). understanding of processes controlling bioavailabi I-Level Types of Responses Effects at ity and uptake by benthic organisms. The accumu-Next Level lation of trace metal and organic contaminants by lIoxic inetabolites aquatic organisms is a complicated function of
- Biocheinical- Toxication Cellular i, 'letabolic impairmnent DisruptioniI physical, chemical, and biological processes that
[Cellular damage energetics and influence exposure concentrations, bioavailability, Detoxidation cellular pro- and uptake, elimination and storage of contami-cesses nants by an organism (Fisher, 1995). In the benthic
'Adaptation environment, nonpolar organic contaminants will Or.anismni- Physioloogical changes 'Reduction in partition among all accessible phases according to
'Behavioral changes population per- the capacity of each phase to accumulate the con-Susceptibility to disease formance taminant. Usually, these partitioning processes are ReproduCtive effort Regulation and described using equilibrium models. wvhere equilib-
'Larval viability 1adaptation of rium among all phases is assumed. This forms the Adjustment in rate populations basis for Sediment Quality Criteria based on eclui-functions libriurn partitioning (Shea, 1988; Di Toro et al.
1hnmtine responses 1991 ). Recent studies, however, suggest that Population.ge/'S ize structure l~ffects on spec.ies! bioavai lability of lipophilic contaminants is not lRecruitment productivity based on equilibrium theory alone (McGroddy and
!Mortality Farrington, 1995; McDowell and Shea, 1997). The and coexisting Biomass species and 1 hydrophobicity of specific contaminants, the source Adjustment of repro- com in unity of contaminants, and the sorption of contaminants ductive output and Adaptation of (especially pyrogenically derived PAH) on organic other demographic population carbon' particles can greatly influence the rates at characteristics which equilibrium may (or may not) be obtained, and hence the availability and uptake of contami-Community [Species abund aance Replacement by iSpecies distribbution inore adaptive i nants by benthic species.
Biomass competitors Similar concerns exist when considering the
'Trophicintera ctions !Reduced sec- bioavailability of trace metals to benthic organisms.
'Ecosystem adaaptition ondary produc- Characterizing the bioavailability of trace metals tion based on the acid volatile sulfide fraction of sediment No change in led to some greater predictability of bioavailability community potential (DiToro et al., 1990) but other sediment structure and features and processes (e.g., POC, DOC, metal fuinction hydroxides, redox, bioturbation) may also influence bioavailability (Valette-Silver, 1999). Luoma et al.
(1997) suggested a combined approach utilizing of contaminants. Recent work has extended this field observations of sediment concentrations and approach to other species of bivalve molluscs and geochemical properties and laboratory observations to assessment of population level responses of uptake and elimination of specific trace metals (Widdows et al., 1990; Leavitt et al., 1990; from both dissolved and particulate phases (Luoma Weinberg et al., 1997; McDowell and Shea, 1997). and Fisher, 1997; Wang et al., 1997). Bioenergetic-based kinetic models are being developed that can OUFTAKE AND AccUMULATION better predict the relationship between field and laboratory' observations of uptake and accumulation Understanding the relationship between sedi- of metals in benthic organisms (Wang et al., 1996; ment contamination and potential for uptake and Wang and Fisher. 1997). accumulation of contaminants by benthic organ-isms is a challenging problem. Recent advances in
I22? I.:r)OWE f. BIOTRANSFORANIrON ANt) DIsEl"ASL RSI-'ONSES Table 7.2. Conccntration of organic contaminants in oysters, Crassostreavirginica, exposed to sediments Research on biotransformation mechanisms in firom Black Rock Harbor'. marine bivalve molluscs has paralleled efforts oil vertebrate species for over two decades. In compar- [co0mpounid . ........... [omoun ................. ed men .s ai o ison, bivalve molluscs have been considered to dry wt.1 dr wt. have a relatively low capacitylfor detoxifying organic contaminants through cytochrome P-450 Siufficient evidence as monooxygenase reactions (Anderson. 1978, Benz(a)anthracene 695 -,3450 0.20 Livingstone and Farrar, 1984; Stegeman, 1985). The dominant metabolites of benzo(a)pyrene Benzo(a)pyrene 881 3160 0.02 detected in molluscs have been primarily quinone Benzfluoranthene 364 5970 0.06 derivatives, rather than the diol derivatives observed in fish (Stegeman. 1985; Stegeman and lndeno(I .2,3-cd)pyrene 22 1 2 Dibenz(a.h)anthracene_ _ _ 1,__ 99 I -- _ i_ _ _ Lech, 1991), although Anderson (1985) did observe H-exachlorobenzene 0.21 -- relatively high concentrations of diol derivatives as well. Stegeman (1985) suggested that PAIlI Chlordanes 100 --- metabolism in bivalve molluscs may proceed Limited evidence as carcinogens through several catalvtic mechanisms including peroxidative mechanisms in addition to cytochrome .. ...... Chry-sene ...... ................
...i.......1260 4450.. 10.
. 2218 P-450 monooxygenase. The formation of oxyradi- Inadequateevidence as carcinogens cals and binding of these reactive compounds to DNA and other macromolecules (Livingstone et al., Benzo(e)pyrenc 264 - 2880 0.09 1990; Garcia-Martiriez and Livingstone, 1995) pose Fluorene 42 - 635 0.07 a link with observations of cell damage noted by P-ienanthrene '5 4020 0 14 other investigators. Metabolism of other com-pounds such as aromatic amines yields metabolites [Perylene 17 i 504 0.03 with mutagenic properties (Anderson and Doos, Benz(g,h,i)perylene 37 ..
1983; Kurelec et aL., 1985; Kurelec and Krca, Coronene 1.3 - 1987; Knezovich et al., 1988) and DNA adducts No evidence as carcino-ens (Kurelec et al., 1988). The relationship between biotransfornmation and disease processes in bivalve Anthracene 191 1330 - 0.14 1 molluscs has been suggested by several investiga- lluoranthene 1777 5800 0.31 tors (Moore et al., 1980; Stegeman and Lech, 1991). Promoters The reactive compounds formed during biotrans-formation could result in histopathological damage DDT and metabolites 1183 of molluscan tissues. PCBs (Aroclor 1254) 1143 0.16 Mix (1986, 1988) reviewed the relationship Pyrene 2950 0.41 among contaminant tissue burdens, biotransforma-tion and histopathology/disease in marine bivalve aData from Gardner et al. ( 199 1) molluscs. Although no conclusions could be made, he suggested that our limited understanding at that Crassostreavirginica with exposure to sediments time of specific contaminant effects on cellular and from Black Rock Harbor (Long Island Sound, USA; physiological processes and mechanisms of bio- Table 7.2). As information continues to be gathered transformation hindered our ability to explore the on the relationship between shellfish diseases and relationship between contaminant exposure and contaminant accumulation and transformation, the disease progression. Gardner et al. (1991) reported role of contaminants in disease processes should be promising evidence on the relationship between elucidated. contaminant distributions and metabolism and the prevalence of specific tissue neoplasias in the oyster
(ON VA'MINA Ij1ON 1: FlF S ý\Nr) MNHIN10R I NG OIF \M*R I NE SII(1 1-LFIS II 13 CI-I..I.UilAR AND PI-1ISiCoI..oCGICAI. RESPONSES routinely synthesized within cells in response to exposure of the cell to a \vide variety of physical Cellular and physiological responses of bivalve and chemical conditions (l~ightower, 1993). Some molluscs to contaminants provide the basis of link- stress proteins are produced in general response to ing observations of contaminant chemistry with a wide range of stressors, whereas other stress pro-observed disruption in physiological function. teins are unique to a specific chemical or physical Numerous indicators of cell function have been stress (Bradley, 1993). A stress protein "finger-proposed as biomarkers of cell damage in response print" can be measured and used as a marker of to contaminant exposure. Alterations in lysosomal contaminant effects in the environment (Randall et structure and function are consistent with observa- al.. 1989). At the present time, heat shock protein tions of degeneration of digestive gland epithelium, 60 (Sanders et al., 1991 ) and heat shock protein 70 atrophy of digestive tubules, and degeneration of (Steinert and Pickwell, 1993) appear to be appro-reproductive tissues (Lowe et al., 1981; Moore and priate as biomarkers of environmental stressors in Clarke, 1982; Couch. 1984; Pipe and Moore, 1985; marine bivalves. Recent studies by Clayton (1996), Lowe and Pipe, 1985, 1986, 1987: Moore et al., however, caution that the site of collection, season, 1989). These observations have been linked in and tissues samnpled need to be carefully considered bivalve mollIscs with exposure to high levels of in order for heat shock proteins to be used as IipophilI ic contaminants in the mussel N'f vtih/s biomarkers of contaminant effects. edidis (Lowe, 1988: McDowell et al., 1999). Lowe In addition to acting as indicators of contami-and Pipe (1987) suggested that the reallocation of nant exposure, the presence of these biomarkers energy reserves fiomn resorbed oocytes to storage may be indicative of sublethal damage to the cells might serve as a resistance strategy to survive organism that may have consequences for individu-the effects of hydrocarbon exposure. al survival. reproduction. and population processes. Ringwood et al. (1999) observed alterations in The implications of genotoxic agents in terms of lysosomnal function and glutathione concentrations damaged DNA are obvious with respect to the in juvenile oysters (Crassostreavirginica) exposed overall impact on the transcription and replication to contaminated sediments with a mixture of trace of the DNA molecule. Sanders et al. (1991) metals. Responses of cell function varied signifi- observed the accumulation of heat shock protein 60 cantly with contaminant loading and the data (hsp 60) in conjiunction with a decrease in scope agreed well with other estimates of sediment toxic- for growth (SFG) measurements in ,1v1ilus edulis ity (Long et al., 1995). exposed to sublethal concentrations of copper. Other indicators of contaminant effects in Accumulation of hsp 60 was a more sensitive indi-bivalve molluscs show promise as monitoring tools cator of copper exposure than reductions in bioen-or biomarkers of exposure to chemical contami- ergetics as measured by scope for growth. nants and biochemical or cellular damage. These Alterations in growth rates of bivalve molluscs include the presence of single-strand breaks or occur as a result of reductions in feeding rates, alkaline labile areas in the DNA complement of higher respiratory metabolism, and reduced diges-individual cells (Shugart et al., 1989) and the pres- tive efficiencies. Reductions in physiological mea-ence of stress proteins within the cell (Hightower., surements (e.g., respiration rates, carbon turnover, 1993). Many compounds have been shown to have and scope for growth) have correlated with reduced genotoxic effects in marine organisms including growth rates measured for bivalve populations methyl methane sulfonate (Nacci and Jackim, from contaminated habitats (Gilfillan et al., 1976; 1989) and N-methyl-N'-nitro-N-nitrosoguanidine Gilfillan and Vandermeulen, 1978; Capuzzo and (Nacci et al., 1992). In each case, significant Sasner, 1977). Alterations in bioenergetics and increases in DNA breakage occurred in a dose growth of bivalve molluscs following exposure to dependent fashion. Cells have the capability of petroleum hydrocarbons appear to be related to tis-repairing damage to the DNA molecule (Martinelli sue burdens of specific aromatic compounds et al., 1989), thus, providing a potential means of (Gilfillan et al., 1977; Widdows et al.. 1982, 1987; timing the exposure event and subsequent recovery. Donkin et al., 1990). Widdows et al. (1982) Stress proteins are a group of proteins that are demonstrated a negative correlation between
124 FA:O\V
',d cellular and physiological stress indices (lysosonial Table 7.3. Condition indices and reproductive effort of properties and scope for growth) and tissue concen- mussels. .1,vtiihis edulis, transplanted to New Bedford trations of aromatic hydrocarbons with long-term Harbor. and reference sites.
exposure of Al/Vilus edulis to low concentrations of station M..aximium Rep-oductive North Sea crude oil. Recovery of mussels follow- I Condition Index Eflbrt ing long-term exposure to low concentrations of Pre-spawning % RE/Total diesel oil coincided with deputation of aromatic mg Dry Wt./Shell Energyb hydrocarbons (Widdows et al., 1987). Donkin et al. \Volumea (1990) suggested that reductions in scope for growth in ,V. edulis were related to the accumula- Nantucket 335+.. Sound 0.88 tion of two- and three-ring aromatic hydrocarbons, as these compounds induced a narcotizing effect on Cleveland [ C340+20 0.71 ciliary feeding mechanisms.' Ledge Diminished scope for growth, alterations in lysosomal function, and decreased reproductive New Bedford 230+15 0.34 effort appear to be general responses to contami- Harbor nant exposure and may be indicative of general ')ata from McDowell Captzzo (1996); Mean I S.E. reduction in physiological conditions. The response "Calculated fiom mean values from eight individual of the turkey wing Mussel (Arca zebra) to contami- animals at each site. nants along a gradient in the waters surrounding Bermuda included reduced feeding rates and POPULATION LEVEL RESPONSES. increases in metabolic expenditures associated with significant accumulation of lead, tri- and di-butyltin, petroleum hydrocarbons and their polar oxyguenated derivatives, and PCBs (Widdows et al., The r-oot problem is that we - and this 1990). Mussels collected along the same gradient includes ecotoxicologists and ecologists - showed changes in biochemical composition, espe- still do not know enough about ecological cially in the ratio of neutral to polar lipids and car- systems to be able to identif, what it is bohydrate content (Leavitt et al., 1990). we want to protect about them and hence, A'lyiihis editis transplanted to New Bedford t/,hat we should be measuring. Clearlv, Harbor (Buzzards Bay, MA) showed reduced this is most acute at community and reproductive effort and increased degeneration and ecosystem levels. -Peter-Calow, 1994 premature resorption of oocytes, coincident with high body burdens of PCBs and PAHs (Table 7.3, McDowell et al., 1999). The greatest differences in Chronic exposure to chemical contaminants condition index and lipid reserves of mussels were can cause alterations in reproductive and develop-observed during the pre-spawning period, consis- mental potential of populations of marine organ-tent with the accumulation and utilization of lipid isms, resulting in possible changes in population reserves for reproductive development. Following structure and dynamics. It is difficult to ascertain, spawning no differences in condition index were however, the relationship between chronic respons-evident and lipid reserves were diminished to mini- esof organisms to contaminants and large-scale mum levels. Resident populations of mussels from alterations in the functioning of marine ecosystems New Bedford Harbor also showed extensive signs or the sustainable yield of harvestable species. of gonad degeneration. Cairns (1983) argued that our ability to detect toxic effects at higher levels of biological organization is limited by the lack of reliable predictive tests at population, conmmunity, and ecosystem levels. Much research effort is needed in these areas before environmental hazards as a result of contaminant inputs can be adequately addressed.
CONIA kN1IN.V NO FFE([ AND
.'[S ONITiOIINCi OF- MAKINE S1IIFLIFI:SHlI~
Koojiman and Metz ( 1984) suggested that the sub- with energetic processes (3, 4, and 7), biosynthetic lethal effects of contaminant exposure should be processes (4), and structural development (2, 5) in interpreted in light of the survival probabilities and addition to contaminant accumulation and depura-reproductive success of populations, thus bridging tion (I, 6). Alterations in bioenergetics linked with the gap between individual and population responses. observations of" reduced fecundity and viability of Although many indices have been proposed for larvae, abnormalities in gamete and embryological evaluation of chronic responses of organisms to development, and reduced reproductive success contaminants, few have been linked to the survival provide a strong empirical basis for examination of potential of the individual organism or the repro- population responses. Incorporation of these ductive potential of the population (McIntyre and responses in demographic models may lead to new Pearce, 1980). Experimental studies directed at insights on adaptations of specific life history determining effects on energy metabolism or stages to contaminant perturbations and the popula-effects that influence growth and reproduction tion consequences of stage- or age-specific effects would be most appropriate for linking effects at of contaminants. Reduced scope for growth and higher levels of organization. When investigating decreased fecundity in mussels exposed to high biological effects of contaminants, many variables levels of PCBs in New Bedford suggest population must be recognized and assessed. Differential sen- consequences (McDowell et al., 1999). For species sitivity off different species of organisms, various that have planktonic life history stages, resettle-life history stages, and species froom different habi- ment in highly contaminated areas may obscure tats may be related to contaminant bioavailability, demographic changes due to impaired bioenergetics. capacity for contaminant biotranslformation, and The population dynamics of bivalve species the metabolic consequences of contaminant expo- have received considerable scientific attention due sure. The increased sensitivity of early develop- to the importance of many bivalves as commercially mental stages and the seasonal difterences in the harvested fisheries. Demographic models have responses of adult animals may be related to stage- been developed to examine the importance of spe-specific or seasonal dependency on particular cific life history characteristics on population pro-metabolic processes (e.g., storage and mobilization cesses. Such models include: (1) analysis of the of energy reserves, hormonal processes), with the sensitivity of population growth rate to life cycle result of altering developmental and reproductive perturbation, (2) life table response experiments, success (Capuzzo. 1987). and (3) population projection and prediction Reproductive success and development of an (Caswell, 1989ab). In addition to quantifying the organism may be affected by contaminant exposure impact of fishing pressure on bivalve populations, by: demographic models have been used to assess the I. deposition of contaminants in gametes and importance of environmental perturbations (e.g., developing embryos; disease, contaminant effects, etc.) on bivalve physi-
- 2. lysosomal dysfunction associated with oocyte ology and population dynamics (Weinberg et al.,
resorption; 1997).
- 3. interference with feeding mechanisms, such Ayers (1956) suggested that larval mortality that exposure mimics starvation responses; was one of the most important considerations in
- 4. failure to incorporate sufficient yolk in monitoring the population dynamics of the soft-oocytes; shell clam. yl~a arenaria,an observation consistent
- 5. morphological abnormalities during embryoge- with numerous studies of bivalve species nesis resulting from failure of morphological (Brousseau, 1978; Brousseau et al., 1982; Weinberg systems to develop properly; et al., 1986). Brousseau et al. (1982) suggested that
- 6. limited capacity of developmental stages to larval mortality could be further separated into metabolize or depurate contaminants; and mortality that occurred during (a) fertilization, (b)
- 7. limited capacity of early developmental stages the free-swimming larval phase, or (c) early post-and reproducing adults to draw on excess ener- larval attachment (see also Brousseau, Chapter 6).
gy reserves (Capuzzo et al., 1988). Using sensitivity analysis, Brousseau and Baglivo Thus, responses can be categorized as interfering (1984) addressed changes in the population growth
126 % I \X'I o ,[I.ho rate attributable to changes in settlement rates of bioavailability' of specific compounds varied at dif-larvae and in age-specific fecundity and survivor- ferent sites. Estimates of the fraction of contaminants ship rates of the soft-shell clam. They concluded available in porewater and sediments for equilibrium that population growth rate was insensitive to abso- partitioning (AEP) provided the best predictor of lute values in egg production and most sensitive to relative bioavailability. changes in egg and larval viability which con- The reproductive cycle of clam populations tribute to the success of larval settlement. from the five sites varied with respect to the timing Malinowski and Whitlatch (1988) further docu- and extent of the spawning season but not with mented that population growth rates were two to respect to the number of developing oocytes during three orders of magnitude more sensitive to a spawning event. Both female and male clams changes in survivorship in larval and juvenile from the reference sites had advanced stages of stages of the life cycle than proportional changes in gamete development during tile late spring and either survivorship or fecundity in adult size classes. spawning continued through the early fall. The Since sensitivity analysis has identified that the large relative size of the digestive gland-gonad larval stage is the most critical life history stage complex and accumulated lipid provided sufficient controlling population growth rate, experiments energy for this extended reproductive season. and field collections designed to quantify the vital Populations from the upper Massachusetts Bay rates associated with larval survival and viability sites (Fort Point Channel, Saugus River and are needed. Processes 'elated to the allocation of Neponset River) did not spawn until mid-summer energy to developing eggs and larvae that influence and spawning occurred for only a short period of not just numbers of developing eggs but size and time. Asynchrony in gamete development between quality of energy reserves for larval development males and females was niot observed at any of the are especially important. These data can then be five sites.'In addition to an abbreviated spawning applied to a demographic model to ascertain how season, clam populations from the contaminated perturbations in larval viability may affect popula- sites also showed a high prevalence of gonadal tion growth and development. Any factor (e.g., dis- inflammation (cell proliferation) that was signifi-ease, contaminant exposure, etc.) that alters the cantly different (p<O.O01) from reference popula-allocation of energy reserves to developing eggs tions especially during tile late fall to early winter and larvae may result in a reduction in larval via- (September to December). At the most contaminated bility and post-settlement success. Among the site (Fort Point Channel), levels of hematopoietic classes of contaminants that are prevalent in neoplasia also reached 100% in December 1995 Boston Harbor and Massachusetts and Cape Cod (McDowell and Shea, 1997). Bays that may specifically alter energetic and Population growth rates were determined for reproductive processes in bivalve molluscs are the all populations using a deterministic matrix model. chlorinated hydrocarbons (including PCBs and pes- Trends in population growth rates were not directly ticides) and polycyclic aromatic hydrocarbons. related to contaminant concentrations at each site, Population models could be used to differentiate as other site features such as predator abundance the effects of contaminants, fishing pressure and and hydrographic features had strong influences on habitat alteration on population structure of bivalve recruitment success (McDowell and Shea, 1997). molluscs. The deterministic model was relatively insensitive Studies have recently been completed in to the differences in reproductive physiology related Massachusetts Bay to examine the effects of poly- to contaminant exposure. High inter-annual and cyclic aromatic hydrocarbons and chlorinated inter-site variability in recruitment patterns may hydrocarbons on population processes in the soft- mask contaminant effects on population processes. shell clam, MI arenaria(McDowell and Shea, 1997). Stochastic models such as those developed by Contaminants were detected in clam tissues and Ripley and Caswell (1996) may add more insights sediments collected along a sediment gradient of on variability in' population structure as a result of polycyclic aromatic hydrocarbon contamination in the interactive effect of contaminants and other Boston Harbor and Massachusetts and Cape Cod habitat features. Bays (300 to 66,000 ng per g dry weight), but the
CONTAM INAvto 110\ :(r .xt)SN tDONt'1'0ýIN G 01: MA..R A INi:ttn.L
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SUNI\IAIR\ AND CONCi.tSIOsNS Anderson. R.S. 1985. Metabolism ofta model environmental carcino-This chapter addresses the effects of contami- gen bv bivalve molluscs. Mar. EInviron. Res. 17: 137-140. Anderson, R.S and I.E. Doos. 1983. Activation ol inmainalian car-nants on shellfish populations in coastal habitats. cinogens to bacterial Inutaicns by. iicrosomal enzymes from a Accumulation of contaminants in shallow-water pelecypod mollusc. Mutat. Res. 16:247-256. benthic habitats has led to contamination of shell- Arinstrong, P.B., GM. Hanson andMCI I F. audIcc. 1976. Minor cle-ments in sediments ofhGreat Bay estuary, New Hampshire. fish resources at many locations along the New Environ. Geol. 1:207-214, England coastline, especially in habitats adjacent to Ayers. J.C. 1956. Population dtnamics of the marine clam, Mya are-
. nuria. Liniol. Occanoer. 1.:6-34.
