ML072060545
| ML072060545 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek |
| Issue date: | 10/01/1983 |
| From: | Benson N, Dewitt R, Shanks L, John Stanley Univ of Maine, US Dept of Interior, Fish & Wildlife Service, US Dept of the Army, Corps of Engineers |
| To: | Office of Nuclear Reactor Regulation |
| Davis J NRR/DLR/REBB, 415-3835 | |
| Shared Package | |
| ML072060321 | List:
|
| References | |
| TR EL-82-4 FWS/OBS-82/11.18 | |
| Download: ML072060545 (29) | |
Text
REFERENCE COPY Do Not Remove from the Libror",
U. S. Fish and Wild!ife Servie
'KWao4Wni A4...... em-FWSIOBS-82/11.18 - Cajun Dome Bou-evard TR EL-82-4 700- - '- ,-. - -. - ,ý . f k'-3 I I ý-"11f'rv October 1983 Lafayette, Louisiana 70506 Species Profiles: Life Histories and Environmental Requirements of Coastal Fishes and Invertebrates (North Atlantic)
HARD CLAM Coastal Ecology Group Fish and Wildlife Service Waterways Experiment Station U.S. Department of the Interior U.S. Army Corps of Engineers CýkL F41DLV5L
FWS/OBS-82/11.18 TR EL-82-4 October 1983 Species Profiles: Life Histories and Environmental Requirements of Coastal Fishes and Invertebrates (North Atlantic)
HARD CLAM by Jon G. Stanley and Rachael DeWitt Maine Cooperative Fishery Research Unit 313 Murray Hall University of Maine Orono, ME 04469 Project Manager Larry Shanks Project Officer Norman Benson National Coastal Ecosystems Team U.S. Fish and Wildlife Service 1010 Gause Boulevard Slidell, LA 70458 Performed for Coastal Ecology Group Waterways Experiment Station U.S. Army Corps of Engineers Vicksburg, MS 39180 and National Coastal Ecosystems Team Division of Biological Services Research and. Development Fish and Wildlife Service U.S. Department of the Interior Washington, DC 20240
This series should be referenced as follows:
U.S. Fish and Wildlife Service. 1983. Species profiles: life histories and environmental requirements of coastal fishes and invertebrates. U.S. Fish Wildi. Serv. FWS/OBS-82/11. U.S. Army Corps of Engineers, TR EL-82-4.
This profile should be cited as follows:
Stanley, J. G., and R. DeWitt. 1983. Species profiles: life histories and environmental requirements of coastal fishes and invertebrates (North Atlantic)
-- hard clam. U.S. Fish Wildl. Serv. FWS/OBS-82/11.18. U.S. Army Corps of Engineers, TR EL-82-4. 19 pp.
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PREFACE This species profile is one of a series on coastal aquatic organisms, principally fish, of sport, commercial, or ecological importance. The profiles are designed to provide coastal managers, engineers, and biologists with a brief comprehensive sketch of the biological characteristics and environmental require-ments of the species and to describe how populations of the species may be expected to react to environmental changes caused by coastal development. Each profile has sections on taxonomy, life history, ecological role, environmental requirements, and economic importance, if applicable. A three-ring binder is used for this series so that new profiles can be added as they are prepared.
This project is jointly planned 'and financed by the U.S. Army Corps of Engineers and the U.S. Fish and Wildlife Service.
A Habitat Suitability Index (HSI) model is being prepared by the U.S. Fish and Wildlife Service for the hard clam. HSI models are designed to provide a numerical index of the relative value of a given site as fish or wildlife habitat.
Suggestions or questions regarding this report should be directed to:
Information Transfer Specialist National Coastal Ecosystems Team U.S. Fish and Wildlife Service NASA-Slidell Computer Complex 1010 Gause Boulevard Slidell, LA 70458 or U.S. Army Engineer Waterways Experiment Station Attention: WESER Post Office Box 631 Vicksburg, MS 39180 i*ii
CONTENTS Page PREFACE....................................
CONVERSION TABLE ......... ..... ..... ............................. vi ACKNOWLEDGMENTS .... ............. ........ . ................ vii NOMENCLATURE/TAXONOMY/RANGE .............. ... ...................... I MORPHOLOGY/IDENTIFICATION AIDS ....... ......... ...................... 1 REASON FOR INCLUSION IN SERIES ....... ......... ...................... 2 LIFE HISTORY ..... 22..........................
Spawning ."............2 2................
Fecundity and Eggs ....... ....... ..... ........................... 3 Larvae ..................... 33..............
Juvenile Seed Clam ....... ....... ..... ........................... 3 Adult 44..................................
COMMERCIAL/SPORT FISHERIES ..... . ...... ......... .................. 5 Fisheries ........ ....... ..... .................................. 5 Population Dynamics ........ ......... ........................... 7 GROWTH CHARACTERISTICS ....... ....... ... .......................... 8 ECOLOGICAL ROLE ........ ....... ..... .............................. 9 Feeding Habits . .. .... ..... ........ ......... ................. 9 Predation ........ ....... ... ...................... .......... 9 ENVIRONMENTAL REQUIREMENTSr .......... .................. . . ...... 10 Temperature .............................. .................. 10 Salinity . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . 11 Dissolved Oxygen ........ ..... ... ........................ * .' 12 Substrate ................................................. ... 12 Currents ................................. ................. 12 Turbidity . ......... ... ....... ......... . ......... . ........ 13 Habitat Alteration ......... ..... .................. . ......... 13 LITERATURE CITED .......... ... ....... ..... ........................ 14 v
CONVERSION FACTORS Metric to U.S. Customary Multiply To Obtain millimeters (mm) 0.03937 inches centimeters (cm) 0.3937 inches meters (m) 3.281 feet kilometers (km) 0.6214 miles square meters (m-) 10.76 square feet square kilometers (kmi) 0.3861 square miles hectares (ha) 2.471 acres liters (1) 0.2642 gallons cubic meters (m') 35.31 cubic feet cubic meters 0.0008110 acre-feet milligrams (mg) 0.00003527 ounces grams (g) 0.03527. ounces kilograms (kg) 2.205 pounds metric tons (mt) 2205.0 pounds metric tons 1.102 short tons kilocalories (kcal) 3.968 BTU Celsius degrees 1.8(C°) + 32 Fahrenheit degrees U.S. Customary to Metric inches 25.40 millimeters inches 2.54 centimeters feet (ft) 0.3048 meters fathoms 1.829 meters miles (mi) 1.609 kilometers nautical miles (nmi) 1.852 kilometers square feet (ft*) 0.0929 square meters acres 0.4047 hectares square miles (mi 2 ) 2.590 square kilometers gallons (gal) 3.785 liters cubic feet (ft:) 0.02831 cubic meters acre-feet 1233.0 cubic meters ounces (oz) 28.35 grams pounds (lb) 0.4536 kilograms short tons (ton) 0.9072 metric tons BTU 0.2520 kilocalories Fahrenheit degrees 0.5556(F° - 32) Celsius degrees vi
ACKNOWLEDGMENTS The cover is adapted from an illustration by Trudy Nicholson and is used with permission from Grass Medical Instruments and the artist. Figure 4 is reproduced with permission from the General Secretary of the Conseil Interna-tional Pour L'Exploration de la Mer. We are grateful for the review by Robert L. Dow, Maine Department of Marine Resources, Augusta.
