ML20096D377
| ML20096D377 | |
| Person / Time | |
|---|---|
| Site: | Pilgrim |
| Issue date: | 12/31/1991 |
| From: | Wagner E BOSTON EDISON CO. |
| To: | MASSACHUSETTS, COMMONWEALTH OF |
| References | |
| BEC-92-50, BEC0-92-050, NUDOCS 9205180012 | |
| Download: ML20096D377 (385) | |
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. ROSTONEDISON 76 Braintree Hd Othcn Pan Brainuee Manachusette o7184 April 29, 1992 E. J. Ww - BECo 92-050 vu .ww.m .
Nocker Engneerng NPDES Program Operations Section (HCP) Environmental Protection Agency P.O. Box 8127 , Boston, MA 02114 RP_ DES PERMIT MARINE ECOLOGY HONITORING REFORT
Dear Sirs:
.In accordance with Part I, Paragraphs A.8.b & e, and Attachment A. Paragraph I.F. of the Pilgrim Nuclear Power Station W ES Permit No. S',0003S57.(federal) and No. 359 (State) Semi-Annual Marine Ecology R3 port No. 39 is submitted.
This covers the period from January through December 1991. lb [ 0 Lt LtN t' r E. J. Hagner
Attachment:
Semi-Annual Marine Ecology Report No. 39 RDA/ cab /6287 I b
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-9205180012 911231 PDR ADOCK 05000293 : d' i R PDR
1 0 L BOSTON EDISON 25 Biaintree R4 Othce Paik Braintice Massachusetts o2184 l April 29, 1992 E. J. Wegnw vo neseent BECo 92-050 . Nsciur Engnoirme l Hass. Division of Hater Pollution Control Regulatory Branch - 7th floor One Winter Street l Boston, MA 02108 EQ{S PERMIT PMINE ECOLOGY HONITORING RFPORT
Dear Sirs:
In accordance with Part I, Paragraphs A.8.b & e, and Attachment A, Paragraph 1.F. of the Pilgrim Nucicar Power Station NPDES Fermit No. MA0003557 (Federal) and ho. 359 (State). Semi-Annual Marine Ecology Report No. 39 is submitted. This covers the period from January through December 1991, t e E. J. Hagner '
Attachment:
Semi-Annual Marine Ecology Report No. 39 RDA/ cab /6287 W i 3 cc: Hass. Division of-Water Pollution Control Lakeville Hospital
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Lakeville, MA 02346 l' w. (
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![ marineecologg/tudief y Reloted to Operotion ofPilgrim/totion l SEMI-ANNUAL REPORT NUMBER 39 'Y JANUARY 1991 - DECEMBER 1991 A_
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I I BRINEEC0LOGYSTUDIES l RELATEDTOOPERATIONOfPILGRIMSTATION I SEMI-ANWVALREPORTN0.39 g l REPORTPERIOD: JANUARY 1991THROUGHDECEMBER1991 g DATEOfISSUE: APRIL 30,1992 l E 1 E I I compiled and Reviewed by: , <[h.se , F li0kant?"eriesemeest I I E LI
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I VABLE OF CONTENTS SECTION I
SUMMARY
II INTRODUCTION III MARINE BIOTA STUDIES g IIIA Marine Fisheries Monitoring IIIA.) Annual Report on Monitoring to Assess !mpact of the Pilgrim Nuclear Power Station on the Marine Fisneries Resources of Western Cape Cod Bay, January - December 1991 (Characteriza-I tion of Fisheries Resources) - (Mass. Dept. of Fisheries, Hildlife and Environmental Law Enforcement; Division of Marine Fisheries) IIIA.2 Annual Report on Monitoring to Assess Impact of the Pilgrim Nuclear Power Station on the Marine Fisheries Resources of Western Cape Cod Bay, January - December 1991 (Impact on I Indicator Species) - (Mass. Dept. of Fisheries, Hildlife and Environmental Law Enforcement; Division of Marine Fisheries) g IIIB Benthic honitoring and Impact IIIB.1 Benthic Algal and Faunal Monitoring at the Pilgrim Nuclear Power Station, January - 9ecember 1991 (Characterizat' n of i Benthic Communities) - (Science Applications International Corp.) I III.B.2 Benthic Algal and Faunal Monitorlag at the Pilgrim Nuclear Power Station, January - December 1991 (Impact on Benthic Communities) - (Science Applications International Corp.) IIIC Entrainment Honitorina and Impact IIIC.1 Ichthyoplankton Entrainment Monitoring at Pilgrim Oclear I Power Station, January - December 1991 (Results) - (Marine Research, Inc.)
-l IIIC.2 Ichthyoplankton Entrainment Monitoring at Pilgrim Nuclear Power Station, January - December 1991 (Impact Perspective)
- (Marine Research, Inc.)
IIID Impingement Monitoring and Impact
< Impingement of Organisms at Pilgrim Nuclear Power Station: January
- December 1991. (Boston Edison Company) q I I ii I
I
SUMMARY
Highlights of the Environmental Surveillance and lionttoring Program re-sults obtained over this reporting period (January - December 1991) are presented below. (Note: PHPS was operating at normal power level from January - December 1991 with the exception of outages during most of the Hay-August period and in November.) I M4rioellihert1LB0JLLt0LLOg: 1 In the mid Hay-August 1991 shorefront sportfish survey at Pil- - grim Station, 1,492 angler visits accounted for 900 fishes caught. Bluefish (71%) and cunner (27%) dominated the sportfish catch. The presence of a strong thermal discharge component Juring most of 1990 and 1991 resulted in good I sportfishary success compared with outage and low power years covering the shorefront angling season.
- 2. Pelagic fish mean CPUE (Catch Per Unit Effort) for 1991 at the gill net station (32.3 fishes / set) increased 20% from 1990 to the second lowest level recorded since 1971. Pollock (41%) and Atlantic herring (23%) were 64% of the total catch. Both Atlantic herring and pollock increased from 1990. A significant positive correlation was found for cunner catch (third highest in 1991) and seasonal, Pilgrim Station operational output (thermal loading to the environment) prior to 1985.
I I I-l
I
- 3. Shrimp trawl catch for 1991 recorded 21 benthic fish species with Atlantic herring (60%), winter flounder (15%), and little skate (9%) composing 84% of the total. Mean CPUE for all spettes was 0.1 (lowest) at the Warren Cove station, 10.4 (highest) at the Priscilla Beach station and 3.9 (same as 1990) for all stations pooled in 1991. The presence of a large numocr of Atlantic herring caught off Priscilla Beach during one trawl made in the spring influenced CPUE index ,
interpretations. l
- 4. Adult lobster mean nonthly catch rate per pot Saul, in May -
1!l October 1991, was 0.37 lobsters which i s 16% lower than the 1990 rate (0.44). The surveillance area (thermal plume) catch l rate was 0.35 while the reference area (control) was also i 0.35. A significant negative correlation was noted between legal lobster c at t.h rate for thermal plume areas, and mean seasonal (May - November) Pilgrim Station output for the period from 1973 - 1983, but not when 1985, 1990 and 1991 data were included. The legal lobster catch rate tur I preoperational/ outage years has not becn significantly lower in the thermal plume area than in control areas. The lobster research study, which commenced in 1986, found significant negative correlations t'etween plant HDC and sublegal catch rates at stations closest to the discharge canal and no significant relationship between Pilgrim operation and legal catch in 1991. I I I-2 g
i
- 5. In May - October 1991 fish observational dive surveys, 8 species were observed in the thermal plume area. Cunner (64%), striped bass (13%), bluefish (11%) and tautog (10%) were the most numerous fishes seen, the latter three species being l most abundant in the direct path of the Pilgrim disc.harge current. Total number of fishes observed was 25% lower than in 1990. Most fishes were in greatest concentrations at stations in the discharge zone (61%), followed by the control zone (28%)
and the stunted zone (101). These results were different than - 1984/1987/1988 (outage years with reduced discharge current), when most fish were observed relatively evenly divided between
- discharge and control zones, and similar to 1985/1986/1989/1990 (higher discharge current years) when fish seemed to greatly favor being in the path of the effluent.
I 6. Atlantic silverside accounted for 46% of the 1991 haul seine (shore zone) fish catch with a total of 27 species collected. The PNPS intake showed higher species diversity compared to I exposed coastal stations, fish captured in the PNPS Intake embayment were greatly dominated by Atlantic nerring, particularly during early summer when a large school of jiuveniles accounted for a major fish impingement incident. A deeper seine net (10' compared to 6'), to more effectively sample the intake, was utilized beginning in 1984 and results have generally indicated this area i s more similar in fish fauna attraction to an estuary than exposed coastal areas. I E m g
I
- 7. A total of 738 cunner were tagged in 1990/1991 and 53 (7%)
i recovered in the Pilgrim incinity. Time at large and locations of recovered fish indicate that movement of this species is local which reflects its residential nature. I linpJngementlonitorJng:
- 1. The mean January - December 1991 impingement collection rate was 6.27 fish /hr. The rate ranged from 0.18 fish /hr (August)
^
to 24.57 fish /hr (July) with Atlantic hcrring comprising 75.47. of the catch, followed by Atlantic silverside 8.7%, Atlantic menhaden 3.6%, winter flounder 2.1% and grubby 1.5%. Fish impingement rates in 1985, 1986 and 1989 - 1991 were several times hinher than in 1984, 1987 and 1958 when Pilgrim Station outages had both circulating water pumps off for various periods of time, g
- 2. In June and July 1991, Atlantic herring impingement accounted for 98% of this species annual collection. They have been the most abundant species impinged on an annual basis at Pilgrim Station in only two other years, 1986 and 1976.
- 3. A large, fish impingement incident was notea from July 22-25 when a rate of 52.29 Atlantic herring /hr. was recorded, resulting in an estimated mortality of over 4,000 juvenile';.
- 4. The mean January - December 1991 invertebrate collection rate I
was 1.40+/hr with jellyfish and blue mussels dominating, and comm n starfish a'id sesenspine bay shrimp accounting for 25.4% and 22.3% of the enumerated catch, respectively. Fifty-four I-4 g
I American lobsters were sampled. The invertebrate impingement rates in 1985, 1986 and 1989 - 1991 were 'imilar to those recorded at Pilgrim Station during the 1987 and 1988 outage years, despite lower circulating water pump availability in the outage years.
- 5. Impinged fish, initial survival at the end of the Pilgrim Sta-tion intale slutteway was approximately 57% during stati: screen washes and 50% during continuous washes. Three of the dominant -
l species showed greater than 50% survival, overall. , Fi sh__ Surveil l ante: Fish overflights in 1991 spotted all four major species I categories: herring, Atlantic menhaden, At! antic mackerel and baitfish. Eloht sightings of fish in the nearfield Pilgrim vicinity were made, mostly Atlantic herring. On both August ;5 and 24 over 100,000 pounds of this species, and on Ane 26 300,000 pounds of menhaden, were observed within a few miles or Pilgrim Station. None of these occurrences were reported to regulatory authorities as they were not within 1/2 mile of the discharge canal. l BRDtlLiLliolli1QLing:
- 1. No new taxa of invertebrates were added to the list of biota for PNPS benthic surveys as a result of analysis of the 1991 samples. A toto of 107 species were recorded (28%
polychaetes, 28% mollusks, 32% crustaceans). I I-5
1 I'
- 2. No notable difference in species richness existed between the Effluent and Reference stations based on results of fall 1988 -
spring 1991 sampilng. The reference stations, which have J.aracteristically ranked ahead of the Effluent station in ipecies numbers, appeared more similar to the discharge area in late 1988 - early 1991 indicating a lack of respons to PNPS thermal effluent effects. Habitat mooiilcations by mussel population fluctuations may account, inpart, for the highest , number of species recorded anywhere, at the effluent station in fall 1991. g
- 3. Review of overall faunal connunity structure, via cluster an-alysis, showed that the Effluent Station had a low degree of similarity compared with the reference stations in spring 1991, but higher in the fall. In contrast, faunal clusterings and algal community overlap / biomass values showed a general recovery of benthic community structure at the Fffluent site compared with reference sites during the three year outage ended in early 1989.
- 4. The warm-water species, GGL.'larl4 ilkuhlae, decreased in the I
area of the Effluent station during 1986, was completely absent in 1987 and 1988, and reappeared in the fall of 1989 - 1991 dur ag PNPS operation. It was also rare in 1984, before it normally colonized in 198S, indicating a direct relationship to the lack of thermal effluent in 1984, 1986, 1987 and 1988. Additional evidence of PNPS impacts
- he Effluent discharge zone was the prevalent appearance of the cold-water alga, I
I-6 g
I Laminatla, in the Effluent area only during outage years (1984, 1987. 1988) and the spring of 1989 transect surveys. ' l 5. Four observations of the near-shore acute impact zones were performed during this reporting period. Denuded and stunted zone boundaries were indistinguishable during September 1987 - June 1989 discharge surveys as a result of the PNP 5 shutdown. These surveys noted delineated, denuded impact areas in fall L I 1989 - 1991, primarily because two circulating water pumps were in cperation most of the time, resulting in maximum discharge current flow. The area of PNPS-induced Scouring impacts varied t from 1,080 m2 (October) to 1,320 m2 (March) in 1991.
' Enitainment 110al10 ring:
- 1. A total of 34 species fish eggs and/or larvae were found in the January - December 1991 entrainment collections (21-eggs, 30-larvae).
- 4. Seasonal egg collections for 1991 were dominated by Atlantic cod and American plalce (winter - early spring);
Atlantic mackerel and labrids (late spring - early summer); windowpane and rockling/ hakes (late summer - autumn).
- 3. Seasonal larval collections for 1991 were dominated by rock gunnel and sculpin (winter -
early spring); Atlantic
.I mackerel and radiated shanny (late spring - early summer);
cunner and fourbeard rockling (late summer - autumn). I l I-7
I
- 4. No lobster larvae were collected in the entrainment samples for 1991.
- 5. In 1991 an estimated 1.326 x 109 fish eggs and 2.887 x 108 fish larvae were entrained at Pilgrim Station, assuming iull flow capacity of all seawater pumps. On an annual l
basis, eggs were dominated by Atlantic mackerel and the labrid - Pleuronettes group, and larvae by tunner and sculpin spp.
- 6. Total numbers of fish larvae collected for similar volumes I
of water sampled, in spring and summer 1984 and 1987, were noteably lower than for ti similar periods in 1983, 1985, 1986 and 1988 - 1991. These results were shown significant I to the fact that both Pilgrim Station circulatine water g pum:15 were offline during most of the spring / summer period 1984/1987, but at least one circulating water pump was operating during the majority of this period in the other g years. N
- 7. On no occesions in 1991 were "unusuaily abundant" I
ichthyoplankton densities recorded in samples, as defined - by the entrainment contingency sampling plan. I I t I1 I-8 g
I INTRODUCTION A. Scope and Obiective l This is the thirty-nineth semi-annual report on the status and results of the Environmental Surveillance and Monitoring Program related to the operation of Pilgrim Nuclear Power Station (PNPS). The monitoring programs discussed in this report relate specifically to the Cape Cod Bay ecosystem with particular emphasis on the Rocky Point area. This is the twenty-seventh semi-annual report in accordance with the environmental monitoring and reporting requirements of the PNPS Unit 1 NPDES Permit from the U.S. Environ-mental Protection Agency (#MA0003557) and Massachusetts Division of Hater Pollution Control (#359). A multi-year (1969-1977) report incorporating marine fisheries, benthic, plankton /entrainment and impingement studies was submitted to the NRC in July 1978, as required by the PNPS Appendix B Tech. Specs. Programs in these areas have been continued under the PNPS NPDES permit. Amendment #67 (1983) to the PNPS Tech. Specs. deleted Appendix B non-radiological water quality I requirements as the NRC felt they are covered in the NPDES Permit. I The objectives of the Environmental Surveillance and Monitoring Program are to determine whether the operation'of PNPS results in measurable effects on the marine ecology and to evaluate the significance of any observed ef-fects. If an effect of significance is detected. Boston Edison Company has committed to take steps to correct or mitigate any adverse situation. 1 11-1 1
3 . I These studies are guided by the Pilgrim Administrative-Technical Committee G ATC) which was chaired by a member of the Mass. Division of Water Dollu-tion Control in 1991, and whose membership includes representathes f rom the University of Massachusetts, the Mass. Division of Water Pollution Con-trol, the Mass. Division of Marine Fisheries, the National Marine Fisheries Service (NOAA), the Masc. Office of Coastal Zone Management, the U.S En-vironmental Protection Agency and Boston Edison Company. Copies of the Minutes of the Pilgrim Station Administrative-Ter.hnical Committee meetings held dt.'ng this reporting period are included in Section V. B. Marine Biota Studies E
- 1. Marine Fisheries Monitorinj l
A Sodified version of the marine fisheries monitoring, initiated in 1981, is being conducted by the Commonwealth of Massachusetts, Olvision of Marine Fisheries (DMF). The occurrence and distribution of fish around Pilgrim Station and at sites outside the area of temperature increase are being monitored. Pelagic species were sampled using gill net (1 station) collections (Figure 1) made at monthly intervals. In 1981, shrimp trawling and haul seining were initiated which provide more PNPS impact-related sampling of benthic fish and shore zone fish, respectively. Shrimp trawling was done once/ month (January - Merch) and twice/ month ( April
- December) at 4 stations (Figure 2) and haul setning twice/ month during June - November at 4 stations (Figure 1).
11-2 5
=
I Monitoring is conducted for local lobster stock catch statistics in areas in the proximity of Pilgrim Station (Figure 4). Catch statistics are collected approximately biweekly throughout the fishing season (May-November). I A finfish observational dive program was initiated in June 1978. SCUBA gear is utilized on biweekly dives from May-October (weekly mid-August to mid-September) at 5 stattors (Figure 2) in the PNPS thermal plume area. I In 1986, an experimental, lobster pot trawl monitoring effort was initiated to eliminate any biases associated with the collection of lobster stock catch statistics for determining PNPS effects. Ten 5-pot lobster trawls were fished in the thermal plume and control areas around PNPS during 1991 (Figure 3). Results of the marine fisheries monitoring during the reporting period are presented in Section IIIA.) and IIIA.2.
- 2. Benthic Monitoring The benthic moni tc ring described in this report was conducted by Scientific Applications International Corporation, Woods Hole, Massachusetts.
I 1 I II-3
I The benthic flora and fauna were sampled at three locations at depths of 10 feet (MLW) (Figure 1). Quantitative (rock substratum) samples ' were collected, and the dominant flora and fauna in each plot were re-corded. Sampling was conducted two times per year (March and Septem-ber) to determine biotic changes, if any. ; Transect sampling off the discharge canal to determine the extent of the denuded and stunted zones is conducted four times a year (March, June, September and December). l i l Results of the benthic surveys and impact analysis during this period j are discussed in Section IIIB.1 and IIIB.2.
- 3. Plankton Monitoring Marine Research, Inc. (MRI) of Falmouth, Massachusetts, has been moni-I toring entralnment in Pilgrim Station cooling water of fish eggs and larvae, and lobster larvae (from 1973-1975 phytoplankton and zoo-plankton were also studied). Figure 5 shows the entrainment contingen-cy sampling station locatic.ns to be sampled should the number of eggs /
larvae entrained greatly exceed recorded historical averages. Informa-tion generated through this monitoring has been utilized to make perio-dic modifications in the sampling program to more efficiently address the question of the effects of entrainment. These modifications have been developed by the contractor, and reviewed and approved by the PATC on the basis of the program results. Plankton monitoring in 1991 emphasized consideration of ichthyoplankton entrainment. Results of l the ichthyoplankton entrainment monitoring and impact analysis for this reporting period are discussed in Section IIIC.1 and IIIC.2. II-4 g
F
- 4. Impincemnnt Monitoring l f
The Pilgrim Station impingement monitoring a7d survival program speciates, quantifies and determines viability of the organisms carried ; onto the four intake traveling scraens. Since January 1979, Marine Research, Inc. has been conducting impingement sampling with results being reported on by Boston Edison Company. I A new screen wash sluiceway system was installed at Pilgrim in 1979 at a total cost of approximately $150,000. This new sluiceway system was required by the U.S. Environmental Protection Agency and the Mass. Division of Hater Pollution Control as a part of NPDES Permit
#MA0003557. Special fish survival studies conducted from 1980-1983 to determine its effectiveness in protecting marine life were terminated in 1984, and a final report on them appears in Marine Ecology Semi-Annual Report #23.
I Results of the impingement monitoring and survival program, as well as impact analysis, for this reporting period are discussed in Section III0. C. Fish Surveillance Studies i March - November, weekly fish spotting overflights were conducted as part of a continuing effort to monitor the times when large concentrations of fish might be expected in the Pilgrim vicinity. II-5 l
l An annual summary report for this effort for 1991 is presented in Section l IVA. D. Station Operation Histon 1 The daily average, reactor thermal power levels from January through December, 1986-1991 are shown in Figure 6. As can be seen, PNPS was in an operating stage during most of this reporting period with a 1991 capacity factor (MDC) of 58.4%. cumulative capacity far. tor from 1973-1991 is 47.4%. E E. 1992 Environmental Programs I A planning schedule bar chart for 1992 environmantal monitoring programs related to the operation of Pilgrim Station, showing task activities and nilestones from December 1991 - June 1993, is included as figure 7. Both marine fisheries haul st.las and benthic quantitative nonttoring activities were terminated in 1992. l 5 I I I II-6 I I a
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- I ;
I ANNUAL REPORT ON
- g ENVIRONMENTAL IMPACT MONITORING
- g:
OF PILGRIM NUCLEAR POWER STATION (CHARACTERIZATION OF THE MARINE FISHERIES RESOURCEji) Project Report No. 52 (January-December, 1991)
=
(Volume 1 of 2)
- l gy Robert P. Lawton, Brian C. Kelly, I..
Vincent J. Malkoski And Mando Borgatti
- g; g
April 6, 1992 lm- Massachusetts Department of Fisheries, L- g Wildlife,.and Environmental Law Enforcement Division of Marine Fisheries ! 100 Cambridge Street Bcston, Massachusetts 02202
- g-I
I TABLE .r CONTENTS
'g Section pag 2 I. EXECUTIVE
SUMMARY
1 II. INTRODUCTION 2 III. METHODS AND MATERIALS 3 IV. 'RESULTS AND DISCUSSION 14 A. Fisheries - Lobster 14
- 1. Commercial Lobster Pot-Catch Fishery 14 p 2. Research Lobster Trap 'ishery 15 2
B '. Fisheries - Finfish 20
- 1. Nearshore Benthic Finfish 22
- 2. Pelagic and Benthi-Pelagic Fishes 26
- 3. Shorezons Fishes 29
- 4. Underwater Finfish Observations 32
- 5. .Sportfishing Survey 35
.6. Cunner Tagging and Aging 37
~
V. HIGHLIGHTS 41 v1. AcxNoetEDcEMENTS 4e g. VII.- LITERATURE CITED 47 I
-I LI 1
'I LIST OF TABLES Table Pacte I 1. Checklist of finfish species (following classification 20 of Robins et al. 1991)- collected or observed in the adjacent marine waters off Pilgrim Station, 1991.
- 2. Expanded catch snd percent composition of groundfish 22 I captured by. bottom trawling at four stations in the vicinity of Pilgrim Station, January to December, 1991.
- 3. Bottom trawl catch data for dominant groundfish in the 24 vicinity of Pilgrim Station, January to December, 1991.
- 4. Catch in number and porcent composition of the top 10 26 I fish species sampled by gill net (7 panels of 3.8-15.2 cm mesh) in the immediate vicinity of Pilgrim Station January-December, 1991.
- 5. Shore-zone fishes captured by haul seine in the vicinity 29 of Pilgrim Nuclear Power Station, June to October, 1991.
--- 6. Abundance and distribution of finfish species recorded 33 during underwater observations, May to October, 1991.
- 7. Age composition in number of fish and (percent of total) 40
.I_ with total length measurements (cm) of cunner captured off Pilgrim Station in 1991.
g I
- I I:
I lI ul I 4
I LIST OF FIGURES Liqure b.aq
- 1. Iocation of Marine Fisheries sampling areas (hatched) 4 for trawl, gill net, haul seine, lobster, dive, and E sportfish surveys in the Pilgrim study area. E
- 2. Lobster pot sampling grid for the commercial lobsterman 5 g monitored in the Pilgrim Power Plant area (surveillance g (H-11, H-12, I-11, and I-12) and reference (E-13, E-14, and F-13) quadrats are shaded) and distribution of his traps sampled in 1991.
- 3. Sportfish survey form used at the Pilgrim Shorefront, 12
- 4. Floy plastic anchor tag and tagging gun used to tag 13 cunner off Pilgrim Station. Location of tag on a tagged cunner is also shown.
- 5. Monthly commercial lobster catch per trap-haul in the 14
. Pilgrim area, 1991.
- 6. Monthly legal lobster catch rates (CTHSOD) by area 16 from research lobster gear fished in the vicinity of Pilgrim Station, 1991.
- 7. Monthly sublegal lobster catch rates (CTH) by area 17 from research lobster gear fished in the vicinity of Pilgrim Station, 1991.
B. Size distribution of lobster captured in the research lu trap study off Pilgrim Station in 1991. 9 ., Size distribution of lobster captured in the research 19 trap study off Pilgrim Station from 1986 to 1991.
- 10. Mean annual catch per tow by station for pooled species 23 trawled in the environs of Pilgrim Nuclear Power Station, 1982-1991.
- 11. Mean annual catch per tow by station for winter flounder 23 trawled in the vicinity of Pilgrim Station, 1982-1991.