urban areas. Contaminated sediments have con- Bayne. B.L.. R.F. Addison. JAM. Capuezo I'.K Clarke .I. S. Grav tributed to habitat degradation and have resulted in MN. Moore and R.M. 'Warvick. 1988. An overview otfthe GEEP restricted access to shellfish resources. In spite of workshop. Mar. Ecol. Pro" Ser 46 235-243. Bayne, B.L., D.A. Brown, K. Burns, I) R Dixon, A. Ivanovici, [). these problems, shellfish populations in contami- Livingstone, D.M. Lowe, M.N. Moore, AR.D. Stebbing and J. nated habitats may be quite abundant even though Widdows. 1985. The EtTects of Stress and Pollution on Marine reduced reproductive effort and high disease preva- Animals. Praeger, New York 381 pp. Br3lly. 111)P1993. Are tile stress, ptoteins indicators of extposure or lence are also observed. Areas closed to fishing effect? Mar Environ. Res. 35:85-8. such as those studied in the more urban sections of Brousseau, D.J. 1978. Population dynamics of the sbft-shell clam l,'/a Massachusetts Bay show populations with a wider arenaria" Mlar. Biol. 50:63-71 Brousseau, DT. and J.A. laglivo. !984. Sensitivity of the population distribution of size and age classes than those sites growth late to changes in liice history parmietlrs: its appli-that are routinely harvested (Brousseau, Chapter 6). cation to .4t4cW n*Iir1 Mollusca:Pelecypoda). Fish tiul l W1147 When moderately contaminated areas are open to 82:537-541. Brousseau, DJ., J.A. Baglivo and G.E. Lang, Jr. 1982. Estimation of periodic harvesting for relaying contaminated equilibrium settlement rates for benthic marine invertebrates: its stocks, a discontinuity in size classes is observed application to Mya arenaria (Mollusca:Pelecypoda). Fish. Bull. 80:642-648. (Brousseau, Chapter 6). The sporadic recruitment Butler, P.A. 1973. Residue in fish, wildlife and estuaries. success of bivalve populations at shallow-water Organochlorinc residues in estuarine ito1llusks, 1965-72. National benthic sites appears to be the dominant feature Pesticide Monitoring 'rograin. Pest. Moniit. .1.6:238-246.- Cairns .i. 1983. Are single species tests alone aidequate or estimating influencing population size and age structure. environmental hazaid? IHvdrobiologia. 100: 17-57. Recruitment of newly settled bivalves to contami- Calow. P. 1994. Ecotoxicology: What are we trying to protect? nated sites even when reproductive effort of adult Environ. Toxicol. Chem. 13:1549 Capuzzo. J.IN. 1981. Predicting pollution eff'ects in the marine envi-shellfish at those sites is reduced will balance the ronment. Oceanus 24(11:2i-33. losses related to disease and loss of reproductive Capuzzo, JiMl. 1987, Biological elliects ol petroleum hydrocarbons: potential. The comparison of contaminant effects Assessments Iltot experimncttal results. It:l.ong-term Environmental Effects oftO ttshore Oil and Gas Development. and overexploitation of shellfish populations is dif- D.F. Boesch and N.N. Rabalais. (eds.). Elsevier Applied Science, ficult to make as fishing mortality may represent London. pp. 3,43-410. one of the major losses to population abundance in Capuzzo, J. M. and F. E. Anderson. 1973. The use of modern chromi-um accumulations to determine estuarine sedimentation rates. uncontaminated habitats. For shellfish stocks that. Mar. Geol. 14:225-235. are overexploited even in uncontaminated .habitats Capuzzo, J. M. and J. J. Sasner. 1977. The effect of'chromium on fil-tration rates and inetabolic'activity of/Myti/ts ecilis L.. and AM/ya sporadic recruitment patterns of many bivalve mol-arenaria L. In: Physiological Responses of Marine Biota to luscs may require long periods between harvesting Pollutants. F. J. Vernberg, A. Calabrese, F. P. Ihurberg and W. B. to compensate for the discontinuity in size classes. 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12'8 \,-[ot,,,.,iit Di'l: ro. f.M ., ..11).Mahony I).J. lHansen. KJ. Scott. IM.B. [ icks, .- I..Brooks atid G.J. IDeniotux 1994. Setitineni c0iiita:tttlltits in . S.M. Mayr and M.S. Redmnond 1990. Toxicity of cadnitum in Casco Bay, Maine: Inventories, sources, and potential lor biologi-sediments: The role of acid volatile sulfide. Environ. loxicol. cal impact. Environ. Sci. Technol. 28: 1-15 Cheitn. 11.1487-1502, Knezovich. J.P.. N-I Laston and F.L. I larrison. 198S. It vivo Di-oro, L.M., C.S. Zarba. DJ Hlansen, W.J. BeFiy, R.C. Swartz, C.F metiabolisit of'aromatic amties by the bay mnssel, -'Iyti/tls ct/ti/is. Cowen. S.1. Pavlou. F-.E. Allen N.A Thomas and P.R Paquin. Mar Eniviron Res 24:89-91. 191)1. 'Icchnlical basis loi cstabl ishng sedim ent qual ity critcrii Kooji ttant S.iL..M. and .1AL Mctz. 1984. Ol thie dyntaniics ot" for nonionic chemicals using equilibrium Partitioning. Fnviron. chemically stressed populations: The deduction oif popnlation Toxicol. Chem. 12:1541-1583. consequences from effects oii individuals. Ecotoxicol. I:in-viron. Donkin, P.. I. Widdows. S.V Evans, CM. Worrall and M. Carr 1990. Safety 8:254-274. Qtlantitati c Structure-activity rilationships for tile eflect of Kurelec, 13 and S. Krca. 1987 Metabolic activatioti01 2- inoIllut1o-hydrophobic chemicals on rate of feccding by imussels (TVht/us rene. 2- acetylamtrio- Illuorene and N-hydroxyacetyslainittohl1Lo-ed/iis). AqUiat. Toxicol 14:277-294. eric to bacterial itutagens with mussel (Mytilus Farrington, I.W., El.D. Goldhbetg RVW Risebrough, J.H. Martin and galloprovintcialis)and carp (t.ypt titus crI7)io) suibcel ltlar prepara-V.1. lBowei. 1983. U.S. "Mussel Watch" 1976-1978: An overview tions. Comp. Biocheti. Physiol 88C: 171-177. of the trace metal, DDEl, PCB, hy-drocarbon and artificial Kurelec, B., S. Britvic and R.K. Zahn 1985. The activation of aro-radionuclide data. Environ. Sci Technol. 17:490-496. matic amnines in some marine invertebrates. Mar. Enviroti. Res. Fisher, S.W. 1995. M/lechanisms of Bioaccumulation in Aquatic 17:141-144. Systiemas. Rev: Etnviron. Contain. -loxicol 142 87-11 7. KrelCec. B.. M. Chacko and R C, Gupta. 1988. Postlabeliutg analysis Garcia-Mairtinez, P. and D.R. Livingstone. 1995. Benzo[alpyrene l' carciniogcn-DNA adducts in mussel, Myti/us ia//oproriiiia/is. dione stimulated oxyradical production by microsories of diges- Mar Environ* Res 24 317-320. tive cland of the coinmmon mussel -l,/tilus edid's I. Mar. En viroil. Larsen; P.F. 1992. Marine Environmental Qtmalitv in tile Gulf of Res. 39:185-189. Maine: A Review. Rev. Aquat. Sci. 6:67-87. Gardner, C.R., P1P'.Yevich, I.C. lHarshbargel a-nd A.R. Malcoim. 1991. Larsen, P.F._I).F Cadbois and A.C.- ohnson. 1986. Distributiont of Carcinocenicity of Black Rock Harbor sediment to the Eastern polycylic aromatic iydrocarbons ill surficial sediments of the oy.ster and troplhic transfer o0 Black Rock FFarbor carcinogens deeper waters of th Gulf of Mainae NIar. Pollut. Bull. 18:231-from the blue muiussel to the winter flounder. Environ. Health 244. Perspect 90:53-66. Leavitt, D.F., B.A. Lancaster, A.S. Lancaster and J. NMcDowNell Gilfillan, E.S. and J.H. Vandermetilen. 1978. Alterations in grow-th Capuzzo. 1990. Changes in the biochemical composition tfa and physiology of solt shell clams, Myva arenaria: Chronically subtropical bivalve, Area Zebra, ii response to contaminant gradi-oiled with Bunker C f-oin Chedabucto Bay, Nova Scotia, 1970- " ents in Bermuda. J. Exp Mat. Biol F.col. 138:85-98.
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BiOLOGN. A]. PERSPECIAVI"S ON 1.01111TK I ' I Chanter VIII Are We Overfishing the American Lobster? Some Biological Perspectives ROBERT S. STENECK University of M11laine Darling Marine Center WIalpole, M14E 04573 USA Note: The fbllowing contribution was written in 1996 there is widespread concern for its health. For before the 2000 assessment was completed by the nearly a century this concern has centered on Atlantic States Marine Fisheries Commission. My article overfishing. However a growing number of scien-reflected managenient positions and approaches prior to tists have questioned whether overfishing is its the new assessment, and it considered the ongoing diffi- most serious threat, or if it is, how will we know? culty in determining whether lobster stocks are over-When harvesting exceeds the ability of an fished. It is possible that several specific concerns iden-tified in my paper will be addressed in that assessmnent. exploited species to replace itself' it is overfished. However, this paper predates the ASMFC assessment There are myriad examples of overfished stocks process and thus contains no information derived from that have collapsed such as cod, haddock and right that assessment. Two papers that had been "in prep" whales. Then there is the unusual case of the have since been published and are referenced as such in American lobster. Despite repeated warnings for this chapter. nearly a century that lobster stocks are overfished and collapse is imminent, stocks throughout the western North Atlantic remained stable and in Unfbrtunately,/brmany years past we recent years surged dramatically. In fact, landings have watched... [the American lobster] in Canada and the United States in the 1990s have decline until some have even thought that exceeded record highs and most fisheries scientists commercial extinction... awaitedthe entire agree that this increase is primarily driven by high fishery" What is the matter with the abundance rather than simply increased fishing lobster? -Herrick, 1909 effort (Elner and Campbell, 1991; Pezzack, 1992; Anon. 1993a; Miller, 1994). Were determinations of overfishing wrong?.Should other factors not cur-rently in the spotlight be considered more seriously? Why, are there so manjy American If the primary concern is for the health of lobster lobsters? -Miller; 1994 stocks, how might we best monitor it? In other words, how do we best put our fingers on the pulse of this marine resource? In this chapter, 1 will describe how overfishing on lobsters is currently determined, what strengths and weaknesses exist in INTRODUCTION this approach, and whether other factors such as Because the American lobster, Homarus amern- environmental variability, habitat, and pollution caraus, is the single most valuable species to the have been sufficiently considered. fisheries of New England, it is understandable that
13 2) ST FNF K 20000. "The Boom" 18000 16000 14000 12000 (Ai C_ 10000 AT\ I. f+ISD 800 Average
-ISD 60001 40001.
2000 "The Bust" 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 Year Figure 8.1. Lobster landings in Maine from 1880 to 1994 with average and variance (+ I standard deviation) over the period indicated by the three horizontal lines. The period below one standard deviation below the mean is called "the bust" and above one standard deviation above is called "the boom". Data from Maine Department of Marine Resources. TEIPORAL. TRENDS IN AMIERICAN LoT;isiFi AND continues in some regions today (e.g., Elner and FIsiliNG EFFORT Campbell, 1991; Miller, 1994; Acheson and Steneck, 1997). In between the bust and boom My review focuses heavily on Maine because periods, landings varied in different regions but in it has the largest harvest of lobsters in the United Maine and most of the Gulf of Maine there was a States and because good records have existed for significant increase in landings during the 1940s. more than a century. As others have pointed out Although for the next 40 years stocks were remark-(e.g., Elner and Campbell. 1991 ) some of the most ably stable, there. were repeated concerns that they striking patterns in Maine have been paralleled in were overfished (discussed below). most areas throughout the western North Atlantic. One reason often cited for the general increase One of the strongest patterns observed in the in landings from the 1930s into the 1990s is western North Atlantic is the decline in landings increased fishing pressure or effort (e.g., Fogarty, observed froom the turn of the century to about 1.995). Fishing effort on lobsters, expressed as the 1925 (Figure 8.1). This pattern was evident in all number of traps fished per year, shows a strong major lobster producing regions of Canada (Nova increase since World War I1especially during the Scotia, Newfoundland, and Gulf of St. Lawrence; 1970s, after which (until very recently) it has largely Elner and Campbell, 1991; Pezzack, 1992; Anon., stabilized (Figure 8.2A; see Thomas 1980 for a 1995) and the United States (Harding et al., 1983; more complete discussion of effort). Many argue Miller, 1994). In Maine, this resulted in the all-that this is only part of the story and that effective time population low that occurred between the effort has continuously increased due to longer World Wars and ended in the mid-1940s (labeled soak time, improved trapping, hauling and navigat- "The Bust" in Figure 8. 1; Acheson and Steneck, ing capabilities (Anon., 1996a). 1997). Traditionally landings increase with increasing Equally. striking as the bust is the "boom" peri-effort until the maximum sustainable yield is od which began between the 1970s and 1980s and
fN(~OL0,U(AL P'ERSII P E4 XE_ýN(l I.0 115rFER 0 -(,\ SIS I I\ (i 13 A 3( Annual Effoi B Landings Relative to Effort The Boom I-- '(a U) 2 CD C) a) E C3 t~ CD M11
=-
C: 0 w
< i '0 C:
-o 977) 1880 1900 1920 1940 1960 1980 500 1000 1500 2000 2500 Year Number of Traps (thousands)
Figure 8.2. Lobster landings in Maine and fishing effort (i.e., number of traps fished) since 1880. A. Temporal trends in fishing effort. B. Landings relative to tishing effort. Effori is approximated by number of traps fished. Two best-lit polynomial curves yielded different results. Dow (1977) calculated a curve in 1974 showing a distinct decrease in landings with effort after landings highs recorded in 1957 and 1960. A reanalysis with data through 1994 shows a dis-tinct increase during the boom of the 1990s. Data friom Maine's Department of Marine Resources. achieved. After that point, landings will decline The causes of the declinc of/thc fishe/1v with continued increases in effort. It was believed are tluin-v evideni. M/ore lobsters have thatthe fishing effort on lobsters reached in the been taken fiom the sea than nature has late 1950s and early 1960s attained the maximum been able to replace by the slow process sustainable yield (Dow, 1977; Figure 8.2B). The of reproduction and growth. dramatic increase in effort in the 1970s (Figure -Herrick, 1909 8.2A) was coincident with a decline in landings (Figure 8. 1). By 1974 the trend of declining catch with increasing effort was interpreted as clear evi- Lobster stocks have long been assutmed to be dence of overfishing (see curve labeled "1974" in overfished. As indicated in Herrick's (1909) quota-Figure 8.2B; Dow, 1977). In subsequent years, tion above, the principal overfishing concern however, the declining trend reversed to the record relates to the reproductive capacity of the stocks. levels of the recent boom. This resilience despite Stocks that are reproductively limited have insuffi-enormous effort has surprised managers and has cient fertilized eggs to maintain population densities contributed to a lack of confidence in fisheries sci- and are thus "recruitment overfished". This is the ence held by some in the industry. major biological and management concern (Anon., 1996a). Economic concerns such as improving yield (e.g., "growth overfishing") are usually con-FLUCTUATIONS IN LOBSTER STOCK: sidered a separate matter especially if the brood-OVERFISHING AND/OR TIE ENVIRONMIENTl? stock and reproductive potential remain strong. It is possible that."growth overfishing" or harvesting lobsters before they can provide the maximum sus-EVIDENCE FOR OVERFISHING: tainable yield per recruit could also have ecological ARE STOCKS REPRODUCTIVELY LIMITED? consequences to the stock (e.g., by shifting the size Is BROODSTOCK DECLINING? structure of the population toward smaller individ-uals) but to date, there are no indications that this affects reproduction or sustainability of the resource.
134 STENECK 18000 A low level of roodstock (recruil over-17000 1074 (N\WS 1 t1, SAW)' fishing) was a t-opu/ar exlilanationftr 16)000, the depressed catch rales chrillg the 1500*" ovr tit.Ihing I (tor (1(77) I970s...: however the very lacye year 14000 13000 (ar'cii iced for Lovcrl hc classes which occurred in i/e 1980s. biolo", at nianeorat~w some of which were produced by these 1E.2000 o, f2OOO- ritii(Kro,-r 1973) 1ttatOt
.E 10000 low population levels, wseakens this 10000" argueneriu.
9000 7000 1945 1950 1955 1960 196i 1970 1975 1980 1985 1990 1995 A decline in the reproductive potential of lob-Year ster stocks can only result friom a decline in the abundance of broodstock lobsters. The reproductive Figure 8.3. Overfishing and management concerns voiced by federal and Maine state fisheries managers. potenitial is the broodstock sufficient to maintain the population assuming that adequate conditions for larval survival, growth and settlement prevail. Since 1945 most warnin-s ofoverfishintz have To date, there is no direct indication that brood-been coincident with periods .of declines in landings stock is declining in abundance. For example, there (Figure 8.3; Miller, 1994). As Anthony and Caddy is no significant trend in abundance among lobsters (1980) stated, "Landing declines are often inter.- at or above harvestable size in the National Marine preted to be stock collapse due to overfishing". Fisheries Service's groundfish trawl surveys However in every case, lobster stocks rebounded (Figure 8.4.; Anon., 1993a) over the 12 year period without a reduction in fishing effort. The fact that from 1980 to 1992. These surveys provide the only lobster population densities throughout their range direct estimate of abundance used for population have increased significantly in recent years indi- data on which overfishing determinations are based
- cates that they are not currently reproductively lim- (discussed below).
ited and thus not literally recruitment overfished. Despite the long history of suspecting stocks This point was amplified by Pezzack (1992) who were overfished, there is little hard evidence to pointed out: support that thesis. As pointed out by Elner and Campbell (1991), "...the events with lobsters in the Greater Than Harvestable Size Females Less Than Harvestable Size Females A (Incl. Broodstock) B I (All Juvenile) 0.61] 0.5' C 6- 0.5 0.4' 40 C. 7) C 0.4ý 6 0.3' 0 0 0 6 C 0.3 40 0 0 0.2' 0.2 0 S .40
- 4) 7)
C, 0.1' 0.1 0 4,7 4,7 a oo y 2.21033 12'933.-2., W2 M3 7
-u80 82 84 86 88 9( )92 80 82 84 86 88 90.92 Year Year Figure 8.4. Trawl survey data on lobster abundance (Anon., 1993a). A) Fully recruited lobsters (i.e., > 83 mm CL) include all potential broodstock. There is no temporal trend in the abundanceof this component of the population. B)
Prerecruits (< 83 mm CL) all of which are juveniles. There is a significant increase in this component of the popula-tion. Data from NMFS Northeast Fisheries Science Center Autumn trawl survey (Anon., 1993a). Recently revised data through 1995 continue the above trend (Anon., 1996b).