vii
Figure 1. Hard clam.
(
HARD CLAM NOMENCLATURE/TAXONOMY/RANGE Gulf of St. Lawrence to Texas.
The hard clam is most abundant Scientific name . . . . Mercenaria from Massachusetts to Virginia.,
mercenaria L. Widely known as Venus It has been introduced to Europe mercenaria before Wells (1957) reas- and California. A similar spe-signed the species to the genus Lin- cies, M.. campechiensis, occurs neaus originally applied from North Carolina southward to Preferred common names . . Quahog in Mexico and is also called the the Northern United States, hard hard clam.
clam in the Southern United States (Figure 1)
Other common names . . . . Quahaug, MORPHOLOGY/IDENTIFICATION AIDS hard-shelled clam, round clam, cher-rystone clam, little-necked clam The hard clam has a thick shell Class ........ Bivalvia (Pelecypoda) with a violet border and short Order .... ....... Eulamellibranchia siphons (Verrill 1873; Stanley 1970; Suborder ........... .. Heterodonta Morris 1973). The mean length of the Family ....... .......... Veneridae thick solid shell is 60 to 70 mm, but some are 120 to 130 mm. The ratios of Geographical range: The hard clam oc- length (L), height (H) and width (W) curs in intertidal and subtidal are: L/H 1.25; H/W 1.52; L/W 1.90. The areas to depths of 15 m along the thickness index (ratio of shell volume Atlantic and gulf coasts from the to internal volume) is 0.60.
The external surface has numerous LIFE HISTORY concentric lines, conspicuous and closely spaced near the ends, more Spawning widely spaced around the umbo, espe-cially in younger shells. The center The spawning season extends from of each valve is smoother than the May through August, dependent on lati-distal portion. The umbo is anterior tude and temperature. In temperate and projects nearly to the front of latitudes the largest and densest the shell. The elliptical, somewhat spawns occur during July (Carriker pointed shell has a grayish-white 1961). In the York River, Virginia, exterior and a white interior with a the peak is in May, and is progres-dark violet border near the margins. sively later in Raritan Bay, New The colored part of the shell was Jersey, and Narragansett Bay, Rhode fashioned into wampum by the American Island (Jeffries 1964). Female hard Indians for use as money, hence the clams require 2 to 2.5 months to spawn scientific name. The interior ven- out completely, but the greatest re-tral margins are denticulate. lease of ,eggs is during the initial spawning of the season (Ansell 1967a).
The internal anatomy also has Spawning is more intense during neap distinctive characteristics. Short tides than spring tides, presumably siphons are united from their bases to because of higher temperatures during near the ends; the incurrent siphon neap tides (Carriker 1961).
has a short fringe of tentacles. The siphon tubes areyellowish- or brownish- Temperature is the decisive fac-orange toward the end and may be tor for final gamete maturation. In a streaked with dark brown or opaque 2-year study in the Lower Little Egg white. The foot is large, muscular, Harbor, New Jersey, the median daily and plow shaped. The mantle lobes are spawning temperature was 25.7°C with a separate along the front and ventral range of 22' to 3U°C (Carriker 1961).
edges of the shell with thin edges Seventy-three percent of the spawnings folded into delicate frills, some of occurred during 2 to 3 days of rising which are elongated near the siphons. temperatures. Kennish and Olsson Foot and mantle edges are white. (1975) cited 21' to 250 C as the re-quired or preferred temperature range.
Spawning in England takes places at REASON FOR INCLUSION IN SERIES 18° to 200C (Mitchell 1974). When threshold temperatures are reached, Hard clams are the most exten- males release semen that contains sively distributed commercial clam in pheromones. The pheromones are carried the United States and have the great- by water currents to the females, est total market value (Ritchie 1977). which are then stimulated to release Their occurrence in clean substrates eggs (Nelson and Haskin 1949).
accessible to the public makes the hard clam a popular recreational spe- Sexual maturity usually is cies. Their shore habitat is vulner- reached at 2 years of age (3 years in able to coastal construction projects many areas in the North Atlantic re-and pollution from urban. and indus- gion). The shell length at this age is trial development. The absence of between 32 and 38 mm. Size, not age, hard clam populations is an ecological determines sexual maturity, so that indicator of disturbances. Because slower growing individuals mature la-adults do not . move, repopulation of ter than 2 years of age. The peak of annihilated hard clam beds depends on reproductive potential is reached at transport of larvae and several years 60 mm; larger, older hard clams grad-growth. Hence, a temporary disturb- ually lose the reproductive capacity ance causes a long-term impact. (Belding 1931).
2
Fecundity and Eggs larvae are more evenly mixed in the water column.