- 12. Mean annual chtch per tow by station for little skate 25 trawled in the vicinity of Pilgrim Station, 1982-1991.
- 13. Mean annual catch per tow by station for windowpane 25 trawled in the vicinity of Pilgrim Station, 1982-1991.
I iv 5 a
+
l~ 1 I I c, - Floure Eaae E 14. Indices of relative abundance (CPUE) for pooled E 27 finfish species captured near Pilgrim Station based ca 5 panels of 3.8 - 8.9 cm mesh, 1971-1991.
- 15. Indices of relative abundance (CPUE) for pollock 27 captured near Pilgrim Station based on 5 panels of 3.8 - 8.9 cm mesh, 1971-1991.
5 l 88-
- 16. Indices of relative abundance (CPUE) for Atlantic 28 herring captured near Pilgrim Station based on 5 panels of 3.8 - 8.9 cm mesh, 1971-1991.
g 17. Indices of relative abundance (CPUE) for cunner 28 captured near Pilgrim Station based on 5 panels of I 3.8 - 8.9 cm mesh, 1971-1991.
- 18. Average catch per seine set of shore-zone fish I spooled species) in the vicinity of Pilgrim Station from 1984 to 1991.
30 3 19. Iridices of relative abundance (fish per dive) for all 33 ! species (pooled) observed by divers at Pilgrim E- _ Station,'1981-1991. l I 20. Indices of relative. abundance (fish per dive) for cunner observed by divers at Pilgrim Station, 1981-1991. 34 ! l
-E 21. Indices of relative abundance (fish per dive) for tautog 35 E observed by divers at Pilgrim Station, 1981-1991.
I 3 I I I V I
l f '. I. EXECUTIVE
SUMMARY
A modified version of marine fisheries monitoring for Pilgrim Nuclear Power Station, initiated in 1981, was conducted by the Massachusetts Division of Marine Fisheries in 1991. The occurrence, distribution, and relative abundance of finfish and lobster were monitored according to standardized sampling schemes to identify trends and relationships in the sampling data collected from the study area over time. We focused our efforts on commercially and recreationally important fisheries resources. Nearshore botton, trawling, haul seining, experimental gill-net sampling, monitoring of local commercial lobster catch statistics, experimental lobster trapping, observational diving, and a sportfishing creel survey rounded out investigations. Catch rates ja the Pilgrim area declined from 1990 to 1991 for the top three groundfish (winter flounder, litt e skate, and windowpane) trawled. The - gill-not catch of pollock, Atlantic herring, and cunner increased from last year. Se!ne catch rates or I_ Atlantic silverside and juvenile Atlantic herring increased substantially from last year. The overall number of fish sighted during the diving study decreased,-due to a substantial decline in the relative abundance of tautog. Angling effort at the Shorefront increased, with sportfish catches nearly doubling last year's total. Tagging returns have suggested there '. s limited summer movement of cunner off the outer intake breakwater. Total lobster catch rates in both the experimental and commercial studies leveled off this year, with legal catch rates declining slightly, and sublegal rates increasing. I
m. I
.II. INTRODUCTLQH-A narine monitoring program was conducted in 1991 by the -
Massachusetts Division of Marine Fisheries (DMF) to assess impact I of Pilgrim Nuclear Power Station (PNPS), under Purchase Order No. 68004 to Boston Edison Compar.y (BECo). Our campling cmploys various gear types and strategies that characterize the lobstar and numerous finfish populations present in the Pilgrim area. With each sampling gear, the pairing of an impacted station or stations with comparable reference station (s) is a prime consideration when collecting sampling data. When possible, we have established more than one reference station. Reference site data are needed to address natural changes in populations versus those caused by anthropogenic impacts. We collected data on the occurrence, distribution, and relative abundance of lobster and various finfish species, following a standardized sampling regime. Measurements, counts, percentages, and indices are used, and statistical tests run in the analyses. This report (Volume 1) focuses on fisheries resources in the Pilgrim area as a .whole. Essential findings are presented; however, detailed data presentations, including statistical tests and supportive data, are available upon request. The intent-is to condense subject matter but maintain clarity of I.ta reporting and interpretation in a comprehensive manner. I I 2 5 m
l III. METHODS AND MATERIALS Commercial Tobster Catch I_
. Commercial and recreational lobstermen harvest the American
-lobster in the environs of-Pilgrim Nuclear Power Station. With numerous landing sites tor their catch along the western shore of Cape' Cod Bay, it is not feasible to monitor the entire local lobster fishery. Instead, we are sampling the trap-catch of a commercial lobsterman in the Pilgrim study area (Figure 1), and we
. use his catch as an index of the fishery.
Twice a month from tday through November, we sample the catch of this lobsterman. To facilitate data collecting and the subsequent analyses, the study area is partitioned into a grid (0.8 km2 quadrats) on a nautical chart (Figure 2), and the catch is associated with the quadrats as located by LORAN C bearings and/or
-I. visual-sightings in the field. Data are pooled for reference and surveillance areas. Our analysis included data from 1983-1991.
Prior .to 1983, we sampled the catch of another lobsterman which
-differed'in fishing power and-gear design.
Researph Lobster Trao Fishina
.I Six years ago, we implemented a field research lobster program to augment our commercial study. We are able to assess mcre accurately the impact of the thermal discharge from Pilgrim Station on the local lobster population / fishery. This study has allowed us to control sampling effort in time and space and, in general, to standardize operations. Experimental trap fishing is conducted from June through September in the area of the thermal discharge and at two reference locations in the Pilgrim area using
-standardized procedures and gear to improve data accuracf and 13
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hj , b' ,$ g Figure 2. Lobster pot sampling grid for the commercial lobsterman monitored in the Pilgrim Power Plant area [ surveillance (R-ll, H-12, 1-11, and I-12) and reference (E-13, E-14, end F-13) quadrats are shaded) and distribution of his
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precision. ' Not often are natural populations uniformly distributed in space.- Stations are marked with an anchor-buoy arrangement: four (E-H) in the discharge area and six (A-D; I-J) in the two I reference areas (see Figure 3 in Section II (Introduction) of Semi-Annual Report No. 39). Randomization was initially applied in the selection of stations within an area. Standard commercial, vinyl-coat (3 wire lobster traps (91 cm x 51 cm x 30 cm) are fished in trawls. Ten trawls, consisting of five traps (spaced 30 m apart) per trawl, provide spatial replicates. One trawl occupied each station. Pots are hauled every other day in the morning, wea.ther permitting. This controls soak time (duration of a set) . The data from each sampling ' day previde replicates over-time. Water temperature is measured at each station on a sampling outing. Traps - are emptied of their- contents, rebaited, and relocated on station. Only flounder racks are used as an attractant-in-the pots to standardize the effect of bait type on a lobster catchability. For each pot -hauled, the lobster are $ counted, measured, and sexed. They are also examined for missing claws, presence of eggs, shell hardness, and disease and then released in the area of capture. Periodically, a sub-sample of lobster is retained for radiological analysis. We have three seasons (1986-88) of base-line data collected under essentially unstressed conditions when Pilgrim Station was in a prolonged outage. In 1989, the discharge site was sampled for the first time in this study under the influence of some waste heat and generally stronger current as the power plant gradually increased operational load du*ing the lobster sampling. In 1990, the plant
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operated at an annual capacity of 72%, with both circulating seawater pumps rimning from June through September. However, there I_ was a reduction in heat discharged during July and September. In 1991, the plant's thermal capacity was 0% in June and July and only 28% in August during an outage period; Pilgrim operated at 96% thermal capacity in September. The 1986-1988 outage at the plant provided us with a baseline pericci where our work became a uniform'.ty trial of 'ishing standard commercial traps in a standardized manner in the defined g study area. As noted in other baited trap studies (Mille r 1990) , we anticipated large differences in catch rates over seemingly homogenous bottom type (e.g , the two reference areas). Variance control in any pot study therefore becomes paramount (Miller 1990)
- the less statistical noise, the more precise the final impact analysis. Over the course of our research lobster experiment, we I have used the same bait, soak time, time of gear haulback and processing, and trap design. The proper pairing of potentially I
impacted / surveillance areas (with stations randomly selected within) with non-impacted / reference areas was a prime concern. We believe the station pairs selected would reflect natural environmental changes'in a similar way. Bottom Trawlina Groundfish in the nearshore Pilgrim area are sampled via small , vessel (6.7 m) bottom trawling, begun in 1981. Four stations are trawled monthly January through March and biweekly April through December during the daytime (See Figure 2 in Section II (Introduction) of Semi-Annual Report No. 39). The surveillance stations are T-3 (Discharge) and T-6 (Intake), and the reference I - - - - -
I. stations _ are T-1 in Warren Cove and T-4 located northwest of - Priscilla Beach. Stations were selected based on available substrate 'for trawling, water depth, bottou type, and known patterns of the thermal plume. Duplicate 15-minute tows are made at each station using a 9.8 m Wilcox trawl (9.8 m sweep, 7.0 m headrope, of 11.4 cm stretch mesh; and fitted with a 6.4 mm stretch mesh cod-end liner). If a standard tow was not obtained because of interference with lobster gear, catch values are extrapolated using a weighting function. Standard survey procedures and trawl log sheets are used. Fish are identified, enumerated, measured, and released alive, except for quarterly samples which are retained for radiological analyses. Invertebrates are identified and counted; lobster in addition, are measured as to being legal or sublegal. Water tnmperatures are collected while sampling at each station. Observational Divinct The underwater observational program consists of SCUBA dives a made at six permanently marked stations _by biologist-divers (see E Figure 2 in Section II (Introduction) of Semi-Annual Report No. 39). The present sampling stations were selected in 1981. Research dives are made biweekly from May through mid-August, weekly frcm mid-August until mid-September, and then biweekly through October. During" ecch dive, which occurs at high tide, divers descend to the bottom from off a boat anchored just outside the discharge canal. Each station is occupied consecutively, and visual observations are made of marine life. The emphasis is on identifying, counting, est.imating size, and evaluating the general condition and behavior of finfish in the area. Bottom water
.s
.. .. ~. ..
temperatures are taken with a hand-held thermometer, and visibility estimates made using a Secchi disk. Gill-Net Samplinct Pelagic and benthi-pelagic fish in the Pilgrim area are sampled by-gill net fished parallel to shore at a depth of about three metersL(MLW)., near a ledge extending north from the mouth of the discharge canal (See Figure 1 in Section II (Introduction) of Semi-Annual Report No.39). The sampling site is partially within --- the discharge area. Sampling is conducted monthly throughout the year. The sets are standardized with the not being act before
. sunset and retrieved at sunrise the following day. This takes advantage of the greater sampling efficiency of a gill net (passive gear) after dark.
- We employ a sinking monofilament gill net (213. 4 m long by 3.0 m deep), which is anchored on station. The net fishes almost the '
. e entire wcter column at low tide. To counter bias .in gear selectivity, an experimental net is used, consisting of seven 30.5 m panels of the following stretch mesh sizes: 38 mm, 50 mm, 63 mm, 75 mm, 88 m, 114 mm, and 152 mm, strung end to end. To further reduce bias, the end of the net positioned closest to the discharge canal is reversed on alternate sets. Water temperatures (bottom and surface) are.taken at each end of the net when setting and
.I nauling.
Our objectives are to provide systematic collections of finfish for radiological analysis and to obtain data records of relative abundance for dominant finfish species. I am ~ 9 g. _m_ _ _ _ _ - _ . _ _ --
L I 11aul seinina To monitor finfish occurring along the shoreline, i.e.y the intertidal and shallow subtidal zones, haul seining has been conducted since 1981. We have sampled biweeklf during the daytime at four stutions from June-November, when many fishes inhabit the shoreline (see Figure 1 in Section II (Introduction) of Semi-Annual Report No. 39). Winter /early spring sampling was omitted because cold temperatures reduce or occlude fish distribution in shoal waters. Found along the shore are forage species and the juveniles of many important commercial ar.d sport species. We have conducted standardized beach seining at Stations S-2, S-4, and S-5 using a 45.7 m by-1.8 m haul seine with a 1.8 m3 bag of 0.48 cm square mesh (twine #63). Sampling is constrained by the greater deptn at the surveillance site (Station S-3, Intake); thus a deeper seine (45.7 m by 3.0 m ) set from a small powered skif f is used there. Duplicate hauls are made at each station within 12 hours of low tide. Surface water-temperature and salinity are , measured at each station. I For each station, we have endeavored to keep the area (m 2) seined constant to standardize effort within a site over time. Captured fish are identified, enumerated, and up to 50 individuals of each species measured. Unusually large catches are subsampled to reduce mortality, with total catch extrapolated from volume-unit counts. Catch per unit effort (defined as catch per seine haul) has been calculated for numerically dominant species. Snortfish Survey The recreational catch at Pilgrim Station's Shorefront area has been monitored from June through August by public relations' 10 g
I personnel at the waterfront. This has allowed us to n.aintain a database on sportfishing in the Pilgrim area. Daily catch data have beLn recorded on a questionnaire (Figure 3). He also spot-checked the area for recreational fishing during April, May, and September and October. Cunner Canture and Taccina To capture cunner off the power plant, we use weighted baited eel pots constructed of vinyl coated wire with the following dimensions: 30.5 cm x 30.5 cm x 58.4 cm with a 1 cm2 opening in the mesh of the wire. The bait is frozen fish (pollock, bluefish) h and/or crushed blue mussels. The-tag we selected had to be suitable for a relatively small fish (as is the cunner) and had to be visible to divers. We selected the floy t-bar anchor tag (63.5 mm in length) to mark Individual fish. The tag is inserted into the dorsal musculature on the left side using a tagging gun (Figure 4). Red-colored tags were used in the discharge area and blue ones in the reference area in 1991. I I , I! I I I 11
Interviewer's sheet # Initials 1991 Recreational Fish Survey - PNPS Shorefront Date I Weather Wind Direction and Speed Number of Anglers for the Day Fishing Locations Hours the Shorefront was open and fishing allowed (e.g., 6 am - 5:30 pm) Species Total Number C2ught for Day , Flounder (Flatfish) Striped Bass . Bluefish Cod
- Pollock Tautog .
Hackerel Cunner (Sea Perch) - Other Comments:- I I Figure 3. Sportfish survey form used at the Pilgrim Shorefront. 12 5
-,m3 w------------------w-- - - - - , , - , . , ,_,,
I I I I:
, /V *L -/.a I' '.
l f\
\
I \ ~S s .I
? LAG I \
I I fI - e_g -. J2Ef8-4 3Y N_U[d__F4 _-s_ E%17Y_ WLk,a m=%. - w$NhbSS I j
/
/ ----m--
F% w-. 6s 3 Q' ,&G "i
/
_I ! l E 6 - ANCMCR
.I g
Figure 4. Ffoy plastic anchor tag and tagging gun used to tag cunner I' off Pilgri Station. Location of tag on a tagged cunner is also shen. I I 13
I IV. RESULTS AND DISCUSSION A. FISHERIES - LOBSTRB
- 1. Commercial lobster cot-catch fisherv Monitoring the commercial American lobster (Homarus americanus) fishery in 1991 in the Pilgrim study area began in K' and concluded in O'ctober. Lobster catch statistics and biological data (i.e., carapace length - CL, sex, shell hardness) were collected over the six months during 11 sampling trips aboard a commercial -
lobster boat. Data were obtained on 5,562 lobster taken f rom 2,432 lobster pot-hauls. Overall catch per pot of legal - CL 282.6 mm - and sublegal lobster from the Pilgrim area was 2.3, while last year's value was 2.5. Sixteen percent (894) of the total catch we e legal lobster for an annual catch rate of 0.37 lega.'s per trap-haul, which is 16% lower than last year's rate of 0.44. Relatively low monthly legal catch rates occurred May through July (0.20-0.35), followed by higher rates (0.41-0.63) in August 'and September (Figure 5) , eer w eni m The monthly catch rates of both es- E
- I sublegal' and legal lobster 80' h) !? 1 te- !$
jj {4Il
! 'a j
generally paralleled that of the - g y j f nil jg gj lib
!!)g E
pooled. lobster catch rates. The oe- g
- n 4 ;il!!! j
- annual ratio of sublegal to go ..
=
hk sun aut N"3-ava p& gjmL to oc' E MONTH E Jegal lobster was 5.2:1. ma raucasten c a tac e irr.a sue u x s Males comprised 55% of the Figure 5. Monthly cocinercial tobster catch per trap haul in the Pilgrim area, 1991, I sampled catch, with monthly sex ratios for June through September favoring males and with May and 14 E' E
L I October slightly favoring females. There were 109 ovigerous (egg-bearing) females sampled (4.4% of the female catch), of which 76 (3.0% of all females and 70% of all ovigorous females) were sublegal. The overall percentage of ovigerous females was again higher from late summer through early fall (September 6.8% and Octcber 2 5. 2.% ) as compared to summer (1.7% in June and 0.0% in July). The elevated value in October is higher than usual for this month, and may be an artifact of a relatively small sample size. _ The seasonality in the incidence of egg-bearing females reflects the two-year reproductive cycle of the American lobster ( Aiken and Waddy 1982). Sexually mature females generally mate after the summer molt, but it is not until fall of the following year that they extrude their fertilized eggs which are carried externally throughout the winter, hatching from late spring into the summer.
- 2. Research Lobster Trap Fishina We trapped lobster from June through September 1991 in the environs of Pilgrim Station. This year was the sixth of our
~
research trap fishing. We completed 53 sampling trips on a contracted commercial lobster boat. Effort consisted of 2,650 I trap-hauls, 'while sample size totaled 9,682 lobster of which 10.0% were legal-sized. For the past two years, the minimum legal size for lobster retention in Massachusetts has remained at > 82.55 mm _ _(3.25 inches) carapace . Length (CL) , after having undergone a gauge increase in 1988 and 1989. These changes in legal size were not I accompanied by an increase in the size of the escape vent in each of our traps. This contributed directly to increased catches of sublegal lobster as compared to legals and is reflected in the annual catch ratio of sublegal to legal which was 5.8:1 in 1988, g
1 I 6.G:1 in 1989, 8.1:1 in 1990, and 9.0:1 in 1991. Enhanced . recruitment of sublegals into the pre-recruit and legal size range most likely was the reason, as the Cape Cod Bay lobster resource appears to be over-exploited (Estrella and Cadrin 1989). Ennis (1983) found that with lobster exploitation rates as high as 94% in Comfort Cove of-Notre Dame Bay, Newfoundland, recruitment via the mc,, is the main factor influencing the abundance of legal-sized lobster in a given year. The number of lobster of all sizes captured over a two-day set ranged from 0 to 12 per trap-haul, with legal catch ranging from 0 to 5 and sublegal, O to 12. In 4% of the hauled traps, no lobster were taken. The overall seasonal (June-September) mean . 3 6.ch-per-trap-haul (CTH) in the study area of lobster (pooled for size and sex) has increased, ranging from 1.2 in 1986 to 3.7 in 1990 and 1991.- Monthly catch rates as catch per trap-haul per set-over day, 'CTHSOD, of legal and CTH of sublegal lobster in the study area for .1991 are plotted in Figures 6 and 7, respectively. The legal m catch rates generally peaked in om - w 3 N M Auciust and September. Sublegal ji
%~
gg-,, p g
'I
'were w 7 7 U 7
catch rates generally y di i highest in July or August. JEm h
%. }h$ h
!!jWM JUN JL.A. AUG BEP Males again outnumbered umm me m an ta noen mn
-females in the research trap mn .cist, ca .,.. . catches, comprising 57% of the Figure 6. Monthly legal tchster catch rates (CTHSOD) by area f rom research lobster gear fished in
'"'^*'""# ' '"**
total'. Conversely, females hsve typically outnumbered males in past commercial catches made in the slightly deeper waters of western Cape Cod Bay (Kelly et al. 1987; 16 B u
I Lawton et al. 1990). However, ,,, _ ,, this year, males predominated , , IE - c _. (55%) in the commercial catch. 3 . r-p i!!! : males ' ' ((m [jj g ijhi I A preponderance shoal water pot-catches also was of in {M k gj 3g 3 J un f{ JUN #JL 400 SEP reported by Briggs and Muschacke mot (TH I. , M tm40mam0E C aCCav Point (1979) in Long Island Sound, am n,.cua a mu.umw There were 61 egg-bearing Figurc 7. Monthly subtegat tobster catch rates (CTM) by area from research lobster gear fished in the
i*i"i'Y *' * '* " ' " "' " '
(ovigerous) females sampled which represents 1.5% of the research catch of females. The percent of females ovigerous was 1.2% in last year's research catch. Over the years, this value has typically hovered near 1% in commercial catches from western Cape Cod Bay (4.4 % in 1991, see Volume 2). I Culls (lobster with missing and/or regenerating claw (s)) captured during research fishing in 1991 comprised 29% of the catch. The cull rate in 1990 was similar and somewhat higher than I in 1989 (27%) and in 1988 (23%). In general, the cull rate obtained by sampling commercial catches has increased in the Pilgrim area during the past decade, concomitant with an expansion in commercial and recreational lobstering efforts. The commercial lobster traps employed in this study each contain a rectangular escape vent (44.5 mm x 152.4 mm) and are designed to retain legal-sized lobster; however, sublegals are captured to an extent. The size range (CL) of lobster sampled the summer of 1991 was 33 mm to 114 mm. The overall mean size was 75.3 mm, which is less than 1 mm smaller than the average for 1990. Sublegals averaged 73.9 mm CL, and legals, 87.2 mm CL. 17
I Size-catch distributions were plotted for 1991 data (Figure 8) and for all six years (1986-1991) together (Figure 9). The length- . ., , frequency histograms display ) effects of lobster availability, l vulnerability, and fishing , ;
,, ; q... ... . . . _ .
mortality. The general stepwise . . .. increase in catch between 50 and } s ~
, "sememm 44ehfm'M #f W SC SS 60 65 70 76 to as 80 e5 10 0 106 75 mn CL suggests that between carapace Lenatn (mrr] in t nrn increments those measurements, lobster are Figure 8. size distribution of tobster captured in the research trap study off Pilgrim Station in 1991.
increasingly vulnerable to retention in the traps. The mode was at the pre-recruit size of 79 mm CL. Reduced catches of lobster < 73 mm are most likely influenced by gear design (vent escapement) . The lower numbers of lobster at legal size and greater reflect high fishing mortality via intensive commercial and recreational lobster fisheries in the Pilgrim Station area, em I 5 I I" I 18 I R E
- muu .uns nung '. uns - sum . iuma sms uma~ sus uma uma asus. ums .aus sunt uma see usu aus
l l Relative Frequency ~(%)
/
/
/
,/ .
c 14 - 12 - c
/
g 10 - e 3 -. -
..e t >.
8-e c1 ~ i
~
4
$ T ,
}
6-- .
.g .._
r :
~
$ h:]+if
~
4_. Of
?{k{x-
' . A L
a y , T
,,_a
? '
t -. y yv m _t;;;;;; Alp. 2- s g} n
. dw#sM gg A
q, 2(> g - w~' i 1
; ;2;7
, , m r<
0~m . ...w t 4 3 I ii3 i1 4 4 i i iI ie i.i i 4 ii1 4 1 i iI 6 6 ii+4 4 i .
, =
4 3 1 4 I iii it 6 4 6 4 i J i i6
~
50 55 60 65 70 75 80 85 90 95 100 105 Carapace Length (mm) in 1 mm increments . 1991 ['1990 - 1989 1988 E 1987 3 1986'
. Figure 9. Size distribution of' lobster captured in the research trap study off Pilgrim Station from 1986 to 1991.
1 I B. FISHERIES - n 3 FISH - A species check list of fish observed or collected by all gear types in the Pilarim area in 1991, complete with scientific names (Robins et al. 1991), is found in Table 1. Table 1. Checklist of finfish species (following classification of Robins et al.1991) collected or observed in the adjacent marine waters off Filgrim station, 1991, m-Class: Elasmobranchiomorphi Order Lamniformes Family: Carcherinidae - requiem sharks Mustetus M 1 (Mitchill) smooth dogfish Order: Soualiformes family: Squelidae
- dogfish sharks W
$ w M Ug scenthias Linnaeus spiny dogfish Order: Rajlformes family llajidae a skates jtjtig erinocea (Mitchill) - little skate Class: Osteichthyes Order: Clupelformes Family: Clupeldae herrings Atosa w tivalis (Mitchill) bluebeck herring Alpia pse # arengus (Wilson) - alewife
.Brevoortin M Ln y (Letrobe) Atlantic menhaden Clunes herenaus Lirriacus - Atlantic herring Family: Engraulidae - aichovies Anchos initch{lli (Valenciennes) - bay anchovy Order: Salmontformes W Family: Osmeridse smelts Osmerus enneden (Mitchill) - rainbow smelt .