B"IOL'(!C,\L I'1iRStL(TIVI£\S ON LIMSTIR (1% '\/RFIS[I1N(; 35 northwestern Atlantic over the past 10 years sug- Temperature Anomaly: A Cooler Than Average Year gest [that] recruitment can be independent of fish-ing pressures..... In a similar vein, Miller (1994) questioned the efficacy of management by pointing out that, "'The very large area over which landings Red seed GmWth Rate Reduced Post Larval increased argues against favorable management. Reduced Settlcmient regimes or changes in regimes as causes. Seasons, Trapabilit)v \ mininmm sizes. fishing effort, etc., vary a great deal over the area considered ... and changes in 0 1 2 3 4 5 6 7 8 management during the 1970's and 1980's were Expected Time Lag (Years). small." Could the demographic signal from the Figure 8.5. Expected tine lags after a sea surface environment be stronger than that from fishing temperature anomaly (e.g., a cooler than average year). pressure or management measures? Given the undoubtedly great effort exerted by the fishery. the lobster, by analyzing landings relative to the the environmental control would have to be years since the thermal event, it should be possible extraordinarily large. to evaluate the importance of temperature and to identify the phase in its life cycle where the impact is greatest. For example, factors affecting larval ENVIRONMENTAl.. CONTROL: A CASE FOR WATER settlement may have an immediate impact on popu-TEMPERATlURE ON EARLY LIFE H-ISTORY PHASES lation density but will only be evident at the time Temperature has long been considered a key of recruitment to the fishery after they reach mini-environmental variable for lobsters (Huntsman, mum harvestable size (83 mm carapace length, CL) 1924; McLeese and Wilder, 1958: Flowers and about-seven years after settlement. In contrast, Saila, 1971 ; Dow, 1977; Aiken and Waddy, 1986; changes in growth may be evident a y'ear or two Fogarty, 1988; Campbell et al., 1991 ). Since some after a thermal event whereas trapability will be temporal trends in both lobster landings and sea evident the year of the temperature record (i.e., no surface temperatures correspond broadly through- time tag, McLeese and Wilder, 1958). The particu-out the western North Atlantic (Elner and lar season or month of thermal influence may also Campbell. 1991), temperature is a likely candidate. be important. For example, temperature effects on However, there is no consensus on how tempera- larval biology and behavior are confined to the ture affects landings. summer months when they are in the water column. It is also important to know which phase of the To determine the life cycle phase when the lobster life history is likely to be most impacted by temperature effects on landings are greatest, a pro-temperature. Many species including lobsters have gressive time-lagged regression analysis was per-a "critical period" (sensa Hjort, 1914; Frank and formed (landings and Boothbay Harbor, ME sea Leggett, 1994) or "critical phase" (senssu Langton surface temperature data from Maine's Department et al., 1996) in their life history. The critical phase of Marine Resources). Regressions were run both is the period in the life history of an organism with average and with August sea surface tempera-when cohort size and ultimately population size is tures for the year of the reported catch (i.e., 0 year determined (Langton et al., 1996). If temperature lag) and for each year prior to the landings for 20 controls the success of a critical phase, then it will years (i.e., a 20 year lag). control the abundance of the species; Sea water temperatures around the time of Three ways temperature may control landings post-larval settlement have a significant impact on are by regulating trapability, growth rates, and/or stock size and future landings. The best fit between settlement success (Figure 8.5; Fogarty, 1988, landings from 1946 to 1986 and sea surface tem-1995; Campbell et al., 1991; Addison and Fogarty, perature was determined by the proportion of vari-1992; but see Aiken and Waddy, 1986 for other ance explained (i.e., the r2 value) for each time-temperature effects). Because these temperature lagged regression (Figure 8.6). The strongest sig-effects occur at different times in the life cycle of nificant relationship between landings and average
136 STI:-NFCK A B C) V.- 0
-0.4' 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 LAG (years) LAG (years)
Figure 8.6. The proportion of variance explained by temperature with time lags ranging firom 0 to 20 years. Variance is represented as r2 based on regression analyses of mean annual temperature (A) and mean August temperatures (B). Asterisks represent significant inclusions to a multiple regression model at the 0.05 level. So that landings reflect stock size, rather than interannual variability, I used a three year running mean on landings (method of Ennis. 1986). This is necessary because at the time of harvest a warmer than average year may result in an extra molt and an early recruitment into the fishery and a cooler than average year may result in a delayed molt and a later than average recruitment into the fishery. Such noise is of little long-term consequence to the fishery. The progressive improving of the proportion of variance explained toward and away from the 6 - 8 year lag is probably in part the result of variance in cohort growth rates. No Lag 7 Year Lag 10500 10000 r2.05 9500 9000 8500 8000
-7<AA 1 ý . ý - - - - - - - - - - - - I 14 15 16 17 18 August Temperature August Temperature Figure 8.7. Annual landings and mean August temperatures from 1946 - 1986 for the year of the harvest (A, no lag),
and seven years after the recorded temperatures (B, 7 y lag). temperatures was found around a mode of six to Since settlement occurs primarily during August in seven years (Figure 8.6A). When August tempera- Maine, thermal patterns then may be the single tures were analyzed in this way (Figure 8.6B), a best environmental determinant of future landings. similar but more pronounced spike occurred at the The wider curve resulting from average tempera-period between 6 and 8 years. Both analyses tures may reflect other more behavioral (i.e., trapa-explain approximately the same proportion of vari- bility in year one, Addison and Fogarty, 1992) and ance in landings and both show the strongest signal growth-related impacts in subsequent years, but is around 7 years later which is consistent with the these are minor relative to the very strong signal idea that thermal control of population density is at evident at seven years or around the time of PL set-or around the time of post-larval (PL) settlement. tlement.
I \iH
-I(A.
_ ,ERSI TIVE'$(EN IO S IT ER O\E FR, ISIIIN(; 137 To better visually, interpret this analysis, Figure lobster larval success have been suggested in other 8.7A shows the regression between landings and systems (e.g., river discharge in the Gulf of St. ALgList temperature in the same year (i.e.. no lag). Lawrence; Sutcliffe, 1973. lagged 9 yrs). There are The nonsignificant (p = 0. 12) slope is negative and no studies I know of that indicate a shortage of I` is only 0.05. In contrast, the relationship between broodstock, i.e., recruitment overfishing over the landings and temperatures seven years prior shows last half century. a strong positive and significant (p < 0.001) rela-tionship with an -2 of 0.535 (Figure 8.7B). (Note LOBSTER MANAGEMENT: TiE EGG PER RECRUIT that the r2 values from each of these regressions is in Figure 8.6B). DEi.I:INITIo O1 OIVERlFISHING I focused on environmental inifluences for the 40 years between 1946 and 1986 (Figures 8.6 and 8.7) since declines during that period, were inter- THE EGG-PRODtJCTION-PER-RECRtJIT DEFINIION: preted by fisheries managers to have been the SET AT A PRECAUTIONARY LEVEL. result of overfishing (Figure 8.3). Although ten-Federal law requires "an obtjective and measur-perature may have contributed to some fluctua-able definition of overfishing for each managed tions,this analysis does not indicate that stocks stock or stock complex with an analysis of how the were not threatened over that period or that they definition was determined and how it relates to the are not threatened today by overfishing. However, biological potential," (Anon., 1989). A recent patterns of decline were evidently more attributable report of the Stock Assessment Workshop (Anon.. to environmental factors than to fisheries-related 1993a) concluded that the lobster fishery, as a impacts over that period. Fogarty (1995) showed whole (including Gulf of Maine), is overfished by similar results over this period using a transfer the current definition of overfishing. The applica-function technique. Since these fluctuations in ble definition of overfishting published in landings have no apparent relationship with the Amendment 5 to the Federal American Lobster size of the broodstock they are not evidence of Fisheries Management Plan (1994) is: overfishing. Different analyses of the recent population increase have reached different conclusions. The resounrce is recruitment overfished Whereas Fogarty (1995) found the boom of the when, thr'oughout its range, the fishing 1990s (Figure 8. I) was attributable to temperature. my analysis did not (e.g., Figure 8.6; Acheson and mortality 1;ale t'F) given the regulations in place at that time under the suite of Steneck, 1997). Several theories have been regionalmanagement measures, results advanced to explain this change but beyond the thermal explanation (e.g., Fogarty, 1995), most in a reduction in estimated egg produc-tion per recruit to 10 percent or less of a relate to changes in the biotic component of the eco-non-fished population [110%/o]. system. Prime examples are that effective nursery grounds or juvenile habitats have expanded due to recent increases in kelp and decreases in predator This definition was adopted as a precautionary abundance in the coastal ecosystem (see Habitat measure. That is, it is set at a level that should not and Ecosystem Considerations below). allow reproductive or stock collapse since such an The point is, it is essential for those interested event would be a disaster to the industry for in detecting recruitment overfishing to be able to decades at least (Anon., 1996a). The conundrum is filter out environmental "noise" froom the fisheries that only by experiencing stock collapse can the signal. Clearly, many of the declines in lobster estimated egg production per recruit be calibrated landings in Maine that were interpreted to indicate or the efficacy of the overfishing definition be overfishing (Figure 8.3), in fact turned out to best demonstrated. This definition and the egg-per-correspond with time-lagged temperatures and the recruit (EPR) approach is the guiding light for fish-processes they affect at the time of larval settle-eries management in all lobster producing states ment. Other environmental variables influencing and recently for Canada (Anon., 1995).
138 TEINFCK AsSUMPTIONS AND CONCERNS OFITH EGGS PER not affect the fundamental eggs per recruit RECRUIT OVERFISHING DEFINITION relationship necessary to sustain the popula-tion. The current EPR definition is based onl the idea Arguably the question should be, do we know that fisheries models and statistics are sufficient to elouLIgh to manage lobster stocks this way? Is there estimate the proportion of the lobster population sufficient confidence in this approach to have it be that is harvested or dies each year and sets at a pre- the sole basis for management? There are disturb-cautionary level the proportion of tile population ing voices from fisheries scientists who suggest the that must survive and reproduce to sustain the answer may be "no." Below I outline some of the stocks. There are two primary concerns related to serious questions that have been raised over each this definition: I) it is based on many fundamental of the six assumptions above. estimates or assumptions that are either untested or I) The Slock-recruitnent Relationship Is untestable, and 2) it assumes that the principal Known. Knowing or estimating the relationship threats facing the resource relate to its reproductive between the abundance of parent stock (i.e., brood-health as estimated by the production of eggs per stock) and the resulting yield of recruits to the fish-recruit. cry is central to fisheries management (Frank and There are six key assumptions necessary to Leggett, 1994). Pezzack (.1992) reiterated this determine overfishing: assumption by stating that the "*stockrecruitment
- 1) The stock-recruitment relationship is known; relationship is the basis of much of ... lobster man-
- 2) Stocks can be commensurably quantified agement." However he went on to point out a throughout their range; troubling problem-to date, "no clear stock recruit-
- 3) Mortality (both natural and fishing or F) can be ment relationship has been found in lobsters.".
estimated; The estimated stock-recruitment relationship
- 4) There is no large-scale geographic segregation on which lobster stocks are mnanaged in the US and of tile population and net loss friom a manage- Canada was published by Fogarty and Idoine ment zone due to migration is negligible; (1986; 1988). Since there are no estimates of the
- 5) The necessary proportion of ovigerous lobsters size of parent stock populations, these investigators relative to an unfished population to sustain the used data provided by Scarrett (1964, 1973) on lar-stock is known (i.e., is it 2%. 5% 10% or val abundance to represent broodstock and subse-20%9); quent (time-lagged) landings for the
- 6) Ecosystem change is inconsequential or does A Stock-Recruitment Data B Stock-Recruitment Curve
,0.6" 0.6 0 1953 0 0 .5 0 0.510 1952 6 S 0.4' -e0 0.4 00 lIs4 01956 S S0.3 03 r0 1949 0 0.2' 0.2 01' 0.Il Curve forced through zero 0.0 5 10 15 20 25 30 35 5 10 15 20 25 30 35 Broodstock Broodstock (Stage IV (Post-larvae) Abundance) (Stage IV (Post-larvae) Abundance)
Figure 8.8. The stock-recruitment relationship on which lobsters stocks in the western North Atlantic are managed (Anon., 1995; 1996ab). Broodstock (i.e., parental stock) and its resulting egg production is assumed to be repre-sented by the abundance of Stage IV post-larvae. Recruitment of lobsters to the fishery is assumed to be repre7 sented by landings. A: Data from Scarrett (1973), B: Analysis and curve-fit from Fogarty and Idoine (1986).
111 +'GT(>AL PERSPE-'-'TV\, ON LOBSTER OVER)ISHINi 139 Northuniberland Strait in the Gulf of St. Lawrence may not always correspond with larval abundance. in their analyses. The resulting plot (Figure 8.8A) For example, if postlarvae choose not to settle, or shows no relationship between Stage IV post-lar- if they settle in habitats where early post-settlenient vae abundance and stock size. However, based onl mortality is high (\Wahle and Steneck, 1992), the the asSumLnption that no larvae willI result in no land- resulting landings would be low or absent but not ings, the published curve was forced through the necessarilyvthe result of low post-larval abundance. origin (Figure 8.8B). This curve became the stock- Given this, it may be inappropriate to interpret the recruitment curve on which lobsters throughout the post-larval -recruitment data (Figure 8.8A) as a western North Atlantic are now managed (Anon., curve forced through zero (Figure 8.8B). 1995, 1996a, b). The application of the stock-recruitment curve A consequence of this stock-recruitnment curve generated for Northumberland Strait was interpret-which steeply plunges to the origin, is that there ed by Fogarty (1995) to show -a generally declin-will be virtually no warning of stock-collapse. That ing trend in larval production" with the evident is, over a wide range of broodstock abundance result being "the population declined markedly there is no change in the harvested stock until the shortly after cessation of ... sampling...." in 1968. broodstock reaches very low abundances, at which This is contrary to published landings data for that time stocks are predicted to crash. This interpreta- region (Harding et al., 1983; Pezzack. 1992) which tion of this curve also suggests that landings alone shows a steady decline friom 1960 to mid 19.70s. will not be good indicators of the risk of stock col- The same pattern was recorded in Maine over the lapse. The shape of this curve, especially its slope same period (Figure 8.3) but clearly larvae came near the origin, is critical for the management strat- from different parent stocks. Had larval declines egy applied to lobsters (Anon., 1996ab). been the result of declines in broodstock, a much The most serious flaw in this logic is that there longer period for recovery would have been is no evidence that larval abundances relate to the expected (Fogarty, 1995). However in both cases, size of broodstock..In fact, the data used for the without any significant management action, and lobster stock-recruitment curve (Figure 8.8A) continued increases in fishing effort, this decline shows very rapid interannual fluctuations in larval was followed by a steady population increase for abundance. Extremely low larval abundances well over a decade. recorded in 1949 were followed by the highest The stock-recruitment relationship for lobsters value in 1952 which was followed by low values remains elusive because it is a problem of scale. again in 1953 and 1954. Broodstock abundances Broodstock abundance would more likely relate to do not and cannot fluctuate at that rate. We must landings if the population is "closed". But it is now conclude that larval abundance is a poor indicator widely recognized that larvae come from reproduc-of broodstock abundance and thus the curve tive lobsters that live elsewhere and thus represent (Figure 8.8B) is not a stock-recruitment curve. an open system or a metapopulation (Cobb and That larval abundances are variable and could Wahle, 1994). result in low landings, is not the same as a brood- The stock-recruitment relationship for lobsters stock-collapse resulting from recruitment overfish- is a window into a bigger question. In a recent ing. review by Frank and Leggett (1994) they point out Variability in local larval abundance can result that stock-recruitment models in general have fall-from variation in reproductive success or environ- en under "increasing criticism". They cite papers mental influences. For example, physical oceanog- that argue that "fisheries scientists have shown raphy and meteorology affects ocean current and excessive willingness to impose theory on data wind delivery patterns of competent post-larvae rather than testing the null hypothesis that there is (Incze and Wahle, 1991). Water temperatures influ- no relationship between stock and recruitment." I ence post-larval growth rates (Harding, 1992) or submit it would be difficult to reject that null sounding behavior (Boudreau et al., 1991, 1993). hypothesis using published data for the American All of these factors can account for significant dif- lobster. ferences in larval settlement without any change in 2) Stocks must Be Commensurably Quantified broodstock abundance. Further, larval settlement. Throughout Their Range. It is difficult to quantify
140 srENECK Simall Female Lobsters Large Female Lobsters (< 83 aun CL) (> 83 mm CL) Figure 8.9. Results friom randomized stratified trawl surveys conducted between 1982 and 1991 during Autumn for the Gulf of Maine and southern New England (modified fromn NMFS Northeast Fisheries Science Center). Black blocks had one or more lobsters, unshaded blocks had none. Note that coastal regions in the central Gulf of Maine that have the highest landings have no trawled prerecruit lobsters (i.e.. < 83 mm CL) whereas sand regions of the western Gulf of Maine that have much lower landings have much higher trawled densities of prerecruits. Note that Georges Bank (east of the Great South Channel) is dominated by larger lobsters (i.e., > 83 mm CL). Offshore canyons and the Great South Channel labeled for reference. lobster abundance in regionally commensurable regions where lobstering effort is low or nonexis-ways using current techniques. For example, tent. For example, coastal regions in central Maine NMFS biannual groundfish trawl surveys randomly where most lobsters are harvested and prerecruit go to different trawl locations each year (i.e., strati- densities (in #/m 2-) are greatest are not sampled fied random sampling, Figure 8.9). If in one year (Figure 8.9). Coastal regions in sand-dominated the trawls sample some hot spots but in other years Massachusetts where fewer lobsters are harvested they do not, interannual variability will be great. and prerecruit abundances are less, are sampled. As Trawl samples contain very few lobsters per tow. a result, population patterns derived from trawl Figure 8.4A shows only about one tow in three will sampling are opposite that of landings and demo-contain a female lobster and the resulting annual graphic studies (Figure 8.9). Addison and Fogarty abundance estimates have high interannual vari- (1992) stated that: "the only reliable measure of ability. Some of the variability relates to the sub- true changes in abundance... would be direct cen-stratum type being trawled. Trawl-capture efficien- sus estimates." This ctuTently does not exist. cy will be high in sand where lobster population 3) Mortalit, (Both Naturaland Fishing densities are naturally low and very low in boulder Mortality, or F) Can Be Estimated. Measurements. fields where lobster population densities are high. of natural mortality are lacking (Thomas, 1980; Other variability relates to regions where trawl Conser and Idoine, 1992). An assumed 10% natural sampling can be conducted. To avoid damage of mortality per year is usually used but this may be fixed gear (lobster traps), trawl sampling targets far from the mark especially if applied to the entire
RIOLI,(;(, ki- PF RSIPEC'TIVI\E ON I-BSTEK OVI- ItRFSIIIN(G 141 lobster population. Rates of predation are very high and Wilson, 2001); at the time of post-larval settlement and rapidly There are serious management implications if decreases as they grow (Wahle and Steneck, 1992; regional losses due to migration cannot be distin-Wahle, 1992). When lobsters in coastal Maine guished from mortality. For example, in the 16' grow to near harvestable size (greater than 60 mm Stock Assessment Workshop (Anon., 1993a), the CL) they are virtually immune to predators stock assessment area of Southern Cape Cod-Long (Steneck, 1989., 1995a) because most coastal Island Sound Inshore had the highest estimated rate predators today are small in size (Malpass, 1992; of mortality (exploitation rate of 81%). This zone Witman and Sebens, 1992). In contrast, on Georges also happens to be elongate, largely coastal with an Bank where large lobsters predominate (Campbell abundance of prerecruit lobsters (< 83 mm CL, and Pezzack, 1986), annual rates of natural mortal- Figure 8.9). One would expect the greatest net ity' are likely to be exceedingly low. In all likeli- movement of larger lobsters out of this zone to hood for any given size there will be a significant regions offshore. In contrast, the Georges Bank and habitat-related (e.g., sand vs. boulder) and region- South Offshore stock easement area had the lowest related (e.g., coastal vs. offshore) difference in nat- estimated rate of mortality (exploitation rate of ural mortality. Ontogenetic differences in mortality 35%). This zone is dominated by large lobsters that rates are likely to vary by orders of magnitude. apparently have migrated in from other regions The means of estimating fishing mortality for (see Figure 8.9). Recognition of this problem with lobster is the DeLury method (Conser and Idoine. lobsters was voiced by a fisheries manager who 1992; Anon., 1996a). This method assesses the rel- stated: "...we all could be overestimating 'F' ative abundance of prerecruit lobsters (assumption [Fishing mortality] values due to migration."