The average number of eggs re-leased by a 60-mm female in the wild A shell gland forms opposite the is about 2 million (Belding.1931). In mouth by 24 hr after hatching, and a laboratory tests, the average-sized thin transparent shell is secreted; fem ale released 8 million eggs per the larva is now called a veliger season (Davis and Chanley 1956; Ansell (Belding 1931). The veliger drifts in 1967a). The fecundity of one large fe- ocean and estuarine currents with male was 16.8 million eggs, whereas limited ability to swim horizontally.
small clams (33 mm) had far fewer The veliger is able to move 7 to 8 eggs (Bricelj and Malouf 1980). About cm/min vertically by extending the 2,000 spermatozoa are shed for each ciliated velum (Mileikovsky 1973).
ovum. Vertical swimming may enable the veliger to control horizontal dis-The spherical eggs are 78 Pm in placement and thus travel to better diameter with closely packed yolk areas (Mileikovsky 1973). Vertical granules (Belding 1931). A large migration is stimulated by turbulence, gelatinous capsule distinguishes the which could bring veligers into water hard clam egg from the eggs of otner currents for transport (Carriker 1961).
mollusks. Eggs are released through Greatest numbers of veligers occur in the excurrent siphon, and the capsule the water column 3 hr after low tide swells after contact with water until (Moulton and Coffin 1954), which sug-it is 3.2 times the diameter of the gests differential tidal transport.
egg. The gelatinous capsule imparts By entering the water column on the buoyancy, so that the eggs are pelagic incoming tide, the veligers would be and carried by tidal and coastal cur- transported up the estuary and thus be rents. Spermatozoa swimming in water retained within the estuary. Veli-come into contact with and penetrate gers, however, also migrate upwards the capsule, fertilizing the egg. during daylight regardless of tide (Carriker 1961). Veligers are impor-At about 10 hr the embryo devel- tant zooplankters in estuaries during oping within the capsule becomes cov- the summer (Carriker 1952; Moulton and ered with cilia. The lashing of the Coffin 1954; Jeffries 1964). Densi-cilia tears the membrane and gelati- ties may exceed 500/1.
nous capsule; the ciliated gastrula escapes into the water. The egg may The veliger stage lasts 6 to 12 be carried 2 to 25 km from the spawn- days, depending on temperature. Meta-ing site. morphosis of the veliger occurs at 16 to 30 days at 18'C, 11 to 22 days at Larvae 24°C, and 7 to 16 days at 30%C (Loosa-noff et al. 1951).
The larva develops into a trocho-phore larva 12 to 14 hr after hatching Juvenile Seed Clam (Belding 1931). The shape, like a top, and the cilia onthe blunt ante- When the veliger becomes 2 to 3 rior end result in spiral swimming mm long, the shell thickens, a foot with rotation around the long axis in replaces the velum, and a byssal gland either direction. A functional mouth develops, marking metamorphosis to the develops and the larva commences feed- seed clam. Metamorphosis is inhibited ing on suspended particulates, espe- at salinities below 17.5 to 20 parts cially dinoflagellates. The larvae per thousand (ppt) (Castagna and Chan-concentrate near the surface during ley 1973), perhaps ensuring that seed daylight at about I m below the sur- clams avoid setting in an environment face (Carriker 1952). At night the with salinities unsuitable for adults.
3
Good sets occur in years with low 1973); without cover, seed clams freshwater inflow into the estuary largely disappear. Normally they do (Hibbert 1976). not occur in areas exposed. to wave action or strong currents (Anderson et The byssal gland secretes a tough al. 1978), but in ;, saltwater pond thread, the byssus, which anchors the they survived better on an unstable animal to the substrate. Seed clams bottom because crab predation was ab-set more densely in sand than mud sent (Carriker 1959).
(MacKenzie 1979); bits of shell or de-tritus may also serve as anchors. Dis- Adult tribution of adults sugqests that the average size of substrate particles The adult hard clam lives in the exceeds 2 mm diameter (Saila et al. substrate and burrows with a muscular 1967) although in the laboratory size foot. It remains in essentially the of sand grains was not associated with same location for the remainder of its setting (Keck et al. 1974). The seed life. In 38 days adults moved later-clams prefer setting on a firm surface ally an average of 5 cm and a maximum with a thin layer of detritus (Carri- of 15 cm from the place where seed ker 1952) or on shells coated with mud clams first bedded (Chestnut 1951).
(Carriker 1961). Clams 20 to 30 mm long traveled up to 30 cm in 2 months (Kerswill 1941).
The set may exceed 125 clams/M 2 in Thus, the adult habitat is determined good habitat (Carriker 1961) with ex- by where the juvenile beds.
traordinary sets of 270,000/m2 (Dow and Wallace 1955), but set is not Adults bury deeper in sand (mean necessarily related to adult concen- depth 2 cm) than in mud (mean depth 1 trations because of movements and cm), and small adults burrow deeper mortality. Seed clams seek a pre- than larger ones (Stanley 1970). If ferred habitat: a bottom with a few dug up, the hard clam reburrows, and small rocks and shells. They discern if covered, can escape upward (Belding between silt and sand in the labora- 1931). A 6.8-cm long clam moved ver-tory (Keck et al. 1974), explaining tically at 44 cm/hr (Kranz 1974). A the selection for sand in nature. clam can escape 10 to 50 cm of over-burden if the sediment dumped is the The seed clams begin a final mi- same as surroundings. Foreign sedi-gration to their ultimate habitat in ment reduces escapability.
their second summer (Burbanck et al.
1956). To move, the clam casts off The adult is found in the inter-the byssus and uses the foot for lo- tidal and subtidal areas of bays and comotion (Belding 1931). On finding estuaries. Hard clams are most abun-desirable conditions, the young clam dant in the lower estuary and are sel-spins a new byssus and reattaches it- dom found in the upper estuary (Turner self'to a small object. Byssal fibers 1953). In some locations they are ab-are used for anchorage for about a sent above the mean tide line (Hibbert year, until the young clam is 10 mm 1976). Greenwich Cove, Maine, had long; the juveniles then metamorphose about three times more clams at the and assume the burrowing habits of the. seaward end of the cove than in the adults. A population in Maine was upper cove (Tiller 1950). In Rand's displaced an average of 30 m by a Harbor, Massachusetts, about 50% of storm (Dow and Wallace 1955). the population was on the gravel slope, 25% in the muddy channel, and The habitat distribution of seed 25% in the subtidal zone (Burbanck et clams is altered by predation. Clams al. 1956). In South Carolina, the that set among oyster shells or stones hard clam is usually absent from open are protected (Maurer and Watling estuaries, but is present in small 4
channels and protected areas (Anderson Table 1. Hard clam landings in Maine et al. 1978). In Georgia hard clams and Massachusetts (Current Fishery are largely in intertidal areas pro- Statistics, National Oceanic and Atmo-tected from wave action (Godwin 1968). spheric Administration; Hutchinson and Loosanoff (1946) also mentioned intol- Knutson 1978; and R. L. Dow, Maine De-erance to rough waves. There are, how- partment of Marine Resources, Augusta).