Order: Gadiforaws Family: Cadidae - codfishea Gadus gLor!Lua Linnaeus ' antic cod
~pierocadus temcod (Wi Atlantic tomcod -
Pottechius virens (( .) pollock Urochveis tenuis (Mit .t) - white hake UPOD h YCis Chuss (Wat ;) - red hake Order Atheriniformes Family: Cyprinodontidae - killifishes f_un_dyLu_s maiolig (Walbem) - striped killif tsh Fundutus heteroctItus (Linnaeus) nu michog family: Atherinidae
- silversides Menidle menidia (Linnaeus) - Atlantic silversido WW Orders Gasterestelforses family: Gasterosteldae - sticklebacks Casteresteus oculestus Linneaus - threespine stickleback Anettes cuadracus (Mitchill) - fourspine stickleback family: Syngnathidae pipefishes and seahorses Synanatbus fuscus Storer - northern pipefish 20 E
\
I k. W Order Scorpaentfotows family: Trigtidae sentr%lns Ef_igrjolw af.p&gg (Linnasus) nothern searobin Prionetog gyglana (Linnaeus)
- striped seerobin L family: Cottidae sculpins reitrioterus gnxfAnn (C.melin)
- ses reven f.yf.Lestitt1W1 atn!Lest (MitchI1I) grutby I
Nye n oc er*y pfdss}ecemeinesui (Kitchit t) tor ghorn sculpin f ror et eLr VI litTI1W1 (Linnaeus) shorthorn sculpin family: Cyclopteridae
- lumfishes and snellfitt o Qticoterus LLrm; Linnaeus Ltanpfish Order Pertifornet familya Perciththyldae tegetate basses Morone 13sg11]41 (Watt *c) striped bass family: Serranicas sea besses
-I tentregtltill [Q1311 (Limaeus) black sea bass family: Pometoreldae bluefishes ES"3.!Ed settetrix (Limmeus) bluefish f orelly: Carangidse Jacks lerlele toneta (Mitchill) banded rudderfish i p r epterus lagitf,.t11kra (Cuvier) toJkeret $ cad
-M family: $cInenidae drume Prticirrhun 11: stills (Bloch ered tehneider) northern kingfish (119.11gep11 penthuruse .swpede
- spot family: Sparidae porgies
%tenottvm,r1 cM nons (Lireweus) scup I
family: Hugilidae a mullets B ggl', Lyr,mg Valenclemes - uhlte mut tet family: Labridae wresses 1121p33 onitle (Limaeus) teutos layltStlikT31 &#.It31tisy (Walbaum) cunner Fanity; Zoarcidae eetpouts Meerero. res gmtleenus ($chneider) owan peut I family: Pholldae
- gunnels Eb,9111 gzLntilyt (Limaeus) rock gunnet family: Anrnodytidae
- sand Lances Amndytes amerte,lega Derey American sand lance
'smily: Sconbridae - meckerets gituter 31 pita Limaeus - Atlantic mackerel f arci ty: Stromateldee a tivt terfishes W E.Q.il.W11tjaunthus (Peck) butterfish Order. Pleuronectiformes I., family: Bothidae letteye flounders itsch1.hgMy! Plagfya iMitchILL) windowpane Family: Fleuronectidae
- righteye flounders 3
I order: Tetraodontiformes Pleuronectes f errunineos (Storer) yellowtail fler eer Eleve n etts americanus Walbatan winter flounder Iamily: Tetraodon t i vffers
$phottold_e,l Lna1 E .e doch and $chneider) northe- puf fer 5
g
I
- 1. lin0IShore_Gtpyndtinh The catch from 130 bottom trawls in the study area in 1991 totaled 503 fish, representing 21 species (Table 2). Five species
- Atlantic herring, winter flounder, little skate, Atlantic cod, anri windowpane - comprised 91% of the total. Overall mean catch por tow (a measure of catch per unit effort, or CPUE) calculated from pooled specien and station data was 3.9, identical to the 1990 N uo (Figure 10). Thor'3 has been a downward trend in our trawl f abic 2. Esparded catch' and percent ccarposition of grourdfish captured by tuttom trawling at four stations in the viclntty of Pilgrim Station, January t' Decenter,1991.
Station 1 3 4 6 " Warren Pilgrim Priscilla Pilgrim Percent of
$pecies Cove Olsch rge Beach ittake totals total catch Atlantic herring 0.0 2.0 297.0 .l.0 300.0 59.6 Winter flounder 0.0 15.0 40.0 17.8 72.8 14.5 1.lttle skate 1.0 11.0 11.0 22.9 45.9 9.1 Atlantic cod 0.0 8.0 4.0 2 0 20.0 6.0 Windowpane 0.0 8.0 8.0 ;
19.0 3.8 Attentic silverside 0.0 1.0 7.0 ' 12.5 2.5 Butterfirb 0.0 0.0 5 . f. 9J 5.0 1.0 Rock gunne. 1.0 0.0 4.' #.C 5.0 1.0 Other species' 1.0 6.4 9.c 6.6 23.0 4.6 1etal fish 3.0 f1.4 385.0 '63.8 503.2 Narber of tews 35 34 37 ' 24 130 E Catch per tow Percent of catch 0.1 0.6 1.5 10.2 10.4 76.5 2.7 12.7 3.9 g Nunber of spcies 3 12 14 <10 21
' Catch rates were expanded for tows less than the standard 15 adnute duration.
' Represents pooted totals from 13 species ef low catch ab.edance. E shaded colunya sre data ccitected at survelttance stations.
catches since 190 Low numbers of fish make detection of impact I from the operation of Pilgrim Station difficult, especially to separate ~ plant impact from natural variation. A review of stock
. assessment work by the National Marine Fisheries Service (NMFS)
Northeast Fisheries Center (NEFC 1991) points to the generally l depressed state of groundfish abundance in the Northwest Atlantic. I 22 E
=
I Catch rates also were calculated for individual stations, the highest being found at Priscilla Beach (station 4) with a mean CPUE (pooled species) of 10.4 fish It should be noted, I per tow. however, that the magnitude of ,, p n, n3, ,,, n ,
......m............
. a this index was greatly n-
; gi l q, influenced by the capture of "f l k nearly 300 juvenile Atlantic ,
su m w w w w ses a nn ,m (jj}d herring during a single tow made viu I there in the spring. The a cwo4-w ,w, , a swo. s a ,,c,c,a n ,,mo, zu i, won occurrence of this species in Figure 10. Henn annual catch per ttaw t+y stet ton for fooled SpeClet (fswled in the erwirons C,f Pilgrim our bottom trawl catches is rare "x t ur Podr Stat ion.1N 1791-because this species is pelagic. Exclusion of these data from the calculation yields a mean catch rate of 2.4 at this station. The Intake (Station 6) and the Discharge (Station 3) catch rates were 2.7 and 1.5, respectively, while that in Warren Cove (Station 1) was 0.1, Winter fl oundoy. Ranked secord in trawl I catch (14.5% - all stations =
" ~
'I pooled), winter numerically dominant at Station flounder uas to -
' t, "'
' ' I
- 4. Overall CPUE declined for ,t , .
the fifth consecutivo year to o 5 h g, gg %
'=,-
I
/
vrm G.6 (Figure 11). The NMFS C3 swon a suno,4 s IElil swo. 4 reported that winter flounder " * * * " U " "" *"* abundance in the Gulf of Maine gure . Mun amat catch pu tow by Statign int winter flourder trawled in the vicinity of Pilgrim I declined overall in 1990 to its station, 1982 1971. 23
I
*towest level of the last 10 years (NEFC 1991). Off Priscilla Beach, the winter flounder catch ranked first, with an annual mean CPUE of 1.1 (Tuble 3). Annual mean CPUE in the Intake dropped from 3.4 (1990) to 0.7, and in the Discharge from 1.2 (1990) to 0.4. No winter flounder were trawled in Warren Cove.
A comparison of the annual mean size of winter flounder captured at each station (Table 3) revealed little variation between stations in 1991. Table 3. Bottom *rawl catch data' for daminant groundfinn in the vicinity of Pilgrim Station, .anuary to Deca rrtter,1991. Winter Little Station flounder skate Wind:>wpane 1 Mean catch per tow 0.0 0.03 0.0 heen site (cm) - 44
- lite range (cm) * *
- 3 Mean catch pct tow 0.4 04) 0.2 Mean slie (em)- 26 35 25 Stre range (cm) . 12-39 24 48 16+37 4
Mean catch per tow 1.1 0.3 0.2 Mean sit 6 (cm) 26 36 25 slae range (cm) 9 41 24 48 16 31
- keen catch per ,w 4
-0.7 '1.0 0.1 l
g Mean site (cm) 27 16 - 23 -
$1:e range (ca)- 11 14 20 55 17 28
' Catch rates were experded for tows less than the stardard 15 mirute dur ation. W shaded rows are data collected at surveillance stations.
Idtlle skate Little skate comprised 9% of the overall trawl catch. Mean annual catch per tow for all stations pooled was 0.4 (Figure 12), down 50% trom 0.8 in 1990 and the lowest value recorded for this species in our study. A comparison with Gulf of Maine catch rates was not possible; the NMFS does not differentiate between catches 24 I E u
I of little skate and winter skate _c,,,,,,,,,,,,
. . . . , . ~ . . . . . . . .
(Rafa occllata) . The highest annual u - p ; I station catch rate (1.0 little
+
S
...[
t [
., a
{ 1" if l skate per tow) was recorded in , . the Jrtake Embayment, followed '( g jf;)),g3 o ,a [J}[,(4gL,,,, I 492 196J 1994 1s06 1968 19F P ,98 4 1909 WW W91 both by Priscilla Beach and the YEAR Dicchar9e at 0.3 (Table 3). The Ele sianon a C3 Ksxto stAneus I )ovest relative abundance was in Figure 12. me n annual catch per tew t>y station for little skete trawled in the vicinity of Pilgrim Warren Cove with 0.03 fish pet station, 1582 1991 tow. Comparing data over the years (Figure 12) reveals a marked drop in relative abundance occurred at all stations in 1988, with the stock remaining deprecsed thereafter. Windownane Windowpano ranked fifth in overall trawl catch (3.8% - pooled data). Mean annual CPUE for all stations combined was 0.1, down from a value of 0.7 in 1990 (Figure 13). Following a sharp ,,3m o, n,, y , ,c, I decline in 1988, relative 'l M. s . f. l '" p ,
. . w i ..i .. . . .... . ... 1 abundance has remained at a ,
4 p1 I depressed level. A very thin-
.3 d:
.r p 4
- j d bodied fish, windowpano were (Qy g gg.g 4 82 $83 1904 W 406 1s87 1969 tM9 GSO Ys01 formerly not exploited YEAR commercially. They have become $ "*"[ ' , $ [" *, E" "'" " '
more sought af ter in the absence Figure 13. I or low abundance of more station. 1982-1991, Meen imal caten per tow by station for windowpane trawled in the vicinity of Pilgrim desirable species. The windowpane has not been a target species for stock assessment, and little or no HMFS data were available. 25
l Among the four sampling stations, annual CPUE for windowpanc wan i fairly consistent, ranging from 0.1-0.2 fish per tow. other Snecien i;1 l Comprising 13% of the total trawl catch, the remaining 17 species were not captured in abundant, numbert. Overall catch rate for this group (pooled species and stations) was 0.5 fish. i
- 2. Polanic and benthi-colaalg L{. phpa _I.
Monthly gill-net catches in 1991 yielded 20 finfich cpecies numbering 1012 fish. The top 10 species are listed in Tabic 4. 11 0 set was made in December because of i- '.ement weather. Table 4 Catch in rud.er ard percent ctroosition of the top 10 fish specie 6 sanpled t>y gill ret (7 panels of 3.815.2 ce mesh) in the imediate vicinity of Pilgrim WI
$tation, January Decenter 1991 Percent of Species Wadser Total Catch
- 1. Pollock 417 41.2
- 2. Atlantic herring 233 23.0
- 3. Cunner 64 6.3 4 Tautop 53 5.2
- 5. Stuefish 51 5.0
- 6. Striped bass 48 4.7
- 7. Snooth dogfish
- 8. $ cup 43 24 4.2 2.4 M
g
- 9. sitver hake 16 1.6
- 10. Northern searobin 13 1.3 Total 10 species 962 95.1 The annual mean catch rate (catch per standard set) for pooled species by gill not (5 panels of 3.8 -
8.9 cm mesh) increased l slightly to 82.3 fish par set from last year's all-time low of 68.8 fish per set (Figure 14) . Catches of pc,ilock and Atlantic herring, the two dotrinant species in gill-not catches over the years, increased in 1991 and contributed to the higher overall catch rate. l Pollock ranked first at 41% of the catch, and Atlantic herring second at 23%. Cunner (6.3% of the catch) regained its traditional 25 5 3
l t third place position in the
. m , m at e__. tut hierarchy of gill-net catch and I was followed by tautog at 5% of teO' The I the catch.
species first three consistently have iso -
'm M dominated gill-not catches since 1971, with faw exceptions. rivive 4vstevivavo se essass34 es no er se o sosi rigure 14. ireices of relative stowance <trun P*
- s of aNmeeY19I1N1 I
'd Poll o_ch Pollock were caught primarily from May through November, with the greatest quantity in June. The five-panel catch rate for pollock increased in 1991, yet remains at a depressed level relative to the entire 1971-1991
~
dataset (Figure 15) . This long- , , , , , , _ , , , , , term time series of annual wo . relative pollock abundances reveals a wide range in catch n - rates from a low of about 20 pollock per gill-not set in 1975 8' and 1990 to a high of nearly 3 40 y En"""""""""" I in 1977 and 1980. Figure 15. r f3.8s",Ic 0 treices of retettve atueence <cpun E, $!$1. The great majority of the Atlantic horring caught this year were obtained in November. The catch rate for Atlantic '. erring increased slightly tewards the 1989 value from the near record low level of 1990 (Figure 16), overall, the catches of herring have fluctuated as greatly as any fish species sampled by the gill net. This species was at its
, 2> !
I lowest point in abundanco in the , , , , , _ , , , , , , Pilgrim area in 1985 but reached ,u . L zenith in 1988. u - ' Cunner
; Cunner were caught every o -
month from April through gj g i October. The relative abundance """"""""""v"[n*"""""""*" of cunner in the Pilgrim area Figure 16. Irdico et relativeTbundance (crun for Atlantic herring taptured hear Pilgrim Stetion based has remained low since 1985, with this year's catch rate being the second lowest of the 20-year , time series, portraying a slight increase from last year's value ; (Tigure 17). Other facAleji The catch rate for bluefish ,,,,,,,ut,,,,,,,,,, increased substantially from 60 - last year, while tautog, striped E u - B bass, Atlantic menhaden, and , n - g Atlantic mackerel decreased in 5 10 relative abundance. No Atlantic g cod were caught this year. """"""""*""[n""""""""'"' y Striped bass and bluefish Figure 17. iMices of relative abundance <cruo E for cunner captured near Pilgrim $tation tesed on S g have an affinity for the thermal effluent at Pilgrim Station (Iowton et al. 1987). Their numbers (reflected in our gill-not abundance indices) are generally low in the Pilgrim area when the power plant is not fully operationa.1 I Pilgrim Station decreased its overall annual operational capacity, l and thermal component, from 72% in 1990 to 584 in 1991, and with I L 28 L E 1; .. - . .- . .. --
I that, gill not catch rates rose from 2.5 to 4.3 fish per set for bluefish but fell from 7.1 to 2.8 for striped bass. g b 3. Shore-zone FirdLqp, A aum of 56,566 finfish comprising 27 species was seined from June to October, 1991 along the Plymouth shoreline (Table 5). 11 0 sampling was conducted in llovember because of a severe five-day northeast storm in late October that caused extensive beach crosion at all sampling sites and damage to access roads. Water terperature and calinity measured during sampling operations ranged from 12*C to 20*C (E = 16. 6
- C) and 30 0/00 to 33 0/00 (5 = 31.1 0/00), respectively. Three fish species comprised 97% of the total seine catch - Atlantic silverside (46%), Atlantic herring (41%),
and sand lance spp.(10%). The mean catch per standard seine haul, pooling stations and species, rose from 254.4 in 1990 to 912.4 in 1991 or about a 3.5-fold increase in catch rate. Shore sone fishes capturM by bout seine in tne vicinity I Table 5. of Pilgrim Wuclear Power st6 tion, June to October, 1991. Alfil20 I species Warren Cove Pilgrim Intake' Manon.e t Point Long Point totat Fercent Total Cat;h Rate I Attentic silverside 4ttantic herring Sand Lance sr~ Other specie' 2,398
$,077 5
133 6741 22,075 320
?O4/
1,030 381 0 8 22,053 7 5 372 26,155 22,910 5.410 2,091 46 41 10 3 421.8 396,6 87.3 33.7 I Tota l hunter of sets Catch per set la ter of species 7,613 18 422.9 16
- 24,D?6 17 . .
'1,417.4 17 -
1.419 9 22,437 18 157.7 1,302.1 6 22 56,566 62 912.4 27 Percent of total catch 14 43 3 40 100
'45.7 m x 3.0 m seine; other sites sampled with 45.7 m x 1.5 m seine.
' Represents pooted total f or species of Lower aburdance.
Shaded colum is data from surveillance statico. Large increases in the catches of the Atlantic silverside, Atlantic herring, and sand lance brought about the overall increase I - J
I in catch rate for the study area o,o ,, isoa - in 1991. Catches of juvenile $4M - 1 ,, 1850-river herring (majority were a ^ E 7 blueback herring) and Atlantic eco- v
, y menhaden, and both juvenile and *hvil R RF m O Ql M,1 g
=4 see w$e wer ......u.
l w.$ adult northern pipefish also ma _ _ . _ , m _ _. increased from last year. Catch a = = n *=av a u~oewt _ rates (pooled species) increased shore-tone Figure fish 18.(pooledAverage cetch per seine set of species) in the vicinity of
~
Pilgrim Stetton frca 1984 to 1991, at three of the stations and remained about the same at the fourth (Figure 18). The seine catch by station was highest overall in the Pilgrim Intake, where 43% of the total was obtained, followed by Lo t Point p (40%) (Table 5). The former was a direct result of the , 'sually large catch of juvenile Atlantic herring made there. The overall catch rate in the Intake increased 10-fold from last year and was l5 the highest of the entire study (Figure 18). The catch rate at Long Point increased 4.5-fold from last year and was the highest value obtained at this station during the entire study. Atlantic Silverside The Atlantic silverside ranked first in number of fish captured, as it has every year of seining operations. This species accounted for 46% of the fish seined in 1991. Of the silverside catch, 84%' was obtained at Long Point. Low silverside abundance in June in the Pilgrim area was followed by good catches of both (. juveniles and adults in July. Dominating all catches from July through october, abundance peaked in September. Their overall l catch rate (pooled station data) almost doubled frou last year. I 30 E E'
I M1Dptic IN- ina anLEanLLanC2_ Ranking second in seine catch, Atlantic herring were captured in greatest nurbers (95%) in Pilgrim's Ihake, whure a large school of juvenile sea herring resided in early summer. The highest catch, by far, occurred in June. l 1990. The catch rate of sand lance increaned about 10-fold from Ninety-four percent of their catch came from Warren Cove. Diy.orsity - Spatial and Temporal The highest cunulative number of species (22) was seined at Long Point in 1991. As to monthly totals, the highest number of species (18) was captured in July, August, and September. Of the 27 species seined overall, only 5 were taken at all 4 sampling sites, while 8 were collected at single sites. Of the latter, five species were coined exclusively at Long Point and two in the Intake. Pilgrim Intake and Long Point shared the most species in common (14) and had the highest catches in number of fish. Both locations are generally protected from heavy surf and possess cover that includes vegetation. This provides suitable habitat for small fish. Conversely, Manomet Point and Warren Cove have sparse cover and are subject to heavy surf. The least populated areas are generally devoid of vegetation, where protection is lacking and food is a limiting factor. Over the years, we consistently have collected more spncies in the Intake and at Long Point. I. The overall seine catch (number of fish) at Warren Cove was dominated by sand lance (67% of the Station total) and Atlantic silverside (31%). Atlantic herring comprised 95% of the catch in the Intake. The highest cctch of juvenile winter flounder was 31 I __
I recorded in the Intake (72% of the study area total). At Manomet Point, 73% of the catch were silversides and 26%, Atlantic menhaden (juve. tiles) . The largest catch of menhaden was obtained at Manomet Point (79% of the study area total). The catch at Long Point was numerically dominated by Atlantic silversides (94% of the station total). At this site, we recorded the highest catches of Atlantic tomcod (100% of the total), cunner (97%), river herring (97%), silversides (84%), and northern pipofish (82%). As to ts.@ oral changes in catch composition, June's catch was dominated by Atlantic herring, comprising 93% of the month's total. In July, Atlantic silversides (53% of the monthly total) and sand lance (40%) predominated. Silversides led all catches in August (88% of total), F mtember (981 , and October (92%). River herring (mostly blueback herring) also surged in August.
- 4. Underwater Finfish Observqtions I Observational diving began in early May, with a total of 13 l dives made through mid-October. Over 1,900 fish, corprising 8 species (Table 6), were observed at the sampling stacions (See Figure 2 in Section II (Introduction) of S;mi-Annual Report #39).
Invertebrates noted included the blue mussel (Myri!ns ed:elis) , lobster, I starfish (As!crias spp.) , and rock crab (Cancer ir oranu) . Estimates of lateral visibility (obtained with a diver-held secchi disk and metered line) ranged from 1.5-9 m (average 4.6 m), depending on sea condition and incident light. In an attempt to determine the degree of influence of visibility as a controlling factor in diver observations, we plotted mean annual fish per dive values against average visibility for the years 1981 to 1991. No I 32 5 m
I relationship was discernablo (e.g., in 1987, visibility averaged 6.3 m with sightings of 41 fish per dive, whereas in 1984, visibility averaged 3.7 m and divers observed nearly 200 fish per dive). I f able 6. Aburdince and distribution of finfish species recorded during underwster observations, Ma/ to 0 tober,1991. Wster Percent Station I Spec'es tunner observed by divers 1,219 of tctet 63.7 where most abundant 0, striped bass 255 13.3 D, e t wef it,h 203 10.6 D, -I Tautog Other* 191 47 10.0 D, 2.4 I Total 8 species
- Pollock, Rock gumel, Winter flounder, and Crulhy 1,915 I The total number of fish recorded in 1991 (1,915) was 25%
lower than in 1990 (2,563 fish), due primarily to decreased sightings of tautog, striped bass, and bluefish. Using number of fish cighted per dive as an index of relative abundance, data from 1981 through 1991 are plotted (Figure 19). In 1991, prohet .. soe . ;- divers reported an average of =i ( ; 147 fish per dive, a 20% " $ = c_.~
,=
decrease from 1990 (183 fish per '# 5 dive), but still substantially Se-higher than that recorded from .
~
, . , , ,mM wat es ass wa4 a n was w usa teae ieeo i.ei 1985 to 1989- . As 'shown in m ,, %, ,, ,, l Figure 19, more fish were I observed '7 the discharge area Per dive) for all SPeti'5 (Pool'd) observed by divers at Figure 19. trdices of relative abundance (fish Pilgrim Station, 1981 1991.
I 33 I -
I (61%) than in the control (28%) and stunted (10%) areas. Cunner Occurring at all stations, cunner was the finfish species observed in greatest numbers by project divers, comprising 64% of all sightings (Table 6). Cunner were equally distributed in diver counts between the discharge (43.6%) and control (43.6%) areas, with the remaining 12.7 % found in the stunted area. A cunner per dive index of 94 was similar to that noted in 1990 (98). A plot of conner per dive data (Figure 20) for the entire study period ,, roo reveals the 1991 index to be on a par with pre-1984 levels. _ gy Examination of individual e ~f' %_ h v _ li 4 5 h'i K y 9 length estimaten made by project : - '~ !: ;' :).g E % to -
, l &:,
- 3 g &
; ; v . $ #: ;
divers revealed that far fewer p g. g,, j p: s. g b g g i. . g small cunner (2-3 cm) were sighted in 1991 (27% of the Figure 20. Indieu of relative abundance (fish per dive) for cunner observed by divers et Pilgrim a total observed) than in 1990 l (74%). This is most likely relatea to year-class strength. Striped Bass and Bluefish __ Striped bass and bluefish ranked second and third, respectively, in our 1991 diver observations (Table 6) . Indices of 19.6 fish p u dive for striped bass and 15.6 fish for bluefish are the second highest recorded in the diving study. Local occurrence and abundance o#f Pilgrim Station of both species can be strongly I affected by year-class strength and fishing mortality. Commonly angled from the discharge jetties, both species were sighted by divers almost exclusively at Station D 2 , inside the mouth of the 34 I
I discharge canal. On several dives, we observed both bass and bluefish noving in the discharge area at the same time. With very little intermingling, the bass were layered at or near the bottom while the bluefish were arrayed above them from mid-water to just belos the surface. ME Ranked fourth in fish sighted (Table 6), tautog were recorded in much lower numbers than in 1990. A substantial decrease in catch per unit effort for this species; in 1991 was also noted in project gill-net catches. A comparison of data on fich por dive for this species (Figure 21) indicates that local abundance is still far higher than in 1987 and 1988, but no where near as ,,, high as in 1990. It should be 33 . noted, however, that the number '5 ' w: 1 4 I of tautog observed by divers in T o . the discharge area has ,o . 7 , T , {J'a fluctuated widely since the ' l jf5
] [
ir.ception of observational "' "' ' '" "I[
- g * * * * '
~
diving. Tautog generally were Figure 21. Indices of relative abundance (fish per dive) for tautog observed by divers at Filgrim found to be nilling about the " * " " ' mouth of the discharge canal, most commonly on the inside of the southern-most discharge jetty.
- 5. Sportfishica Surve_y I The Shorefront recreational area at Pilgrim Station was opened to the public in 1991 on the first of April and was closed at the end of October following a severe /five-day northeast storm that caused extensive lamage along the western shore of Cape Cod Bay.