- f2)and based on estimated rates of growth. aSsum- (Anthony and Caddy, 1980). It was also identified ing there is no migration (assumption #4) and natu- as a general fisheries management problem by ral mortality is 10% (assumption #3). the expected Frank and Leggett (1 994) who point out that: "pop-harvestable biomass oflan unfished population can ulation dynamic models applied to fish populations be approximated. The amount observed less than frequently ignore dispersive processes such as that expected of an unfished population is assumed immigration andemigration...." Especially since, to reflect fishing mortality. Most of the assump- "emigration... has commonly been viewed as the tions used to estimate mortality will be difficult to equivalent of mortality..... They go on to point out test. However. the assumption of no migration that this has been well known among ecologists (assumption 44) creates a particular problem. (e.g.. Wynne-Edwards, 1962) who "believed that
- 4) There is No Large-scale Geogratphic dispersal acted as a safety valve providing immedi-Segregation of the Populationand Net Loss from a ate relief to the potentially negative effects of over-Management Zone Due to Migration is Negligible. population." Frank and Leggett (1994) go on to This assumption was reiterated by Fogarty (1995) conclude that "recruitment dynamics may be seri-for the population dynamics models for lobster: "a ously misinterpreted if such dispersive processes closed population is assumed in which immigration are ignored."
and emigration are negligible...." It is well known 5) The Necessary Proportionof Ovigerous that the range of lobster movement increases with Lobsters to Sustain the Stock Is Known (i.e., is it 2, body size (Krouse, 1980). Large, reproductive lob- 5, 10, or 20%?*). If we assume the egg per recruit sters, may migrate hundreds of kilometers management approach works, what proportion of (Campbell and Stasko, 1985; Campbell, 1986, the population must be reproductive to sustain 1989) whereas young of the year lobsters may not stocks'? The target estimated egg production per move more than a meter (R. A. Wahle, personal recruit of 10 percent of an unfished population was communication). As a result, there are off-shore proposed as a precautionary level which was and deep water regions dominated only by large acknowledged to be a rather rough educated guess reproductive lobsters (Figure 8.9; Skud and based on estimates from fin fish and other exploit-Perkins, 1969; Campbell and Pezzack, 1986; ed crustaceans. Since lobster stocks were deter-Steneck. in prep) and shallow coastal regions dom- mined to have suffered overall mortality rates that inated by juvenile lobsters (Steneck, 1989; Steneck result in less than 10% egg production per recruit
142 S rC(fN CK for 8 of the 10 years analyzed (Anon., 1993a), yet believe that these and other important components lobster populations increased over this time, this of the ecosystem have changed over tile past century. value cannot indicate the limit of the stock's repro- Obviouslv some abiotic chanoes such as water ductive potential. According to NMFS scientists temperature described above may change ecosys-(Anon., 1993b): teni function, but there are also some relatively recent biotic changes that may be important to lob-ster stock abundance. The fishinzg mortality rate which would Predator-prey.interactions are undoubtedly dif-result in a rectrtitment/ailureis not ferent since groundfish were depleted from coastal known Jbr lobster populations in the locations. Whereas cod and other groundfish were United States. It is' true that there is abundant in coastal Maine during the 1920s (Rich, uncericainty about whether the 10% level 1930), they have been depleted from coastal zones is 'correct'.However, the onlv way to since the 1950s (Witman and Sebens, 1992; know fori sure is to reduce the population Steneck, 1995a, 1997; Conkling arid Ames, 1996). to the point where it collapses and to Thus natural mortality has probably declined over observe the level of egg pr-odtuction where the past several decades as fewer and smaller size the collapse occurredc. 1hor obvious rea- classes of lobsters remained vulnerable to predators. sons, we do not want to see this happen.... It is also possible that nursery grounds or sites for successful settlement have increased recently. Harvesting of the green sea urchin, Strongylocen-The certainty expressed in "the only way to trotus droebachiensis,over the past decade deplet-know for sure...." may be unwarranted. If environ- ed populations of this major inacroalgal herbivore mental conditions can impact lobster stocks by from coastal zones. As a result kelp beds have causing several years of failure in larval settlement, expanded throughout the Gulf of Maine (Steneck et then stocks could collapse but not due to insuffi- al., 1995) and this may provide mnore sites for lob-cient broodstock or a reduced reproductive poten- ster settlement. Wahle and Steneck ( 1991) found tial. As shown above, stock declines or even a that besides cobble rock some newly settled lob-short-term collapse does not necessarily indicate sters can be found in kelp as a nursery habitat. It recruitment overfishing, .sensiu striclt. Thus the was also suggested that a relatively small change in question remains, how should this biological refer- predation rates early in life may significantly ence point be determined and tested? Uncertainty change the population size (R. A. Wahle. personal regarding the 10% reference point was reflected in communication). the Canadian decision to apply the 'egg per recruit Kelp and other macroalgae provide shelter for approach but recommended a 5% biological refer- larger lobsters and can significantly change the ence point (Anon., 1995). local carrying capacity of some habitats, such as
- 6) Ecosystem Change 1.s Inconsequentialor relatively featureless ledge or bedrock, for larger Does Not Affect the FundamentalEggs per Recruit adolescent phase lobsters (> 40 mmn CL; Breen and Relationship Necessaij to Sustain the Population. Mann. 1976, Bologna and Steneck, 1993). In The final assumption relates to changes in the effect, this could retain harvestable lobsters in ecosystem. The egg per recruit approach simplifies coastal zones that would otherwise migrate off-many of the complex problems described above shore or to deeper water.
into a few simple elements. In essence it assumes Thus, the changes to the ecosystem are likely that the population dynamics of the resource to detract fiom the efficacy of the egg per recruit depends primarily on the broodstock. While in the determination of overfishing. In other words, it is extreme case of reproductive collapse this is unde- entirely possible that the proportion of reproductive niably correct, as the singular guiding principle for lobsters necessary to maintain lobster populations recruitment overfishing, it may be an oversimplifi- are likely to vary with some of these changes in the cation. This approach tacitly assumes that other abiotic (e.g., temperature) and biotic (e.g., preda-changes in natural mortality or larval settlement tors, nursery grounds, habitable space) components success will be negligible. There are reasons to of the ecosystem.
itIIL,( AL N:-RSPI'(.1 I\ES ON IOIWSSIL R (\
.\C LRFISIII N I 3 ARE LOBSTERS OVI*RFISII iD? Wiio KNows? Diffe2rent regions with different oceanographic characteristics will have different effective brood-stocks. Therefore, not only will the effective broodstock for Long Island Sound be different Consideringthe imnprecision associated from that of the Gulf of Maine, but also sizable with stock definition, the extent to which populations of reproductive lobsters within the lbactors other than spawning stock size Gulf of Maine may have equally little impact to seem to cause variability in recruitment, sustain their local stocks. As an additional manage-and the lack bf understandingof hlrval ment goal, it wouIld be very useful to locate, moni-recruitment processes, deternmination ofa tor and protect the effective broodstock. Because stock-recruitmentrelationshipfir the reproductive female lobsters produce large larvae American lobster is unlikely in the near after a long period of parental care, the per-egg future. -Ennis, 1986 survival rates are likely to be much greater than they are for most marine organisms. Also, since lobsters are long-lived (maximurm age may be as Because there may be serious problems with high as 100 years, Cooper and Uzinann, 1980) and the stock-recruitment relationship and the egg per have a long reproductive life, larval supply to nurs-recruit approach for lobster management does not ery grounds may remain high even after several mean stocks are not nearly overfished - they may years of settlement failure. All of this suggests that be. The central concern should be, if they are, how will we know? Because of the nature of the current a more "surgical approach" to fisheries manage-ment is possible for this species than is or has tra-best estimate of the egg per recruit relationship for ditionallv been used (Steneck. 1996). If effective lobsters (Fogarty and ldoine, 1986. 1988), the pre-broodstock persists in deepwater refugia, then steps cautionary level for the allowable F is applied so should be taken to protect that component of the that a surplus supply of eggs is always available.
population. For example, it Would be prudent and However fisheries scientists have openly ques-more risk-averse to prohibit the harvest of over-tioned whether this is the best goal for manage-sized and v-notch lobsters in other state and federal ment. For example, Elner and Campbell (1991) waters. Recent interest in metapopulation models wonder if environmental controls make "recruit-for managing the American lobster (Anon., 1996a) ment... independent of fishing pressure...". It fol-tacitly recognizes the significance of self-segregat-lows then that "traditional fisheries models based ing broodstock persisting in a ref'uge fr'om highly on concepts such as surplus production and stable vulnerable juvenile stocks. Until there is consensus recruitment would be largely redundant." Further, on the best approach for conserving broodstock, it could be argued that simplifying the biological multiple independent approaches should be less concerns for lobsters to only a recruitment over-risky. fishing argument distracts attention from other stock-threatening activities or events which could have impacts as great as reproductive collapse. CONCERNS OTHER THAN OVERFISHING Concerns about recruitment overfishing are really concerns about the reproductive potential If lobster stocks crashed due to factors other necessary to sustain current lobster stocks. A critical than broodstock abundance or egg production, the gap in our knowledge of what sustains the stocks is economic impact would be just as severe. For this not knowing the location or size of their effective reason, other key factors should be considered in broodstock. Effective broodstock are reproductive assessing the health of lobster stocks. Two impor-lobsters that contribute to landed lobster stocks. tant issues that relate more to the lobster's environ-Gravid females that release their larvae into ocean ment than to its reproductive health, are habitat currents that take them away from nursery grounds degradation and pollution. will not be contributing their offspring to the fish-ery and thus are not part of the stock's effective HABITAT: A DEMOGRAPHIC BOTTtLENECK IN TIlE broodstock. EARIY BENTHIC PHASE?
144 sf*'K*r-If lobster population densities are regulated by 4 14 settlement success as has been shown for reef fish (Doherty and Fowler, 1994), barnacles (Connell, 1985; Gaines and Roughgarden, 1985) and for ben-thic assemblages in general (Underwood and 2 Fairweather, 1989), then factors contributing to successful settlement may well play a larger role in C I their demographic success than will broodstock C) size per se. In any location, successful settlement CA requires (I) available competent larvae (which 5 ir 1011 20 n requires sufficient laral production and oceano-Collector Depths graphic dispersal; see Underwood and Fairweather, 1989), (2) the propensity to settle (e.g., sounding Figure 8.10. Lobster settlement as a function of depth in behavior, Boudreau et al., 1991 ; and appropriate coastal Maine. Data firomn artificial lobster post-larval tactile, visual or chemical cues, Schelterna, 1974) collectors placed 1 July and retrieved 15 September 2 and (3) available nursery grounds (Wahle and 1995. Number of n1 collectors is represented above Steneck, 1991). each bar. Error bar indicates one standard deviation. Successful settlement requires each of the con-ditions be met. For example, a demonstration of oceanographic control on lobster larval availability Habitat Distance from Shore is evident in the larval shadow created by the lee E Watershed Intertidal Subtidal Nearshore Oflfhore side of islands where settlement is significantly Pelagic reduced (Incze and Wahle, 1991). The propensity X-2 [-Laraac X I of lobster post-larvae to settle may be controlled by Z Benthic U 7F,. Clay water temperature (Boudreau et al., 1991 and dis- S Mud
¢.) Sand f'Att -Adults cussed above). Assuming those first two conditions Gravel are met, available nursery grounds may control Cobble X3 recruitment of lobsters to the benthos (Steneck, - Boulder 1989; Cobb and Wahle, 1994) and thereby control Figure 8.11. A habitat-life history matrix for the the ecosystem's carrying capacity. American lobster (Langton et al., 1996). Ontogenetic Newly settled lobsters have very specific habi- phases (XI, youngest to X5, adult) relative to the dis-tat requirements for small shelter-providing habi- tance firom shore, or water depth and substrate complex-tats such as peat reefs or cobble beds (Able et al., ity. The point X3 represents early benthic stages which 1988; Cobb and Wahle, 1994). Experiments have are critical phases in the life history of this species shown that settling lobsters suffer extraordinarily (most habitat-restricted). Shallow cobble bottoms are an high rates of predation outside of refugia (Wahle essential habitat because only there are settling lobsters and Steneck, 1992). The median time to the first safe from predators.
attack from small, commercially-unimportant predatory finfish is 15 minutes (Wahle and "essential habitat" (sensu Langton et al., 1996) or a Steneck, 1992; Boudreau et al., 1993). These fish demographic bottleneck for this species (represent-predators (primarily juvenile cunner, sculpins and ed as the constriction in Figure 8. 11). Furthermore, shannys) are ubiquitous in shallow coastal zones because early benthic phase lobsters are concentrated where average densities of nearly one per meter in cobble bottoms for the first several years of their square have been recorded (Malpass, 1992). life and this habitat comprises no more than 2 to Coastal settlement of lobsters is primarily within 10% of coastal substrates (Kelley, 1987). this habi-the upper 20 meters (Figure 8.10). tat is particularly at risk and should be a high prior-Since lobster settlement is largely confined to ity for protection (Steneck, 1995b). shallow (Figure 8.10) cobble nursery grounds (Wahle and Steneck, 1991), this habitat is an
[IU)I.)(.(CAL PILRSE('IVS
'1 N LESON IER Q\ERHF[IS ING 145 FISHING IMR'ACTS ON HABITAT lobsters to contaminant exposures (Hlarding, 1992:
Mercaldo-Allen and Kuropat, 1994) numerous lobster nursery grounds and preferred habitats accounts were given of detectable levels of various are vulnerable to some fishinng and other human pollutants and, when known, lethal limits. It is activities. The primary risks are friom sedimenta- beyond the scope of this paper to review this sub-tion (i.e., dredged materials) and dragging, both of ject in detail. However very little data exist on how which reduce spatial complexity (Auster et al., most pollutants impact natural lobster populations. 1996) and from pollution (Harding, 1992). For Most described pollution effects are relatively example, the increased effort in sea urchin harvest- local. While lobsters readily accumulate detectable ing has recently accelerated dragging activity in levels numerous heavy metals, polycyclic aromatic some coastal zones and adds to the growing list of hydrocarbons, pesticides and other anthropogenic other species harvested that way such as scallops compounds,-there is little evidence that these and mussels. Recent studies by Canada's impact the population dynamics of lobsters. Often Department of Fisheries and Oceans assessing the concentrations in nature are well below those iden-impacts of dragging for sea urchins in tified as having a lethal impact, however, oil spills* Passamaquoddy Bay. reported the following are a notable exception. (Robinson et al., 1995): As with other contaminants, spills of oil and other petroleum products can be highly variable in their impact. Crude oil contains hydrocarbons and Visual!y. the e/jkcts o/lhe /rags on the metals. Mortality impact is greater for larval and habitat were the disruption ofthe bottom juvenile stages than it is for adults in general. substrateas maony1 boulders have been Exposure to no. 2 fuel oil at <0.15 mg/L for 5 d turned over and dislodgedfrom the secli- can make lobsters unresponsive to food. Higher Inere.... There was ...some loss of exposure (1.5 mg/L) causes- gross neuromuscular mnacroalgae due to the dragging. responses with a loss of coordination and equilibri-Draggingalso had an imnpact on the lob- urm. Demographic impacts are variable because ster pPotulationsat the MVinister's lslcind weather (wind, sea), temperature and the nature of site as the density of lobsters in the the petroleum product control exposure and physio-experimental /)lot decreased to zero over logical effects. For example, in 1970, Bunker C the course of the draggingwhile the con- fuel oil was spilled in Chedabuco Bay, Nova Scotia trol plot remained constant. and in 1979 a similar incident occurred in Cabot Strait, but in neither case was there a measurable impact on mortality or harvest. In contrast, about Although Robinson et al. (1995) only looked 825,000 gallons of No. 2 fuel oil leaked into for large, relatively mobile, lobsters (which they coastal waters of Rhode Island in January 1996. conclude may have evacuated the area), the smaller This was coincident with turbulent weather and early benthic stage lobsters, if present, would be resulted in significant lobster mortality. unable to exit the drag area because of the added "Preliminary estimates suggest that ...a million lob-risk of encountering predators (Wahle, 1992), such sters were stranded" (Cobb and Clancy, 1996). as scUlpins, which often increase in abundance as a Adjacent coves exposed to the same storm swell result of dragging. but no fuel oil had no washed up lobsters (Stan Cobb, personal communication). Studies are con-POLLUTION CONCERNS: DEMOGRAPHIC IMPACT?"9 tinuing but it is felt that highly turbulent conditions and cold weather (poor evaporation) conspired to Pollution is often a source of concern for all mix sufficient fuel oil downward into the water marine organisms. This is particularly true for column to have had a toxic impact on the local organisms such as juvenile lobsters that live in population. While this has been locally devastating, shallow and heavily populated (including industri- it is unknown how widespread the affects will be. al) regions. In major reviews of the responses of
146 SI N H:( 'K CONCiIUSIONS AND SOMi)E MANAGENIENT acted oil more effectively. Understanding environ-IN IPIICATIONS mentally-induced changes in stock size is impor-tant so that industry and managers alike do not Despite nuimerous predictions that lobster mistake short-term declines for fisheries-induced stocks were recruitment overfished and on the reproductive collapse (recruitment overfishing). verge of reproductive collapse, landings have Such knowledge would also improve scientists' remained remarkably constant and in the past ability, to predict natural changes in stock size decade significantly increased. Although repeated which. if demonstrably correct, should improve the and recent reviews by fisheries scientists affirmed credibility of the scientific process in the eyes of past determinations of overfishing, there are rea-industry. The ultimate goal for lobster managers is sons voiced by other fisheries scientists to question not just to answer the question, "are we overfishing some of those conclusions. Fundamental compo-the American Lobster?", but to convince industry nents of fisheries models employed for lobsters to take action when it is clear that they need to do have been insufficiently tested and perhaps are so. In the meantime, a risk-averse strategy of pro-untestable. There are published and logical argu-tecting effective broodstock and nursery grounds ments against accepting stock-recruitment curves, would be a logical course of action. It requires pro-estimates of total mortality and assumptions of tecting essential habitats for critical life-history ecosystem stability. Until the abundance of the phases (sensu Langton et al., 1996) but if the effective broodstock for harvested stocks of lob-appropriate spatial scales are selected, this action sters is known, the stock-recruitment relationship could be done surgically (Steneck, 1996). cannot be estimated. Furthermore, fisheries scien-tists have been unable to sort environmental noise from fisheries-induced signals. As a result, the pri- ACKNONXLEDG XIENTS mary reliance on specific estimates Of egg produc-tion per recruit relative to estimated unfished popu- Ideas and perspectives presented here resulted from years of mostly productive discussions and lations requires a level of resolution that to date may be unattainable. If this is the case, then we. debates with numerous colleagues. Jim Acheson, must conclude that we simply do not know if lob- Bill Adler, Robin Alden, Ted Ames, Peter Auster, ster stocks are recruitment overfished. Thus.the Herman (Junior) Backman, Bob Bayer, Stan Cobb, concern about risk of "commercial extinction" Dick Cooper, Dave Cousens, Dave Dow, Bruce voiced nearly 90 years ago by Herrick (1909) Estrella, Mike Fogarty, Arnie Gamage (and the remains, but scientific evidence in support of that South Bristol Fishermen's Coop), Joe Idoine, Lew concern is still lacking. Incze, Jay Krouse, Peter Lawton, Doug McNaught, I raise these concerns with the hope that a Jack Merrill, Alvaro Palma, Judith Pederson, Doug more prudent course of action will be initiated Pezzack, Peter Sale, Rick Wahle, Bob Wall, Pat which includes additional new multiple indepen- White, Carl Wilson and Jim Wilson. Drafts were dent estimates of the health of lobster stocks. read by Peter Auster, Robert Buchsbaum, Mike Specifically, the distribution, abundance and loca- Fogarty, Bill Robinson, Rick Wahle, Jim Wilson tion of.the effective broodstock should be deter- and Steff Zimsen. Some strongly disagree with mined, monitored and if possible protected. The some of my conclusions, others agree, and to all I same should be done for lobster nursery grounds. am grateful. Whereas some good ideas no doubt To that end, regional and temporal patterns in lob- came from some of those listed above, all errors ster settlement should be determined and moni- are entirely attributable to me. I am indebted to tored. This diverse approach for determining over- NOAA's National Undersea Research Program's fishing on lobsters uses appropriate spatial scales, National Research Center at the Univ. of considers differences in lobster ontogeny, associat- Connecticut at Avery Point (Grant No. ed changes in habitat requirements (e.g., segregat- NA46RUO 146 and UCAZP 94-121) and the ed life history phases), and it should filter out envi- University of Maine Sea Grant College Program ronmental noise so that real threats to the reproduc- for funding research cited herein. tive capacity of the stocks can be identified and
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In: 1994 Workshop ott tnatural population of American lobster. 1onti't.s a"nei iccIalils. tile Mana'l aenet and Biolosv of tie Green Sea UIrchin alone the Mainre Coast Fish. Bull 71: 165-173. (.S1ot,,liiocelt/rotus dtosi'octibctt sis t. floothbay Harbor Me. Pp Krouse, J. S. 1980. Summary of lobster. Hotnarus antericanus,tag- 34-73. grig studies in American waters ( 1898-1978). Ca'. Tech, Rep Stenseck, R. S. and C. J. Wilson. 2001. Long-termi and large scale spa-Fish. AqLat. Sci. 932: 135-151. tial and temporal patterns in demographs and latdings of tlse Langton, R., R. Steneck, V. Gotceitas, F. JuLanes and P. Lawton. American lobster, Homarus aniericaonts in Maine. .1. Mar. 1996. The interface between fisheries research and habitat man- Freshwater Ras. 52: 1302-1319. aeclilent. N. Am J. Fish. Manaat. 1-7. Suttclitre, W. 1. Jr. 1973. Correlations between seasonal river dis- 'Malpass, W. 1992. The Role of'Snall Predatory Fmifish in the charge and local landings of Aierican Iobster (Homiarns ateri-Structure of Coastal Benthic ComnMatities in Maine. M.S. catts) and Atlantic halibut (Hp)pogtossus hipjpoglosstsl it tlte "lhlesis. I.)epartmnent ol Oceanog rapllh, I nisiv.of daine. GulfLf St. I..Lawrcil.e. . Fish Res Bolarc Caii. 30: 856-85Q. MeLeese, 1). W. and D. G Wilder, 1958. The activity and catchabilitv Thomas, J. 1980. Measure ofeflort. In Proceedinas of thle Canada - of the lobster (Homatnrus antercants) in relation to tamperature. U.S. Workshop ofAssessment Sciencea for N. W. Atlantic lobster 45 54 J. Fish. Res. Bd. Can 15- 13 -13 . (I!ontarus americanits)Stocks. V.C Anthony and J. F. Caddy Mercaldo-Allen, R. and C. A. Kuropat. 1994. Review o1'American (eds.). St. Andrews, NB.. Oct. 24-26, 1978. Can. Tech. Rept. of Lobster (Homartis americanus) HIabitat ReClui remenits and Fisheries and Aquat. Sci. 932. 1Pp85-92. Responses to Contaminant Exposure. NOAA Technical Thotnas, J. 1983. L.obstermen, b ilogists dispute future o 'catch. In: Memorandum NMFS-N'-105.) Kennebec Journal October 8, 1983. W. Cockerhatt Pg. 17. Miller. R. 1. 1994. Why are there so many American lobsters? The Underwood, A J. and P. G. Fairweather. 1989. Supply-side ecology Lobster Newsletter 7:.14-15. and benthic marinc assemblagesI Trends Ecol. svoll 4: 16-19. Pezzack, D. S. 1992. A review of lobster (Hoaictrusamericanlts) Wahle. R. A. 1992. Body-size dependent antipredator mechanisms of landing trends in thle Northwest Atlantic 1947-1986. J. North. thle American lobster. Oikos. 63: I-9. Allt. Fish. Sci. 14: 115 - 127. W\ahlc, R. A. and R. S. Steneck. 19 1. Recruittiment ihbitats and sintrs-Rich, W. I-I. 1930. Fishing grounds of the Gullf of Maine. Report of er grounds of the American lobster lHomanitis amieiicatits Millie the United States Commissioner of Fisheries 1929: 51-117. Edwards): A'dettiographic bottleneck? Mar. Ecol. Pro,. Ser. 69: Robinson, S., A. Macintyre and S. Bemier. 1995. The impact of scal- 131-243. lop drags on sea urchin grounds. In: 1994 Workshop on tite Waltlc, R. A. and R. S. Stetteck. 1992 Habitat restrictions in early Manaoenment and Biologv of the Green Sea Urchin benthic life: Experiments on habitat selection and in situ preda-(Sironzilocentrotmsdroebachiensis). Boothbay Harbor ME. Pp tion with the American lobster. J Exp. Miar. Biol. Eeol. 157: 91-102-121. 114. Scarrett, D. J. 1964. Abundance and distribution of lobster larvae Witman. J. 1). and K: P. Sebens. 1992. Regional variation in fish pre-(Homnarus americanus) in Northumberland Strait. J. Fish. Res. dation intensity: Ati historical perspective its the Gulf otf 'Maine. Board Can. 21: 661-680. lecolotia 90: 305-315. Scarrett, D. J. 1973. Abundance, survival, and vertical and diurnal Wynne-Edwards V C. 1962. Animal Dispersion in Relation to Social distribution of lobster larvae in Northumberland Strait, 1962- Behaviour. Edinburgh: Oliver & Boyd. 1963, and their relationship with commercial stocks. J Fish. Res. Board Can. 30: 1819-1824. Scheltema, R.S. 1974. Biological interactions determining larval set-tlement of marine invertebrates. "TJalassiaJugosl. 10: 263-296. Skud, B. E. and 1I. C. Perkins. 1969. Size Composition. Sex Ratio. and Size at Maturity of Offshore Northern Lobsters. U. S. Fish and Wildlife Service Special Scientific Report. 598: 1-10. Steneck, R. S. 1989. The ecological ontogeny of lobsters: In situ stud-ies with demographic implications. In: Proc. Lobster Life History Workshop. 1. Kornfield (ed.). Orono, Me. 1: 30-33. Steneck, R. S. 1995a. The GuIf of Maine: A case Study of over-exploitation. In: Fundamentals of Conservation Biology. M.L. Hunter, Jr. Blackwell Science. Pp 209-212.