ever, oceanic populations, e.g., in the shoals of Nantucket Sound (Turner Meat Weight (100 kg) 1953). Several reviews (Belding 1931; Year Maine Massachusetts Loosanoff 1946) state that hard clams 1931 898 NA1 occur to depths of 15 m; Burbanck et 1932 611 NA al. (1956) reported the maximum depth 1933 53 NA to be 8 m. 1935 8 NA 1937 60 NA 1938 250 NA COMMERCIAL/SPORT FISHERIES 1939 2 NA 1940 17 NA Fisheries 1941 540 NA 1942 555 NA The hard clam is harvested for 1943 358 NA commerce and recreation. It is more 1944 140 NA widely distributed than any other clam 1945 1,367 NA species in U.S. waters and is the most 1946 763 NA valuable commercial species (Ritchie 1947 437 NA 1977). The fishery is located chiefly 1948 1,310 NA along the mid-Atlantic Bight. North of 1949 2,675 NA Cape Cod (Figure 2) and in the Gulf of 1950 2,283 NA Mexico it is important only in isolat- 1951 2,580 NA ed areas (McHugh 1979). In Maine, for 1952 1,924 NA example, the only hard clam fishery 1953 1,520 NA was in Casco Bay with good year class- 1954 1,323 NA es in 1937, 1947, and 1952 (Dow 1955); 1955 1,133 NA the catch is now insignificant(Table 1). 1956 1,306 NA 1957 1,635 NA Hard clams are harvested commer- 1958 1,146 NA cially by bullrakes, hand tongs, and 1959 727 NA power dredges. The power dredge dis- 1960 290 6,355 turbs the substrate no more than bull- 1961 57 7,550 raking, and all evidence of harvesting 1962 5 5,983 disappears within 500 days (Glude and 1963 10 6,686 Landers 1953). A power dredge with an 1964 10 6,532 escalator caused only temporary dis- 1965 12 4,808 turbance of the substrate and in- 1966 >1 5,997 creased the catch of the more valuable 1967 NA 6,305 small clams relative to larger clams o1968 >1 5,221 (Godcharles 1971). Dredging, however, 1969 40 5,257 destroys seagrasses and benthic algae 1970 37 5,700 that recolonize dredged areas slowly; 1971 29 5,330 thus dredging has a long-term impact. 1972 31 4,84U 1973 14 5,611 The annual landings of hard clam 1974 >1 4,922 along the Atlantic seaboard average 1975 36 5,035 about 14 million pounds (McHugh 1979). 1976 14 4,296 All harvest reported is meat weight. 1 NA = Data not available.
The harvest in Massachusetts in 1970 5
Figure 2. Major populations of hard clam in the North Atlantic. region.
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was 532,000 ]b, worth $1,461,132 (Na- The number of seed clams that set tional Marine Fisheries Service 1979). in Little Egg Harbor, New Jersey was In the same year, Maine landed only estimated to be 125/mz (Carriker 605 lb. Hard clam harvest peaked in 1961). Populations of seed clams in New England in 1953, with 7.2 million restricted locations in Casco Bay, pounds (Dow 1977). The U.S. landings Maine, may reach 270,000/rm2 (Dow and declined between 1965 and 1975, con- Wallace 1955).
comitant with a 300% increase in value (Zakaria 1979). About 40% of the U.S. Adult population density varies harvest is from Great South Bay on widely depending on numerous environ-Long Island (MacKenzie 1977). mental factors discussed below. In Maine, populations in Boothbay Harbor 2
The price of the hard clam varies ranged from 4 /m 2 to 13/m (Tiller With their size and the season. The 1950). In Rhode Island, populations2 2 littlenecks (46 mm) command a higher in Greenwich Bay ranged from /m to 2
- price ($60/bu) than cherrystones (77 12/M (Stickney and Stringer 1957).
mm, $22/bu), or chowder clams (97 mm, Along the Georgia coast abundance
$13/bu)(Ritchie 1977). Hard clams are ranged from 0.1/mr2 to 21/mr2 (Godwin also processed and marketed as clam 1968). Introduced populations in Great juice. The market for fresh hard Britain reached densities of 6 to clams is made possible because the 8/M 2 (Ansell 1963). Biomass (meat clams remain al-ive for 1 to 3 weeks weight) ranged from 1.6 g/m 2 in poor out of water if kept cool. In con- habitat to 36 g/m 2 in good habitat trast, Mercenaria campechiensis does (O'Conner 1972). In Maine, populations not remain alive nearly as long out of of 2,000 bushels/acre (bu/A), 1,500 water even though it too has a thick bu/A, and 1,250 bu/A were estimated shell. in three areas (Dow 2 1952). Densities of 110/M 2 and 540/mr were mentioned.'
In heavily fished areas clams are harvested as soon as they reach a mar- Natural mortality is enormous in ketable size (Ritchie 1977), i.e., at the larval and seed clam stages, but 2 to 3 years old. Such harvest is the nil once the shell becomes thick best use of the resource because the enough to resist predators. Based on smaller clams are more valuable, and densities of different life stages, the larger clams grow more slowly. monthly mortality coefficients (Z)
Older clams are found only in areas of 1.7 for eggs and 1.5 for larvae that are not actively fished (Greene were calculated. The annual mortal-1979); here the maximum life span of ity coefficient from seed clam to 20 to 25 years may be reached (Belding adult was 3.0. Figures are avail-1931). able for calculating mortality coeffi-cients of natural populations. Based Population Dynamics on nine estimates, of adult mortality in England, an average annual mortal-Larval hard clams may be one of ity coefficient was calculated to be the most abundant plankters in estu- 0.80 (Hibbert 1976). The mortality aries. Population densities of 25/1 coefficient of adult clams held in (Carriker 1952) and 572/1 (Carriker trays and protected from predators 1961) have been measured. On the basis in South Carolina was 0.13 (Eldridge of these estimates and the bottom and Eversole 1982). These mortalities area, we calculated that there would represent natural mortality, which be 50,000 to 1.1 million larvae/m2 in equals the instantaneous total mortal-an estuary 2 m deep. About 6 million ity Z in the absence of harvest. Over-larvae are produced from spawning of winter mortality of hard clams in two the three pairs of adults found on a sites in Maine was 30% and 40% (Dow typical 1 m2 of bottom. 1965).