35 I - - --
I Salt water sportfishing is allowed at the Shorefront during daylight hours, and an informal survey of this shore-based fishery was conducted by seasonal public relations perse mel from Boston Edison Company. Creel data were obtained during uhe period of 18 May through 31 August, which included 80 sampling days. Before and after the survey, DMF biologists made spot checks at the Shorefront to monitor sportfishing activity. A reported 1,492 angler-trips were made to the Shoreft ;nt in 1991 during the actual survey and 903 finfish caught, comprising 6 species. The daily average number of shore fishermen at the plant site was 19, which is not much different from last year's mean of 18 anglers per day. Species recorded in the sportfishery in 1991 included two pelagic fish - bluefish and striped bass - and four groundfish - cunner, tautog, pollock, and skate spp. The pooled monthly catch rate peaked in August, averaging 1.0 fish per angler-trip, while the overall seasonal mean was 0.6. In 1990, the overall average catch was 0.4 fish per angler-trip. No creel data were collected from April through mid-May. From our observations, however, fishing pressure was f airly light in April and early May. Fishing effort (angler-trips) increased throughout the summer, peaking in August. A core group of anglers sought bluefish and- striped bass in September and October. However, the is:mber of bottom fisherman and overall effort declined. in the fall. Bluefish (71%) and cunner (27%) comprised 98% of the surveyed I sportfish catch. As for monthly catch totals, bluefish and cunner [ predominated in June at 58% and 35% of the catch, respectively; cunner (66%) and bluefish (30%) in July; and bluefish (90%) alone in l 36 5 m l
I August. The highest monthly catch occurred in August, when 63% of the pooled seasonal total was obtained. Catches by species peaked as follows; bluef*'h in August, cunner and tautog in July, and striped bass in June. Cunner, tautog, pollock, and skate spp. were taken off the outer breakwater, while bacs and many of the bluefish were caught in the discharge outf all area. Some bluefish were c.lso landed in the Intake embayment, where a school of juvenile Atlantic horring abounded this summer. - We me.de the following observations in the f cill . On several occasions in September and October, we witnessed numbers of bluefish swirling and " breaking" in and on the periphery of the thermal plume of 1)llgrim Station. Anglers fishing from of f the two discharge jetties e.nd from anchored boats hooked numbers of bluefish on surface lures (mainly poppers). These fish caught in the fall were not included in the sportfishing survey records, but undoubtedly would have increased substantially the anglers' success statistics. I 6. Cunner Taccina and Acina We have tagged cunner to aid our investigation of their movement patterns and spatial distribution in relation to the rock structure (with emphasis on the outer intake breakwater) in the Iilgrim area and to the thermal discharge from the Power Station. Our intent is to increase information on the behavior and dispersion of local cunner, stressing their susceptibility to impact of the effluent current, our collaborative aging work is ongoing to characterize the age-structure of the local cunner population as we tag and release fich off the plant. I m
I This species forms discrete, local populations that inhabit l temperate marine rocky reefs - including ledges, outcrops, and man-made rock structures, e.g. , jetties and breakwaters - that serve as IiI refuge areas. They are bottom fish that occupy small home ranges, exhibiting only seasonal inshore / offshore movements that are temperature regulated. ' 1
, Cunner were frequently sighted by us, while we were diving in !
the Pilgrir area. They of ten resido under rock outcrops and within the interstices of the outer intake breakwater at Pilgrim Station d'1 ring the warmer months. The large boulders comprising the breakwater provide substrate for attachment of macroalgae and sessile fauna that serve as cover and a food source, respectively. The rocks and associated crevices provide shelter (home sites) for this structure-criented fish which requires a safe haven during its nocturnal sleep phase. Cunner are active during the daytime and often aggregate in loose foraging groups to feed on planktonic organisms in the water column and on epibenthic and infaunal species on current-exposed surfaces of hard substrates. During August and Septe-ber of 1990, we captured and tagged 84 cunner just seaward of the outer intake breakwater at a reference location. In late May 1991, we resumed trapping cunner. Numbers of cunner were obtained off the outer breakwater at tLis time; some were ripening. From these captured fish, we retained a sub-sample for aging, releasing the others. Between June 20 and October 10, 1991, we made 18 outings to tag cunner off Pilgrim Station. We I captured 1,515 cunner in 1991, tagging 654 (h 11 cm total length). All tagged fish were released in the area of capture, while most of I 38 5 m
II l i l the untagged fish likewise were released. This allowed for the possibility of recaptures. Of the fish captured (1,515) in 1991, 77% were taken in the reference area and 23% in the surveillance area. Of the fish tagged (654) in 1991, 76% were captured, tagged, and released in the reference area, while 24% were tagged in the surveillance (discharge) area. Over the last two years, a total of 738 cunner has been tagged off Pilgrim Station. In 1991, 53 cunner were recaptured, representing 7.2% of the total tagged to date. of the recaptures, 40 were resightings by biologist-divers on SCUBA surveys,11 were recaptured in baited eel pots, one was taken in an experimental gill net, and one was caught by an angler at the Shorefront. As to tagging location for the recaptures, all but one were tagged in the reference area; the one exception was tagged in the surveillance area. All returns came from the reference area except for one, which came from the gill-not station location. The time-at-large included a few fish that were recaptured the same day they were tagged to cunner at large for almost a year. Most of the recaptures were taken within a month of their tagging. From the collaborative aging work done on cunner (n= 56) off the Power Plant this summer, eight age-groups were present in the sampling: ages 2-8, and 10 (Table 7). Young-of-the year and yearlings were observed in the study area but were not captured in I the aging sample. The fish that were aged rt nged in size from 8-30 cm total length (T. L. ) . All 8-10 cm TL cunner were two year-olds. Forty-three percent of the fish aged were two and three year olds. I
, 29
. . - - - . . . . . ~ .- - .---._..-.. ..--... - ... ... .....- --.~ - - - - .- - .-.. - .----. .-.
l The majority of fish tagged were presumably two and thrco years old (61%), ranging in SiZO from 12-14 Cm T.L. Table 7. ADe cottEn$ltion in ruter of fish ard (percent of total) with t;tal length 3 seasurecents (cm) of cunner captured of f Pilgrim Station in 1971. Age kwter Mean St arderd Range of ' Group of Fish length Deviation Lengths 11 14 (25) 10 1.5 8 13 111 10 (18) 13 1.1 11 14 ly 9 (16) 16 1.1 15 1B y 9 (16) 17 1.1 15 19 7 y1 $ ( 9) 20 0.7 19 21 yll $ ( V) 21 2.4 18 24 ylli 3(5) 24 0.0 24 , n 1 ( 2) 30 0.0 30 I: I I I. I' I-I t a I I 40 E' i - -.
I V. HIGHLIGHTS LQb_itel._- Commercial Fishery
- 1. Catch statistics and biological data for the commercial 1
{ lobster fishery in the Pilgrim area were collected from 5,562 ) lobster sampled from May through October, 1991.
- 2. Catch per unit effort of total lobster (2.3 CTH) decreased 8%
from 1990 (2.5 CTH)
- 3. Legal catch rate decreased 16% from last yec.r, declining from I 0.44 to 0.37 legals per trap-haul.
Lobster - Research Stusly
- 1. Fifty-three sampling days of research pot fishing (June to September, 1991)-yielded 9,682 lobster (57% male; 43% female) captured from 2,650 trap-hauls, with legals comprising 10% of the catch.
- 2. Study area catch rate of legals (2 82.6 mm carapace length-CL) declined 12% from 1990, the second consecutive annual decline in the six-year time series. Study area sublegal (< 82.6 mm CL) catch rate remained unchanged from 1990, after having I risen annually since 1986.
- 3. Only 1.5% of the research catch of female lobster were ovigorous (carrying eggs).
- 4. Carapace lengths of lobster in research catches ranged from 33-114 mm, and averaged 75.3 mm, which is slightly smaller I than the mean size from last year.
- 5. The cull rate remained at 29%, identical to last yaar's value.
I 41
I Nearnhore GIpyndfirsh
- 1. Twenty-one fish species were collected oy bottom trawling in the nearshore area of Pilgrim Station.
- 2. The average catch per standard tow for all species and stations combined declined to 3.9 fish / tow.
- 3. Atlantic herring ranked first in total catch, however, this was due primarily to the capture of 300 juveniles during one tow off Priscilla Beach. This species is rarely caught by our trawl.
- 4. Winter flounder ranked second in total catch at 14.5%. Catch-per-unit-effort declined for the fifth year to 0.6 fish per tow.
- 5. Little skato ranked third in total catch '9%); overall abundance dropped by 50% to 0.4 fish / tow.
Polacic and Benthi-Delanic rishes
- 1. Comprising 20 species, 1,012 finfish were gill netted during 11 overnight sets.
l 2. Annual mean CPUE of pooled species (82.3) increased 20% from a l 1990. E
- 3. Pollock ranked first, comprising 41% of the catch. Atlantic herring was second (23%),and cunner was third (6%).
I Shore-Zone Fish
- 1. Twenty-seven finfish species were haul seined from June I through October, 1991 in the Pilgrim area; three of these species - Atlantic silverside , Atlantic herring, and sand lance - comprised 99% of the catch.
I 42 E E
I
- 2. Increases from 1990 in the catches of Atlantic silverside,
. Atlantic herring, and sand lance contributed to the increase in the overall 1991 seine catch r%e in the Pilgrim area.
- 3. Seine catch rates (pooled species) increased from last year at three of the four sampling sites.
- 4. Atlantic silverside continued to dominate seine catches, comprising 46% of the total. They ranked first in overall catch per unit effort and in percent frequency of occurrente -
in the catches. Their relative abundance almost doubled from last year.
- 5. Atlantic herring (all juveniles) ranked second in seine catch abundance, with most taken in the Intake embayment at Pilgrim Station.
- 6. The total number of fish seined was greatest in the Intake, but species diversity was highest in the catches at Long Point.
Underwater Finfish Observations
- 1. A total of 1,915 fish, comprising 8 species were observed during 13 dives in 1991.
- 2. Total number of fish observed was 25% lower than in 1990, due primarily to decreased sightings of tautog, striped bass, and bluefish. Observed fish were distributed as follows: 61 % in the denuded zone, 28% in the control zone, and 10% in the stunted zone.
- 3. Cunner was the most common species seen (64% of the total) and was found at all stations. Fewer small cunner were sighted than in 1990.
, 43
Il
- 4. Fish per dive indices for striped bass, and bluefish were the second highest recorded for the dive study.
- 5. Far fewer tautog were S. ed than in 1990 and were found primarily in the discharge area.
fippy111shina Survey
- 1. Sportfishing was surveyed at the Pilgrim Shorefront from mid--
May through August 1991. I
- 2. A reported 1,492 angler-trips were made by shore-based fishermen to the Shorefront and about 900 fish, representing 6 species, were caught during the survey.
- 3. Bluefish (71%) and cunner (27%) comprised 98% of the surveyed recreational catch.
- 4. Overall effort and catch were up from last year. The catch of bluefish was up, but striped bass catches were down.
Cunner Taccina and Acina 1.- Collaborative aging work is ongoing to characterize the age-structure of the local cunnar population off Pilgrim Station.
- 2. The fish aged this summer measured 8-30 cm in total length (TL) and were from 8 age groups 8 and 10 year-olds.
- 3. We tagged 84 cunner in 1990 and 654 cunner (2 11 cm TL) in 1991 off Pilgrim Station using Floy T-bar anchor tags.
4.- In 1991, 53 tagged cunner were recaptured, representing , 7.2% of the total tagged to date.
- 5. The time-at-large ranged from recaptures the same day of tagging to fish at large for almost one year.
44 g a
I
- 6. From recaptures, movement of cunner off Pilgrim Station appears to be limited at 1 cast during the warmer months of the I year.
I I I I g I I I I - I I I -I I I I '
VI. ACKNOWLEDGEMENTS The authors thank staff members, John Chisholm and John Costa, for collecting and processing field data and acknowledge Neil I Churchill, Paul Caruso and H. Arnold carr who assisted in diving operations. We thank Chris Kyranos for his valuable assistance in lobster sampling, and Raymond Dand and Robert Ellenberger for collecting sportfish data at the Pilgrim Shorefront. Jay Burne't of the Nationa) Marine Fisheries Service at Woods Hole aged cunner collected from the Pilgrim area using otoliths and scales. Much , thanks to Kim Trotto of the Division for word-processing various sections of this report. Finally, we appreciate the continued guidance of Robert D. Anderson of Boston Edison Company, W. Leigh Bridges of the Division, and members of the Pilgrim Administrative-Technical Committee. Their input on study programs and editorial comments on project reports and pap <3rs have been most helpful. I 5 I I I ' ( 46
-(>
LI l VII. _ LITERATURE CITED I Aiken, D.E., and S.L. Waddy. 1982. Cement gland development, ovary maturation, and reproductive cycles in the American lobster, H<vnams an.cricanus. Journal of Crustacean Biology 2 (3): 315-327. Briggs, P.T., and F.M. Mushacke. 1979. The American lobster in western Long Island Sound. New York Fish and Game Journal I 26(1): 59-86. Ennis, G.P. 1983. Annual variations in standing stock in a I Netfoundland population of lobsters. Porth American Journal of Fisheries Management 3:26-33. I Estrella, B.T., and S.X. Cadrin. 1989. Massachusetts Coastal Commercial lobster trap sampling program May-November, 1988. Commonwealth of Massachusetts, Division of Marine Fisheries. 23 pp. Kelly, B.C. , V.J. Malkoski, S.J. Correia, R. P. Lawton, M. Bor gatti, at:d B. Hollister.1987. Annual report on monitoring to assess I impact of the Pilgrim Nuclear Power Station on marine fisheries resources of western Cape Cod Bay (vol. ;). Project Report No. 42. in: Marine Ecology Studies Related to Operation of Pilgrim Station. Semi-Annual Report I BECo, Braintree, MA. No. 29. Lawton , R. P. , V. Malkoski, S. Correia, B. Kelly, C. Sheehan, I M. Borgatti, and P. Brady. 1987. Final Report on Marine Recreational Fishing at the Pilgrim Station Shorefront:1973-1975, 1983-1986. Pilgrim Nuclear Power Station Marine I Environmental Program Report Series No. 3. Boston Edison Company. 53 pp. Lauton, R.P., W.T. Sides, E.A. Kouloheras, R.B. Fairbanks, I M. Borgatti, and W.S. Collings. 1978. Final report on the assessment of possible effects of Pilgrim Nuclear Power Station on the marine environment. Project Report No. 24 I (1970-1977). Massachusetts Division of Marine Fisheries. ID: Marine Ecology Studies Related to Operation of Pilgrim Station. Final Report, July 1969-December 1977. Vol.1, sect. III.9, 19 pp. Nuclear Engineering Department, Boston Edison I. Company, 800 Boylston Street, Boston, MA 02199. Lawton, R.P., B.C. Kelly, V.J. Malkoski, M.R.Borgatti, and J.F. I Battaglia. 1990. Annual Report on monitoring to assess impact of Pilgrim Nuclear Power Station on marine fisheries resources of western Cape Cod Bay.- Project Report No. 48 (Jan.-Dec. I 1989). 10: Marine Ecology Studies Related to Operation of Pilgrim Station. Company, Braintree, MA. Semi-Annual Report. 35. Boston Edison I 47 I i
I Miller, R.J.1983. Considerations for conducting field experiments with baited traps. 'icheries 8(5): 14-17. Miller, R.J. 1990. Ef fectiveness of crab and lobster pots. Can. J. Fish. Aquat. Sci. 47: 1228-1251. Northeast Fisheries Center. 1991. Status of the Fisheries E Resources off the Northeastern United States for 1991. E National Marine Fisheries Service, Woods Hole, MA 110 pp. Robins, C.R., R.M. Dailey, C.E. Send, J. R. Drooker, E.A. Lachner, R.M. Lea, and W.D. Scott. 1991. Common and Scientific Names of Fishes from the Uni:cd States and Canada. 5th Edition. Special Publication No. 20. American Fisheries Society. 183 PP. I I I I L I I tti
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1 I 48 l l 5
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- l I ANNUAL REPORT E_ ON
-E- ENVIRONMENTAL IMPACT MONITORING OP
- PII. GRIM NUCLEAR POWER STATION (JJ4 PACT ON MARINE INDICATOP. SPECIWSS1 Project Report No. 52 (January-December, 1991)
- (Volume 2 of 2)
I By I~ Robert P. Lawton, Brian C. Felly, Vincent J. Malkoski and Mando borgatti i JI I I iE- April 6, 1992-
'g'- ' Massachusetts Department of s'isheries,
-Wildlife, and Envir;orimerital Law Enforcement Division of'Mt..rinn Finheries
,l* 100 Cambridge Street Boston, Massachusettu 02202 4g I
g l
7
- v
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TABLE OF CONTENTS Sectip_D Pace I. EXECUTIVE
SUMMARY
1 II. INTRODUCTION 2 III. RESULTS AND DISCUSSION 4 A. Physical (Abiotic) Factors 4
- 1. Power Output and Thermal C"nacity 4
-2. Discharge Current 5 J. Water Temperatuc 7 B. Impact of Pilgrim Station on Indicator Species 10 1.- Cunner 10 2.- Lobster 18
- 3. Striped Bass and Bluefish 33
- , 4. Atlantic'Silverside 40 r ,
- 5. Atlantic Menhaden 44
- 6. Winter Flounder 48
- 7. Tautog 51 IV. ' IMPACT PERSPECTIVE 59
. V. CONCLUSIONS' 60 VI. ACKNOWLEDGEMENTS 68 VII. LITERA'/JRE CITED 69 I
g 11 g
LIST OF TABLES Table Eggg
- 1. -Indicator-species selected to assess impact 3 of Pilgrim Nuclear Power Station.
- 2. Catch per _ unit effortt - from research lobster 26 gear in the Pilgrim area for 1991.
- 3. Striped bass' recorded off Pilgrim Nuclear Ctation 35 l (PNPS) and plant operational capacity (MDC) for 1983-1991.
~
I LI I i g 3
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'.ST OF FIGURTIS Fiaure Ease
- 1. Annual means and 19-year cumulative mean 4 Pilgrim Station Unit I Capacity Factor (MD0 Not-t) for 1973-1991.
- 2. Circulating seawater pumps operating by 6 month at Pilgrim Station, 1983-1991. .
- 3. Surface water temperatures in the Pilgrim 8 area averaged by season for the years, 1983-1991.
- 4. Avarage seasonal standard 5-panel gill-net 14 catch for cunner and respective seasonal MDC Net % at Pilgrim Station, 1973-1991.
- 5. Annual legal lobster catch per trap-haul in 21 control and impact areas near Pilgrim Station, 1983-1991.
- 6. Commercial legal lobster catch rates (catch per 22 trap-haul per set-over-day) for western Cape Cod Bay, 1981-1991.
- 7. Legal lobster catch rates (CTHSOD) by area from 26 E research lobster gear fished in the vicinity of 5 Pilgrim Station, 1986-1991.
- 8. Sublegal lobster catch rates (CTH) by area from 27 researen lobster gear fished in the vicinity of Pilgrim Station, 1986-1991. g
- 9. ' Monthly legal lobster catch rates (CTHSOD) by area 28 -
from research lobster gear fished in the vicinity of Pilgrim Station, 1991. 10 :. . Monthly sublegal lobster catch rates (CTH) by area 29 from resaarch lobster gear fished in the vicinity of Pilgrim Station, 1991. .
- 11. Mean catch per standard haul seine set of Atlantic 43 silverside collected along the Plymouth shorelines
.of wastern Cape Cod Bay, 1984-1991.
- 12. Mean.. annual gill-net catch of (5-panels) of Atlantic 45 g menhaden and annual MDC operational level at Pilgrim g Station, 1973-1991.
I iv sK u - __ - - _____________-__ -_-_________________ - _____-_-_______ - _ - - _____ ___ _ - -_ _ _ -
I I 13 . . Mean annual catch per tow of winter flounder and 51 annual % MDC operational level at Pilgrim Station for I 1982-1991.
- 14. Mean annual 5-panel gill-net catch of tautog and 58 annual % MDC operational level at Pilgrim Station for 1973-1991.
I I I I I I I - 1 I I i 1 I ' I
I LIST OF PLATES I l Plate 1. Biologist collecting length-frequency data from the catch of a commercial lobsterman in the proximity of Pilgrim Station. Lobsters constitute the area's most valuable l
-fishery resource.
Plate 2. Operations aboard a fishing vessel used during the ! experinental lobster study. This investigation is designed to better assess the impact or- lobscers of the El E , thermal effluent at Pilgrim Station, l Plate 3. Retrieval of the experimental gill net after a standardized overnight set in the thermal plume area. Caught in the net is a smooth dog!ish, a common summer migrant in the Pilgrim area. Plate 4. Fishes caught by gill-net in'the area of the thermal plume at Pilgrim Station. Gill-net catches include gi commercially important species, e.g., Atlantic cod, g pollock, . Atlantic mackerel, striped bass, and winter flounder. Plate 5. Bottom trawl being set to sample groundfish in the inshore waters of western Cape Cod Bay. Catches are used I to measure potential impacts of Pilgrim Station on the E benthic fish community. E . Plate- 6. Typical trawl catch is processed which includes 3 identifying, enumerating, and measurjng the different I species for environmental assessment. Catches of winter
-flounder have been consistently. largest at the Pilgrim Station intake trawl stat. ion.
Plate .7.. '{aul seining in the intake embayment at Pil@im Station: the net'is being set from a powered-skiff to enclose a rectangular area. Seine catches can be integrated with 5 impingement data for a more comprehensive evaluation of potential impact on shorezone fishes. Plate 8. Haul seine catch processed on the beach near the Pilgrim Station intake (fish are enumerated and measured) . Among the-shorezone fishes are important forage fish such as the Atlantic silverside and sand lance, and the juvenile stages of several commercial species such as the winter flounder and Atlantic menhaden. I vi a_
4
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.s Plate 9. Tagged cunner seen swimming off the seaward side of the outer intake breakwater at Pi.lgrim Station. Diver t observations have recorded the greatest number of fish sighted of f Pilgrim Station to be cunner, which are structure oriented.
Plate 10. A winter flounder on the bottom near diving station D3 (approximately 50 m seaward of the discharge canal) in the " denuded" cone off Pilgrim Station. An important I. commercial and recreational fish, flounder inhabit the Pilgrim area throughout the year and have been used as an
" indicator" species to assess stress imposed by the release of the heated effluent.
Plate 11. Pictured is the thermal effluent discharging into Cape j Cod Bay and anglers fishing off the dincharge jetties and B from boats in the plume which is visible in the background by the caln water. Striped bass and bloefish, g which are attracted to and concentrate . in the_ thermal the dominant species sought by sport 5 curreut, are fishermen at this location. Plate 12. Striped bass aggregate in the thermal discharge current
.<I at Pilgrim _ Station, often swimming just off the bottom into and out of $he discharge canal. Eass are attracted to moving water as a feeding ground.
1 I 1: I g: I g vii E I _ _____ _
I I. EXECUTIVE,JUMMARY In accordance with the Pilgrim Nuclear Power Station NPDES Permit requirements of, the Massachusetts Division of Water Pollution Control and the U.S. Environmental Protection Agency, marine fisheries monitoring and reporting were completed for 3991. Fisheries data were collented to .sroat impact of Pilgrim Station. We emphasized data comparisons of high operational years with years of low or no output. During the past year, operational status at Pilgrim Station was 58.4% of capacity. The following is a summary of findings. 4 Sportfish and gill-net catches and diver observations of bluefish and striped bass indicate that the heat and current of the thermal dischargo effect a shift in the rpatial distributions of both species in the Pilgrim area. 9- The cumulativo effects of entrainmerit, impingement, and sportfishing have contributed to a reduction in the local cunner population. 9 Our research lobster program indicates a negative correlation l-between;sublegal lobster catch rate at sampling stations in the l discharge area and the release of the cooling water disc:.arge.
- 8 While diving, we have observed few lobster ' residing in the immediate outfall area when the plant is operating most likely because of the discharge current which would limit their mobility.
9 Losses of Atlantic -silverside, _ Atlantic- menhaden, winter flounder, and tantog via entrainment, impingement, sportfishing, L and gas bubble disease do not appear to be significant. I I
I II. JNTPODU_qTJQM The Massachusetts Division of Marine Fisheries conducts a field' monitoring program to assess impact of Pilgrim Nuclear Power Station (PNPS) on mar 3ne fisheries resources in the offsite waters of western Cape Cod Bay. This investigation is funded by Boston Edison Company (Purchase Order No. 68004 in 1991). Focusing on the lobster population and finfish populations in the Pilgrim area, we sample at surveillance and comparable reference sites employing a variety of gear types. Data on measurements, counts, percentages, and indices of abundance are used to exaraine for relationships both spatially and temporally. These data are summarized in graphs, plots, and tables to elucidate patterns or trends. Descriptive and inferential statisti al proccdures are used to test station I differences or differences over time between plant operational and non-operational periods. Volume 2 is an assessment of PNPS impact on selected indicator species in the Pilgrim area. We have gone from a presentation of g data results by gear type to one of an indicator species, focusing on eight species (Table 1). The following plates (1-12) depict vs.rious field sampling operations in our assessment program. I I I I a
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Table 1. Indicator species selected to_ assess impact of Pilgrim Nuclear Power Station. Besis for Possible Background Selection as an Sources Sanpling Species History- Indicator Species of I @ect Method American tobster RIS d,r,c I,E,T/C intake screens / trap / trawl / diving /gittnet Atlantic silverside RIS d,r I.E 1/C,G intake screens /haut seine / trawl Atlantic menhaden- RIS d,c I,E,T,G intake screens / seine / gilt net Cunner RIL d,r,s 1.E.T/C intake screens / diving / seine / gitt net /sportfish catch Winter floundar RtS d,r,c,s 1,E,T/C intake screens / trawl / diving / seine /sportfish catch /gittnet Tsutog IS d,c,s,r (seasonally) I,E,T/C int.ke screens / diving /gitt net /sportfish catch Bluefish IS c,s,d (erssonalty) T/C,I diving /gitt net /sportfish catch / seine / intake screens y Striped bass IS c,s,d (seat switty? T/C diving /gitt net /sportfish catch RIS - representaCve species selected in the originet 316 (a and b) Dem,nstration Doc +snent to assess Pilgrim Station inpact (Stone and Webster 1975). IS - indicator species; was not an criginal Ris tmt after I decades of data collection, we added it to the list. d- e dcvninant species in the Pilgrim area. r- a local resident c- comnercial irportance s- recreational importance
!- impingement E- entraireent T/C + discharge current effects: thermat/ current G- gas bubble disease
I III. RESULTS AliQ E SCUSSION A. PHYSICAL-(ABIOTIC FACTORS)
~
I 1. Power Out;put and Thermal Canacity When assessing impact of the thermal ditscharge from pilgrim Station on marine populations in the offsite waters of western Cape Cod Bay, we must consider the station's capacity factor (MDC net percent). This index of operational status approximates thermal loading 1:1 the outfall. At 100% MOC, there is a permitted, allowable maximum temperature rise (AT) in the effluent of 18* C (32' F) above ambient. Since power production began in November 1972, the annual MDC at the station has ranged from 0.0% for outage years (i.e., 1987, 1988) to the high of 84.4% in 1985 (Figure 1). The power ' level was 0.1% in 1984, which was essentially an outage year. In addition to 1985, other high output years that exceeded 80% were 1979 and 1983. The output iri 1991 averaged 58.4% of capacity. The overall 19 . year - mean is 47.4%, UNIT 1 CAPAOTY FACTOR (1.) E-with 10 of the years g, E
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0 39[h ($ S ,@p$ h $p In Volume II, data UU~ 7 h: b '$ x If b k g gj I'd h y h ['J 7 E g Jor selected species are [ y [ [ , ana1yzed and 0.y3.j,,73.je,y7.je*70sodi*e2e3'e4'es'60'er'eeso'do01 YEAR comparisons stressed
- i. nu ou. wm ... -mu E3 ANNUAL ME ANS years om mu between the of Figure 1. Arn.at means ard 19 year ctsnulative mean Pilgrim 1983, 1985, and 1990 station unit 1 capacity rector (Hoc wet %) for 1973-1991.