;UNIMA-K% (\ ýN(L{.OUNS 149 Chapter IX The Role of Overfishing, Pollution, and Habitat Degradation on Marine Fish and Shellfish Populations of New England:
Summary and Conclusions ROBERT BUCRSBAUM WassachusentsAudubon Society 346 Grapevine Road [,PFenham,. MA 01984 USA Suddenly the ideaflashed through mv less obvious with the other groups of marine head that there was a unity in this organisms. Habitat degradation, particularly dams complicationt--that the relation of one that block access to spawning areas, have had a resource to another"was not the end of major impact on populations of anadromous fish, the story. Hfere were no longer a lot of but pollution and overfishing have also influenced difte'rent, independent, and often antago- a number of these species. The chapters by nistic questions, each on its own separate Brousseau and Steneck suggest that populations of little island, as we had been in the habit lobster and nearshore bivalves are largely deter-f/thinking. hI place of them, here was mined by natui-al variability in yearly recruitment one single question wiith many parts. of juveniles, at least in the areas they studied. This Seen in this new light, all these separate variability may mask any anthropogenic influences questionsfitted into and made up the one on these two groups, although the absence of reliable great centralproblem of the use of the population data, particularly with nearshore earthfor the good of man. bivalves, makes predictions difficult.
-Gijford Pinchot, 1947 DENIERSAL SPF.CIES (GRouNDIwSu1)
The purpose of this chapter is to synthesize the information provided in the earlier chapters on the impacts of overfishing, pollution, and habitat THE ROLE OF OVERFISHING AS A CONTROl. degradation on certain groups of fish and shellfish. ON GROUNDFISH populations in the Northeast and to consider what It would be hard to dispute the notion that the implication are for the future of the marine overfishing has been the major factor leading to the ecosystem. These three anthropogenic impacts current decline in groundfish in the Northeast. As have affected groundfish, anadromous fish, inshore Murawski describes in Chapter 2, populations of bivalves and lobster differently. The chapter by groundfish most important to the commercial fish-Murawski makes a convincing case for overfishing ing industry are presently at low population num-as the major factor responsible for the recent. bers compared to historic levels. The cause of these decline in New England groundfish species. The population declines has been extremely high rates relative importance of each of the three factors is
I () [,].{- fjsi l-" of fishing mortality on most groundfish stocks been low since foreign vessels left New England throughout the 1980s and up to the mid-1990s. waters after the passage of the Magnuson Fisheries During this period, not only did gear. become more Conservation and Management Act of 1976. The efficient at catching fish but also there was a rapid biomass of these two species has increased increase in the number of people entering the fishery, markedly in the past 30 years, and they) are both spurred by government programs. listed as underexploited and at high abundance by About one-third of groundfish. species managed NMFS (1998). Striped bass, whose allowable catch by the New England Fisheries Management by both commercial and recreational fishers was Council are currently classified as overfished based drastically reduced in the 1980s as a management on rate of harvest and long term overfishing defini- response to low populations, are now considered tions (NMFS, 2001). Groundfish stocks. have been recovered and are touted as a fisheries management characterized by both growth and recruitment over- success story. The recovery of these species has fishing (i.e. declines in yield attributable to har- been a direct responseto lower exploitation rates. vesting smaller and smaller fish and declines in recruitment ofjuveniles due to low spawning stocks). Catch per unit effort, another indicator of I IAVE TI IERE 1EEN POPULA'rION Er- :IF(CS ON the status of fish stocks in relation to fishing effort, GROUNDFISII FROM Toxic POIJAMTANTS? steadily' has declined for.groundfish despite the The population effects of toxic pol.lution are improvements in fishing technolooy. less clear than overfishing. With the exception of The influence of fishing on New England com- oil spills, pollution rarely causes direct mortality, rnercial fish is not just evident from the past two but rather makes fish more vulnerable to other decades. Murawski points out that fish populations, sources of mortality. such as cod, haddock, and Atlantic herring, have The Gulf of Maine contains a number of the historically reflected the intensity of fishing effort. most contaminated sites in United States coastal This has been particularly pronounced since the watersfor polycyclic aromatic hydrocarbons increased industrialization of fisheries in the early, (PAHs), chlorinated hydrocarbons (e.g. chlorinated part of the 20th Century. pesticides and PCBs), and several trace metals. The There have been some recent improvements in effects of pollutants at the cellular, physiological, 'some fish stocks, such as Georges Bank yellowtail and whole organism level in fish from some of and haddock, in response to restrictions on fishing these contaminated harbors can be quite striking.. effort and area closures, implemented with increas- Thurberg and Gould (Chapter 4) cite numerous ing severity since the early 1990s. With reduced examples of physiological alterations on gadids fishing mortality, older, larger fish are surviving and flounders caused by heavy metals and organic longer, leading to anticipated improved spawning contaminants. For fish exposed to pollutants, the success and less dependence .of the fishery on new survivorship of eggs and juveniles is lower than recruits. Overall biomass numbers, however, are that of adults, although physiological impacts are still too low for groundfish to support increases in observed at all life stages. There is very little infor-fishing effort at this time. Exploitation rates of mation on the population effects of these pollutants Gulf of Maine cod and whiting are still above even where effects on reproductive physiology' rebuilding target. have been noted. One piece of evidence that relates the decline As difficult as it is to relate toxic pollution to in groundfish to overfishing is the observation that populations of fish in the most contaminated sites the recent decline in groundfish has been limited to in the Northeast, it is even more challenging to those commercial species that have been heavily understand what the subtle effects, if any, are of exploited by commercial fishers. Species that are long term exposure to low levels of contaminants. not being targeted or that are subject to strict man- This latter situation is more relevant to the overall agement measures have not been depleted or have region since the concentrations of contaminants in recovered. As an example, fishing effort on two all but a few urban harbors within Massachusetts pelagic species, Atlantic herring and mackerel, has Bays and the Gulf of Maine are below the level
SIJNIMMKY AND ( ONCLA;MONS 15 1' where acute effects are possible. Even pelagic EFFECTS OF HABITAT LOSS AND D[IGRADATION species that may travel far offshore, such as tuna ON GROtJNDFISF-I and swordfish, are exposed to some level of land-based pollutants, as evident fiom the recent Destruction and degradation of large sections Environmental Protection Agency/Food and Drug of coastal and nearshore habitats have occurred Administration fish advisory oil nmercury3 contami- throtughout the New England coast since the arrival nation in seafood of European colonists. Even if habitat effects have (http://wwwv.epa.gov/hercurv/advisories htm ) not played a major role in the recent New England (USEPA, 2004). groundfish crisis, anthropogenic impacts on habitats Studies of impacts of toxicants in New could slow or inhibit the recovery of groundfish England have been carried out on winter flounder, when restrictive fishing measures are implemented. an inhabitant of some Pollhted harbors. The goal of Deegan and Buchsbaum (Chapter 5) reviewed much of this research has been to examine site- impacts to finfish caused by losses of coastal wet-specific effects on the fish or to explore public lands, hydrological alterations, dams., eutrophica-health risks. Other than direct toxicity from oil tion, damage from fishing gear. ditching for spills, the effects of even high levels of contaminants mosqtlito control, power plants, and exotic species. on the populations of flounder and other marine Like pollution, most habitat impacts on fish are organisms have proven very difficult to isolate indirect, in that they do not cause direct mortality from other variables that influence reproductive themselves, but make the fish more susceptible to behavior and success in the environment. As an other sources of mortality, such as increased preda-example, polluted harbors are also organically tion on juveniles due to loss of hiding places. Such enriched, thereby providing a greater amount of indirect impacts are therefore hard to quantify. food to winter flounder, either directly or indirectly There have been a number of difficulties in throtigh augmented prey populations. This could relating habitat changes to changes in fish poptIla-lead to Faster growth rates of flounder even in the tions. First, we do not know under what conditions presence of toxicants. fish populations are limited by the availability of Based on physiological information, pollutants suitable habitats, even for those species for which have the potential to impair reprodtIction and there- habitat preferences are established. As an example, fore reduce recruitment. The extent to which this we do not know whether the loss of 30 to 50 per-actually happens in the field is not known. A num- cent of the precolonial salt marsh acreage has ber of studies cited by Thurberg and Gould relate reduced populations of estuarine-dependent fish, high pollutant concentrations to lowered reproduc- since they may be more affected by other factors. tive success. These include winter flounder On the other hand, recent studies of cod and hake exposed to PCBs in Long Island Sound and suggest that there may be some critical habitats at Atlantic cod exposed to oil spills in the North Sea. particular life stages that are limiting (Auster and Thurberg and Gould state that such effects in the Langton, 1999; Lindholm et al., 1999). This was field would vary "erratically with time and site." If the rationale for the New England Fisheries a pollution "signal" is occurring, one would predict Management Council's 1998 designation of a cobý that the decline in fish populations would be more ble habitat in Georges Bank as a "Habitat Area of pronounced in those species or populations that Particular Concern" for juvenile cod. A second dif-occur nearshore, at the higher end of any pollution ficulty is that habitat types that are important to gradient emanating from land-based sources. fish are not necessarily obvious to uIs. It may be Although historically hearshore species were likely relatively easy to characterize the fish community overharvested first before fishing effort moved fur- and boundaries of a cobble area or an eelgrass bed, ther offshore, the present decline in fisheries has but the location of an offshore salinity discontinuity occurred both nearshore and offshore. We conclude that may be important to fish larvae changes that the major cause of low recruitment has been depending on the relative flow of rivers and tidal low initial spawning biomass related to overfishing. currents. A third problem is that it is very difficult to characterize all the potential habitat interactions that may affect a species. Habitat impacts on
I >* n cin ix predators. prey, and competitors may all influence suitable habitat provided by epibenthic animals that tile population. Fourth and closely related to (3) is are prone to removal by bottom dragging. Boreman a general lack of knowledge of fish-habitat rela- et al. (1993) concluded that increasing juvenile suir-tionships. Up until recently, the major focus of vival of inshore winter flounder in the northeast fisheries managers and fisheries researchers friom United States through habitat restoration in combi-federal agencies has been on the population biology nation with reduced fishing pressure on adults of individual species. not on ecological relationships. results in a greater overall benefit to the population Before 1990. most of the well-documented than reducing fishing effort alone. Based on a sim-studies of habitat losses and degradation were of ulation model, Schaafet al. (1 993) predict that coastal wetlands and shallow nearshore habitats destroying only I% of the estuarine habitat ofjuve-because that was where the most obvious physical nile menhaden could result in a 58% decline in changes had occurred. In addition, the logistics for population levels after 10 years. carrying out studies, primarily by university researchers who do not have ready access to off-TiE RoLE OF NATEURA\L ENVIRONMENTAL shore fisheries research vessels, were easiest. In those parts of the United States and in Australia F1.C-I.Irux-IrONS ON GROUNDFISH where fisheries are heavily dependent on estuarine The suggestion that variations in natural envi-and nearshore species, declines in commercial fish- ronmental factors has had a severe impact on New eries have been directly linked to loss of coastal England groundfish species was the basis for the wetlands. Research by Deegan and her coworkers application by Commonwealth of Mvlassachusetts showed that eutrophication of coastal embayments for federal disaster relief for its commercial fishing results in ameasurable change in the fish commu- industry in 1995. Recruitment does vary from year nities within eelgrass beds (Deegan and to year based on climatic and other ecological con-Buchsbaum, Chapter 5). ditions, however Murawski (Chapter 2) shows that Recent research on the impacts of fishing gear poor recruitment is not the cause of recent ground-on benthic communities in fishing grounds further fish declines. His simulation model suggests that offshore has raised serious concerns about habitat poor recruitment may have had the effect of exac-changes that may at a minimum be affecting erbating declines caused by overfishing, but that recruitment of certain species and under a worse 2 overfishing was clearly the major driving force. case scenario, altering the integrity of the entire For a sustainably-m anaged fishery, exploitation marine ecosystem (see Dorsev and Pederson. 1998: rates should account for the potential for poor Auster and Langton. 1999, Watling and Norse recruitment in any given year. 1999; NRC 2002 for reviews). Changes in the Recruitment of yellowtail flounder has been physical structure of benthic communities as a related to seawater temperatures, based on a result of the activities of draggers have been docu- decline in recruitment and landings during a warm-mented in both nearshore and offshore waters of ing period in the 1940s and 50s and a subsequent New England. Dragging disturbs physical and bio- increase when temperatures cooled. The last major genic habitat features that are attractive to various period of consistent change in seawater tempera-species of juvenile fish. Lindholm et al. (1999) and ture, however, was a warming in the early 1960s. Olney and Boehlert (1988) suggest that loss of Since that time seawater temperature has shown habitat structure, such as that which occurs during yearly variations but no consistent trend upward or bottom dragging or dredging of seagrass beds, downward that would likely affect recruitment of increases predation on juvenile fish. yellowtail flounder or any other species in a con-Three modeling efforts cited by Deegan and sistent way (Murawski, 1993). Changes in the Buchsbaum suggest that habitat degradation does amount of runoff from the Saint Lawrence River have an impact on some fisheries. In the Northwest have been discounted as a cause of decline in cod Shelf region of Australia, dynamic models indicated (Frank et al., 1994). Even if there were clear-cut that the abundance of some commercially impor- environmental trends that might impact the recruit-tant fish species were limited by the amount of ment or migratory patterns of groundfish, one
SUNIM.-RN AND) (uCII>.fl,ýiONS 15 3 would expect that the changes would be observed that are superimposed on human impacts, Myers et in a variety of species and not just coincidentally in al. (1995) suggest that fish stocks in general can those species that happen to be heavily fished. recover if the overfishing problem is addressed, Fisheries managers in their projections of New however there is no .indication that the population England groundfish populations have generally of Atlantic cod off Newfoundland has returned relied on the assumption of a constant level of despite many years of a fishing moratorium. The instantaneous natural mortality (M), typically set at anticipated recovery of New England groundfish M=0.2. Habitat quality has never been factored due to reduced fishing effort and closures of large into these models, perhaps because the high level areas provide an opportunity to better understand of fishing mortality in recent years has made the effects of ecological factors that mnay regulate variations in natural mortality a minor factor in giroundfish populations. predicting Populations. With the decline in fishing mortality rates in the late 1990s and early 2000s under strict regulations, changes in natural mortali- ANADROMOUS Fisll ty and mortality associated with habitat degrada- Moring (Chapter 3) makes it clear that over-tion will likely become a more significant factor in fishing, pollution, and habitat degradation have all population trends. reduced populations of anadromous fish from their former levels of abundance in precolonial times. Anadriomous species were declining in southern MUIrF'PI.E STRESSORS ANI) RECOVERY New England as early as 1870., primarily due to The biological community of the Gulf of dams and pollution, two products of the Industrial Maine ecosystem has changed in a number of ways Revolution. Today, habitat degradation and poilu= because of overfishing of groundfish (Witman and tion still affect population trends. Sebens, 1992). Some species may experience rapid Blockage of migration routes by dams and population growth once the strong influence of a other structures across rivers and streams has elim-limiting factor (i.e., overfishing in this case) is inated access to large areas of potential spawning removed. This is particularly the case if, as sug- habitat. By 1950, damming of rivers had left less gested by Sinclair (1997), overfishing has not than 2% of the original habitat for Atlantic salmon changed the basic structure of the biological coin- in New England accessible to the fish. A recent munity. On the other hand, the reduction of many survey of 215 coastal streams in southeastern populations to their present low levels may have Massachusetts documented 380 obstructions to fish changed the community dynamics such that certain passage, the majority of which are "manmade" species may no longer be able to achieve their for- dams (Rebeck et al., 2004). Many rivers now have mer abundance, at least in the short term. fishways around dams, but these still are not as The populations of different marine species in efficient in allowing fish to successfully migrate New England are likely never in a state of equilib- both up and downstream as are free flowing rivers. rium in relation to each other. Natural changes in There have been efforts to remove dams that are no fish communities occur in response to long term longer serving a useful function, such as the and yearly climatic trends or as different species Edwards Dam on the Kennebec River in Augusta, influence each other through competition and pre- Maine. dation. Species that are prey for cod, for example, Although dams have been the most serious fac-may become more abundant because of overfishing tor in declining anadromous fish runs, other habifat of groundfish and then exert a controlling influence factors have also been of concern. These include on future cod numbers by feeding on juveniles. increased water temperatures and siltation of One cannot assume that there is some predeter- spawning areas due to the removal of streamside mined level that a population trajectory will reach vegetation, siltation caused by sanding of roads in once a major source of mortality is removed, par- winter, and algal growth on spawning sites due to ticularly for an ecosystem that is subject to natural eutrophication. environmental variations over different time scales Striped bass provide an example of an anadro-mous fish that in the past suffered from the effects
154 flqai of both overfishing and pollution. Overfishing in degradation to inshore bivalve populations is. the 1970s and early 1980s led to severe population clouded by the limited data available. Brousseau declines. The fish have now recovered well after a (Chapter 6) indicates that scientists cannot accu-period of severe restrictions on both commercial rately assess the status of the three major inshore and recreational fishing, so overfishing was clearly bivalve species harvested in Massachusetts (hard-a ma)or factor in the decline. Moring also cites pol- shell clams, soft-shell clams and bay scallops) nor lution reduction activities in the Chesapeake Bay can they say whether these species are being over-region, the major spawning area along the east fished or not. There is a lack of reliable population coast, as contributing to the recovery of the stock. data and only limited quantitative understanding Recent problems with other species of anadro- about the natural and biological factors that influ-mous fish have been more difficult to characterize ence recruitment of juveniles. Landings data for than those of striped bass. American shad and blue- bivalves, although notoriously unreliable, suggest back herring runs in Massachusetts increased until that there has been an overall decline in landings of 1993 but have been declining since then for rea- hard-shell clams over the last twenty years. Total sons that are not understood. Despite intensive bay scallop landings have shown a great deal of efforts at restoration, Atlantic salmon runs to larger year-to-year variability with no overall trends New England rivers are still very tenuous, and the except for some losses in specific areas. There has Gulf of Maine population segment is now federally been little overall change in landings of soft-shell listed as endangered. Moring suggests that some as clams. yet undetermined factor occurring when these fish Landings data for bivalves are suspect because are at sea may be the primary cause for the recent they are collected by individual towns with no con-trends in these species. Declines in rainbow smelt sistent methodology or quality control. In addition, runs throughout much of Massachusetts have been the abundance of the shellfish resource is only one linked to site-specific habitat degradation (e.g. sil- of a number of factors that determine how much is tation, nutrient enrichment) in individual spawning landed. If the local economy is depressed or if streams. A modeling study cited by Moring pre- shellfish prices are high, more people may turn to dicted that smelt can also be severely impacted by shellfishing to earn extra income, leading to an recreational angling. increase in landings. Declining water quality, Since the decline in anadromous fish has been which reduces the acreage of shellfish beds open to the result of a variety of factors, some of which are harvesting, may depress landings without influenc-still mysterious, their recovery, will require a multi- ing the size of the population. Landings per unit faceted approach. Groundfish recovery is compli- effort, therefore, provides a better barometer of cated because of politics, less so due to their biology. how the stocks are doing over time. The assumption is that groundfish will recover if There are other difficulties in trying to under-overfishing is stopped. In contrast, anadromous stand the status of inshore shellfish resources and fish present both political and biological challenges. how to manage them wisely. Traditional fisheries Recovery programs must include controlling over- models based on finfish population dynamics do fishing and mitigating land-based habitat alterations not work well for these bivalves because of the dif-and pollution, but these still do not guarantee suc- ficultyvin defining what a stock is and thereby cess due to ecological interactions that are not well establishing a stock-recruitment relationship. There understood but likely beyond human control. may be little relationship between the size of a local shellfish population and subsequent recruit-ment in the locality since the planktonic larvae BIVALVE SHELLFISH may come from a larger functional population that encompasses a much larger region. Thus fishing on a small, local subpopulation may have little influ-DIFFICULTY OF STOCK ASSESSMENTS OF BIVALVES ence on the future population size in that particular area. If this is true then shellfish resources are An evaluation of the relative importance of probably better managed at a regional level than overfishing, pollution, and habitat loss and town by town.