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Because of the method of fishing GROWTH CHARACTERISTICS described above, it was not possible to arrive at a meaningful estimate of The hard clam grows rapidly in fishing mortality F. Hard clams tend favorable environments. The veliger to be completely harvested in any par- larvae, grow from 10 Pm to 200 Pm in 7 ticular bed, resulting in instantan- days (Carriker 1952). At 18'C the lar-eous mortality of a different sort. vae increased from 105 Pm to 183 Pm in Mortality of sublegal hard clams was 20 days, whereas at 30 0 C they grew to estimated to be 30% each time a flat this size in 12 days (Loosanoff et al.
was disturbed by digging (Dow 1953). 1951). The daily percent growth rate of veligers as a function of tempera-ture and salinity is:
Survivorship follows an exponen-Growth =.-288 + 12.40T + 14.09S tial decay (Figure 3). Very few of the larvae successfully set, and few - 0.33T2 - 0.37S 2 + 0.24TS of the seed clams reach adulthood. The where T is the temperature in 'C and S mortality rate appears to decrease is the salinity in ppt (Lough 1975).
slightly in the adults. Obviously sur- At 20 0 C and 30 ppt, for example, the vivorship depends on the microhabitat daily growth would be 68%.
that individuals happen to occupy.
Survival of hard clams planted in Cas-Seed clams at the end of their co Bay, Maine, was 91% over one summer first summer are 2 to 4 mm in Canadian (Gustafson 1954). There is little re- waters, 5 to 7 mm in New York, and 16 lationship between stock size and re- mm in Florida (Ansell 1967b). The cruitment of young; a few adults pro- size reached depends largely on the duce sufficient offspring to sustain length of the growing season.
the populations.
The dependence of adult growth on the length of the growing season re-sults in a pronounced latitudinal ef-fect (Figure 4). The annual increment 11 N
0 12 0 seed clam 10-ddult° 5 10 15 Estimated Age Months Figure 4. The increase in shell length Figure 3. Survivorship of hard clams with age of hard clams from Florida, from eggs to adult, based on a com- North Carolina, New Jersey, Maine, and posite of the data cited in the text. Prince Edward Island (Ansell 1967b).
8
in shell length, estimated from Figure feeding (Tenore and Dunstan 1973).
4 during the 2 to 5 years of linear increase, was 10 mm in Canada, 13 mm Food and other materials are in Maine, 14 mm in New Jersey, and 23 taken in through the incurrent siphon.
mm in North Carolina. The annual rate Tentacles on the siphon detect exces-,
of shell formation was about the same sive concentrations or oversized par-between North Carolina and Florida. ticles in the water and cause the si-In Casco Bay, Maine, 20- to 2 5 -mm phon to close. The mantle, visceral clams increased by 13 to 16 mm in one mass, and gills are ciliated and sec-year, whereas 46- to 50-mm clams rete mucus. Particles brought in increased only 5 to 12 mm (Wallace through the incurrent siphon attach to 1952). The daily shell increment is the mucus. Deposits on the gills are about the same during peak growth re- collected by the cilia and carried to-gardless of latitude (Ansell 1967b), wards the mouth (Kellogg 1903). The again suggesting that it is the length palps at the mouth entrance determine, of the growing season that is decisive by volume, whether the particle mass in determining annual growth. will be ingested or rejected. Only small masses are selected for diges-Adult growth rate slows with tion. Complex patterns of cilia move-increase in length. Clams of 35- to ment remove the waste, called pseudo-39-mm length grow about three times as feces,-from palps and gills. Eventu-fast as clams that are 65 to 69 mm ally all waste materials are collected (Pratt and Campbell 1956). on the mantle and carried to the base of the incurrent siphon, avoiding the Of interest to clam managers is stream of incoming seawater. When the time required to reach the minimum sufficient waste has been collected, legal size, which in most states is the adductor muscle suddenly con-reached in about 3 years. In Massa- tracts, forcibly ejecting a stream of chusetts hard clams are about 3.5 water containing the waste mass from years old by the time they *reach the the incurrent siphon (Kellogg 1903).
50-mm legal size. In Rhode Island and Connecticut, where growth is faster, Predation clams reach the 4 4 -mm legal size in about 2.5 years. At the opposite ex- Predation is the primary natural treme, Florida has a size limit of 56 control of hard clam populations (Vir-mm, and clams reach this size in about stein 1977). It is preyed on by fish, 3 years. In Maine, however, the 51-mm birds, starfish, crabs, and other mol-size limit is not attained until about lusks. Its defenses are burrowing and 5 years. setting among shells or rocks. Without shell or rock cover the juvenile hard ECOLOGICAL ROLE clam is nearly exterminated by preda-tors. Survival in penned sites was 94%
Feeding Habits compared to 9% in an unpenned area (Kraeuter and Castagna 1980).
The adult hard clam feeds by fil-tering out plankton and microorganisms Crabs are the most serious pred-that are carried along the bottom by ators of hard clams. The crabs crush currents (Chestnut 1951). Ansell smaller clams with their claws, but (1967a) suggested that hard. clams chip the edges of the shells of larger depend on plankton abundance before clams. A rock crab (Cancer irruratus) and during spawning to furnish suffi- may consume 30 small clams/hr; a mud cient energy to ripen the gonads. If crab (Neopanope sayi), 14 clams/hr the food supply is inadequate, spawn- (MacKenzie 1971). Mud crabs may be as ing will not occur. Food densities of dense as 50/m . One reason crabs are 300.mg/l of carbon are optimal for effective predators is that they 9
2xtract the clam from the sediment. temperature and populations of adult The rock crab, blue crab (Callinectes hard clams.
sa idus), and green crab (Carcinides maenas) dig up the clams, whereas mud Spawning occurred over the range crabs bury themselves to crush the 220 to 300 C median daily temperature clam in place (MacKenzie 1977). Hard in Little Egg Harbor, New Jersey (Car-clams greater than 7 mm long are not riker 1961) and 210 to 25'C in Barne-vulnerable to mud crabs, and clams gat Bay, New Jersey (Kennish and Ols-longer than 15 mm are not vulnerable son 1975). Spawning generally oc-to rock crabs (MacKenzie 1977). curred during periods of rising tem-perature.