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e.g., Atlantic cod, pellock, Atlantic mackerel, striped bass, and winter flounder, a' E
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. Catches of winter flounder have been consistently' largest at the Pil-grim Station intske trawl station.
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,E recorded the. greatest number of fish sighted off Pilgrim Statica E? to be cunner, which are structure oriented.
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Plate 10. ' A winter flounder on the bottom near diving Station Di (- 50 m, seaward of the discharge canal)- in the " denuded" zone off Pilgrim Station. An important comercial and recreational fish, flounder inhabit the Pilgrim area throughout the year and have been used as
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's r. e pn ~ , W . , g g~ ee m n g.m , g%g. I ggggg w m s g ~ pgg g ~p g y-t 3%:m4;0h. i pgMEMBIE Plate'11. Pittered is thet thermal' effluent discharging into cape Cod-Bay, and anglers fishing off the discharge jetties and from boats in F
- i. the plume which is visible in the background as the calm water.
L Stri ped bass-and' bluefish.. which are attracted to and concentrate -
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I (high operational output) and years of low or no output: 1984, 1986-198P. In 1991, the thermal capacity was 0.0% for May-July,
.I-28.5% in f.ugust, and 23.7% in November because of outages.
- 2. Discharoe Current The circulating seawater pumps at Pilgrim Station induce a localized current. The once-through cooling-water system draws water p om the intake ch*.nnel to remove wasto heat, primarily from the plant's condenser tubes. The waste water is discharged in a
/ current of water back to Cape Cod Bay. The moving water, which can reach velocities approaching 2.1 m/sec (7 ft/sec) at low tide, has a scouring effect on the Bay bottom. The two circulating seawater pumps draw in 1.17 x 10 6 liters / minute (310,000 gal / minute) of ,
water from the intake embayment. In late November 1991, we took measurements of the discharge current velocity on an ebbing tide with both circulating pumps operating. At 100 m from the discharge canal we obtained velocity measurements of 84 cm/sec (2.8 ft/sec) at the surface and bottom. Auster (1987) reported that a tidal current velocity approaching 50 cm/sec (1 kt) is current-limiting to many reef fish species. Both circulating water pumps were run simultaneously for most 1 of 1983 and 1965 and all but the months of March and April in 1990. During the outage in 1984, both pumpe were off from late March to mid-August, thus markedly reducing disenarge flow (Figure 2). In 1986, both pumps ' were operated f rom January to early March; but thereafter, during the prolonged outage, only one pump was operated at a time. As the outage continued into 1987, both circulating
I NUMBER OF PUMPS IN OPERATION I 2- -- --- - - I I i I g,. .I' \
\
l ? 4 l t i I I O- , . m. m. . l.4 983 198 1985 1 B8 987 1688 19 9 1 90 99 Figure 2. circutettr5 seawater puros operating by month at piterim station, 1983 1991. la pumps were turned off from late February through early September, while one pump generally ran for the rest of the time. In 1988, with the outage still ongoing, one pump was on for most of January-Merch and .une-December, but from mid-April to early June, both pumps were again off. In 1989, the plant gradually increased power production as it returned to full operational status, one pump was operated .in January, February, May and October; otherwise, both were run. In 1991, only one pump was run from May-July and in much of November during outage periods. I E
- 3. Water Tercerature Water temperatures it. the Pilgrim area over the last nine years (1983-1991) were highest in the discharge outfall (Area 3) in 1983 and 1985 (>80% power plant capacity) and in 3990 (> 70%
output), as a result of the waste heat (Figure 3). Conversely, i surface temperatures in the discharge area were markedly lower for the outage years: 1984, and 1986-88, when waste heat and current are-minimal. In 1989, with Pilgrim's thermal capacity averaging 28.9%, there was some thermal elevation at the surface in the
-immediate receiving waters. The years, 1983 and 1985, show-the maximum temperature difference that occurs between the discharge area and other sites during.the seasons and, therefore, the impact potential of waste heat on the environment (Figure 3).
With Pilgrim Station fully operational, the near-field area impacted by the thermal discharge has contained a 1,100-1,400 m3
' denuded' zone, believed to be primarily a result of scouring. A peripheral-zone of ' stunted' algal growth occurs of about 1,900 -
2,900 m2 in area, most likely resulting from the thermal component of the discharge. In late November 1991 on an ebbing tide, we ran a transect perpendicular to shore, out from the discharge structure, and measured surface and bottom water temperatures. We found a temperature rise at 100 m on the surface and bottom. When Pilgrim Station has operated at full capacity, an Tilowable temperature rise of 18' C can occur in late summer in the l effluent water. The highest temperature recorded in the thermal l plume has been 32' C, recorded both on the surface and bottom. In l
I u MEAN SURFACE WATER TEMPERATURE DlbCHARGE ARE A* Il
.. TE MPE A ATURE C g
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I I. TEMPER A!UFit C 20- - 15-9 -mI
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I ,$. , i t 234 5 1 2 3 4 5 1 234 5 1 2 34 S E-C 1993 C3 ices ! a WINTER SPRING SUMMER FALL
. No can e:Lasta som inis anna iN wiNtem E
AR(A EfYg
- 1. G R Af 's D E AC M 4 L0t 9 P0lNT
- 2. mRREN COVE 4 ROCXY POIN T
- 4. Ol8CNARGE AREA 4 6 N TA E E
- 5. WMBT$ HOR 5t 4 MANOMET P 0 6 8. T Figure 3. Surface water temperatures in the Pilgrim area !
average A-* season for the years, 1983-1991, I:, 8 h i
._ L n.a.--.4.6 - wa- -am-, A- w,- a & _
I: 1984 (outage year), 1986 (Outage April-December), and 1987-88 (outage years), water temperatures in the outfall area mirrored ambient.- ! l l l . I i I I I I; l
- I .
LI l I.. u ! l-; I I:
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g I
I B. IMPACT OF PILGRIM STATION ON INDICATOR SPECIES
Background
The cunner is an abundant groundfish resident in the inshore vatera'off-Pilgrim Station. Being shelter dependent, they reside in rochy areas that abound off the Plymouth shoreline, including the man-made breakwaters and jetties at the power station. Cunner occur in discrete populations and are more likely to be measurably I affected by point-source pollution than a species waich exists as essentially one interbreeding population throughout an extensive geographical range, e.g., Atlantic menhaden. A good indicator organism'to assess plant impact, cunner have small home ranges and, as such, may be exposed to increased sportfishing mortality and potential effects of inshore pollutants. Cunner are especially
' vulnerable after dark, since low responsiveness to stimuli, characteristic of the sleep state of labrid fish, reduces their ability to avoid environmental stresses that might occur at night.
B. From recaptured fish in our cunner tagging study off Pilgrim E Station, we have evidence of their site tenacity. All but one of the returns came from the area of-tagging, indicating the fish were relatively sedentary at least during the warmer months. Gill-net, diving, and creel sampling data document that the cunner is a dominant fish off Pilgrim Station. The power plant's intake breakwaters and discharge canal jetties provide added structure to the naturally occurring glacial till for a temperate-water reef community, of which the cunner is a member. The large I l B_ '
.. boulders provide shelter imperative to this species sleep phase and cover to . escape current velocities that impair the fish's maneuverability.
Normally distributed at depths of 3 m to 10 m, some populations do occur in deeper water (Grosslein 1969) . Year-round residents throughout much of their range (Green and Farwell 1971; Olla et al. 1975), cunner will move seasonally to deeper water to I. escape cold temperatures. In the Gulf of Maine (Bigelow and Schroeder. 1953 ) and off Newfoundland (Green and Farwell 1971), cunner activity wr 'ound to decrease at water temperature below 8' C. -Olla =et al. (1975) found that in the fall at temperatures of 5-6' C, cunner become inactive and then torpid, remaining so until the water warms above 6' C in the spring. Life Stages Impacted and Sampling Protocol Potentially, cunner may be impacted by Pilgrim Station via mechanical and waste heat / current effects. Cunner appear to spawn near the power plant. We captured ripe cunner seaward of the outer intake. breakwater in May 1991. Because the eggs and resultant larvae are pelagic, they are subject to entrainment in the plant's circulating seawater system. Routine entrainment sampling at Pilgrim Station provides quantitative data on the early life stages of cunner drawn into the plant's condenser' tubes. Juveniles and adults (aged to 10 years off Pilgrim Station) occur off the plant, including in the intake
.I -
embayment, and are subject to impingement on the travelling-water screens. Impingement data routinely collected at the plant and 11
.I-
I haul seine sampling in the intake provide information on plant-
. induced mortality, seasonal occurrence, and general abundance of cunner. The discharge current laden with waste heat and periodically with chlorine can influence all life stages of cunner in the receiving waters. Gill-net, observational dive, and sportfish creel sampling together with tagging provide data on cunner in the discharge area and its environs. Cunner are expected to be most affected by station operation during summer and fall I when they are active and most abundant off Pilgrim Station.
Impingement and Entrainment Effects Impincement Adult and juvenile cunner have been entrapped on the intake screens at Pilgrim Station. This species has been among the dominates impinged from 1976-1980 (Lawton and Anderson et al.1984) and from 1981-1991. .In 1991, cunner were first impinged in January and last-in October, leading the impingement collection in May. Over the years, more cunner have been impinged from June through September. Impingement can be relatively high as it was in 1980, when about 1,700 cunner were impinged at Pilgrim Station. There is some survivorship of impinged cunner at the power plant, e.g., 24% in 1989. Nevertheless, an impingement of this magnitude could impact the local population in a given year when combined with
'sportfishing mortality and a depressed stock size. The present population appears to have declined in abundance.
I I. n
l I l Entrainmerit
-Numbers of cunner eggc and larvae are entrained at Pilgrim Station'every year.
The labrid and Labridae - Limanda (Pleuronecies)
; groups dominate collections of fish eggs at the station during the history of plant operation, comprising >90% of the eggs entrained.
Johansen (1925) reported cunner spawn from May to August in New England-and Canadian waters. Williams (1967) reported spawning temperatures of 10*- 26' C. In 1991, cunner eggs were entrained at Pilgrim Station from May-September but were most abundant in June samples. An especially high density of cunner eggs was entrained at +9e station in June 1989 which might have explain the unusually i_ ge number of 5 cm cunner observed by us while diving just outside the clischarge canal in 1990. Over the years of plant operation, cunner eggs have been entrained as early as March or April when ambient water temperature has been as low as 2.6* C (Scherer 1984) . Scherer (1984) hypothesized that mature cunner may ripen and spawn earlier
\
E. in the area warmed by the thermal discharge. In 1991, cunner larvae were entrained at Pilgrim Station beginning in late May. Highest densities were obtained in June, while the last larvae were sampled in September. Unusually high densities af cunner larvae were entrained in June of 1989 and in July and August of 1990. No such densities were obtained in 1991. Marine Research, Inc. (1991) concluded that large quantities
.I- of spawn (fish eggs and larvae) can be entrained at Pilgrim Station during a year and are assumed to be lost from the I 13 I
l l l respective populations. A high percentage of these are cunner. l 5 Discharge and Sportfishing - Related Effects on the Population Population si;Lq In 1991, cunner ranked in its traditional third position in the hierarchy of gill-net catch composition off Pilgrim Station. The local population appeared to be fairly stable from 1971 to 1976 (Figure 4); over these years, the mean catch rate was 22 cunner per standard gill-net set. From 1977 to 1983, the yearly catch , , , . , , , , , 100 loo rates generally doubled (X = 41 eo - - so fish per set). This suggests ,, . y 'l M 7 . ,, g there was a marked change in .. .
" I t IIf y, di 77 j c 2 i!
kE f} c $ h y 9 I jjj distribution or abundan:;e of the no 7 - ro
! !s r kF p:
~
};,),, ',,,,
*gf g7, g, i,< ,,,,a' y:,,
local population. The catch '
~g,, ,o YEAR rate had been declining l CCUNNER CATCH = MAY OCT MDC gradually from 1981 to 1984, but F e 4. wmuawsw %'te net catch for cunner and respective seascnal MDC idet %
then dropped sharply in 1985, et pilgrim station, 1973-1991, remaining at a low level thereafter. Over the last seven years, the gill-net catch rate of cunner has declined by 70% from the previous eight years, averaging only about 12 fish per set. The local stock evidently has declined, with the 1990 and 1991 catch rates of recruitable cunner being the lowest on record (Figure 4). Discharae: thermal / current Temperature tolerance data on cunner (Kinne 1969; Briggs 1973) suggest that the waste-heat effluent from Pilgrim Station should 14 a.
not cause overt mortality of this species outside the discharge canal. Ilowever, during the late summer and early fall when ambient water temperatures peak in Cape Cod Bay (Lawton et al. 1983), if the power plant is fully opera.lonal there likely is created an exclusion area to cunner within and just outside the confines of the discharge canal. Observations during our research dives in the discharge area (limited to flood tide) in August and September 1991 revealed there were substantially fewer cunner at the mouth of the discharge than out at 60 m in the path of the thermal plume. We ressured bottom temperatures in excess of 30* C in September at the discharge canal-mouth. These temperatures are stressful to cunner and would be avoided if possible. Kinne (1969) reportcd the upper thermal tolerance for adult cunner to be 29' - 30' C at an acclimation temperature of 18' - 22' C. During spring, temperatures in the thermal plume outside the effluent canal at Pilgrim Station are ideal for the hatching of cunner eggs. According to Williams (1967) cunner hatching occurs in less than 48 hours at 27.1* - 22.2* C. The preferred temperature range of adult cunner is 13' - 26' C (Stone and Webster 1975). In autumn, ideal conditions for cunner growth should exist immediately outside Pilgrim's discharge channel. We graphed plant output, i.e., thermal capacity, for the spring and summer seasons, when cunner are most active innhore, versus the gill-net catch rates for cunner over the years (Figure 4). When catch rates for the period prior to the crash in cunner stock abundance were statistically compared to seasonal power plant 15 4:. ,
I MDC for operational years, wc. found a significant positive correlation (P $ 0.05) and a highly significant F ratio (P( 0.01) using regression analysis. Thirty-nine percent of the variability in gill-net catch rate could be explained by variation in plant load. Eleven years of observations mado during the course of 146 SCUBA dives off Pilgrim Station revealed that cunner has been the finfish species of greatest abundance in the vicinity of the o outfall. For example, in 1990 and 1991, 53% and 64%, respectively, of the fish docurented by project divers were cunner. Diving observations and gill-not data suggest that cunner of about 5 cm and larger are attracted to Pilgrim 4s discharge flow at high tide. Woolner and Lyman (1984) reported that bottom-feeding [ fish, for the most part, are nore active when the tide it. moving as opposed to slack. During plant operational periods, and at high tido, we have observed greater numbers of the larger size class individuals in the faster current region of the ' denuded zor.e' than un in either of the peripheral ' stunted' or ' control' zones. Even 5 without a great amount of waste heat released at the station, the 3 generation of a water current produced by at least one of the two 3 circulating seawater pumps at Pilgrim Station is of sufficient velocity to shif t the small-scale spatial distribrtion of cunner by size class. However, during times when little or no discharge current was rele -sed from the power stetion, more cunner were found in the ' control' area. Cunner are attracted to moving water to feed, as they will I u
1 I forage on surfac.as exposed to current for epifaunal and infaunal prey and in the water column f or planktonie organisms. I Olla et al. (1975) observed that when cunner are feeding in the water column j with a current present, they will face into the moving water while visually searching ict food to be carried by them in a scan-and-pick feeding modes It is known that small cunner, e.g., 2-; cm fish (young-of-I the-year), do not move far from their home shelter. Furthermore, i l _ the speed of the offluent curren: at Pilgrim Station, which can reach 2.1 m/sec (7ft/sec) at low tide, is too ctrong for these small fish to spend any amount of time in the discharge when the plant is operating. When small cunner abound in the Pilgrim ares i. and if the plant is operational, these individuals most often will reside in the ' control' area. noster (1987) found at different sites throughout New England that larger cunner foraged further from roof substrate and on current exposed surfaces for longer time periods. As current velocity decreased, he found smaller size classes of cunner moved up into the water column out of the reef infrastructure ar.d onto current-exposed surf aces to feed. As the speed of the current increased the process was reversed. Soortfishina Effects over tha years that the Pilgrim Station Shorefront has been open to the public, cunner of ten has led the shore-based sportfish catch. Cunner are caught readily by anglers bottom fishing off the outer intake breakwater at the station. They ranked second in the l sportfish catch at the Shorefront in 1991. In mid-July, an angler L ' l 17 1
I' caught one of our tagged cunner on the seaward side of the outer breakwater. Cunner have small home ranges which they occupy for an extended time period. This exposes them to the potential of 1 increased sportfishing mortality. Most cunner caught at Pilgrim Shorefront have been allowed to die, and fishing mortality on the local. populstion can be aigh. In 1983 and 1985, for example, about j 2,600 and 3,500 cunner, respectively, were landed by anglers at *. . Shorefront. Interestingly enough, the gill-net catch rate of ' cunner for 1985 dropped precipitously off Pimyrim Station. To address fishing mortality, we are encouraging fishermen, via posters placed at the shoref.ont, to release their catch alive if the cunner are not kept for consumption. Presently, there is no market for the sale of cunner.
- 2. Lobster
Background
The American lobster inhabits rock-strewn ledge and sand bottoms of Cape Cod Bay and is the object of intensive commercial and recreational fisheries in the Pilgrim area. It takes approximately seven to eight years for lobster to molt to legal size in Cape Cod Bay. Fertilized lobster eggs, typically extruded in late summer, are carried through the winter by females and hatch from late spring until summer. The young lebster enter a three wenk plor.ktonic stage before taking to the bottom. Entrainment at Pilgrjm Station of lobster larvae would be expected during late
- 18 5
_m . _ _ _ _ _ _ I spring and summor. Juvenile and ad' alt lobster move stomewhat offshore to deeper water to overwinter. In April as water temperrtures warm, lobster move inshore and remain until the late-fall offshore migration. It in during their inshore stay that lobster may be either impinged at the plant intake or affected by the waste heat and discharge current at Pilgrim Station. Life Stages Impacted and Sampling Protocol Any potential impact of Pilgrim Station on the lobster would most likely_ occur during the benthic-dwelling juvenile and adult stages. Few lobster larvae have been entrained over the years of operation at Pilgrim Station. Intake impingement sampling has recorded low numbers of juvenile lobster over the years. For example, in 1991, a total of 51 sublegal lobster (mean size 47 mm CL) were collected on Pilgrim's intake screens, which equates to i almost. 900 sublegail lobster annually impinged at 100% operation of Pilgrim Station. We typically ca ure quantities of sublegal lobster from May t I through July during our travling survey. catches are not used to assess power plant However, trawl lobster impact, due to sporadicity and unpredictability of lobster occurrence in the net. Gill-not catches of juvenile and adult lobster are low. To ascertair, impact of plant operation on the local lobster population, we raly on our trap sampling p:ograms: commercial and research. Discussion of the results of those programs for 1991 follows. 19 t
I Discharge Related Effects Commerciql_Lpbster Pot-Catch Fishery Pooled lobster catch statistics from the surveillance (discharge) quadrants (H-11, 11 - 1 2 , I-11, and I-1.2) were compared with data from the reference quadrants (E-13, E-14, and F-13) located in Warren Cove (see Figure 2 in Vol.1) to assess impact of Pilgrim Station on the local lobster population and fishery. Realistically, we can compare surveillance and reference area catch rates from 1984-91 (1985 and 1990 being the only high output on-line years in that period) because the same lobsterman supplied all of the data. Catch data from 1983 are included in our discussion because this also was an on-line year of high operational status. Males outnumbered females in the commercial catch from the Pilgrim study area in 1991, comprising 55% of the total. This preponderance of males existed at both the surveillance (52%) and reference (61%) areas. As in the previous five years, the percentage of culls in the surveillance area (20%) in 1991 was lower than in the reference area (25%). A chi-square test (Sokal and Rohlf 1969) showed this difference to be non-significant (P = 0.06) for the first time in six years. An increase in the loNter cull rate is promoted by lobster fishing and bottom trawling (Keser et al. 1983; Estrella and McKiernan 1986) . Both study locations are subject to intensive commercial lobster *ishing. In addition, commercial bottom l trawling in Warren Cove is seasonally (November through March) l conducted for groundfish; this aay account for the higher cull rate r I R l
there. The 1991 mean commercial legal lobster catch rate (expressed a.3 catch-per- trap-haul, or CTH) increased 30% and 9% at the reference and surveillance sites, respectively (Figure 5). In the surveillance area, CTH increased only slightly from 0.32 to 0.35 __. legals per trap-haul, while in " y es- - e t=, the reference arca the catch "
,,. ; e
]
rate rose from 0.27 to 0.36. es. . - : Annual lobster catch rates in M > j 1, kA I 1 .m a& I,= m the impact area do not appear as =4 au an ar ma me no mi YEAR measurably difforent between museo m ot em l years of on-line and off-line Figure S. Annuat (egal totster catch per trap-haul in control and Inpact areas near Pilgelm $tation, plant status, in that the CTH N 1*
- ratios of impact versus control sites from the high operational years of 1983 and 1985 are comparable with the ratios from the off-l line years of 1984 and 1986, as is that of the on-line year 1900 contrasted with that of the off-line year 1988 (Figure 5). Since 1987, catch rate in the impact area has been equal to or greater than that of the control area. There is no apparent relationship in the annual catch ratios between these study sites to the annual operational status of the Pilgrim Power Plant.