S..'DI-MMK\ AND ( (-N( [AISIONS 1 ý5 It has been difficult to incorporate into models degeneration of oocytes compared to mussels the tremendous yearly variation in recruitment that transplanted into less contaminated areas. characterizes these bivalves. Variable hydrodynamic The interactions between population growth and climatic conditions likely' have a major effect and contaminants are complicated by other environ-on the. success of settling. Benthic predators may mental influences as well as human harvesting strongly affect the early' survival ofjuveniles. patterns. In a study of the impact of PAH concentra-Sensitivity' analysis described by Brousseau indi- tions on populations of Alva arenariaalong a pol-cates that population growth rates of a number of lutant gradient in Massachusetts Bay, McDowell commercially important shellfish are more sensi- and Shea (1997) found that clams from the most tive to changes in larval survival and recruitment contaminated sites differed in the timing of gamete than they are to adult survivorship or fecundity. development and had high levels of gonadal infla-mation and hematopoictic neoplasia, however pop-ulation growth rates as estimated from a determin-ARE SOFT-SHELL CLAMS OVERFISI[ED IN istic model were not directly related to contaminant MlASSAC1 IUStTTS'? concentrations. Predator and hydrological varia-Based on four Massachusetts towns that harvest tions had a strong influence on recruitment patterns soft-shell clams; A'va arenaria,almost exclusively, regardless of contaminant levels. Brousseau showed that landings per unit effort Recruitment of larvae into a contaminated area fluctuated intensely from 1970-1995 without any from a clean outside area may provide a periodic consistent trends in either direction. There was also source of new individuals. As described, for much scatter but no trends when landings per unit groundfish, individuals settling in a contaminated area may grow more rapidly than those in a clean effort were plotted as a function of effort. Thus these particular data, admittedly limited, do not area due to organic enrichment, but they. may ulti-support the notion that soft-shell clams are being matly end up with impaired ability to reproduce. overfished. at least to the point where recruitment Clam flats are closed in most urbanized coastal is being affected. communities not because of toxicants but because of high levels of fecal coliform bacteria. Populations of soft shell clams may be quite abundant in these EFFECTS OF Po'Ir'rUNTS ON BIvk\ivi.s areas despite the fecal contamination. Fecal col-iform contamination is a human health rather than In Chapter 7 McDowell describes a range of an ecological concern, unless, of course, it co-physiological effects exhibited by bivalve mollusks occurs with heavy metals or toxic organic com-living or transplanted into areas heavily contami- pounds. Such closed clam flats could serve as a nated with organic contaminants and heavy metals. source of new recruits to uncontaminated areas. Moore et al. (1994), for example, found that the prevalence of a wide range of pathologies of Mya arenariaand Ilvtilus edilis (blue mussel) was EFFECTS OF HABITAT. LOSSES AND DEGRADATION strongly correlated with high levels of PCB con-tamination. Although direct population effects have One of the best examples of the impact of habi-not been documented in the New England region, a tat loss on a commercially important marine animal number of the physiological responses of some is the relationship between eelgrass and bay' scallops described by Deegan and Buchsbaum (Chapter 5). bivalves to lipophilic compounds, such as PAlis have implications for reproductive success. These The wasting disease epidemic of the 1930s, which include impairment of feeding, slower overall wiped out most of the eelgrass along the east coast growth rates (which reduce reproductive output), of the United States, resulted in an almost immedi-developmental abnormalities, and degeneration of ate crash in bay scallop landings (documented for reproductive tissues. McDowell's research indicated Chesapeake Bay), which lasted until the eelgrass that Mi'tihts edulis transplanted into highly PCB began to recover. Eelgrass fluctuations still occur and PAH-contaminated New Bedford Harbor naturally and due to eutrophication, and these still impact local populations of bay scallops. showed reduced reproductive effort and
1 56 n :l*n'i-There is little information on the impact of perspective. Although the lobster fishery is not cur-habitat losses on other species of bivalves. The rently in as bad a condition as groundfish, lobsters historical filling of tidal flats in places like are still classified as overexploited by NMt-FS due Boston's Back Bay undoubtedly caused losses of to high fishing mortality (NMFS, 2001 ). NMFS suitable habitat for soft-shell clams. Such bases this on an extremely high rate of fishing widespread filling is now limited by wetlands mortality and the heavy dependency of tile fishery protection regulations, however small scale losses on new recruits. They define the recruitment over-from legal dredging. dock and pier construction. fishing level for lobsters as the fishing mortality and illegal activities still are likely to occur in the rate that results in a reduction of the production of region. eggs per recruit to 10% of that of an unfished pop-ulation. Steneck presents data from Maine showing that THE ROLE O1 MULTIPLE FACTORS the total tonnage of lobsters landed increased from Dramatictfliuctuations in adult bivalve popula- the mid 1980s throtilg the 1990s with no evidence tions are probably natural in the northeast, and that the brood stock declined. Despite increased these may mask any affect of overfishing, pollu- fishing effort oni this species and the decline in the tion, or recent habitat changes. Both Brousseau and average size of individuals landed, the annual land-McDowell suggest that populations of bivalves are ings petr effort ratio increased in recent years. Thus more sensitive to changes in larval survival and he disputes whether recruitment overfishing is recruitment than to variations in adult survival, occurring now. thus anything that reduces the growth and .survivor- In his analysis of data from Maine, Steneck ship of bivalve eggs and larvae could have serious relates periods of lower lobster abundance to lower population consequences. The timing of a habitat water temperatures that reduces the success of post alteration, whether human induced (e.g., siltation., larval settlement. Given tile extremely high rate of dragging. remobilization of toxicants) or natural fishing for lobsters, it is surprising that such an (e.g., drought, storms, annual temperature fluctua- environmental signal is detectable. In an analysis tions, etc.), is probably critical during the period of a larger data set, Drinkwater et al. (1996) did not when larvae are in the water and probably lead to find the same specific relationship between higher the yearly fluctuations in recruitment. seawater temperatures and the increased catch of It is questionable whether hutnan-induced lobsters from Newfoundland to the Mid-Atlantic changes in habitat have currently occurred on a Bight during the 1980s and early 1990s. wide enough spatial scale to affect recent recruit- Nonetheless, these authors still propose that a real ment in any way, except locally. What is needed to increase in lobster abundance during this period was better manage inshore bivalves is to understand related to some as yet undetected environmental factors that affect larval recruitment. to establish control. the appropriate geographical boundaries of stocks Steneck also questions the accuracy of popula-and to collect more reliable population data. This tion estimates and the stock recruitment relation-information will enable us to understand better the ship used to conclude that lobsters are overfished. impact of fishing, pollution, and physical changes Hle argues that it is very difficult to get accurate in habitats oil these inshore bivalves. statistics on the stock-recruitment relationship, nat-ural mortality, and the size of the populations throughout the entire range. In addition, the models LOBSTERS that NMFS uses in their assessments do not factor in ecosystem changes. The overfishing of lobster predators, such as groundfish, and an increase in ARE LOBsTrERS OVERFISHED? kelp habitats attributed to the development of a fishery for sea urchins (a major kelp herbivore) Steneck (Chapter 8) describes a debate about have favored lobsters in recent years. the status of American lobsters, the most valuable Steneck suggests threats other than fishing are fishery in New England from an economic equally or perhaps more important to this crustacean.
SUMM:MI-R' AND {\SLI[NS
'M 157 These threats include degradation of the rather lim- LOBSTERS VS. GROUNDFISH ited cobble habitat required by newly settled juve-niles and the negative effects of pollution. Fie also It is interesting to speculate whether the argu-raises the issue of protecting a major part of the ment Steneck presents about the limited ability of broodstock (i.e. large females that may inhabit lobster statistics to accurately allowa definition of deepwater refugia that are not fished with traps). overfishing can also be applied to groundfish. Do These may be the major source of eggs and have we accurately know the stock-recruitment relation-been. up to recently, relatively free from fishing ship and do we have an accurate measurement of pressure. stock sizes and accurate estimates of natural and fishing mortality? The data presented by Murawski (Chapter 2) indicate that for many groundfish AN ALTERNAfE PERSPECTIVE species, we have a good idea of the size of the spawning stock biomass necessary to produce an In contrast to Steneck, other scientists, particu- adequate number of potential new recruits to the larly those from the National Marine Fisheries fishery. The NMFS trawl surveys undoubtedly por-Service, have been concerned that a fishery so con- tray the populations and the age structures of the centrated on new recruits could be devastated if various groundfish species with a much greater there were a few poor recruitment years in a row. degree of confidence than is now possible for lob-From their perspective, it is necessary to set the sters. As a consistent, repeated survey, the trawl overfishing definition at a precautionary level as a surveys do provide an index of lobster abundance, buffer against changes in environmental conditions however the catch per tow is very low on lobsters that, in concert with fishing pressure, could lead to leading to much higher statistical variability than a population crash (NI. F'ogarty, pers. comnm.). The one would expect for groundfish. The problem is 10% egg production level should be seen in that that trawls cannot sample in those habitats where context rather than a threshold below which lobster the nreatest densities of lobsters are likely to be populations will definitely collapse. found. i.e., nearshore rocky areas where fixed gear The trend of the fishery in recent years toward is in place and catch efficiencies are low.
a smaller average size of lobsters and increasing One important way in which lobsters differ dependency on new recruits is evidence for growth from groundfish is in the long time lag between overfishing and is similar to what was observed in egg production and growth to reproductive age, groundfish before the collapse of a number of about six to seven years in lobsters, but much less those stocks. There may be long-term conse- in most groundfish species (i.e., 2-3 years in cod quences to the populations of a fishery-induced and haddock, 3-4 in yellowtail). Thus, it takes a truncation of age structure, at least in nearshore number of years before anything that influences populations where most individuals only have the juvenile survival of lobsters is reflected in the chance to spawn once before they are caught. The catch. large lobsters that currently contribute most to the broodstock would not be limited to deeper offshore habitats if it were not for overfishing nearshore. POLLUTION AND HABITAT IMPACTS ON LOBSTERS There are also economic consequences of the current fishing pressure on lobster. The overall Pollution is not likely a major factor control-yield of lobsters is not high as it could be if lob- ling lobster populations over the whole region, sters had a chance to grow to larger average sizes however it can be locally important and of concern under lower fishing rates. NMFS believes that to human consumers. Oil spills can have devastat-higher long term yields and a healthier lobster pop- ing, localized effects, as illustrated by the 1996 ulation would result from a reduction in the North Cape oil spill in Rhode Island (NOAA et al., amount of fishing effort on lobsters. 1999). For chronic pollutants, the cobble habitats preferred by juveniles tend to be areas that are rea-sonably well flushed and therefore relatively clean. Adults that occur in soft-bottomed urban harbors are more exposed to toxic organic compounds and
f~I heavy metals. There may be some potential for a the populations of these species. localized effect on reproduction, but whether that causes population impacts, even within urban liar-SEA SCAL,\CPS bors, is unknown. The habitat issue of most concern to Steneck Fishing pressure on sea scallops, Placopeclii, (Chapter 5) is the potential for damnage to juvenile mnagellanicus, is intense. Some impacts of natural cobble habitat due to sedimentation and mobile environmental fluctuations on the success of year fishing gear. If the availability of this habitat is classes have also been identified. Variations in the really limiting lobster populations. then its protec- success of recruitment of different year classes tion should be a major management goal. have been related to differences in the "tightness" of the autumnal gyre in Georges Bank (Packer et OTHER GROUPS OF FisiI AND SIIELLFISII al., 1998). Sea scallops also occur nearshore, par-ticularly in the northern part of the Gulf of Maine, The reports in this volume focused on New but there has been no research to indicate whether England groundfish, anadromous fish, lobsters, and coastal habitat degradation has had any influence nearshore bivalve shellfish. Our intent was not to on nearshore populations. The rapid increase in the provide a survey of all ecologically and commer- population densities and sizes of scallops in areas cially important species in New England, but to of the Gulf of Maine and Georges Bank closed to explore the question of the relative importance of all gear types in the late 1990s due to the ground-overfishiing, pollution, and habitat destruction to fish crisis shows that sea scallop populations have representative groups for which there are some the potential to respond very rapidly when freed data on all three factors. For the sake of complete- from fishintg pressure in a protected area. ness, here is a brief look at other groups and the issues they raise. COMPETITION ANt) TROiHIic I Nt.IE ACIIONS HIGHLY MIGRArORY PELAGiC Fisn Herring and mackerel, along with other smaller pelagic organisms. such as krill, ate considered The recent steep declines in populations of a important components of the marine food chain number of pelagic "highly migratory" fish-- since they serve as forage for larger fish, marine Western Atlantic bluefin, bigeve and albacore tuna, mammals, and marine birds. Fishing pressure on North Atlantic swordfish, and large coastal herring has been cited as the cause of the alteration sharks-are due to intense overfishing. These are of the biological community that resulted in an currently classified by the National Marine increase in sand lance in the 1970s (Sherman et al., Fisheries Service as overfished (NMFS1 2001). 1981). The mechanism was presumably competi-Their pelagic, migratory life histories make it diffi- tion between the two species for food. In recent cult to connect their population fluctuations with years, both herring and sand lance have co-habitat or pollution-related factors. The relatively occurred in abundance in the Gulf of Maine, leading long life span of these species tends to mask Sinclair (1997) to conclude that sand lance abun-impacts, if any, of natural environmental variations dance is independent of that of Atlantic herring. on populations. The prime focus of managers and Both vary according to environmental factors scientists has been on managing fishing effort and rather than from food chain relationships. understanding populations dynamics and demogra- The potential for increasing the commercial phy. (NMFS, 1997, 1998) without any emphasis on catch of herring and krill has raised the issue of habitat-related factors. Less is known about the potential trophic impacts of the large-scale removal environmental factors that influence larval recruit- of these species if they are targeted for increased ment in these pelagic fish than in groundfish or fishing (Partington, 1996). Along with clarifying anadromous species. At the moment, no hypotheses the actual status of herring populations, trophic have been proposed that suggest that anthropogenic modeling will be needed. factors other than fishing mortality is influencing A related topic is how predation by marine
SIIMMAKY AND CON\.LUS[ONS I 5C mammals and birds affects the recovery of fish. based on physiological studies. One would Moring (Chapter 3) attributed the loss of seven expect population impacts to be most obvious percent of downstream migrating Atlantic salmon in heavily polluted urban harbors. smiolts in the Penobscot River to predation by cor- 3. Studies from otherregions that have simultane-morants. One modeling effort attributes much of an ously examined habitat quality and fishing increase in natural mortality of juvenile cod in the mortality have shown that habitat quality can Gulf of Saint Lawrence to predation by the rapidly be very influential on some fish populations. increasing population of gray seals (Sinclair, 1997).
- 4. At low population levels, habitat effects could Although the actual percent mortality due to the have a strong impact on recovery of ground-seals is uncertain, predation by the seals now likely fish, even if such impacts were not the initial exceeds that by fishing. Sinclair pointed out that cause of declines. The patterns of recovery will the potential for predation by seals is much less in also be affected by any changes in the biological the Gulf of Maine due to the much lower abun- community that have occurred as a result of dance and diversity of seals compared to the Gulf overfishing.
of Saint Lawrence. In sum, although a number of 5. Habitat loss and degradation (including pollu-studies have addressed this subject, there is no tion) have been strong influences on popula-solid evidence that mammalian and avian predators tions of anadromous fish in New England. in the Gulf of Maine and Georges Bank have Overfishing has also been a significant factor caused the decline in any fish species or will hinder for some species. Some unknown factor(s) recovery. when these fish are out at sea is apparently contributing to recent population declines and lack of recovery of some species. CONCLUjSIONS: OVERIISHING VS. POLLUTION 6. Population fluctuations in bivalve shellfish are vs. HAlBirIF DEGRADATION more strongly related to interannual variation in recruitment than to fishing pressure. We can-not presently factor out the effects of pollution, M4an had always assumed that he was habitat degradation, and natural environmental
,nore intelligent than dolphins because he variation on recruitment processes.
had achieved so much... the wheel, New 7. Despite heavy fishing pressure, lobster popula-Ibrk, wars, and so on, ivhilst all the dol- tions have remained high. Natural environmen-phins had ever done was muck about in tal factors that affect settling by larval lobsters the water having a good time. But con- may have a stronger impact on lobster popula-versely the dolphins believed themselves tions than fishing mortality. There is disagree-to be more intelligent than man for pre- ment among lobster biologists about whether cisely the samne reasons. lobsters should be considered overfished.
-Douglas Adarns, 1984 8. Ecosystem-level research is needed to under-stand the impacts of habitats and other ecologi-cal factors on commercially important fish and I. Overfishing is by far the greatest cause of the shellfish. Some research topics of special decline in groundfish species in New England. importance to the questions raised in this book:.
The "signals" from pollution and other forms . habitat relationships of groundfish, particu-of habitat degradation have been impossible to larly how habitat alterations by fishing detect, given the "noise" from overfishing. gear impact fish populations, Managing fishing effort is the single most
- population impacts of pollutants important key to the recovery of these ground- . causes of presumed mortality of anadro-fish stocks. mous fish at sea.
- 2. There have been no documented impacts of . stock-recruitment relationships in bivalves pollution on populations of fish and shellfish in and lobsters.