Mollusca are the next most impor-tant predators. Oyster drills (Urosal- The optimum temperature for lar-pinx cinerea and Eupleura caudata) and vae was 22.50 to 250 C in brackish wa-the moon snails (Polinices duplicata ter and 17.50 to 30'C at a higher sal-and Lunatia heros) drill holes 'in the inity (Davis and Calabrese 1964).
shell and remove the clam's body tis- Carriker (1961) stated that larvae sues. The whelks (Busycon canalicula- tolerated 13' to 30 0 C. Lough (1975) tum and B. caria) chip off the outer found that eggs required temperatures edge of the shell to make a hole above 7.2 0 C, but that larva, survival through which they insert their pro- was highest between 190 and 29.5 0C.
boscises and ingest the clam's soft Maximum growth occurred at 22.50 to parts by alternately rasping and swal- 36.5°C. Embryos and veliger larvae lowing (Carriker 1951). Hard clams developed abnormally and died at 15*C are vulnerable to oyster drills until and 330 C; hinged larvae tolerated 20 mm long and to moon snails until 50 these temperature extremes (Loosanoff mm (MacKenzie 1977). In addition, the et al. 1951). The minimum temperature adult hard clam may destroy its own for growth when clams were fed naked larvae by taking them through in the dinoflagellates was 12.5 0 C, but higher incurrent siphon. temperatures were needed to digest algae (Davis and Calabrese 1964).
The sea star (Asterias forbesi) Thus, temperature, salinity and food pulls the valves of adults apart with are all interrelated.
its-tube feet and inverts its stomach into the body cavity (MacKenzie 1979; The adult hard clam tolerates Doering 1982a). If a sea star is pre- temperatures from below freezing to sent, hard clams bury deeper (Pratt about 350 C. The adult can survive to and Campbell 1956; Doering 1982b). -60 C, but dies when 64% of the tissue Fish, such as flounder, and waterfowl water has changed to ice (Williams feed on larvae and young (Belding 1970). Hard .clams located in bars 1931). elevated above the gradient of the mud flats had 100% winter mortality, prob-ably because of freezing (Dow and ENVIRONMENTAL REQUIREMENTS Wallace 1951). Summer temperatures of 330 to 340 C are tolerated (Van Winkle Temperature et al. 1976; Mackenzie 1979).
Temperature is the most important Sublethal effects of temperature factor in growth and reproduction. The include little growth below IU°C harvest of the hard clam in Maine was (Pratt and Campbell 1956). Shell highly correlated (r = 0.80) to the growth ceases below 80C (Belding August sea temperature 2 years pre- 1931). The hard clam hibernates at viously (Sutcliffe et al. 1977). Dow temperatures of 5' to 60 C (Loosanoff (1977) recorded a high significant 1939). Pumping water required for correlation between mean annual sea feeding ceases below 6 0 C and above 10
32'C (Hamwi 1968). The extension of to 32 ppt; at 35 ppt only 10% develop-the siphon also indicates pumping; the ed (Davis 1958). Veliger survival was temperature range for siphon extension low during high rainfall (Carriker was I to 341C (Van Winkle et al. 1961). Veliger growth was best at 20 1976). The limits for growth also may to 27 ppt. Castagna and Chanley (1973) depend on the type of food. stated that larvae required higher salinities than adults and noted that Estimates of the optimum tempera- metamorphosis to seed clams did not ture for hard clam growth vary from occur below 17.5 to 20 ppt. Embryos about 23'C (Pratt and Campbell 1956) developed normally between 20 and 35 to about 20% (Ansell 1967b). An opti- ppt, with an optimum at 27.5 ppt. The mum mean annual temperature of 10'C minimum salinity for larvae was 15 was cited by Dow (1977). Other biolog- ppt. In Southampton Water, England, ical activities may indicate thermal young occurred only in years of low optima. Hamwi (1968) found maximum freshwater inflow from the River Test pumping at 240 to 26'C. Siphon exten- (Mitchell 1974).
sion was greatest in the range of 11%
to 22% (VanWinkle et al. 1976). There were two optima for shell calcium dep- Juveniles and adults close their osition: 13° to 16'C, and 24'C (Storr shells during episodes of diluted sea-et al. 1982). The optimum range for water and hence tolerate low salini-burrowing is 210 to 31'C (Savage ties. Juveniles remained alive in 1976). freshwater for 22 days in the labora-tory (Chanley 1958). At 10 ppt they Hard clams are adversely affected began dying at 28 days; at 1U and 15 by rapid temperature changes. Rapid ppt there was little feeding or bur-temperature fluctuations of + 5'C in rowing. Burrell (1977) reported that the discharge from a nuclear power adult hard clams exposed to salinities plant have caused breaks in shell as low as 0.3 ppt in the Santee River growth (Kennish 1976). Summer growth system, South Carolina, survived for was reduced 60% to 90% in hard clams 14 days; less than 5% died because of transplanted to this discharge site. heavy freshwater runoff. Pumping in the laboratory ceased below 15 ppt and Salinity above 40 ppt, with maximum pumping at 23 to 27 ppt (Hamwi 1968). The siphons The hard clam occurs in environ- were rarely extended in the laboratory ments with salinities ranging from at salinities below 17 ppt and above about 10 ppt to about 35 ppt, with 38 ppt (VanWinkle et al. 1976). The possible geographic difference. optimum salinity range for siphon ex-Belding (1931) cited 23 to 32 ppt as tension was 24 to 32 ppt. The slight-the general range of tolerance. In ly different findings noted above are Wellfleet Harbor, Massachusetts, sal- probably a result of temperature-inity ranged from 20 to 34 ppt (Curley salinity interactions. Davis and et al. 1972). The normal range of Calabrese (1964) reported an optimum salinities given by MacKenzie (1979) salinity for larvae of 27 ppt. At re-was 15 to 35 ppt. In South Carolina duced salinities, e.g., 22.5 ppt, the hard clams do not usually occur below temperature tolerance was reduced.
18 ppt (Anderson et al. 1978). Nat- Lough (1975) also measured a strong ural beds occur at salinities of 10 to interaction between temperature and 28 ppt (Loosanoff 1946). salinity; maximum survival of eggs was above 28 ppt and above 7.2'C and of Salinity appears to be most larvae, between 21 and 29 ppt at 190 critical dur ing the egg and larval to 29.5'C. The larvae grew best be-stages. The embryos in Long Island tween 21.5 and 30 ppt at 22.50 to Sound develop only in the range of 20 36.5 0C.
11
)
Dissolved Oxygen A series of studies indicate that larvae prefer to set on sand rather Changes in dissolved oxygen do than mud. Larvae set more densely on not affect hard clams as much as sand than on mud (MacKenzie 1979), and changes in temperature and salinity. Keck et al. (1974) found an associa-All life stages tolerate nearly anoxic tion between grain size and setting; conditions for long periods, but may 781 set on mud of 0.05-mm diameter, cease growing. Embryos require only whereas 2,083 set on sand of O.SU mm.