A brief discussion of the annual commercial lobster catch lzm- rates (Figure 6) and landings for western Cape Cod Bay and for g Massachusetts' coastal waters in general provides a basis with which to compara annual Pilgrim Station impact and surveillance 21 I-I
I area lobster catch rates. A ,,,,3,,,, cooler ambient temperature a u ' 5 regime in 1984 (Estrella 1935) m / ,,,, q j
, ;; w ~
v _ ' M apparently depressed or at least '
- m ,
, g. .
delayed tho early season lobster s, e; y& y; v-
.:p ,
g
$ h '5 molt, which, in turn, would have 3 Y f affected subsequent recruitment c # V
' Ti .ife ... ... nu
~
sj
... ..j, .'en ... i$it.T
? -
-, 3l I
to legal size and would also Figure 6. conrereint teset tobster catch rs. l (cetch per trap haut per set over day) f or western Cape have lowered lobster activity cod Bay, 1981 1991. (Campbell 1983; Estrella 1985). This is reflected in the mean ! ccmmercial catch rate of 0.48 legals per trap-haul in western Cape l Cod Bay in 1984 (Lawton et al.1985), which represented a reduction of 30% from the 1983 value (0.68) (Figure 6). Accord 2ng to Estrella (1985) and Estrella and McKiernan (1986), the coast-wide commercial catch rate (catch per trap haul) of marketable Jobster i in 1984 was lower than in 1983 and 1985 by 19% and 20%, respectively. Commercial legal catch rates for western Cape Cod Bay then I rose to 0.72 in 1985 and 0.82 in 1986 (Figure 6). Record lobster landings were documented along the entire Massachusetts coant in 1985 and 1986 (Estrella and McKiernan 1986). Cape Cod Bay lobstermen had to contend with cooler spring temperatures again in 1987, and a 34% reduction in the coastal commercial landings resulted (Estrella and Cadrin 1988). The Bay legal catch rate declined markedly to 0.53 in 1987. Catch rates in the Bay were as follows: 0.75 in 1988, 0.53 in 1989, 0.63 in 3990 and 0.60 in 1991. I e a
I
'L Tne upswing in the overall 1988 catch rate in Cape Cod Bay may well have been influenced by a more normal spring bottom water temperature regimo. Actual commercial landingr (in pounds of lobster) for all of Cape Cod Day in 1989 increased 20% fron the previous year, which suggests that the relatively low overall commercial CTH for vestern Cape Cod Bay in 1989 (Figure 6) may be a sampling artifact of the lobsterman sampled (Bruce Estrella, L $
5 personal communication). The mean legal catch rate la the discharge area declined from 1983-1987, thereafter stabilizing with the exception of an upswing in 1989. This trend contrasts somewhat with the commercial lobster catch rates (Figure 6) and landings for ostern Cape Cod Bay as dir,cusred above. Annual legal CTH in our control area (Warren Cove) did not parallel these commercial data from 1983-1986, but did reflect a drop in 1987 and subsequent increase through 1989. Our selection of reference quadrants changed during the time series of lobster data collections. The present reference quadrants, all located in Warren Cove, have been in use since 1984, during which time there have been only two years (1985 and 1990) of
.I high plant operational status; in 1991 the plant was off-line for half the inshore lobstering season (May-July).
d Impact area lobster catch rato data (not normally distributed) and plant thermal output vore examined for a relationship using a nonparametric test for association, Kendall's coefficient of rank corrolation (Sokal and Rohlf 1969). The association analysis utilit.ed the mean Unit I thermal output for the period of May 23 I -
I through November, which encompasses the inshore lobster fishing season, versus '<. gal catch rates for tha surveillance area during the full and partial on-line fears (1973-1983, 1985, and 1990-1991). A nonsignificant Kendall's concordance of 0.440 (P=0.58) was found. Earlier in the study, we ran a parametric correlation test of the data from 1973-1983 and found a significant negative , correlation (P50.05). l As to the limiting effect of current on catch rate, Auster (1985) reported that a water flow above a critical velocity (46 cm por sec) will retard the foraging behavior of lobster by inhibiting mobility. It is reasonable to expect there would be reduced trap ' catches in the immediate discharge area, where current velocity can reach over 2 meters per second (7 feet per second) at low tide. In fact, our diving observations have revealed few lobster in the immediate area of the discharge canal. However, a direct cause ad effect relationship between the thermal discharge current and the commercial lobster pot catch in , the impact quadrats is difficult to substantiate because we have no 5 control of fishing effort, including the location of traps fished. We have been investigating this relationship with our research lobster study, which is discussed later in this section. In 1988, with considerably more current (though at ambient temparature) emanating from the discharge canal than in 1987, the commercial catch rate of legal lobster remained unchanged in the surveillance area. In 1989, with seasonal thermal capacity at 36% and with one or both circulating water pumps operating, CTH i^. the impact area L u n
increased substantially. In 1990, with seasonal thermal capacity at 77% and both circulating pumps usually running, the impact catch I rate declined. In 1991, with a seasonal thermal capacity of 37% and one pump running from May-July, the catch rate increased. These differences most likely reflect natural year-to-year variability in this area. Commercial gear sampled in the impact quadrats is often deployed at a distance far enough from the discharge canal that the effluent current is most likely not a major factor affecting lobster distribution and resultant catch. In a continuing effort to standardize commercial lobster catch data with our experimental lobster data, the commercial legal lobster catch information in the discharge and surveillance areas I were weighted ty immersion time (days between pot-hauls) of the pots to generate catch per trap-haul pc.r set-over-day (CTHSOD) , a more accurate measure of catch per unit effort. In 1991, the legal CTHSOD incroaced slightly in the control area from 0.08 in 1990 to 0.12. Conversely, CTHSOD declined from O.17 to 0.14 in the impact area. Besearch Lobster Trap Fishing Research lobster trap campling was conducted for the sixth consecutive year (June through September, 1991). Our objective is to assess the impact of the operation of Pilgrim Station on the local lobster population. The following parameters have been examined: i I catch rates of legals and sublegals, size frequencies, sex ratios, culls (lobster with missing or regenerating claw (s)), and ovigorous (ogg-carrying) females, 2e g g
I fable 2. Catch per unit ef fort' f rom research lobster gear in the Pilgrim area for 1991. Legal stred Lc6 ster Sublegal Lobster itB2.6 m CL2 MMpJ } Mean +2 Mean y Arcs CTH!.C0 $tardard trrors C1H $tarderd Errors Discharge Area 0.154 0.145 0.163 2.990 2.928 3.0i.6 ($urveillance) Rocky Point (Reference) 0.162 0.153 0.171 3.706 3.645 3.767 Priscilla Beach (Reference) 0.199 0.185 0.213 3.062 2.902 3.1/2
'CTH represents catch per t.sp haul; CTHLT ltdicates catch per trap haut per set.over day.
We sampled 9,682 lobster from 2,ss3 trap-hauls in the study I area. Catch data for sublegal lobster overall, as measured by catch por trap haul (CTH), averaged 3.29, the same rate as in 1990. CTH for legals in 1991 declined from 0.41 (1990) to 0.36. When weighted by immersion time (days between pot-hauls) of the pots (CTHSOD), which is a more appropriate measure of catch per unit of effort for legal lobster, the overall catch rate fell slightly from 0.19 to 0.17 for the study area in 1991. The 1991 legal catch , rates (Table 2, Figure 7) declined slightly at both reference sites (Priscilla Beach and Rocky 8 5 Point) buc decreased more at the ,, m n u m u tun = m impact **' site ' (Dischargo). , ]
*2 1 M , e However, the catch rates of g,, p .p fn m,g e s y]{
lj- 3 di ' sublegals (Figure 8) were '
.l "
.h l! h hj bpg I!!
esse.1tially unchanged from last c,o. J f! T 1asa E I[3 j 1987 j
^
.!! k inaa 5 i i Rj tote jj taso
?fi JR e{ N E 10a1 s
[ g' year in all three areas. " as . ua. ca .euu a 8"*"""' C'""'"" The overall study area' sex g ratio of males to femaler in the Figure 7. Legat lobsm catch retu' (Cmm) by area from research lobster gear fished in the vicinity of Pilgrim Station, 1986 1991 1991 research catch was 1.3:1, - l 8
I similar to 1990 ratio of SUBLEGAL CATCH RATE (CTH) 1.2:1. The annual research ]9 gj I lobster sex raLio has been n 7 9 M E , 5h! 's li! 1! Ei e yi ppj j f c I }(( I relatively constant for the f! s q s y '
-Tis > jp
- S h '
; 'l fi!
j six year study off Pilgrim ' :- G '
}] 3 EU .'
i!D Hs E e r" I Mi !! station. 8
- d. ,,,, ,,6 e; ,;; ,
YEAR The percentage of , _ , am I females ovigorous in the 1991 Figure 8. swtegat teester catch rctes <ctH) by area i research catch was 1.5% (61 f rom research totater seer fished in the vicinity of Pilgrim
$tation, 1986 1991.
eggers), ac c mpared to 1.2% last year. The percent females ovigorous was similar at each of the three sites. During the six-year study, no pattern in the distribution of ovigerous females has emerged amongst the sampling zones. I The percentage of culls in the research data increased from 27% in 1989 to 29% in 1990, where it remained in 1991. Over the six years, the cull rate has been lcaest in the Discharge area. The rate was highest at Priscilla/ White Horse Beach in 1986 and 1987, at Rocky Point in 1988, about equally high at both reference areas in 1989 and 1990, and highest at Rocky Point in 1991. Initial analysis of 1991 legal CTHSOD and sublegal (CTH) lobster catch rates revealed the data was non-normally distributed which could not be satisfactorily corrected by transformation. Hence, nonparametric Kruskal-Wallis tests were performed, corresponding to the experimental design of a nested ANOVA (Sokal and Rohlf 1969), using the BMDP statistical software (BMDP I 27 I !
l Statistical Software, Inc. 1990). To test for differences amongst the three ar9sta in 1991, legal catch rates were initially tested 'o ascertain if data across
, I.
months within stations at a site could be pooled. We first had to l insure we could statistically pool monthly catch data within a station, and only then would pooling of station data for an area be considered valid. At four of the ten stations (these all boing at Rocky Point), the S6ptember legal catch rates were significantly greater than some or all of the other months (Figure 9). e,,,,, 0.9 Therefore, higher 3evel testing us. , ,
- n. !? E 'e m of catch rates by pooling !n (( _ N!r t y !!! m I l gd Mi E stations and comparing areas was c.
d - in@ .A m u 3 J! {5 j 2 g iE Si not undertaken. g in : a $l g O g JUN AA AUG SEP Data analyses subsequently Wom um ==.. t: noon ... changed from pooling months ma r .au ta == usaaro l within stations to pooling Figure 9. Monthly legal Lobster catch rates (Cih500) by area f rorn research lobster sear fished in g stations within a site on a * * ^ * ' " " " ' " * " " ' a monthly basis, and then areas were contrasted on a monthly basis. As there were no significant differences (P>0.05) amcngst monthly station data at any of the sites, station data were subsequently pooled- month 2y within each site. Monthly comparisons of legal catch rates amongst the three sites were performed using 1991 data. The legal catch rate off Priscilla Beach was significantly greater (P50.05) than at both the Rock) Point and Discharge sites in July, while for September, the rate at Rocky Point was significantly 28 5
I greater (P50.05) than at the Discharge. A markedly lower catch rate in the Discharge may be related to the full operation of I Pilgrim Station in September with a substantial amount of waste heat and current present. Sublegal catch rates were analyzed using nested Kruskal-Wallis analyrus across months, after initial analyses showed suolegal monthly catch lata could not be pooled within a station. On the lower level monthly tests (within uite by month) for June and July, there were sites with station (s) significantly different (P50.05) from eacn other, while in August and September, there were no significant differences amongst the stations within each of the arcas. Hence, pooling of montniy sublegal catch 1 ;es was ,,, m _ I statistically questionable for June and July. After inspecting :
~;6 E
m-f[d!!h $ta 7 e mn E the data (Figure 10), we ' h h SI I decided to make monthly areal comparisons of sublegal catch
- =y .
uours
=j d$ ...
rates by month, with an attached as ,.a . cm . = .... ma .. cua ca ma mmio statistical caution. There were Figure 10. M,mthly sublegal catch rates (CTH) by area from research tobster gear fished in the vicinity no significant difforences ""'""**i'"'** l amongst the sites in June. 'In July, the Rocky Point sublegal catch rate was significantly greater (P20.05) than that at the other two sites, a pattern also observed in 1990. As in 1990, the sublegal l catch rate at Rocky Point was significantly greater (P50.05) than the Discharge in August, while in September, *Le catch rate at I " I _ ._ .
Rocky Point was significantly greater (P50.001) than at the other ' sites. Analyses of sublegal catch data by month for the Discharge I area revealed that Station H had the highest sublegal catch rato of all four discharge stations for every month. Stations E, F, and G had signifie ntly lower (Ps0. 05) sublegal catch rates than at Station H in June; while in July, the catch rate at Station G was significantly less (P50.05) than Station H. Stations F and G would I most likely be affected by Pilgrim Station's thermal discharge, as they are closest to the discharge canal, while Station H would be least expected to be impacted (see Figure 2, Vol. 1). We measured the speed of the bottom discharge current at Station G to reach 69 cm per sec at low tide. This could impact the sublegal catch rate by reducing the mobility und maneuverability of small lobster (Auster 1985), thus chifting the small scale spatial distribution by size class in the discharge area. Howard and Nunny (1983) showed with the lobster, Homams gammamt, that their distributicn is limited by tidal current and wave action to low current areas on the bottom on a size selective basis. This study provirica u wich an opportunity to examine for a relationship between lobster research catch data from the Discharge area and Pilgrim Station's thermal output (as an index of plant operational level) within a season. The nonparametric Kcndall's coefficient of rank average correlation was performed on 1991 data. Average Unit I Pilgrim Station Capacity factor (MDC Net %), calculated for those days when we fished pots in the discharge, was 30 m.
I correlated with sublegal catch rates and then with legal catch rates per sampling day at each of the Discharge stations during the on-line period of mid-August through September. Data from thL period June through mid-August were not used for this analysis, as the MDC Not % was zero. There were no significant correlations between legal catch rates (CTHSOD) and plant MDL. However, significant negative correlations between sublegal catch Iste an1 MDC were noted at Station F (P=0.004), Station G (P=0.007) and Station H (P=0.02). Due to the limited dataset available to use in this analysis, we must be cautious in our interpretation of the results. Catches at the adjacent control site at Priscilla Beach also fell from August to September. This may reflect a generalized local movement of lobster in the Priscilla/ Discharge area. A possible inverse relationship between plant operation and sublegal catch rates at Stations P, G, and H is nonetheless interesting. 7 summarize, sublegal catch in 1991 was shown to be typically 1 mr at Station G than at the other discharge stations by Kruskal-Wal:is statistical analysis. With only a partial dataset available, three of the four Discharge stations showed a potential inverse relationship between Pilgrim Station operational level and sublegal lobster catch rate. There is another quantitative approach to ascertain Pilgrim Station impact. Limited to a single impact area (treatment) and having two reference areas, we used the extended outage (unstressed) perii4 at the plant (1986-1988) to establish the 31 I - - - -
relationship between areas, using the ratio of the biotic measure (catch rate) obtained at the discharge site (pooled for stations) to the average of the two reference sites (pooled ntation data). Future changes in the ratio during plant operation would be examined for impact on the local lobster population. inis follows the methodology offered by Thomas and Van Voris (1986) for power p'. ant environmental impact assessment. This procedure acknowledges , the intrinsic ' impossibility' of finding identica] reference locations, and therefore trend alterations in the resultant impact / reference ratios are monitored. The grand mean ratio for legals was 0.826 and for sublecals, 0.819 for the three outage years, 1986-1988. For 1989, a transitional year in poar operation, the ratio for legals equaled the three-year average, 0.826; whereas, the ratio for sublegals clir. bed to 0.910. For the full power year, 1990, the legal ratio increased to 1.021; the sublegal ratio was 0.857. For 1991, a summer of low power production, thn ratio for legals was 0.856, , with the sublegal ratio being 0.883. With additional year (s) of 5 on-line data, we can compare the annual research lobster catch rates from the discharge (impa t) area between on-line versus off-line periods. Additional data from high operational years are needed. As in 1989, we viewed 1993 as a low power generation year relative to the period - June through September - with plant output at 31%. I 32 g a
I
- 3. Striped bapp_aud_Illuefish
Background
Striped bass and bluefish are coastal, migratory, pelagic species that are highly prized by recreational and commercial fishermen. Both were among the top three gamefish sought by sport Marine fishermen in Massachusetto (Massachusetts Division of Fisheries 1977). Dluefish and bass have been the r ost sought af ter a fish in the shore-based sportfishery at the Pilgrim Station Shorefront. The former led the sportfish catch and the latter h 1 elected them as ranked third at the "horefront in 1991. of the thermal discharge at indicator species to assess impact Pilgrim Station. They are seasonally abundant in the outfall area as spring to f all migrants, with striped bass arriving inshore in Massachusetts from May to June. Offshore in April and May and bluefish migrations occur normally in October for bluefish and in 11ovember for bass. Both gamefish are voracious predators that are attracted to moving water, e.g., currents and tidal rips, where the velocity of the running water incapacitates smaller fish and invertebrates making them casy prey (Woolner and Lyman 1983) . Ristori (1989) adds that most marine game species feed when there is a current running but cease this activity in slack water. Pilgrim Station's once through, opan-cycle cooling system produces a continuously flowing, pump generated thermal current that can attract game fish to the outfall area. I I I . _ _ _
I Life Stages In.pacted and Sampling Protocol Realistically, tLe potential source of Pilgrim Station impact on striped bass and bluefish is from the discharge via thermal and current-induced effects. The thermal discharge can affect the juveniles and adults of both species in the receiving waters. Entrair.uent of their pelagic eggs and larvae is not a concern because neither spawns anywhere near the power plant. Impingement g has not been a problem because both species are strong swimmers and E generally can avoid plant impingement. Over the years, no bass and only four bluefish, til young of-tha-year (" snappers"), have been impinged at Pilgrim Station. Gill-net fishing, diving, and a creel survey provide data on bass and bluefish in the discharge and intake areas of the plant. Haul seining in the Plyrouth area occasionally has produced catches of " snapper" bluefish. 4 Discharge and Sportfishing Related Effects Discharae: thermal / current Strined bass Despite the precipitous decline in striped bass abundance along the Atlantic coast that began in the mid-1970's, the numbers of bass recorded in the Pilgrim area year to year clearly are related to plant operation (Table 3). Pilgrim Station's thermal discharge attracts, concentrates, and holds bass. When the power plant is operational and discharging a noticeable current of water, bass numbers are up off the plant; and conversely, when the station has been in an outage, low numbers have prevailed. Comparing the years, 1989-1991, in Table 3 illustrates this well. Furthermore, I
I the pooled grand mean 5-panel gill-net catch rate of bass captured during the high operational years of 1;i?,1985, and 1990 was 88% higher than the grand mean for 1984,1986-1989 (outage or low output 3 I fable 3 $triped bass recorded off Pilgrim Wuclear Power Station (PkPs) and plant operational capacity Oct) f or 1983 1991 PWPS No. Observed Sportfish Gill net tot htti, by Diver
- Q,uh Cetch Date 1.t8.t 80.3 24 150+ 0.3 I
1983 1984 0.1 0 0 0.0 1955 84.4 145 =400 5.3 1986 17.5 10 0 0.3 1967 0.0 1 2 1.2 I 1988 1989 1990 1991 L.0 8.9 72.3 58.4 0 52 481 255 3 3 150 9 0.7 0.5 7.1 2.8 I years. During 11 years of diving off the plant, 98% of the bass have been seen in the path of the discharge current. They generally occur in an aggregation, swimming near the bottom up into the discharge canal and back out for about 20-30 m in & presumed search pattern. A second effect of the waste-heat discharge is the exclusion zone to striped bass that occurs in the better part of the thermal plume at Pilgrim Station in August and perhaps part of September because of high water temperatures. The surface temperature usually peaks in August, and the bottom temperature, in September. A surface temperature of 22.7'c has been obtained in August out as far as 0.8 km offshore of the power plant. We recorded bottom temperatures of up to 32*C in August and September of 1990 and 1991 at the mouth of the discharge canal. At 60 m offshore of the canal in the thermal plume, bottom temperatures of 22'-25'C were obtained se y I . _ . . .
I at the same time of year in 1990 (high operational year) . Catches and sightings of base are at their lowest in the discharge area in August. They are especially active at water temperatures between 7* and 21' C (Smith and Wells 1977). The water temperature preferred by striped bass changes with age, with i the juvenile and adult life stugas having different environmental requirements - in particular, the need at larger fish for cool water (Coutant 1985). A summer habitat suitable for adults has E water temperatures between about 18' and 25' C. The thermal tolerance for adult bass is 5 25'C; temperatures above this are harmful and will be avoided. Prolonged exposure to temperatures above 27'C is most likely lethal to bass (Smith and Wello 1977). P_is.Ofish The first bluefish caught in the Pilgrim area traditionally are taking in June it: the thermal plume. Lund and Maltezoc (1970) reported that bluefish migrate inshore when the water warms to 12 *- 15*C and seldom are abundant below these temperatures. The earliest bottom temperature record we have of bluefish occurring ir. Il! the Pilgrim area is 15'C. The thermal elevation of the cooling water has delayed the emigration of bluefish from the outfall area. Normally -absent from the inshore waters of western Cape Cod Bay by October, when the water temperature falls to about 13' to 15' C, bluefish were still being. caught by anglers in the thermal discharge when the sho efront closed at the end of November 1985. At the time, we obtained temperature measurements in the thermal plume of 10*C j 36 i E' E i I
(bottom) and 17'c (surface). Adult bluefish can survive temporarily down to at least 7.5'C (Lund and Maltezos 1970) but will avoid temperatures of 10*C and below, if possible. According to olla and Studholme (1971), the preferred temperature range of bluefish is 19' - 22*C; the optimum is 20'C. With an upper avoidance temperature of 29'C (Wilk 1977), bluefish i I would be excluded from part of the discharge area in August when I l the waste water can exceed 30*C. Diver observations and gill-net catches support this contention. Pilgrim Station's discharge attracts bluefish mainly because of the current. Lyman (1974) reported that bluefish are drawn to moving water (rips, currents, etc). Bluefish of ten rise to the surface at dawn to feed and will continue to do so until satiated or until the tidal current slackens or light intensity increases (Lund and Maltezos 1970). On foggy days, bluefish found in rips often feed near the surface until the current goes slack. When the power plant is operating, a continuous current of water is discharged. On many occasions, we have seen bluefish.
' breaking' for-hours at the surface in and on the edge of the thermal plume. That bluefish concentrate in the outfall is substantiated by our sampling programs. The number of bluefish recor'!ed is generally low in the Pilgrim area when the plant is not g
LM operating or only discharging a low-velocity current, but a conversely, is relatively high with the plant fully operational. Eg l Despite the coastwide decline in commercial and recreational , catches of bluefish throughout the 1980's (Northeast Fisheries l
- I "
l LI
I' Center 1989), the pooled grand mean gill-net catch rate of bluefish off Pilgrim Station for 1983,1985, and 1990 (high output years) was I 45% higher than the overall mean for 1984, 1986-1989 (outage, low output years). Bluefish were seen by our divers off the plant in 1983 and i 1989-1991 (years of at least partial station operation) . Divers sighted no bluefish, however, during the outage years, 1984 and 1986-1988. Ninety-one percent of the bluefish visually were observed in the ' denuded' zone as compared to the ' stunted' or
' control' zones. Our diving index of bluefish relative abundance in the immediato discharge area (i.e., observed fish per dive) increased from 1.5 in 1989 (low plant output - 28.9% of capacity) to 21.0 in 1990 (high operational year- 72.3%), and than declined I somrawhat in 1991 (58.4% plant output) to 15.6. Bluefish typically aggregated in the upper water column and were seen swimming in an elongated oval pattern from the terminus of the discharge je* ties out to about 60 m off the discharge canal.
There is a direct link between station operation and the sportfish catch of bluefish. The presence or absence of a strong thermal discharge current at Pilgrim Station results in good or poor sportfish catches, respectively, in the outfall area. Creel surveys at the P31 grim Shorefront revealed that an estimated 1,000 bluefish were landed by anglers off the plant in 1983, and 2,200, in 1985._ Both were years of high plant output (>80% thermal capacity with two circulating seawater pumps operating). Convers'ely, with little waste heat and a marked reduction in 38 g
.n.
I I ' discharge flow during the summer and f all fishing seasons of 1984, 1986-1988 (outages), the catches of bluefish totalled under 100 fish for the four years. During the attenuated July-August creel survey of 1989 (transitional year in power production), the catch slightly improved with 68 bluefish reported. Whereas, for the May-August surveys of 1990 (high operational year) and 1991 (moderate operational year), the recreational catch for these months was about 950 bluefish for the two years combined. Soortfishina Effec 1g Bluefish and striped bass have ranked second anc fourth, respectively, in recreational catches over the years at the Pilgrim Shorefront. In fact, bluefish ranked first the last few years. The thermal discharge at pilgrim Station alters the small scale distributions of bass and bluefish in the Pilgrim area. This has a positive effect on the sport fishery off Rocky Point because numbers of both species mass for a time at a known location within casting distance from shore. However, on the negative side, this attraction of both species to the outflow results a increased densities which greatly increase vulnerability to human exploitation and the potential to l be stressed by heat or cold shock and gas supersaturation. This can lead to a substantial incI4 -se in the exploitation rate. Sport l fishing can comprise a sizable part of fishing mortality for some game fish (Williams et al.1983) . For example, the sportfish catch l of bass and bluefish has exceeded 600 fish and 2,000 fish, 39 'I
I respectively, at the Pilgrim Shorefront in a given year.