New England, although reproductive impair-ment related to toxicants is well established,
ONE FINAl. TilouclT - HAVE Wi: AcilIvEEI) -ril fishing impacts are more widespread. The spatial Gox.,s SEr OUT FOR rlfis BooO? scale of fish populations is likely much larger than the scale of toxic impacts. Habitat losses have been widespread, but in scattered localities, such that adequate refugia from those impacts may (or may Conservationistsar-e nolot'ious fo)r their not) exist. There are also questions about the ade-dissensions. Superficially these seem to quacy of population data for certain groups of add up to mere coniusion. but a more organisms, particularly nearshore bivalves and lob-careful scrutiny reveals a single plane of sters. If we do not have a firm grasp of population cleavaU.e Como177n017 to man17y spJecialized numbers, demography, the spatial scale of a stock, fields. I7 each field one group (A) and stock-recruitment relationships, then it will be regards the land as soil, and its function very difficult to identify the major constraint on as commodity-production; another group that population quantitatively. Complicating the (B) regards the land as a biota, and its matter is that the natural and human-induced con-
/mac'ion as sometlhing broader: itow straints themselves also varvover spatial and tem-miuch broader is achnittedlv in a slate of poral scales. Nevertheless, we have succeeded in doubt and confitsion.
attempting meaningful comparisons in light of dif-
-Adio Leopold. 1949 ferential spatial and temporal scales.
To the extent that models were discussed that attempted to evaluate the population impacts of As stated repeatedly throughout this work. our factors other than fishing mortality, our effort was major purpose has been to evaluate the relative also successful. Murawski (Chapter 2) showed the importance of overfishing, pollution, and habitat dominance of overfishing as a factor because his. loss and degradation on finfish and shellfish popu-population models require no further inputs other lations, focusing on the Gulf of'Maine region. The than fishing mortality to explain the current low degree to which we have succeeded must be populations of many groundfish species in New judged, ultimately, by our readers. England. Deegan and Buchsbaum (Chapter 5) While acknowledged early in our discussion described models indicating that habitat considera-(Chapter 1), it is clear that finding a common "cur-tions as well as overfishing have the potential to rency" by which scientists who consider these influence at least some populations of fish. The issues can quantify the extent of the impacts they need for more holistic modeling.to resolve the rela-study relative to the other two constraints is diffi-tive importance of habitat and fishing pressure is cult. Given the specialized nature of scientists, it is obvious, particularly now that there has been such a not surprising that those who study the physiologi-large management interest in protecting fish habitats. cal impacts of toxicants do not generally feel com-We believe that the primary value of this work fortable making statements about population is that it put the discussion of multiple stressors on impacts and vice versa. The data on the population fish and shellfish populations in one volume. It impacts of toxicants and other types of habitat forced the authors and editors to try to relate these degradation are quite limited at this time, hence the factors. Hopefully, future efforts based on more reluctance on the part of those working on those comprehensive data collection and increasingly subjects to speculate. Nevertheless, we have suc-sophisticated holistic models will provide more ceeded in advancing the common "currency" complete answers and will aid in the achievement concept. of sustainable fisheries and a healthy marine Although differences in scientific discipline ecosystem. have much to do with it, other factors make it hard to compare fishing impacts, pollution, and habitat degradation. The spatial scale of these major cate- LITERATURE CITED gories of impacts differ. Toxic effects, or at least Adams. D. 1984. So Lone and Thanks for all the Fish. New York: our ability to detect them, are restricted for the Harmony Books. most part to certain urban "hot spots" whereas Auster, P. J. and R.W. Langton. 1999. The effects of fishing on fish habitat. In: L. Benaka (ed.). Fish Habitat: Essential Fish Habitat
STJ~NI~liti AND C:ON, LiSIONS 161 I"FI-I and Rehabiliation. American Fisheries Society, Bethesda, 'artington, I'.FI.1990, Pa'el remiarks: Contemporsry management Mlaryland. issues reCuILiring' scientific research. In: G.T. Wallace and F.. Horcitan. J.. S .1 Correia and I). 13.Withereli. 19193. Et'.ects of Braasch (eds.). Pioceedintus oftile Gulft"of Maine Elcosystet chanCes in aLc-0 survival and fishing mortalitv oil egg produc- Dynattmics Scientific Svnmpositimn and Workshop. RARGOM tion of wintcr fiounder in Cape Cod Bay. Arn. Fish. Soc. Syrip. Report 97- 1. Pp, I- 3 14:39-45. Pinchot, G: 1947. Breakin" New Ground. New York: Harcourt, Brace. Dorsey. E. and J. Pederson (eds.). 1998. Effects of Fishinq Gear on Rebeck. K.L.. RD Brady, K.D. Mcl..aughlin. and CG. Milliken. iie Sea Floor of New Fn'land. Conservation Ilaw Foundation, 2004. A Stirvey ol'Anadromous Fisl l'assaee il Coastal Boston, MA. 168 pp. MIassachltLisetts P'aet I, Southeastern Massachusetts. Drinkwater. K.F.. GC. Harding, KH. Mann, and N. Tanner. 1996. Commonweath of Massachusetts, Massachusetts Division of Temperature as a possible factor in the increased abundance of Marine Fisheries. Pocasset. MA_ Technical Report fR-I 5. American lobster. Homarnis americantus, during the I980s and Schaaf, W. E., D. S. Peters, L. Coston-Clemients, D. S. Vaughn and C. carly I990s Fisheries Oceanogralihy 5:176-193. W. KroUsC. 1993. A simenulat it model of how lile history strate-Frank. K.T., K.F. Drinkwater. 1994. Possible causes of recent trends gies mediate pollution effects on fish populations. Esttaries. and fluctuations in Scotian Shelf Gulf of Maine cod stocks. IC1ES 16:697-702. Marine Sei. Svmposia 198:110-120. Sherman, K., C. Jones, L. Sullivan, W. Smith, P. Berrien and L. Leopold, A. 1949. A Sand County almanac and sketches here and Ejsymont. 1981. Congruent shifts in sand eel abundance in west-there. New York: Oxford University Press. eri and eastern North Atlantic ecosystems. Nature 291:486-489. 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162 MIANAGEMNT SIMPIILICAI IONS 163) Chapter X Management Implications: Looking Ahead JUDITH PEDERSON Massachusetts Institute of Technology Sea Grant College Program 292 Main Street, E38-300 Cambridge, MA 02139 USA WILLIAM E. ROBINSON University of M1assachusetts Boston Department of Environmental, Earth and Ocean Sciences (EEOS)l 100 A'orHsseli Blvd. Boston, MA 02125 USA Ninetv percent of the marine fish comes A growing body of evidence has documented fom ithe thirdof the oceans near land. the accelerating decline of the oceans' most pro-
-Peter Weber; 1994 ductive fisheries, a trend that is amply chronicled in the northwestern Atlantic (NOAA, 1998; FAO, 1997; NRC, 1998; Figure 10. 1). Aside from the obvious concern with landings and the societal Now would I give a thousandfirlongs of impacts to the fishing community, the decline, if seafor an acre of barren ground. prolonged, will continue to elicit sweeping ecologi-
-William Shakespeare, 1623, The Tempest cal consequences. Yet, over the past couple of decades, ecosystem considerations have been over-shadowed by the fishing industry's perspective and 500000 -o 4000 000 3000000 2000000 1000000 0 i 1I 54l ] 1I Ii III I 1i9 H0 II ]qI II q II Ii4II 9I86I Ii 1 990 1i 94 1956 1954 1958 1962 1966 1970 1974 1978 1982 1986 1990 1994
- Other groups 2 56-Clams, cockles, arkshells..
o 31 -Flounders,hali buts,soles,.. o 37-Mack.,snoekscutlassfishes
- 34-Jacks, mullets, sauries,... IS 33-Redfishesbasses,congers,..
- 35-Herrings.sardinesanchavies S 32-Co ds, hakes. haddocks,...
Figure 10.1. Total landings (tons) of groups of marine resources from the northwestern Atlantic Ocean over the period 1950 - 1994 (FAO, 1997). Different hatch patterns distinguish different ISSCAAP fisheries groups. Peak landings in the late 1960s was principally due to ISSCAAP Groups 32 and 35.
164 IVi)ERSO>N & ROBII NSON needs. Stock assessment models, the mainstay of mammals (e.g., harbor seals, Phoca vitudina con-commercial fisheries management, are based on color) and a number of sea birds (e.g., Great Auks, the population level of biological organizationl-- Pinguinus impennis) were hunted to very low pop-individual species of commercially important fish ulation levels or extinction (Williams and Nowak, and shellfish---and are not based on species inter- 1986). These large, top piscivores may have actions and ecosystem dynamics (Applegate et al., shaped species distribution and abundance. Recent 1998). population increases of other fish predators, such Our intent with this volume was to compare as striped bass (Morone saxitilis) and cormorants the effects of overfishing, pollution and habitat (Phalacrocoraxspp.), may also be impacting the alteration on fisheries and identify possible new marine ecosystem, at least locally. approaches to managing fisheries and ecosystems Humans, also a top predator. affect even non-that integrate these factors. We have only been par- targeted fish species. Barndoor skate, Raja laevis, tially successful in broadening the scope of this caught incidentally as bycatchand discarded, were debate with a "common currency" that could allow once plentiful in the northwest Atlantic, but are us to weight the contributions of these three now thought to be on the brink of extinction due to impacts on fisheries' declines. We are limited bycatch (Casey and Myers, 1998). Both the diver-because the scientific information is either lacking sity and complexity of benthic ecosystems have or too fragmented to allow us to rank the relative been markedly reduced in areas subjected to strengths of each contributing factor in a definitive, repeated bottom trawling and dredging (Dorsey unambiguous way for all species. Nor is there a and Pederson, 1998). Industrialization and coastal preponderance of models that could guide us in development have significantly increased pollution this endeavor. As we look forward, the main chal- loading and altered estuarine habitats at unprece-lenge to fisheries managers is the integration of dented rates. All of these combined impacts have ecological concepts, human activities, and social had and will have lasting effects on marine and and economic considerations into sustainable fish- coastal ecosystems, in addition to adversely affect-eries management. ing the fisheries of this region. Overfishing leads to yet another set of ecologi-cal consequences. As a fish stock declines, fisher-Ecosl'sTErN APPROACH men switch to other species that are typically lower The Magnuson Stevens Fisheries and down the trophic level than the original species. In Conservation Act of 1996 (Sustainable Fisheries the northwest Atlantic, for example some fisher-Act; SFA), attempts to institute a more ecosystem- men are switching from gadoids and other ground-based regulatory approach to fisheries management fish to clupeids (fish that feed on plankton and are than has been the case in the past. In practice, how- more abundant) (NEFSC, 1998). This trend, ever, emphasis continues to be on single species, termed "fishing down the food web" (Pauly et al., especially specific finfish, lobsters and scallops, 1998), has been documented in all mature fisheries and to a lesser extent on individual anadromous worldwide over the past 45 years. Other fishermen fish, squid and shallow water bivalves. This have switched to less utilized groundfish (e.g., approach neglects other components of the ecosys- from gadoids to dogfish and monkfish). While the tem, upon which commercially important species shift initially leads to increased catches, it is soon often depend for food and refuge (Applegate et al., followed by the decline of the new fish stock. This 1998). pattern of exploitation is inherently unsustainable, Some ecological shifts that may have already and leads to far-reaching ecosystem changes due to affected marine fisheries have been reported, but the disruption in trophic interrelationships. most have gone undocumented. One dramatic Our current pattern of stock exploitation has change has been the loss of several top predators one additional ecological implication. Somehow in and their replacement with humans who have hunt- the discussion of fisheries' decline, a basic ecologi-ed mammals, birds, and top fish predators or have cal tenet that productivity of the oceans is finite altered their habitats. Over the past two to three has been lost or neglected (Ryther, 1969; Holt, centuries, some fish predators such as marine 1969; Russell-Hunter 1970; Mann 1982; Mann and
MIANA(uENI EN"I NI1PLICAriONS; 165 Lazier 1991). Primary production has narrowly cir- Table 10.1. General categories of research needs that cumscribed limits, that, in turn, modulate the pro- would assist and improve scientifically-based fisheries duction of fish and shellfish that are harvested for nmanagement. Recommended research needs and human consumption. The rise in total fish catch management approaches would address all four of the fisheries discussed in this volume. over the past several decades masked the overex-ploitation of individual fisheries. As early as 1969, Improving our understanding of ecosystem processes as however, scientists were predicting an upper limit they relate to fisheries productivity to fish productivity and expressed concern that " Make better use of historical data in describing fisheries were declining (Holt 1969; Ryther, 1969), trends of relationships between onshore and off-but the switch to new and underutilized species and shore stocks and transport of pelagic larvae and life the incremental contribution from maricul ture tended stages. to allay these concerns. Current estimates indicate " Quantify effects of contaminants on populations that world marine fish production will probably and relate to other impacts. peak at about 93 million tons (exclusive of a sig- " Quantify effects of habitat degradation and relate nificant expansion of mariculture), only 10 million to other impacts. tons higher than today's landings (FAO, 1997). This maximum production can only be sustained if Developing an ecosystem-based fisheries science, current overexploited and fully exploited fisheries including a new suite of models that can be used to are regulated for sustainability (World Resources forecast changes Institute, 2000). " Integrate anthropogenic changes with natural pro-The authors of this book have identified cesses in models. numerous research needs that should be filled to " Include environmental fluctuations (e.g. weather, support informed management decisions (Tables salinity, runoff ) and trends (e.g. global warming)
- 10. I and 10.2). Many of these recommendations into holistic models have been proposed previously (MA DMF, 1985; " Improve calibration and verification of models.
MA MRCC. 1987; Buchsbaum et al., 1991; FAO, " Develop models into forecasting tools for managers. 1997; NRC, 1998, 1999), and would be anticipated by our readers. Most of these recommendations Implementing new management approaches that support need no introduction or detailed explanation. Four sustainability of valued fisheries recommendations that have not been given suffi- " Incorporate the Precautionary Approach into fish-cient consideration by fisheries managers serve as eries management a framework for achieving sustainable fisheries as " Utilize Adaptive Management techniques presented below: (1) adoption of the precautionary " Determine optimal spatial scale fornmanagement approach; (2) the need for an ecosystem-based plans; eliminate management based solely on polit-fisheries science; (3) developing new models; and ical boundaries. (4) the adoption of adaptive management principles. " Integrate natural history information into policy development and fisheries management.
" Develop new electronic data analysis systems, TIlE PRECAUTIONARY APPROACH interfacing geographic informiation systems, histor-ical data sets, the databases that exist in various agencies and organizations.
In theface of uncertainty about potentially " Test the effectiveness of marine refugia and irreversibleenvironmental impacts, deci- management closures on fisheries stocks and sions concerning their use should err on productivity. the side of caution. The burden of proof " Characterize and define essential fish habitats and should shift to those whose activities evaluate the causes and extent of alteration. potentially damage the environment.
- Improve population estimates for species of interest
-Robert Costanza et al., 1998 integrating recommendations from academia, fishermen and managers.
166 ['LD)RSON &s ROBIN\SON Table 10.2. Specific research needs and management options identified by the contributors to this volume.
- a. Research Recommendations Groundfish Anadromous Lobster Bivalve fish Improve current stock assessment X X X X Develop new integrative, holistic models X X X X Improve understanding of population level effects of contaminants X X X X Evaluate contaminant effects on reproduction X X X Detennine the importance of endocrine disrupters on reproduction X X Evaluate effects of biotoxins on mortality X Identify factors at sea affecting mortality X Evaluate predation pressures (e.g. bird, crab, marine mammal) X X X Develop models relating land use to populations X X Identify stock and substock size to improve understanding of population dynamics Develop predictive models and verify with data X X X X
- b. Management Recommendations Reduce fishing effort to increase spawning stock biomass X X Enforce regulations, closures and management efforts X X X Develop and implement a management plan for herring and mackerel Develop shellfish management plans X Develop management plans for restoring in-stream habitats X Develop and implement management plans in conjunction with X X watershed groups Create management units based on appropriate scales X Focus on research to evaluate broodstock trawling on lobsters X Develop a plan for protecting juvenile lobster habitat X Characterize the lag time between adverse or favorable effects on life history stages Determine whether predators are increasing or decreasing X X Develop management options for protecting habitat X X X X The Precautionary Principle calls for precau- environmentally benign. Such an extreme approach tionary actions in response to potential threats to is scientifically unjustifiable, since the scientific the environment or human health, even if causality method can never be used to prove that harm is has not been scientifically established impossible. In contrast, scientific analyses are used (VanderZwaag, 1994). It is often interpreted in to assign probabilities to various actions, and to exclusion of the economic and social factors that estimate the uncertainty around these probability managers must also consider when making their values (e.g., a 40% probability of a 20% change).
decisions. Because the language of the Precautionary In order to include scientifically justified estima-Principle is rather vague and moralistic (Bewers, tions of risks, strict adherence to the Precautionary 1995), it has proven difficult to incorporate into Principle is being replaced by a more workable policy decisions. Strict application of the "precautionary approach" that includes scientific Precautionary Principle would preclude any action justification of estimated risk (VanderZwaag, 1994; unless it could be .proven that the action would be Bewers, 1995). The precautionary approach, which
NIANAG~ENlICNI' I NIVII.CAIION5 167 implicitly recognizes that there is a diversity of Collie, 1998; Auster and Langton, 1999; Watling, ecological as well as socio-economic situations 1998). They recommend categorizing habitats by requiring different strategies, has a more acceptable their vulnerability to trawling and establishing "image" and is more readily applicable to fisheries marine protected areas until data are gathered to management systems (FAO, 1994). demonstrate minimal impacts (Collie,. 1998; Auster The precautionary approach calls for avoidance and Langton, 1999). This is not a new concept: of serious or irreversible damage, by choosing options that have the lowest probability of long-term risk when uncertainty is high. Although decisions Our present information indicates that it based on a precautionary approach are founded on is notfishing with the otter trawl but scientific estimates of probability, they include overtishing which is to be guarded economic and social factors and incentives for against... the restriction of the use of the minimizing environmental damage. otter trawl to certain definite banks and The precautionary approach has not been grounds appears to be the most reason-broadly or enthusiastically endorsed by policy able, just andfeasible method ofregula-makers or managers in the United States. With tion which has presented itself to us. respect to fisheries, U.SI agencies' policies post- -Alexander et al., 1914 poned regulatory action to reduce overfishing until the evidence for stock declines proved overwhelm-ing. This was evident in debates on the northwest Others would claim that many areas have been Atlantic groundfish fishery. The results were disas- fished for years and that habitat alteration by fish-trous. In contrast, early adoption of the precaution- ing gear is comparable to storms and natural envi-ary approach would have incorporated the best sci- ronmental events (Mirarchi, 1998; Pendleton, ence available. This might have included a call for 1998). There is concern by the fishing community lowering levels of total allowable catch for almost that no amount of data will be sufficient to permit all species., requiring changes in gear and mesh fishing and use of all fishing gear types. The fish-sizes, and mandating the adoption of other alterna- erman's concern represents the basic differences tives to prevent overexploitation of fisheries stock between the precautionary principle that restricts (Myers and Mertz, 1998; Applegate, et al., 1998). all use and the precautionary approach that recom-Applying the precautionary approach might also mends caution until evidence is collected showing have resulted in the shutting down of a fishery for there is minimal impact. prolonged periods, such as has occurred with cod The distinction is worth repeating. Proponents fishing off Newfoundland, or in setting aside of the precautionary principle would ban all trawling refuges, such as the temporary closures now in because it negatively impacts habitat. Proponents of effect on Georges Bank (Lauck et al., 1998). the precautionary approach would restrict trawling Since July 1998, the New England Fisheries in vulnerable areas until data were gathered to Management Council (NEFMC) has adopted some demonstrate a management approach to minimize of these more restrictive policies, but for several damage. species the delay in taking action has only added to the length of time needed to reach maximum sus-MANAGING FiSHERIES USING AN ECOSYSTEM tainable yield. APPROACH Another area where a precautionary approach has been touted involves the role of habitat in Although fisheries have traditionally been recovery of fisheries. Proponents of the precaution- managed individually, an ecosystem approach to ary approach want restrictions on selected gear fisheries management is receiving increasing sup-types and protection of vulnerable habitats (such as port. However, there are many definitions of an hard bottoms in waters deeper than 30 m where ecosystem approach and therefore many different recovery of benthic communities takes decades) or expectations of what its application can achieve in in areas where the effects of fishing gear on benth- fisheries management. For example, the SFA pro-ic communities are unknown (Witman, 1998; rmoted an ecosystem approach, by requiring each
168 I'LiFRSON & KOBINS;ON management council to include both demarcation The National Research Council (NRC, 1998) and protection of essential fish habitat in their fish- recently reviewed five major stock assessment eries management plans by October 1998 models and approaches used by NMFS and fishery (Kurland, 1998). Even though the SFA continued managers nationwide. They compared the out-to focus on a single species approach, the new comes of each model using five actual or simulated provisions of the Act encourage research on life his- datasets, covering a 30-year period. None of the tory, biological interactions, and the environmental models were entirely satisfactory in predicting variables that define habitat (physical, geochemi- stock abundance and most overestimated the ensu-cal, and biological components). However, fish ing year's biomass by more than 25%. In addition, habitat is covered in the same large grid size as the models exhibited a multi-year lag time in used by the National Marine Fisheries Service detecting trends (overestimating biomass during a (NMFS) for fish stock assessment (approximately simulated decline, and underestimating biomass 700 km 2 in the northwestern Atlantic). Information during a simulated increase in abundance). on presence and/or absence and available life histo- The current stock assessment models upon ry data are assembled for each species managed for which recent New England groundfish manage-each grid area (NEFMC 1998). Fishers have ment has been based, were criticized by NRC for knowledge on a smaller scale, but it is difficult to not realistically accounting for natural population integrate their data into habitat studies (Pederson variability or environmental fluctuations, and for and Hall-Arber, 1999; Hall-Arber and Pederson, being focused on single species in a multispecies 1999). For many species, growth, reproduction and ecosystem (NRC, 1998). In addition, they ignore productivity data are lacking. Unless new resources interspecies interactions (predator-prey, competition or current research funds are reallocated, fisheries for space .and food), and make no attempt to overlay data collection and research will continue to sup- stochastic environmental variations (seasonal varia-port current studies that are not focused on habitat tions as well as episodic events) or long-term envi-and the relationship of habitat to productivity. The ronmental trends on their deterministic algorithms. recognition that habitat protection is critical for the Natural environmental fluctuations can lead to development of sustainable fisheries is a major step enormous changes in year class strength in some along the path to ecosystem-based fisheries man- fisheries (greater in short-lived or r-selected agement (Langton et al., 1995, 1996; Steneck et al., species than long-lived or K-selected species) and 1997; Deegan and Buchsbaum, Chapter 5). are difficult to assess and incorporate into models (Sutcliffe, 1973; Hofinann and Powell, 1998). Despite its critique of the models, the NRC DEVELOPING NEW MODELS report (.1998) did not recommend abandoning cur-The current approach to fisheries management rent approaches using single species assessment uses various stock assessment models that input models and did not really propose an alternative. It quantitative population data from fisheries inde- did encourage continued research in model devel-pendent surveys, landings data, and the scientific opment. In the short term, single species assess-literature to predict future stock abundance ment models will probably provide the most useful (NEFSC, 1998). These models use previous years' data for fisheries management. However, other data on yield, growth, recruitment and mortality to models, which incorporate both environmental fac-predict rates of productivity and biomass. The tors and multi-species interactions should be vigor-degree to which stocks are exploited, and the exis- ously pursued and added to the current methods of tence of growth or recruitment overfishing can be stock evaluation. These models should include the assessed from a model's output. The predictions effects of contamination, fishing mortality and from stock assessment models are used to recom- habitat issues, plus stochastic factors to account for mend levels of fishing in the future. While applica- temporal environmental variability (Hofmann and ble to the overfishing question, these models are Powell, 1998). Since these newer models incorpo-not designed to incorporate impacts caused by rate the existing single-species assessment models, changes in critical habitat and contaminant effects continued refinement of single-species models can on susceptible life stages. actually be viewed as a step along the way to more
\IANA(~iFNIILNI IMPUL XI[ONS Al 169 ecosystem-based models. data to fish population models, although they warn Attempts to integrate physical and chemical against using their model to predict long-term pop-parameters with biological data are still few in ulation impacts. These authors recognized the simi-number. One local example is the three-dimension- larities in such problems as identifying the cause of al Massachusetts Bay model that has been eight power plant fish kills, projecting optimal fishing years or more in development and is used in effort, and determining the impact of environmen-assessing the effects of an outfall in Massachusetts tal chemicals on fish populations. They were able Bay (HydroQual, 2000). It combines a hydrody- to use this reproductive potential fisheries model, namic model, based on physical parameters with combined with chronic toxicity findings, to assess chemical and biological data (nutrients and phyto- the effects of five chemicals (4 pesticides and plankton response) to forecast plankton productivity. methyl mercury) in Chesapeake Bay striped bass It is considered a successful, chemical-biologically populations (Barnthouse et al., 1989). These toxi-coupled model, yet it fails to identify peaks of cants not only affected survival, but also had a sig-spring and fall blooms, uses general values for pre- nificant impact on fecundity. In a subsequent study, dation by zooplankton and the benthos, and ignores Barnthouse et al. (1990) demonstrated that contam-large species, such as fish and marine mammals inants had a relatively greater impact on overfished (HydroQual, 2000). populations of striped bass and menhaden than on Another physical-biological model is one populations not stressed by overexploitation. Life developed to hindcast the likely source of lobster history models have also been developed for larvae that settled in mid-coast Maine (Incze and bivalves and for assessing the sensitivity of life Naimie, 2000). These investigators predict that lar- history stages to environmental changes (Weinberg vae come from a broad section of the upstream et al., 1997; Caswell, 1996).