0.5 mg/l dissolved oxygen and die only There was not much difference in set-at oxygen levels below 0.2 mg/l (Mor- ting between sand grain sizes of 0.25, rison 1971). Embryos at 0.34 mg/i fail 0.50, 0.71, and 1.00 mm. Larvae dis-to develop to the trochophore stage. criminated between sand (0.25 mm) and Larval growth is nearly zero at such mud (0.05 mm). The highest concentra-low oxygen levels. Growth occurs at tion of seed clams was on shells coat-2.4 mg/l but is best at 4.2 mg/l. ed with mud (Carriker 1961). The young can emerge from a depth of sediment at Adults have tolerated low oxygen least five times their shell height.
in the laboratory, but metabolism was depressed. The hard clam can tolerate Abundance is related to substrate less than I mg/l for 3 weeks and still type. -Twice as many hard clams were be capable of reburrowing (Savage in gravely substrate as in mud (Bur-1976). Growth is surpressed at low banck et al. 1956). The biomass of oxygen. Below 5 mg/l, oxygen consump- clams depended on substrate: sand, tion progressively declines and an 25.5 g/m 2 ; sand without vegetation, 34 oxygen debt is incurred (Hamwi 1969). g/m 2 ; sand with vegetation, 11.3 g/m 2; 2 The oxygen debt is rapidly repaid in a and sand with clayey silt, 1.6 g/m few hours after return to aerobic con- (O'Conner 1972). Allee (1923), how-ditions. Ultimately,, hard clams suc- ever, reported a relative distribution cumb to hypoxic environments. Hard of hard clams of 14 in sand, 19 in clams nearly disappeared from a eutro- mud, 2 in gravel, I in eelgrass, and 4 phic environment near a duck rearing in rockweed. Dow (1955) found hard area on Long Island, New York (O'Con- clams only in sand-clay-silt, and ner 1972). states that in the North Atlantic region sand substrate is not the usual Substrate habitat for the hard clam; they are more often found in mud.
Substrate is obviously important to a species that burrows, and numer- The growth of the hard clam is ous studies have shown that hard clams reflected by the substrate type. Clams are associated with a sandy bottom grew 50% faster in sand than in mud rather than a mud bottom (Allen 1954; (Greene 1975). Clams placed in sand Maurer and Watling 1973; Mitchell grew 24% faster than those placed in 1974). Water circulation may be the mud (Pratt 1953). There was a high decisive element in the distribution correlation (r = 0.88) between shell of hard clams (Greene et al. 1978). length and substrate particle size Because water currents sort bottom (Johnson 1977). The distribution of substrates, the correlation between hard clams has been related to abun-currents. and bottom type is high. dance of particle size greater than 2 Without attempting to determine mm (Saila et al. 1967).
whether substrate or current is more important, we will review the rela- Currents tionships between each and hard clam distribution. Even if substrate per Water movement is important to se is not critical, it does serve as all life stages of the hard clam. Cur-an index to water currents. rents transport eggs and larvae and 12
bring food to the adult. turbidity than are embryos. Ninety percent of the larvae died at concen-Larvae occur in currents of 12 to trations of chalk above 0.25 g/l and 130 cm/sec (Carriker 1952). Carriker of Fuller's earth above 0.5 g/l (Davis (1961) found lower densities near the 1960). The larvae, however, tolerated inlet of an estuary where tidal ex- silt of 4 g/l, and in fact, grew change was greatest. The planktonic faster in low concentrations of silt distribution of larvae was not affect- than did controls in silt-free water.
ed by individual tidal stages, but Growth was depressed by 0.5-g/l clay summing all observations suggested (Davis and Hidu 1969).
greatest numbers 3 hr after low tide (Moulton and Coffin 1954). Little is known about the effects of turbidity in adults, despite the The growth of adults is correlat- postulation of adverse effects on ed with tidal currents (Kerswill 1949; theoretical grounds. Menzel (1963)
Haskin 1952; Wells 1957). Hard clams mentioned that high turbidity in grew better at a velocity of 7.5 summer may have inhibited growth in cm/sec than in a sluggish slough Florida. Pratt and Campbell (1956)
(Kerswill 1949). Very strong currents, hypothesized that processing of par-however, may scour the bottom and ticles accounted for the reduced reduce habitat quality (Wells 1957). growth they observed in muddy habi-tats. Adults in mud expelled pseudo-Turbidity feces 107 times/hr; in fine sand, 19 times/hr; and in coarse sand, 7 times/
Because hard clams filter water hr. Rhoads et al. (1975), however, to obtain food they also collect other believed that a turbid layer near the suspended material. Processing this bottom in Buzzards Bay, Massachusetts, material requires energy and clogs the enhanced the growth of hard clam. The filtering apparatus (Pratt and Camp- layer probably contained detrital food bell 1956). Turbidity can thus reduce utilized by the clams.
the growth of hard clams. The eggs and larvae are also sensitive to turbidity. Habitat Alteration Embryos developed normally in the Dredging may reduce populations presence of silt or sediment except at of hard clams. Hard clams in the path high concentrations of these suspen- of a dredged channel though a lagoon sions (Davis 1960). Some embryos de- on Long Island, New York were destroy-veloped normally with 4 g/l of clay, ed (Kaplan et al. 1974). Hard clams chalk, or Fuller's earth, but the num- that were not directly disturbed and ber developing decreased as the con- were further than 400 m from the centration increased above 0.75 g/l. dredge site were unaffected. Commer-Silt above 3 g/l impeded development. cial clammers in this area reported no Sand had little effect on eggs except noticeable reduction in harvest the for the smallest particles at the following year, whereas scientists highest concentrations (Davis and Hidu found a significant reduction in 1969). Development was normal at 2 standing crop. In Boca Ciega Bay, g/l of particle sizes between 5 and 50 Florida, the hard clam population Pm diameter. failed to return to previous pop-ulation level after dredging (Taylor Larvae are more sensitive to and Soloman 1968).
13
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Prawel. 1982. Effects of tempera-Pratt, D.M. 1953. Abundance and growth ture on calcium deposition in the of Venus mercenaria and Callo- hard-shell clam Mercenaria merce-cardia morrhuana in relation to naria. J. Therm. Biol. 7(1--):57-the character of bottom sedi-ments. J. Mar. Res. 12(l):60-74.