- 4. Atlantic silverside
Background
The Atlantic silverside is an abundant schouing forage fish ranging from New Brunswick to Florida which typically inhabits l shallow marine and estuarine waters. Silversides mature at age one, with only a small percent of the population surviving to two i years of age. Spawning in the Massachusetts Bay area occurs from late April through June in estuarine locations. The adhesive eggs attach to mats of filamentous algae at the high tide mark (Conover and Kynard 1984). As inshore water temperatures decline below 6' C, most adult I silversides in New England waters undergo a late fall offshore migration to overwinter in waters as deep as 50 m on the continental shelf (Conover and Muravski 1982). Conover and Ross (1982) estimated overwintering mortality of Massachusetts g silversides to be 88% south of Cape Cod and 97% north of the Cape. I The number of adults returning to inshore waters in the spring (spawning stock) appears to remain relatively constant regardless of the previoun fall population size, as fish from less abundant year-classes exhibit lower winter mortality than dominant year-classes presumably because of ; cheir larger 7 no body size. Silverside abundance in the PlyInouth area is greatest in summer and early fall. The local population likely spawns in nearby Plymouth-Kingston-Duxbury Bay estuary. Juveniles and adults can be 40 m
l lI af fceted by the thermal discharge and by impingement on Pilgrim Station's traveling screens. l I Gear Types and Life Stages Affected Any likely impact of Pilp Station on the Atlantic silverside population would La due pingement. Silverside eggs are rarely entrained at Pilgr.im Station, and larval entrainment has been relatively light during the years of plant operation. We have haul seined juvenile and adult silversides in the Intake which are potentially subject to impingement. The data collected at established seining stations provide an index of abundance of the local silversido population. Gill not and trawl fishing have captured only low numbers of silversides. Review of Impingement and Entrainment Effects Silverside egg and larval entrainment is low at Pilgrim l Station. Entrainment samples collected at Pilgrim Station by I Marine Research, Inc. from 1980 to 1991 show a low incidence of silverside larvae (Marine Research Inc. 1990; see Entrainment I Monitoring, this Volume). Conservative estimates of annual equivalent adult silverside losses from Pilgrim Station operation, based on fecundity and egg
~
survival estimates, are 187,000 fish por year by impingement and l 8,000 fish per year by entrainment, for a total of 195,000 individuals from the local population (Stone and Webster 1975) . Such a speculative loss appears large, but based on the prolific I I nature and abundance of the species (26,155 captured by seine in 1991 alone) the effect on the population is questionable. 41 I
Discharge Related Effects Based on silverside temperature tolerance data and the predicted thermal plume at Pilgrim Station, it was projected that adult silversides would be excluded from a 4.5 X 10' m2 site in the discharge area in summer (Stone and Webster 1975). The effects of I the thermal plume are probably of little consequence to Atlantic silversides due to their high abundance in the region, the relatively small size of the thermal exclusion zone, and the I species' ability to move to avoid stressful temperatures. Intake Related Effects In 1991, Atlantic silverside comprised 46% of the haul seine catch at all sites combined. At the Intake, the silverside ranked second in seine catch abundance, only exceeded by Atlantic herring - most of which were captured in June. This is the usual pattern in the seasonality of seine data, as the Intake catch typically includes, depending on the year, large catches of clupeids and/or sand lance.. The annual silverside catch rate for all stations , pooled nearly doubled from 216 fish per set in 1990 to 422 in 1991. The silverside catch rate for 1991 in the Intake was similar to last year's value. The catch rate at Long Point showed a pronounced increase while the two remaining sites (Warren Cove and Manomet Point) had declining catches (Figure 11). Seine data collected over the past decade show that the Atlantic silverside is the dominant -species sampled at all stations, typically comprising well over 80% of the annual seine c*tch (Lawton et al. 1990). In the Intake, haul seine catches of I
}
I l I silversides for the June through 1400 m,,,,,,,,,,,., 7 1 llovember sampling period troo I l im . consistently have shown a dearth . - i in abundance of this species in (( ' June, high numbers '" from July { y Q gg I through September, followed by me ... con vra a t o. ...,
~
I 1 a subsequent decline. t m ,,, . . a o o,,,, ,,,, l Pilgrim Station impingement Jigure 11. Mean catch per standard haut seine i i set of Atlantic silvernice collected stong the Plymouth data have consistently enunn of wstern cepe cw say, me. , documented t' ? silverside as a dominant species impinged . Silverside imp.tngement is highest during the colder months of the year, llovember through Aprf.1 (Lawton, Anderson et al. 1984; Marine Research Inc. 1990). In 1991, 2'/ 5 silversides were sampled in ( impingement collections at the station. The monthly mean size of silversides impinged ranged from 9 to 11 <:m total length. These are adult fish which most likely overwinter in the Intake l embayment. Conditions in the deeper water of the Intake channel are apparently adequate for silverside survival during the winter. It in during the time of peak silverside abundance during the summer that silverside impingement is nearly nonexistent at Pilgrim Station. Colwersely, silverside impingement peaks in winter when their numbers inshore are low. Perhaps reduced mobility of the overwintering fish because of cold temperature stress makes them more susceptible to impingement. I 43 I
E
, S. Magt ig_ngphaden '1 manhaden is a pelaaic, migratory species she Atlantic h " cer'derad to cenprise a single population. Ranging from Nova oc Plorida, menhaden spawn on the continental rself and ir.
a :!gelow and Schroeder 1953) . Of f Neu Englar.J, spawning occuri ' spring through fall, with a peak in June or July (Scl 484). The lareas hatch from buoyant eggs and soon move well up . . to low-salinity writers of estuaries (Young 1974). Juvt : .iles school together, eventually moving to higher saline I' waters of an estuary, where they remain until declining water temperatures trigger a coastal migration southward to offshore wintering grcunds off the southeast Atlantic coast. During spring, there is a return wigration northward; individuals summer along the coast by 'titude act -Jing to age / size (Nicholson 1978). Schools l of menhasen arrive off Massachusetts in April as coastal waters warta above 10' C. Menhaden older than two years travel further M north, with few three year-olds occurring south of New Jersey. Atlantic menhaden are extensively fished commercially along the Atlantic coast. In the 1950's, the nenhaden population was comprised primarily of three to eight year-olds, but with increased fishing mortality - in the 1960's, fish under three years of-age constituted the maiority of the coastal stock. A few strong year- E-classes recruited to the population in the 1970's, which are in evidence in aur qill-net catch data (Figure 12). The Uni'.e 3 States Environmental Protection Agency and the I E it--_-________________
I
.,m , ,m, Wassachusetts Di '.sion of Water Pollution Control celected s -
so I as a - .. t Atlantic menhaden . . g _J hY l - a Representative Important Specics I. (RIS) to assess impact of 'p
,gf 6
jy 9
? '7 ff ; m @
1 9 fiJ11lQE;B'", 1
?
Pilgrim Station (Stt.no and ** S "" ** *g" *" 3 S' 5" 55 _I As menhaden are Ca womAno4 cA,ca -nuwt mauAt uil Webster 1975). I sensitive to environmental Figure 12. Mean annual sitt. net caten (5 panets) of Attahtie inenhaden ard annua l HDC operationel tevet at Pitorim station, 1973-1991. stressors resulting from environmental intervention, Young (1974) provided specific examples of detrimental -impacts of coastal powcr plants on the specie.s. Life Stacas Impacted and Savnlina Protocol E Impacts of Pilgrim Station on Atlantic menhaden would most likely result from impingement of adults and juveniles, egg and I larval entrainment, and gas bubble disease (GBD) of adults in the
# thermal discharge. We have sampled juvenile menhaden in the Intake 3 fish are susceptible to cmbayment by haul seining; these Pilgrim Station's intake travelling screens.
impingement on Impingement and gill-net sampling have captured both adult and
-I- juvenile menhaden. Fish overflights are done to moni'.or the inshore western sector of Cape Cod Bay for large schools of fishes In June 1991, cuch as menhaden which may enter the P.Agrim area.
a school of about 300,000 adult menhaden was spotted on an overflight in the vicinity of Pilgrim Station. Review of Impincement _and EntraingeJ1_lf t fects Atlantic menhaden spawn in Cape Cod Bay (Scherer 1984). 45 I.
I! n l Menhaden eggs and ic vae have been sampled at relativ: , low densities. The buoyant eggs are found from April through November, I whilc.the larvae occur from April-December. I: 1 The actual entrainment of menhaden eggs at Pilgrim Station has been relatively low, with the exception of 1982. Larval entrainmen. is uncommon. In 1991, egos were entra ted in May, June and September. en ! Impinguaent of menhaden on the intake screens at Pilgrim ' Rtation generally has been of juveniles. In 1991, 113 menhaden (size range 52-131 mm TL) were sampled in impingement collections from August-December, corresponding to the time juveniles leave estuarine nursery grounds. - Menhaden ranked first in impingement , collections in September and acond in December. ' Haul seine catches from the intake since 1981 have included - large numbers of young clupeids (menhaden / river herring) between i septcuber and November of some years; these fish are subject to impingement. In 1990 and 1991, however, menhaden were not seined in the intake. Stone'and Webster (1975) predicted, via a Ricker stock and recruitment model that losses to the menhaden population from entrainment and impingement at Pilgrim Station are negligible. pischarce Related Effects The . annual gill-net catch ' data from 1971-1991 for adult - menhaden show depressed catch rates since 1980 (Figure 12), when the lowest catch rate was obtained. The rate in 1991 was the
- second lowest of the time-series. A plot of operational status and e
I I
annual mean menhaden gill-net catch does not suggest a relationship between these variables (Figure 12). The thermal tolerance temperature for juvenile menhaden is s 33' C (Young 1974), while adults acclimated to 15' C tolerated temperatures up to 31' C (Stone and Webster 1975). The preferred temperature range for adult menhaden is 10-21' C (Stone and
. Webster, personal communication). Spring migrating menhaden, on occasion, have boon attracted to the Pilgrim Station thermal discharge because the outfall temperauu >:es are within their preferred range when compared to arbient. Summer and early fall discharge temperatures exceed the menhaden's preferred range, thus minimizing the species attraction to the thermal ef fluent at these times.
However, mortalities have occurred at Pilgrim Station. In August 1978, over 2,000 juvenile clupeids (including menhaden) died in the thermal plume at Pilgrim Station because of thermal stress perhaps aggravated by chlorine. Cooling waters from pcwer generating stations also can become supersaturated with dissolved gases. Fish residing too long in supersaturated water can develop I, gas-bubble disease (GBD), where emboli form in the blood and other tissues causing blockage, rupture, and even death. Mortalities occurred to adult menhaden that were residing in the Pilgrim l discharge canal in April of 1973 and 1975; GBD was the causative agent (Lawtt1 et al. 1986). I- Dissolved gas saturations in the Pilgrim thermal discharge are highest in spring and early summe concomitant with increasing o g i
- - l I \
ambient water temperatures and decreasing gas solubilit". In particular, potentially GBD causing-dissolved nitrogen saturations (2115%) occur in the cooling water at Pilgrim Station during the
, nenhaden's inshore stay of April-November. -A fish barrier not was placed in the discharge canal in the fall of 1973-to prevent fish access to the top two-thirds- of the canal. It was hoped this would limit the potential for future GBD incidents. No large concentrations of adult menhaden have occdrred in the discharge I canal or thermal plume for any period of time since. However, in August 1985, an estimated 300' juvenile menhaden, located in the lower end of the canal, were afflicted with GBD; no mortalities were documented.
Stock-recruit relation modeling of the population, incorporating GBD mortalities at Pilgrim Station, forecasted n negligible impact of the plant on menhaden - (Stone and Webcter 1975). _ Winter Flounder
- 6. ,_
Background
familiar resident of bays and estuaries along the Northwest Atlantic coast frca Labrador.to Georgia, the winter flounder has
-been described as the most commen shoal water flatfish found in the Gulf of Maine (Bigelow. and Schroeder 1953). Winter flounder exhibit localized seasonal onshore-offshore migrations (McCracken 1963), and the coast-wide population is considered to be coCrised "of many independent localized stocks" (Perlmutter 1947). In the o
g E
=
I h Pilgrim' Station area, the primary spawning area is believed to be
.the Plymouth, Kingston, Duxbury Bay (PKDB) complex (Stone and Webster 1975; Marine Research, Inc. 1986).
A principal component of the sea.sonal inshore dragger 14.shery t Cape Cod Bay, winter flounder also are caught in great numbers
- by recreational fishermen. Indeed, the National Marine Fisheries Service reports that in recent years, recreational catches have equaled or even exceeded commercial landings (NEFC 1991). In view of their dominance in commercial and recreational catches and the localized nature of the stock in the Pilgrim area, winter flounder was selected as a representative important species (RIS) by the U.S. Environmental Protection Agency and the Massachusetts Division
- I. -of Water Pollution Control.
Life Stages Impacted and Sanpling Protocol For each life stage of the winter flounder, we have identified
; aspects of plant operation that constitute potential sources of impact (Table 1). Tt should be noted, however, that in measuring impact caused by the operation of Pilgrim Station, other impacts must be considered. In particular, exploitation by .:ommercial and recreational fishermen can greatly affect local stock size. The l National Marine Fisheries Service reported a coast-wide decline in overall abundance of winter flounder that has extended from 1981 to 1991, directly attributable to fishing pressure (NEFC 1991).
Review of Entrainment and Impingement Effects F2LtiraiDyent Moving.into the shoal water of bays and estuaries in winter l- 49 t l l
I and early spring (Bigelow and Schroeder 1953), winter flounder spawn damersal, adhesive eggs (unlike those of other local flattishes), that often clump together on the bottom (Breder 1924) in association with filamentous diatoms (Klein-MacPhee 1990). The free-swimming larvae also remain near the bottom while gradually undergoing metamorphosis to the adult form. Juveniles remain in or near shallow natal waters for most of their first two years, moving primarily in response to extremes of heat or cold (Buckley 1982). I A review of long-term entrainment data revealed that low numbers of winter flounder eggs and larvao have been entrained at Pilgrim Station (Marine Researt-h , Inc. 1991), a pattern which continued in :.991 (Marine Research, Inc., this report). As such. entrainment of flounder eggs and larvae does not pose much of a threat to their overall abundance in the Pilgrim area. Jfmpincrement With their affinity for sheltered estuaries and embayments (Bigelow and Schroeder 1953; Pearcy 1962), juvenile and adult , flounder are commonly found in Pilgrim's Intake embayment (Lawton et al. (1990), and it is no surprise that they are one of the more commonly impinged fish ( Anderson 1990) . However, review of the impingement data collected at Pilgrim Station fr m 1981 to 1991 reveals that only-343 winter flounder were actually collected. Clearly, coast-wide fishing mortality (NEFC 1991) must be having a greater impact on the local stock than both entrainment and impingement. Discharge and Sportfish Related Effects e9 g a
I Discharae: Thermal / Current Because flounder are demersal, they are not considered to be at risk from thermal shock caused by tne discharge of cooling water from Pilgrim Station. After exiting the discharge canal, the plume of'herted discharge water rapidly lifts off the bottom, thereby reducing potential impact on the bottom-dwelling flov ler. l Plotting plant output versus winter flounder catch per tow ,, , cy ,,,, ,, ,,,c,,, ,y,3,t ,0c eo - ix
;3 . trawl data (Figure 13) suggests 60 l
there % no relationship between [ , plant operation and flounder I g . ,o ca a in the dissTarge area. 5 L i h;$j (a
! g x
_,1 i W}'jh p;n vo The t arked decline in catch rate oh,g y \f, ,, h$N
,,'s, g, g, ,o Q o YEAR for winter flounder in our trawl C WINTER FLOUNDER ~ PERENT MNML MDC ctudy is believed to mirror the Figure 13. Ie'an erncsl catch per tow of winter flounder ard annual % MDC opecational levet at Filgrim coast-wide decline.
.I. station for 1982 1991.
Soorttishina. Pilgrim Shorefront sportfish records in M91 indicate no winter flounder were captured by land-based anglers from the area of the plant.
.I
- 7. Tautog
Background:
Basis for selection The tautog is a large, stout-bodied member of the Labrid family, common to the. inshore waters of southern New England. Ranging from Nova Scotia to South Carolina, they are most abundant 51 I-
in-the region exterding from south of Cape cod to the Delaware Capes (Clayton et al. 1978). In the Plymouth area, Bigelow and Schroeder (1953) reported the most productive grounds to be the I rocky arean around Manomet Point and the Gurnet. Characteristic of Labrids, tautog are structure oriented and generally found in association with reefs, wrecks, lodges, or jetties. Affording shelter during nocturnal torpor (Olla et al. 1974),- such structures also are a productive source of food, I hosting a profusion of attached and mobile invertebrates such as blue-mussels (Myritus cc Ts) , lobster (Romams amcricanus) and green crabs (Carinus maenas) . ' Blue et ssels are a primary food of tautog, although they will eat other invertebrates. The_ adults leave shelter to feed during the day, occasionally ranging as far as 500 m (Olla et al. 1974), but return at night. Bigelow and Schroeder (1953) reported that tautog will follow a flood tide up above the low water _ mark to feed.in the intertidal zone, dropping back on the ebb. When not feeding, adults have been observed by us to ga' aer in a hole and lie on the bottom unless disturbed. Juvenile tautog, which associate closely with a particular structure during the first 3 years of life (Olla and Studholme 1975), generally range no more_than 2-3 m during feeding. Proximity to shelter can serve as - L protection from predators. Olla et al. (1974) observed a group of juvenile tautog ($ 25 cm) being chased by three striped bass inside the Fire Island Coast Guard Basin. The-tautog remained within 1 m of the breakwater while feeding and cere able to escape -the bass by moving into the deeper crevices between the rocks. 52 g 1
= .
1
m - Adult tautog exhibit seasonal inshorn-offshore migrations in response to changes in temperature and photeperiod (Olla and et al. [ 1980). As temperatures decline below 11' C in the fall, adults i move offshore to shelter in deeper Vater. Olla et a .' . (1980) l theorized that the adults moved because the inshore habitate did not provide enough protection from extreme temperatures or violent sea conditions- during their winter torpor. The adults return inchore in the spring as temperatures warm. The juveniles, which inhabit the same inshore areas as the adulta, remain there throughout the winter, secking shelter rock crevices, Tautog become sexually mature at 3 to 4 years of age (Cooper 1966). Spawning occurs in late spring, primarily in weedy, inshore areas. (Stolgitis 1970), as the adults arrive back inshore from over-wintering grounds. Tautog may engage in group or paired
~
reproduction (Clla et al. 1981). Cooper (1966) found that tautog formed discrete spawning groups in upper Narragansett Bay which became thoroughly mixed as they dispersed after spawning. The eggs are' buoyant and are so like those of -the cunner as to be nearly indistinguishable. Hatching occurs 42.to 50 hours later in 20* C water' (Bigelow and Schroeder 1953). In the Weweantic River,
-Stolgitis ,'1970) collected larvae most frequently near the bottom at stations heavily vegetated with eelgrass near the river's mouth.
Juveniles occupy -typical adult habitat, remaining inshore for approximately three yearn (Cooper 1964; Olla and Studholme 1975). '3 - Examination. of dv.a from - our gill net and diving studies raveals that tautog are common off Pilgrim Station. Though not as
. 53
l
-abundant as cunner, tautog are observed regularly around the outer intake breakwater and discharge anal jettles. Project divers -
report that on a flood tide', tautos are often found at the mouth of the discharge canal. The large boulders forming the discharge jettier provide cover and substrate for beds of blue ' mussels. The attractiveness of this area t- tautog creates the potential for p.lant impact. Olla and Studholme (1975) and Olla et al. (1979) demunstrated in the laboratory that juvenile tautog will remain in I their shelter even if thermally stressed. As temperatures approached the upper tolerance limit, young tautog became less active and began to enter a torpid state, reminiscent of night-time behavior. Tautog have limited con.mercial value north of Cape Cod, because of the discrete localized populations and limited consumer demand. However, they are an important gamefish and excellent table fish. Because of its local occurrence, importance as a gamefish, and potential fer plant impact,.we selected tautog as an indicato: $ Life Stagos Impacted and Sam:ca.ing Protocol We have identified aspects of plant operation that constitute potential: sources of impact to tautog (Table 1). The measurement of impact of the operation of Pilgrin Station can be confour.ded by other impacts from a number of sources. Bay-wide environmental conditions such as water temperature can affect spawning, as well as the survival of eggs and larvae. Bigelow and Schroeder (1953) _ i I a m-
I-reported that tautog abundance fluctuates widely from year to year. Data from our gill' net and dive studies support this finding. I Review of Entrainment and Irpingement Effects Entrainmerd Tautog eggs are buoyant, and the larvae free-swimming. Therefore, bcth are subject to entrainment in the plant's
.- circulating seauter system. However, because tautog eggs are so difficult to separate from those of cunner, the two are grouped
- together and reported in entrainment records as Lacrid eggs. .Later in the season when the two can be distinguished, cunner eggs are so
.I much more abundant that all labrid eggs are reported as cunner (harine Research, Inc. 1991). As such, there is little information on the entrainment of tautog eggs. Tautog larvae are also entrained, but not in great numbers. Indeed, modeling conducted by Marine Research, inc. (1978), suggests that less than 0.2% of the I larval production of labrids (including tautog) in Western Cape Cod Bay is entrained at Pilgrim station. The Intake embayment and surrounding waters are not conducive to tautog spawning, and any i tau" 3. eggs or larvae that are entrained __;- presumed to have drifted ir.to the intake from other areas. From this, we believe natural mortality caused by ' pre.dation and other sources of attrition during the larval stage _have far more impact on the local population than entrainment by Pilgrim Station.
. ImoincqqgI&
So'few tautog'have been sampled in impingement collections (= l ( 60 fish) at Pilgrir Station since 1971 that this is not a major 55 [ WJ
-)
m -
I form of impact. Interestingly, most of the tautog impingement. occurred in late fall, usually December. Possibly these fish initiated the search fer winter Lhelter late and swam into the intake channel seeking deeper water, but ended up entrapped on the screens. Discharge, Intake, and Sportfish Related Effects Discharse: Thermal / Current Using project temperature dsta and findings from thermal I tolerance and behavior studies conducted in the laboratory by olla and Studholme (1975) and Olla et al. (1978), we would assume that the temperature of the discharge waters. even at peak output at the time of highest ar.bient temperatures, will not induce overt mortality of tautoc. The fish, however, would be distressed and may exhibit behavioral changes, such as, reduced activity and
~ decreased aggression and spacing among the aults. There would be a tendency for the juveniles to seek shelter. The latter are especially vulnerable because, when stressed, they will not lea \e ,
their shelter even to the point of death (Olla and Studholme 1975) . During observational dives in the discharge area (flood tide), . we have observed adult tautog moving into and out of the mouth of the discharge canal, while some were sheltering in the rocks of the ' jetties.
-Few juveniles have been sighted in the path of the thermal p?ume, although some have been seen in the control area south of the discharge. On a few of these dives, we measured bottom temperatures in excess of 20* c' at the mouth of the discharge canal. We did not observe any tautog mortality. Tautog, 56 m.
_ most likely, are attracted to the discharge area by the dense growth of blue mussels, moving into the canal mouth on incoming I tide and c : on the ebb. While in cne thermal effluent during late summer, theta fish are probably strsssed. "; heir schooling and sheltering behavior suggest this. However. they apparently tolerate the heat to feed. Some relief can be found in an area of cooler water caused by a counter-current 2% t sets up just inside the seaward . end of the southern-most discharge jetty, where our divers often have observed tautog grouped there. At low tide, the
.I velocity of the discharge current and shallow depth preclude tautog movement into the area. It is doubtful that adult fish seek shelter in the rocks of the discharge jetties at night because of the extreme variation in depth caused by tidal amplitude.
The low number of juvenile tautog sighted by divers suggests that fish this size are not associating with the bouldu that form the discharge canal. In addition to the strong current, the discharge may be too far from their natal area for the young to be found-there in abundance. Regarding their occurrence 17. the Pilgrim area, project q111-
..I-net and ooservational dive data show wide f'uctuations in relative abundance over time. Graphing plant output (% MDC, i.e. thermal
. capacity)=for the spring and nummer seasons, when tautog .re found I inshore, versu, gill-net catch rates for tautog over the years (Figure 14) does not suggest any relationship.
3 57 i .. I
s l Jntake Related Effects ,. mm ,, n .n ,,, , , With the exception of i, - p 7 _ impingemen', we have found no a [ . ,, impact to tautog within the e s
]['; {.g g i ';
!f I 4.
intake embayment. j7j ![ y
; ; $,ro GBmI3ma f '
?
?j4 F
bi gli! M 1 E Sportfishino o g, g, g, g, e, g , ,,, ,,,, g, g,' g TEAR Tautog are held in regard as. a gamefish as they are Figure 14. Mean annual 5-panel olll-net catch of tautog and anrFsal % KC operational level at Pilgrim considered a good fighter on rou. station, 1973-1991. and reel and good to eat. South of Cape Cod and into Rhode Island waters, tautog are sought where there is structure, such as wrecks, ledges, and piers. North of the Cape, they are also popular but are less abundant. 7ff the Pilgrim Shorefront, tautog have been captured by shore-based anglers but not in great numbers. We believe this is due both to a small local population and the limited amount of effort directed
-at tautog. Tautog most often are found in t.?e discharge canal, and as most anglers in that area are targeting striped bass and bluefish. b Mortality induced by recreational fishing is therefore not considered to impact the local tautog population.
I I I-I 58 E un
IV. IMPACT PERSPECTIVE We have selected eight target species _ to assess Pilgrim Station impact on marine biota. The American lobster and winter flounder are benthic' residents in the Pilgrim area, supporting importar.t commercial and recreet,onal fisheries. 8 The predatory bluefish and s+.riped bass are seasonally ubundant off the power station's discharge and are highly prized by spo.:t fishermen in the I- . area. The pelagic schooling Atlantic menhaden is ' commercially harvested by purse seiners. T!.is species was involved in two major
.I documented incidents of gas bubble disease in the thermal discharge at Pilgrim Station. The Atlantic silverside is the most abundant fish in the Pilgrim araa and is an important prey organism. A resident groundfish,- cunner abundantly populate the immediate vicinity of the breakwaters and discharge jetties at Pilgrim Station during the warmer months. The tautog is a groundfish that resides near rock structure off Pilgrim Station, commonly seen by divers and caught by sport fishermen in the area.
To date off the Power Station, which has a relatively low historical operational record (47%), there have been abiotic change.s (e.g., local thermal loading and scouring) and resultant biotic perturbations (e.g., population reductions and shifts in a species' spatial distribution because of avoidance or attraction) ;
. however, these have been localized or occasional events.
3 I se y I - - - - - -
I V. CONCLUSIONS Cunner
- 1. We captured ripe cunner s award of the outer intake breakwater I at - Pilgrim Station in May which suggests there is local spawning. Cunner eggs and larvae were entrained from May tnrough September in 1991. Large numbers of fish eggs and larvae are entrained at nilgrim Station, and a high 1 ercentage of these are cunner, e.g., 33% in 1991. -
- 2. Cunner led the impingement collection in May 1991 at Pilgrim I
Station. 3.- Over the past seven years (1985-1991), the catch rate of cunner, using a gill net, has declined by about 70% from the previous eight years. The 1990 and 1,991 catch rates are the lowest of the time series. -
- 4. Pecause of strassful warm temperatures, cunner avoid the !
'21scharge canal and.r. car-thermal plume during late summer.