coast (both inshore and offshore) of Maine and Thus, a number of studies have demonstrated suggest a link between offshore reproduction and that fisheries models can be integrated with chemni-inshore recruitment. Both the MWRA (2000) and cal, physical and toxicological data. Incorporating the lncze and Namie (2000) models provide infor- these models into fisheries management decisions, mation that can supplement current stock assess- at least as complementary approaches to the cur-ments and provide managers with additional and rent single species models are a good first step. relevant information. The next step in the development of holistic Research efforts, mostly from the emerging approaches is the incorporation of habitat impacts, fields of ecotoxicology and environmental risk e.g., predator-prey relationships, trophic-level assessment, are resulting in better, more compre- interactions, and environmental factors into models hensive fisheries models. Waller et al. (1971) and used by fisheries managers. Development of these Wallis (1975) first proposed to include contaminant models is one of most pressing needs for fisheries effects into fisheries-derived population models to management and should provide information for predict population effects. Similarly, a number of addressing those supporting a precautionary studies incorporated contaminant data into simple approach. ecological models (Daniels & Allen, 1981; Gentile The shift from our current single-species man-et al., 1983). Summers and Rose (1987), analyzing agement to an entirely ecosystem-based approach time series data, were able to differentiate overfish- is a millennium jump. Because of the inherent ing from hydrographic variability and contaminant complexity involved (both physical and biological), effects in striped bass (A1 saxatilis) and American our current data analysis and modeling algorithms shad (A. sapidissima)populations in the Potomac, are not sufficiently developed to allow us to take Delaware and Hudson Rivers. They pointed out an ecosystem-based approach at the present time. that few previous studies have successfully More holistic approaches, using a suite of ecosys-attempted to examine complex environmental vari- tem-based models are clearly needed, to augment ables and, of those that had, most simply correlated stock assessment models, if not to replace them. stock size with environmental parameters using an Models of course are only as good as the data arbitrary time lag. Barnthouse et al. (1987) have that they use. One of the most productive uses of proposed a risk-based method to apply toxicity test modeling is to point out critical data gaps and the
170 PEIWRSON & RO)BIN\SON need for additional monitoring. In addition, models to address the new hypothesis. The scientific pro-can be used to set priorities for new data develop- cess is a continuous one. However, managers are ment, ruling out the collection of data on parame- usually constrained by regulations and a vague ters that have little effect on the critical ecosystem sense of how to incorporate scientific data into relationships. The contributors to this volume have management decisions. Adaptive management is a identified a variety of data gaps/research needs particularly useful technique for managing when (Table 10.2), all of which should be incorporated uncertainty is high. into the holistic approaches and ecosystem-based The recent round of assessments, limiting days models that are recommended. For example, long- at sea, stock reassessments, and area closures in the term monitoring data (multi-decadal) are absolutely Georges Bank groundfish fishery by the New vital to all efforts to test ald verify newly devel- England Fishery Management Council is an adap-oped models. While these data are available for tive management strategy. When it Was obvious offshore groundfish, stock assessment data are that stocks could not be restored first by increasing scant for inshore bivalve populations. Contaminant mesh size and then by limiting the number of days effects on aquatic populations are also relatively at sea and catch quotas (NEFMC, 1994a), more rare, although they are currently receiving much drastic measures were implemented (NEFMC, needed attention by the field of ecotoxicology. 1994b, 1996). Areas throughout the Gulf of Maine Regional and state fisheries management agen- were closed to fishing. Depending on the results of cies are likely to resist adopting these more com- new stock assessments, additional closures and plicated, holistic approaches in their present state restrictions are contemplated. Recent results indi-of development. Nevertheless, these are powerful cate that total biomass of cod has increased in the analytical tools that can be used to better under- closed areas, but that it is too early to see an stand the interactions among a variety of anthro- increase in either the number of juvenile cod or in pogenic impacts on fish stocks and to explore the recruitment (NEFSC, 1998, but see also Murawski, impacts that various management options will have Chapter 2 this volume). It is predicted that rebuild-on these stocks. These models will continue to be ing Georges Bank groundfish stocks will take refined as more data are collected and as more many years (Murawski, Chapter 2; Myers et al., fisheries managers and biologists become familiar 1995). Fisheries managers revise their management with not only the power, but the limitations of decisions repeatedly, as new data are available. these models. Fisheries management can facilitate This adaptive approach needs to be applied to other adoption of new approaches by supporting research fisheries. A suite of management options, (e.g., into model development, testing their robustness days at sea, total allowable catch, closed areas, and usefulness as applied to fisheries issues and mesh size, gear modifications, limited entry, quota adopting those models that are cost-effective. The systems), offer managers tools for employing adap-opportunity exists for innovative approaches that tive management approaches, but not all are avail-will invigorate fisheries management. able to New England managers (e.g., individual take quotas or ITQs that have been successful in selected fisheries). To learn from management ADAPTIVE MANAGEMENT decisions, each option should be scientifically ana-Adaptive management is a scientific approach lyzed to evaluate its effectiveness. Socio-economic that decision-makers can use for a variety of data that link management decisions to long-term environmental problems (Costanza et al., 1998). It sustainability and conversely over-exploitation to is a process whereby managers repeatedly modify long-term impacts on fishing communities are their management decisions based on targeted col- scarce (Hall-Arber, Massachusetts Institute of lection of new data and reassessment of the situa- Technology, Cambridge, MA, pers. comm.) tion. It is akin to scientists stating a hypothesis, and Adaptive management is not effective without then collecting data that either refutes or supports a mechanism for gathering new data. Similarly, the hypothesis. Based on the results of initial unpopular restrictions are difficult to enforce with-experiments, scientists may modify the initial out first gaining the confidence of the fishing hypothesis, and then devise additional experiments community that such restrictions are based on good
MNA..6.(E\IENU INII'LICAAl[ONS 171 information and can be modified as additional impacts on these species (e.g., predation, information becomes available. As an example, competition, habitat alteration, contamni-under the SFA, fishery managemnent plans (FMPs) nation, climate, seasonal weather pat-had to be modified by October 1998 to include terns, episodic events). This need has identification and protection of essential fish habitat. been emphasized repeatedly over the Habitat data were extremely uneven and spotty. years: All of the participatingagencies For New England groundfish, there were some rel- agreed that the number one priority in ative abundance data for several life stages (eggs to any effort to protect/restorethe environ-adults), but there was a paucity of information on mental integrity of our coastal waters is spawning adults and other detailed life history the development and implementation 0/f a data. Management decisions still needed to be research and monitoringprogram. made, regardless of the detail and extent of the -MA MRCC (Marine Resources data on each species. When only presence/absence CoordinatingCommittee), 1987 data were available, fishery councils, applied a pre-cautionary approach and generally designated a larger area of habitat as essential to fish than they might have if more precise habitat information The relative impact of fishing, contami-were accessible. Adaptive management provides nants, and estuarine habitat degradation the framework to routinely review the size of on marinefisheries needs to be evaluat-essential fish habitat, as more habitat and life history ed. This complex issue ultimately needs data become available. to draw on several data sources, such as The adaptive management approach could eas- the semiannual MDMF [Massachusetts ily be applied to a broader spectrum of fishery Division of Marine Fisheries]stock issues (Table 10.2). For example, temporary closed assessment and site specific estuarine areas are being used to help build up groundfish surveys.... -Buchsbaium et al.. 1991 stocks, and the possible need for permanent refuges is being discussed. Because this is a rela-tively new approach, many questions are raised. Do refuges where no fishing is allowed lead to The absence of adequate data is the pri-increased spawning biomass both within and out- mary factor constrainingaccurate stock side the refuge? Is there an optimal size, number, assessment. -NRC, 1998 and distance for protected areas to provide safe refuge? When are seasonal or permanent closures appropriate? How should refuges be managed? Because the cry for 'more data' has been raised Fisheries scientists in collaboration with marine so often, some managers, legislators and the public ecologists can conduct the necessary studies to fill have grown insensitive to the call and no longer in the data gaps. Using adaptive management, the acknowledge it as a vital need. This is unfortunate results of this ongoing research and monitoring because there is a genuine need for specific data to could be incorporated into management review and answer pragmatic and practical questions raised by management decisions modified accordingly. fisheries managers. There are several good exam-ples of projects with well-defined goals that have implemented research and monitoring programs to DATA NEEDS address issues (MWRA, 1991; MBP, 1996). The process identified for developing monitoring pro-grams outlined in Managing Troubled Waters: The One recommendation deserves to be Role of Marine Environmental Monitoring (NRC, highlighted again - the needfor more 1990) should be adapted by fisheries managers in current data on each commercially developing observing systems that address data important species (e.g., population, needs. Effective programs evolve from planning recruitment,habitat)and on the various and involvement of stakeholders. The process,
172 V'IL)IKSON.K, R' fflNSO\ which is easily adapted to identitying research world's resources has been made in a recent publi-needs, involves identifying the goals, reviewing cation of the World Resources Institute (2000). what data exist, developing a monitoring strategy, Single-species management can no longer be relied analyzing results andreviewing the information upon to address the fishing pressure on wild stock. produced with respect to the initial goals. Considering only single stressors (fishing mortality, The resource assessment program, established contaminant toxicity, habitat alteration) limits man-in 1974 in Massachusetts, has a specific goal - agement options and may lead to erroneous deci-sound scientific and statistical input for stock sions that have negative effects on other fisheries. assessment, and is considered a valuable contribu- Because pollution has had an impact on some fish tion to the National Oceanic and Atmospheric (e.g., various anadromous fish; winter flounder Administration (NOAA) database for groundfish (Pseudopleuronectes americanus),windowpane (Howe et al., 1979). To its credit, the program has (Scophthalmus aquosus), striped bass (M sax-changed very little since 1979. It provides over 20 atilis), mussels (Mytilus edulis), and lobsters years of data using consistent methods with NOAA (Homarus americanus)) and habitat modifications effort. To its detriment, the program has changed have affected some species (e.g., anadromous fish very little since 1979. Lack of resources has limited and winter flounder), these factors may be having adding research components or additional monitor- some effect on all of our fish stocks. A variety of ing activities to any significant degree. well-established ecological tenets must now be In addition to the data used for stock assess- incorporated into our management decisions - the ments, food preference data has been collected by finite limitation of marine productivity; the impor-NMFS from 1973 to the present. These data were tance of biodiversity for maintenance of ecosystem summarized and synthesized in analyses and mod- health and vigor; and the reliance on habitat at crit-els that range from basic descriptions and statisti- ical life history stages. It is time to move towards a cally analyses to predictive and theoretical models more holistic, ecosystem-based paradigm for scien-(NEFSC 1998). tific fisheries management. In practical terms, however, the fishing com-munity, including the industry, mainagers, and sci-A FINAL WORD entists) is not ready to make this paradigm shift. Neither the data nor the tools (conceptual and pre-dictive models) are available which would allow us What :'gone and what s past help should to manage any ecosystem. Developing these mod-be past grief -William Shakespeare, els, even though the parameters involved are 1623, The Winter ' Tale numerous and the overall system complex, should be a high priority. In addition to collecting data and refining our existing models, the use of these mod-els will eventually evolve into the holistic tools
...you better start swimmin' that we need.
Or you'll sink like a stone Many data needs have been identified (e.g., For the times they are a changin'. population and recruitment dynamics, predator-
-Bob Dylan, 1963 prey and competition relationships, identification of essential habitat for all life history stages, con-taminant impacts on populations, socio-economic Today, there is an extraordinary need for a effects on fishing communities). In general, the more scientific management of our fisheries. By majority of these parameters are neglected because recognizing that species do not exist in isolation of the complexity involved and our inability to from other species, and that each species has manage complexity. Applying a precautionary adapted to its own specific habitat, the need for approach to actions that may have adverse effects ecosystem-based management of our fisheries is a management option that offers the opportunity becomes apparent. A similar recommendation for to incorporate scientific information and new data.
"ecosystem approach" in the management of our Pilot projects and adaptive management approaches
NIANAGHiMIENI' I M LICA-1tONS 173 should be used to evaluate an action before it is Auster. 1'..J. and R. W. Langton. 1999. The effects of fishing on fish habitat. pp. 150-187 In: Benaka. l..R. (ed.) Fish Habitat: adopted on a broad scale. Investing in obtaining Essential Fish tlabitat and Rehabilitation. Am. Fish. Soc. Symp. data that supports holistic approaches to managing 22. Bethesda. MD. fisheries within an ecosystem framework- will pro- Barnthouse, L.W., G.W. SLter II, A.E. Rosen and J.J. Beauchamp. 1987. Estimating responses of fish populations to toxic contami-vide a basis for an integrative strategy toward man- nants. Environ. Toxicol. Chem. 6: 811-824. aging all species. Barnthouse, L.W., G.W. Suter 11and A.E. Rosen. 1989. Inferring pop-Our observation is that fisheries managers have ulation-level significance from individual-level effects: An extrapolation from fisheries science to ecotoxicology. In: Aquatic not effectively used new sources of information Toxicology and Environmental Fate. I Ith Vol. STP 1007, M. (e.g., research and monitoring data from the Lewis and G.W. Suter 11,eds. American Society for Testing and Materials. Philidclphia, PA pp. 289-300. National Estuarine Program, Sea Grant College BarnthousC, L.W., G.W. Suter 11and A.E. Rosen. 1990. Risks of toxic Programs, US Geological Survey, and contaminants to exploited fish populations: Influence of life his-Massachusetts Water Resources Authority). This tory, data uncertainty and exploitation intensity. Environ, Toxicol. occurs, in part, because fisheries models are cur- Chem. 9: 297-311. Bewers, J.M. 1995. The declining influence of science on marine rently population based and the data have not been environmental policy. Chem. Ecol. 10: 9-23. distributed effectively. Although not discussed Buchsbaum, R.. N. Maciolek, A. McElroy, W. Robinson and J. Schwartz. 1991 1. Report of the I..ving Resources Committee of explicitly, the need for improved data management the Technical Advisory Group for Marine Issues. Report to the and distribution remains key to successful integra- Secretary of Environmental Affairs, Massachusetts Executive tion of research data and models into management Office of Environmental Affairs, Boston, MA . I5 pp. Casey, J.M. and R.A. Myers. 1998. Near extinction of a large, widely decisions. distributed fish. Science 281: 690-692. Scientifically-based fisheries management can Caswell, H. 1989. Analysis of life table response experiments I. only be achieved through multidisciplinary collab- decomposition of effects on population growth rate. Ecological Modelling 46:221-237. oration. Fisheries managers will need to actively Collie. .I 1998. Studies in New England of fishing gear impacts on promote discussion and exchange among practi- the sea floor. pp. 53-62. In: Dorsey, E and J. Pederson (eds.) tioners from a variety of disciplines (e.g., fisheries Efflects of Fishing Gear on the Sea Floor of New England. Conservation Law Foundation, Boston, MA. science, marine ecology, aquatic toxicology, sociol- Costanza, R., FAndrade, 1. Antunes, M. van den Belt, D. Boersma, ogy). In addition, fishermen's knowledge is now D.F. Boesch, F. Catarino, S. Hanna, K. Limburg, B. Low, M. Molitor, J. G. Pereira, S. Rayner, R. Santos, J. Wilson and M. being actively solicited and is recognized as an Young. 1998. Principles for sustainable governance of the important source of data that had previously been oceans. Science 281: 198-199. ignored. Scientific insights into ecosystem dynam- Deegan. L. and R. Buchsbaum. This volume. Chapter 5. Daniels, R.E. and J.D.Allen. 1981. Life table evaluation of chronic ics and management constraints are less than ideal, exposure to a pesticide. Can. J, Fish. Aquat. Sci. 38:485-494. but with a long-term research plan, information can Dorsey, E.M. and J. Pederson (eds.). 1998. Effects of Fishing Gear on be gathered to improve ecosystem-level under- the Sea Floor of New England. Conservation Law Foundation, Boston, MA. 160 pp. standing. The vision for the future is the integration FAO (UN Food and Agricultural Organization). 1994.;The of information from all sources, the development Precautionary Approach to Fisheries with Reference to Straddling of holistic models that realistically represent Fish Stocks and Highly Migratory Fish Stocks. FAO publication A/Conf 164/INF/8, 26 January 1994.25 pp. ecosystems, and the wise use of knowledge for FAO (UN Food and Agricultural Organization). 1997. Review of the improved management decisions. With committed State of the World Fishery Resources: Marine Fisheries. FAO individuals in the planning process, the goal of sus- Fisheries Circular No. 920 FIRM/C920 (ISSN 0429-9329). 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XMAGEM TNIIMPLICATIONS 175 and 1. P'cdcrson (cds.) E'l'ects oi Fishing Gear on the Sea Floor of New England. Conservation Law Foundation, Boston. MA. World Resources Institute. 2000. A Guide to World Resources: 2000-2001. People and Ecosystems. The Fraying Web of Lille. World R*esourcs Institute, Washington, DC.
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