Sutcliffe, W.H.,Jr., K. Drinkwater, Pratt, D.M., and D.A. Campbell. 1956. and B.S. Muir. 1977. Correlations Environmental factors affecting of fish catch and environmental growth in Venus mercenaria. factors in the Gulf of Maine. J.
Limnol. Oceanogr. T(1):2-17. Fish. Res. Board Can. 34:19-30.
Rhoads, D.C., K. Tenore, and M. Taylor, J.F., and C.H. Saloman. 1968.
Browne. 1975. The role of re- Some effects of hydraulic dred-suspended bottom mud in nutrient ging and Coastal development in cycles of shallow embayments. Boca Ciega Bay, Florida. U.S.
Pages 565-579 in L. E. Cronin, Fish Wildl. Serv. Fish. Bull.
ed. Estuarine research. Vol. 1. 67(2):213-241.
Chemistry, biology, and the estu-arine system. Academic Press, Tenore, K.R., and W.M. Dunstan. 1973.
18
Comparison of feeding and biode- England in 1871 and 1872. U.S.
position of three bivalves at Comm. Fish., Washington, D.C.
different food levels. Mar. Biol.
(Berlin) 21:190-195. Virstein, R.W. 1977. The importance of predation by crabs and fishes on Tiller, R.E. 1950. Greenwich Cove Sur- benthic infauna in Chesapeake vey. U.S. Fish Wildi. Serv. Clam Bay. Ecology 58(6):1199-1217.
Invest. Conf. Clam Res. 1:18-19.
Wallace, D.E. 1952. Age determination Turner, H.J.,Jr. 1953. A review of the and growth rate of soft clams and biology of some commercial mtol - quahogs in Maine. U.S. Fish luscs of the east coast of North Wildl. Serv. Clam Invest. Conf.
America. Sixth Rep. Invest. Clam Res. 3:1-3.
Shellfish Mass., Mass. Dep. Nat.
Resour. Div. Mar. Fish: p. 39-74. Wells, H.W. 1957. Status of the name Venus. Ecology 38(l):160-161.
Van Winkle, W., S.Y. Feng, and H.H.
Haskin. 1976. Effect of tempera- Williams, R.J. 1970. Freezing toler-ture and salinity on extension of ance in M tilus edulis. Comp.
siphons by Mercenaria mercenaria. Biochem. hysiol. 35IT)T45-161.
J. Fish. Res. Board Can.33(7T:
1540-1546. Zakaria, S.P. 1979. Depuration as it relates to the hard shell clam of Verrill, A.E. 1873. VIII.- Report Narragansett Bay, Rhode Island.
upon the invertebrate animals of Pages 109-119 in Proceedings of Vineyard Sound and the adjacent the Northeast clam industries:
waters, with an account of the management for the future. Ext.
physical characteristics of the Sea Grant Advisory Program, region. Pages 295-522 in Report Univ. Mass. and M.I.T. Sea Grant on the condition of the sea fish- Program, SP-112.
eries of the south coast of New 19
50272 -101 I 3. Pec.t,.,nts AccCsson No REPORr DOCUMENTATION i1. R:PORT NO.
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PAGE FWS/OBS-82/11.18* _
- 4. Tit," no Subtitle 5. Report Det*
Species Profiles: Life Histories and Environmental Requirements October 1983 of Coastal Fishes and Invertebrates (North Atlantic) -- Hard Clam 6.
- 7. Author(,) 6. P ,0orm.n9 01gantzi~ln R9t). No.
Jon G. Stanley and Rachael DeWitt
- 9. Pdor.,mng Organ;z.,on N.-mne and A 10. roje/t/oTask/Wok Unit No.
U.S. Fish and Wildlife Service Maine Cooperative Fishery Research Unit ltQ1I. CotrC3(C1orGqanttG) No.
313 Murray Hall (C)
University of Maine (G)
Orono, ME 04469
- 12. Spon-orng Oga-li-tio 14- te -nd Address 13. Typt of RoporT Pý1i~d Co-trd National Coastal Ecosystems Team U.S. Army Corps of Engineers Fish and Wildlife Service Waterways Experiment Station U.S. Dept. of the Interior P.O. Box 631 14.
Washinoton. DC 20240 Vicksburg, MS 39180
- U.S. Army Corps of Engineers report No. TR EL-82-4.
It. ktsltaC1 (LimsIt: 200 -OroS)
Species profiles are literature summaries on the taxonomy, morphology, range, life history, and environmental requirements of coastal aquatic species. They are designed to assist in environmental impact assessment. The hard clam, Mercenaria mercenaria, is the most exten-sively distributed commercial clam in the United States, but at the northern end of its range in the North Atlantic region it has large fluctuations in population. Spawning occurs in estuaries for 6 to 12 in summer at 180 to 30'C. Eggs and larvae are carried by currents days, and then seed clams set on sand or pebbles. Seed clams that lack cover of shells or stone largely perish because of predation. Adults filter feed on phytoplankton. Adults survive temperatures of 170 to 30%C and salinities of 10 to 35 ppt, but can withstand freshwater for several days by closing the shell. When the shell is closed they must tolerate anoxic conditions, and they survive less than 1 mg/l oxygen in the water for several days. Even the larvae tolerate 0.5 mg/l of oxygen.
7.CoC-net Anatyl. 1. -1WI Estuaries Clams Growth Feeding
- b. lotnit:fter /(,en-Ended Tefens Hard clam Spawining Mercenaria mercenaria Habi tat Salinity requirements Temperature requirements Fisheries I COS A.T Field/G M...
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REGION I REGION 2 REGION 3 Regional Director Regional Director Regional Director U.S. Fish and Wildlife Service U.S. Fish and Wildlife Service U.S. Fish and Wildlife Service Lloyd Five Hundred Building, Suite 1692 P.O. Box 1306 Federal Building, Fort Snelling 500 N.E. Multnomah Street Albuquerque, New Mexico 87103 Twin Cities, Minnesota 55 111 Portland, Oregon 97232 REGION 4 REGION 5 REGION 6 Regional Director Regional Director Regional Director U.S. Fish and Wildlife Service U.S. Fish and Wildlife Service U.S. Fish and Wildlife Service Richard B. Russell Building One Gateway Center P.O. Box 25486 75 Spring Street, S.W. Newton Corner, Massachusetts 02158 Denver Federal Center Atlanta, Georgia 30303 Denver, Colorado 80225 REGION 7 Regional Director U.S. Fish and Wildlife Service 1011 E. Tudor Road Anchorage, Alaska 99503
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