- 5. The discharge current at the station is of sufficient velocity to sh.ift the small scale distribution of cunner by si ze class,
_ with larger cunner attracted to the discharge current on a flood tide. I F0 E-E
i
- 6. Cunner ranked second in the sportfish catch off Pilgrin Station in 1991. Most are left to die after being caught by anglers at the Shorefront.
I 7. The cumulative effects of entrainment, impingement, and sportfishing have contributed to a reduction in the local cunner population. American Lobster
- 1. Entrainment of lobster larvao has been negli-Jible at Pilgrim Station, while only low numbers of juveniles have been impinged on the intake screens.
I
- 2. The percentage of celle in tbo surveillance area in 1991 was again lower than the reference area, but the difference appears not to be power-plant mated.
- 3. Analysis of commercial Iobster pot-catch data indicate there is no relationship in the annual catch ratics between the I surveillance and reference areas and the operational status of the Power Plant.
- 4. When testing for a relationship between the commercial legal lobster catch rate in the surveillance area and a measure of seasonal plant operation at Filgrim Station (MDC Net %) for B
61 LI
c I the full and partial on-line power years (1973-83,1985, 1990-
-1991) , we found a nonsignificant Kendall's concordance.
We_have no control over positioning of the commercial gear I spatially in the designated surveillance quadrats; lobster pote can be deployed far enough away from the discharge canal that the thermal current is probably not a major factor affecting lobster distribution. I
- 5. -Using a temporally limited dataset, there was no correlation between legal-catch rates at any of the discharge stations and Plant MDC. However, there were significant negative correlations betwer.n sublegal catch rates and Plant MDC at Stations F, G, and H. As these stations (especially G) are most proximal to the discharge canal, we hypotnesized that the -
speed of the discharge current at- these sites impacted sublegal catches by reducing their mobility and this reducing their abundance at these sites, as E Bluefish and Striped Bass
- 1. The stressors of impingement and entrainment at Pilgrim Station do not impact striped bass and bluefish because of their life histories -
no local spanning and few juveniles move into western Cape Cod Bay.
- 2. However, the stressor of the thermal effluent from the Power Station does affect bass and bluefish via two paths - local I
l 5I e
{ heating and induced _ current flow - which shift the spatial distributions of these two species in the Pilgrim area. l
- 3. The discharge current at Pilgrim Station elicits an active behavioral response from bluefish and striped bass. There is an attraction of individual population members to the moving water as a feeding ground.
I
- 4. Concerning the heat, there is likely an attraction of both species to the thermal plume in the spring and lata fall by temperatures close to those preferred.
- 5. Conversely, the waste heat also induces an avoidance response.
I In August and early September, bluefish and bass are repelled by high temperatures in the discharge creating an exclusion zone in the discharge canal and near-field outfall area.
- 6. Shifts in fish distribution induce further population effects.
Attraction produces increased densities of both species in the discharge area which has a positive effect on the sportfiching at the Pilgrim Shorefront from an angler's point of view. However, this has. a negative- side, in that increased population densities increase vulnerability to exploitation, i.e., fishing mortality, and susceptibility to cold shock.. g g 63 _g. L
I I atlan c silverside 1.- The AtlantM silversido is consistently th'e most abundant fish in the Pilgrim area. 88
- 2. Silverside eggs are rarely entrained at Pilgrim St.ation while I
their larvae have a very low incidence of entrainment.
- 3. The Atlantic silverside is the dominant species impinged at g
Pilgrim Station, with most silverside impingement occurring in
.the winter. There are large numbers of silverside seined in the intake each summer.
- 4. Based on thermal tolerance data, there is probably a 4.5 X 10' m2 exclusion area to silversides off the discharge canal in mid-to-late summer.
'5. The effects of the thermal plume are most likely minimal to I the Atlantic silverside- population because of their great abundance in the Pilgrim area and their ability to move out of the discharge area to avoid stressful temperatures. - - Atlantic menhaden
- 1. The ed*ainment of menhaden eggs at Pilgrim Station is relatively low (with the exception of 1982), while larval entrainment is rare.
I 64 E. n1 a
- m. .
- 2. Impit:gement of menhaden was relatively light in 1991 at Pilgtim Station.
I 3. The catch rate by gill not of acnhaden has been down since 1980. The catch Tate in 1991 was the second lowest of our data record (1971-present).
- 4. Spring migrating menhaden, on occasion, have been sttracted to the thermal discharne becaus,e the outfall temperatures are within their preferred range as compared to ambient values.
Substantial documented mortalities of adult menhaden have occurred in the Pilgrim discharge canal in April of 1973 and 1975 caused by gas bubble disease. In the summer of 1978, a fish kill involving over 2,000 juvenile clupeids (including I menhaden) occurred in the discharge area because of thermal stress perhaps aggravated by chlorine residuals.
- 5. Losses to the coast-wide menhaden population via entrainment, impingement, and gas bubble dis.aase have been estimated to be negligible.
I Winter Flounder
- 1. Due to their demersal nature, few winter flounder eggs have been entrained at Pilgrim Station. The entrainment of their larvae does not appear to pose much of a threat to overall
, .t - . .d .
65 Y
l I L
- 2. Winter flounder are commonly impinged at Pilgrim Station, however, so few are collected that impingement is not considered a major form of impact.
- 3. There is no apparent relationship between trawl catch data of I
winter flounder in the area of the discharge and plant operation. The marked decline in catch rate is believed due to depressed coast-wide stocks. I.__-- Tautoa
- 1. Labrid eggs are a traditional dominant in entrainment collections, however due to difficulties in distinguishing cunner and tautog eggs and the abundance of the former, all c labrid eggs are classified as cunner. Little is known of entrainment of tautog eggs, but it is not considered as serious impact. Similarly, the entrainment of their larvae does not appear to pose much of a threat to c <all stock abundance.
- 2. Project dive records reveal that tautog are commonly sighted
- in the discharge canal at or near high tide. We believe they are attracted to the dense bed of blue mussels found growing on the boulders there.
E in
- 3. There is no apparent relationship between gill-net catch data of tautog and plant operation.
e i B E
I
- 4. Tautog are considered an important gamefish, however, catch by recreational anglers was low. Mortality caused by
.g 5 recreational fishing is negligible.
I
- g I
I I I I I t- !I e 67 lE i 5 I l' I. I
I VI. bCKNOWLEDGEMENTS The authors thank staff members - John Chisholm and John Costa for collecting field samplini data and acknowledge 11eil Churchill, Paul Caruso and Steve Cadrin for assisting in diving operations. We thank Chris Kyranos for his assistance in our research lobster sampling program. Raymond Dand and Robert Ellenberger collected sportfish data for us at Pilgrim Shorefront. Jay Burnett from the National Marine Fisheries Service in Woods Hole aged cunner collected from the Pilgrim area using otoliths and scales. A word of thanks to Kim Trotto of the Division for word-processing several sections of this report. We also appreciate the guidance of Robert D. Anderson of Boston Edison Company, W. Leigh Bridges of the Division, and members of the Pilgrim Administrative-Technical Committee. Their input on various studies and editorial comments on project reports and papers have been nost enlightening. I I I I I I 68
~l B
a
I VII. LITERATURE CITED I Anderson, R.D. 1990. Power Station. Impingement of organisms at Pilgrim Nuclear In: Marine Ecology Studies Related to Operation of Pilgrim Station, Semi-annual Report No. 35. Boston Edison Company, Braintree, MA. Auster, P.J. 1985. Factors affecting catch of American lobster, H<vnana americanus, in baited traps. NOAA National Undersea Research, University of Connecticut, Groton, CT. 46 pp. Auster, P.J. 1987. The ef fect of current speed on the small scale I spatial distribution of fishes. NOAA Symp. Ser. for Undersea Res. 2(2): 7-16. 2 I Bigelow, H.B., and W. C. Schroeder. 1953. Fishes of the Gulf of l Maine. U.S. Fish and Wildlife Service Fishery Bulletin 53: 577 PP. I BMDP Statistical Software, Inc. 1990. BMDP Statistical Software Manual Volume 1. 625 pp. I Breder, C.M., Jr. 1924. Some embryonic and larval stages of the winter flounder. Bull. U.S. Bur. Fish. 38:311-315. Buckley, L.J. 1982. Effects of temperature on growth and I biochemical composition of larval winter flounder, rsurdoplewonectcs americanus . Mar. Ecol. Prog. Ser. 8:181-186. Campbell, A. 1983. Growth of tagged lobsters (Ncmams amcricanus) off Port Maitland, Nova Scotia, 1948-1980. Can. Tech. Reo. Fish. Aquat. Sci. No. 1232, 10 pp. Clayton, G., C. Cole, S. Murawski, and J. Parrish. 1978. " Common Marine Fishes of Coastal Massachusetts". Dept. of Forestry and I Wildlife Management. Research Unit. 231 pp. Massachusetts Cooperative Fishery Conover, D.O., and M.R. Ross.1982. Patterns in seasonal abundance, growth and biomass of the Atlantic silverside Mcnidia menidia, in a New England estuary. Estuaries 5(4): 275-286. I Conover, D.O., and S.A. Murawski. 1982. Offshore winter migration of the Atlantic silverside, Menidia menidia. 145-150. Fish. Bull. 80(1): Conover, D.O., and B.E. Kynard. 1984. Field and laboratory observations of spawning periodicity and behavior of a northern ponulation of the Atlantic silverside, Menidia menidia (Pisces: Atherinidae). Envir. Biol. of Fish. 11(3): 161-171. 69 I
I I Cooper, R.A. 1966. Migration and population estimation of the tautog, Tausaga onitis (Linnaeus), from Rhode Island. Trans. Amer. Fish. Soc 95 (3): 239-247. Coutant, C.C. 1985. Striped bass, temperature, and dissolved oxygen: a speculative hypothesis for environmental risk. Trans. Amer. Fish. Soc. 114: 31-61. Estrella, B.T.1985. Massachusetts coastal commercial trap sampling program May-November 1984. Commonwealth of Massachusetts Dept. Fisheries, Wildlife, and Environmental Law Enforcement. Division Marine Fisheries, Boston, MA. 58 pp. Estrella, B.T., and D.J. McKiernan. 1986. Massachusetts coastal -- commercial trap sampling program May-November 1985. Commonwealth of Massachusetts Dept. Fisheries, Wildlife, and Environmental Law Enforcement. Division Marine Fisheries, Boston, MA. 74 pp. Estrella, B.T., and S.X. Cadrin. 1988. Massachusetts coastal commercial trap sampling program May-November 1987. Commonwealth of Massachusetts Dept. Fisheries, Wildlife, and Environmental law Enforcement. Division Marine Fisheries, E Boston, MA. 55 pp. 5 Green, J.M., and M. Farwell. 1971. Winter habits of the cunner, Tautogolabms adspersus (Walbaum 1792), in Newfoundland. Can. J. Zool. 49: 1497-1499. Grosslein, M.D. 1969. Groundfish survey program of BCF Woods Hole. Commer. Fish. Rev. 31(8-9): 22-30.
~
Howard, A.E., and R.S. Nunny. 1983. Effects of near-bed current speeds on the distribution and behaviour of the lobster, Romarus gammams ,(L), J. Exp. Mar. Biol. Ecol. 71: 27-42. Johansen, F.1925. Natural history of the cunner ( Tautcp>labms adspersus Walbaum). Contr. Can. Biol. 2(17): 442-467. Keser, M., D.F. Landers, Jr., and J.D. Mord s . 1983. Population charheteristics of the American lobster, Romarus americanus, in " eastern Long Island Cound, Connecticut. NOAA Tech. Rep. NMFS SSRF-770. Kinne, O., Ed. 1969. Marine Ecology, "A Comprehensive Integrated Treatise on Life in Oceans and Coastal Weters". Wily- 3 Interscience, London. 681 pp. g 70 E E
I Klein-MacPhee, G. 1978. Synopsis of biological data for the winter ilounder, Psurdopleuronectes americanus (Ha) baum) . NOAA Tcchnical Report NMFS Circular 414. FAO Fisheries Synopsis No. 117. Lawton, R.P., C. Sheehan, T. Currier, P. Brady, M. Borgatti, V. Malkoski, and S. Correia. 1986. Final report on dissolved gas saturations in the inshore marine waters of Cape Cod Bay and incidents of gas bubble disease at Pilgrim Nuclear Power Station 1973-1985. Pilgrim Nuclear Power Station Marine Environmental Program Report Series No. 1, Boston Edison Company. 33 pp. Lawton, R., E. Kouloheras, P. Brady, W. Sides, and M. Borgatti. I 1983. Distribution and abundance of larval American lobsters, Homarus amcricarus Milne-Edwards, in the western inshore region of Cape Cod Bay, Massachusetts, p. 47-52. In: M.J. I Fogarty (ed. ) , Distribution and relative ab' . nee of American lobster, Homarus americanus, during 1974-79, 64 pp. larvae: New Englu O investigations NOAA Technical Report. NMFS SSRF-775. Lawton, R.P., R.D. Anderson, P. Brady, C. Sheehan, W. Sides, E. Kouloheras, M. Borgatti, and V. Malkoski, 1984. Fishes of western inshore Cape Cod Bay: studies in the vicinity of the I Rocky Point shareline, p. 191-230. ID: J. D. Davis and D. Merriman (editors), Observations on the ecology and biology of western Cape Cod Bay, Massachusetts. Springer-Verlag, Berlin, FRG. 289 pp. Lawton, R.P. , C. Sheehan, V. Malkoski, S. Correia, and M. Borgatti. 1985. Annual report on monitoring to assess impact of Pilgrim I Nuclear Power Station on marine fishery resources of western Cape Cod Bay. Project Report No. 38 (Jan.-Dec. 1984) Marine Ecology Studies Related to Operation of Pilgrim J3: Station, Semi-annual Report No. 25. Boston Edison Company, I- Braintree, MA. I Lawton, R.P., B.C. Kelly, V J. Malkoski, M.R. Borgatti, and J.F. Battaglia. 1990. Annual report on monitoring to assess impact of Pilgrim Nuclear Power Station on marine fishery resources of western Cape Cod Bay (Vol II) . Project Report No. 48 (Jan.- Dec. 1989). 1D: Marine Ecology Studies Related to Operation of Pilgrim Station, Semi-annual Report No. 35. Boston Edison Company, Braintree, MA. Lund, W.A., Jr., and G.C. Maltezos. 1970. Movements and migrations of the bluefish ( Pomuromus sa!rarrk) tagged in waters ,. of New York and southern New Fngland. Trans. Amer. Fish. Soc. l 4: 719-725. I Lyman, H. 1974. Successful Bluefishing. International Marine Publishing Company. Camden, Maine. 112 pp. 71 I -
I Marine Research, Inc.1978. Entrainment investigations and Cape Cod Bay ichthyoplankton studies, March 1970-June 1972 and March 1974-July 1977. Volume 2, V.1-44. In: Marine Ecology Studies Related to Operation of Pilgrim Station. Final Report. July 1969-December 1977. Boston Edison Company. Marine Research, Inc. 1986. Winter flounder early life history studies related to operation of Pilgrim Station - A review 1975-1984. Pilgrim Nuclear Power Station Marine Environmental Monitoring Program Report Series No. 2. Boston Edison E Company, Braintree, MA. g Marine Research, Inc.1990. Ichthyoplankton entrainment monitoring at Pilgrim Nuclear Power Station, Jan.-Dec. 1989 (Vol 2). In: Marine Ecology Studies Related to operat'on of Pilgrim 1 Station. Final Report. Boston Edison Company. l Marine Research, Inc.1991. Ichthyoplankton entrainmem, monitoring l at Pilgrim Nuclear Power Station, Jan.-Dec. 1990 (Vol 2). In: Marine Ecology Studies Related to Operation of Pilgrim Station. Final Report. Boston Edison Company. Massachusetts Division of Marine Fisheries. 1977. Summarization of Massachusetts marine sportfishing sta'istics, 1975. 100 Cambridge St., Boston, MA 42 pp. l m McCracken, F.D.. 1963. Seasonal movements of the winter flounder, Psuedopleuronectes americanus (Walbaum) on the Atlantic coast. J. Fish. Res. Brd. Can. 20:551-586. Miller, R.J . 198 3. Considerations for conducting field experiments with baited traps. Fisheries 8(5): 14-17. Miller, R.J. 1990. Effectiveness of crab and lobster traps. Can. J. Fish. Aquat. Sci. 47: 1228-1251. Nicholson, W.R. 1978. Movements and population structure of Atlantic menhaden indicated by tag returns. Estuaries 1(3): 141-150. Northeast Fisheries Center. 1989. Status of the Fisheries Resources off the Northeastern United Statcc for 1989. National Marine Fisheries Service, Woods Hole, MA. 110 pp. Northeast Fisheries Center, 1991. Status of the Fisheries Resources off the Northeastern United States for 1991. National Marine Fisheries Service, Woods Hole, MA. 132 pp. I 72 E [ _ _ _ _ _ _ - - -
Olla, B.L., and A.L. Studholme. 1971. The effect of temperature on the activity of bluefish, romatomus saltats L. Biol. Bull. 141: 337-349. , Olla, B.L., A.J. Bejda, and A.D. Martin. 1974. Daily activity, l movements, feeding, and seasonal occurrence in the tautog
'autoga onitis. Fish. Bull. 72 (1): 27-35.
Olla, B. L., A. J. Bejda, and A. D. Martin. 1975. Activity, movements, and feeding behavior of the cunner, Tautopvabrus I a*pmus, and comparison of food habits with young tautog, Tauuga onitis, of f Long Island, New York. Fish. Bt il . 73 (4) : 895-i i 900. I Olla, B.L. and A.L. Studholme. 1975. The effect of temperature on the behavior of young tautog, Tautoga onitis (L. ) . Pages 75-93 in H. l Barnes, editor. Proceedings 9th European Marine Bitlogy
' 5 Symposium. Aberdeen University Press.
Olla, B. L. , A. L. Studholme , A.J. Bejda, C. Samet, and A.D. Martin. 1978. Effect of temperature on activity and social behavior of ! the adult tautog Tautoga onitis under laboratory conditions. Marine Biology 45: 369-378. I 7 Olla, B.L., A.J. Bejda, and A.D. Martin. 1979. Seasonal dispersal and habitat selection of cunner, Tautogdabrus adspersus, and young I tautog Tautoga onitis, in Fire Island Inlet, Long Island, New York. Fish. Bull. 77 (1): 255-261. Olla, B.L., A.L. Studholme, A.J. Bejda, and C. Samet. 1990. Role of temperature in triggering migratory behavior of the adult tautog Tautoga onitis under laboratory conditions. Marine Biology 59: 23-30. Pearcy, W.G. 1962. Ecology of an estuarine population of winter flounder Psuedopicuronectes americanus (Walbaum). Ball. Bingham. Oceanogr. Collect., Yale Univ. 18(1), 78 pp. N rlmutter, A. 1947. The blackback flounder and its fishery in New England and New York. Bull. Bingham. Oceanogr. Collect., Yale Univ. 11(2), 92 pp. Ristori, A. 1989. North American Saltwater Fishing. Gallery Books, N.Y., N.Y. 96 pp. Scherer, M.D. 1984. The ichthyoplankton of Cape Uad Bay, p. 151-190 10: J.D. Davis and D. Merriman (editors) , Observations on the Ecology and Biology of Western Cape Cod Bay, Massachusetts. Springer-Verlag, Berlin, FRG. 289 pp. 73 m
I Smith, W.G., and A. Wells. 1977. Biological and fisheries data on striped bass, Morone satarilis (Walbaum). Sandy Hook Laboratory, National Marine Fisheries Service, Highlands, NJ 42 pp. Sokal, R.R., and F. J. Rohlf. 1969. Biometry: The principles and practice of statistics in biological research. W. H. Freeman and Company, San Francisco. 776 pp. Stolgitis, J. A.. 1970. Some Aspects of the Biology of the Tautog, Tautoga onitis (Linnaeus), from the Weweantic River Estuary, Massachusetts, 1966. 48 pp. Masters Thesis, The University of Massachusetts. Stone and Webster Engineering Corporation. 1975. 316 (a and b) Demonstration for Pilgrin Nuclear Power Station - Units 1 and l
- 2. Boston, Massachusetts.
Thomas, J.M., and P. Van Voris, 1986. Statistical approaches for quantitatively assessing ecological impact and risks. Proceedings: Risk Assessment in Aquatic Ecology. pp 2-63 to 2-81. Wilk, S.J. 1977. Biological and Fisheries Data on Bluefish, Pomatomus saltarrh (Linnaeus). Sandy Hook Laboratory, Northeast . Fisheries Center, National Marine Fisheries Service. Technical Series Report No. 11. 56 pp. Williams, G.C. 1967. Identification and seasonal size changes of eggs of the labrid fi.ches, Tautogolebms adspersus anu Tautoga onitis, of Long Island Sound. Copeia 1967 (2): 452-453 Williams, S.J., T.P. omith, H. Speir, and S. Early. 1983. Maryland Saltwater Sport Fishing Survey - 1980. Maryland Dept. of . - Natural Resources-Tidewater Administration. 124 pp. g Woolner, F., ana H. Lyman. 1983. Striped Bass Fishing. Nick Lyone Books, Winchester Press. 192 pp. Woolner, F., and H. Lyman. 1984. Bottom Fishing. Nick Lyons Books, Winchester Press. 118 pp. Young, J.S. 1974. Menhalen and power plants a growing concern. Mar. Fish. Rsv. 36(10) October, 1974. I I I 74 E a1
I FINAL SEMI. ANNUAL REPORT Number 39 I (Volume 1 of 2) on E BENTlilC ALGAL AND FAUNAL MONITORING AT THE PILGRIM NUCLEAR POWER STATION l (CIIARACTERIZATION OF BENTHIC COMMUNITIES) l January-December 1991 1 to BOSTON EDISON COMPANY Regulatory Affairs Department Licensing Division 25 Draintree Hill OfUce Park Braintree, M:ssachusetts 02184 I I From I SCIENCE APPLICATIONS INTERNATIONAL CORPORATION i 89 Water Street Woods IIole, MA 02543 (508) 540 7882 11
;g i April 1992
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5
l I l TABl.E OF CONTENTS EXECUTIVE SUM MARY . . . . . . . . . . . . . . . . . . . . . . . . I
.................... 1
1.0 INTRODUCTION
............................................... 4 2.0 METil ODS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 5 2.1 FIELD SAMPLIMG ......................................... 4 2.2 LABORATORY AN ALYSIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 2.3 D ATA AN ALYSIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 3.0 RESULTS ................................................... 13 3.1 QUANTITATIVE FAUNAL MONITORING . . . . . . . . . . . . . . . . . . . . . . . . . 13 3.1.1 Systematics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 3.1.2 Species Richness .................................... 13 3.1.3 Faimm1 Density ..................................... 14 1 3.1.4 Species Dominance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 3.1.5 Species Diversity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 g 3.1.6 Community Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 3 3.2 QU AN11TATIVE ALG AL MON 110 RING . . . . . . . . . . . . . . . . . . . . . . . . . . 35 3.2.1 Systematics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 g 3.2.2 Algal Community Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 g 3.2.3 Algal Community Overlap ................. ............ 36 3.2.4 Algal Biomass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 3.3 QUALITATIVE TRANSECT SURVEYS . . . . 44 I
3.3.1 March 1991 Transect Survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 3.3.2 June 1991 Transect Survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 3.3.3 Oc.'aber 1991 Transect Survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 3.3.4 December 1991 Transect Survey 50 1 .......................... 4.0 CONCLU S ION S . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 4.1 FA UN AL STUDIES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 1 4.2 ALG AL STUDIES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 4.3 QUALITATIVE TRANSECT SURVEYS . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 5.0 trrERATURE CTIT.D ........................................... 52 g A r ,E N D 1x i . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A., I g I 1 I
I LIST OF FIGURES Figure 1. location of Benthic Sampling Sites near Pilgrim Station . . . . . . . . . . . . . . . . . 5 Figure 2. - Suction Lift Device Used by Divers to Collect Benthic Samples ...... .... 6 Figure 3. Design of Qualitative Benthic Transect Sampling Program at Pilgrim Station ... 8 Figure 4. Density of Deathic Fauna in March and September of 1991 and March and October of 1991 ................................................ 16 Figure 5. Hurlbert Rarefaction Curves for Total Fauna at the Efiluent, Manamet Point, Rocky Point Stations, 0ctober 1991 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Figure 6. Similarity Analysis Based on Bray-Curtis and Group Average Sorting, Spring and Fall 1991 Data Combined . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..... 25 Figure 7. Similarity Analysis Based on NESS and Grosp Average Sorting, Spring and Fall 1991 Data Combined ......................................... 26 l1 l Figure 8. Similarity Analysis of the Fifty Most Abundant Species, Spring and Fall 1991 Data Combined, Using Bray-Curtis and Group Average Sorting . . . . . . . . . . . . . . . 28 Figure 9. Constancy Diagram for Species Groups mj Sample Groups in 1991. Clustering is with Bray-Curtis and Group Average Sorting . . . . . . . . . . . . . . . . . . . . . . . . . . 30 Figure 10. Fidelity Diagram for Species Groups and Sample Groups in 1991. Clustering is with Bray-Curtis and Group Average Sorting . . . . . . . . . . , . . . . . . . . . . . . . . 31 Figure 11. Constancy Diagram for Species Groups and Station Groups in 1991. Clustering is with Bray-Curtis and Group Average Sorting . . . . . . . . . . . . . . . . . . . . . . . . . . 32
-1 Figure 12. Fiddity Diagram for Species Groups and Station Groups in 1991. Clustering is with Bray-Curtis and Group Average Sorting . . . . . . . . . . . . . . . . . . . . . . . . . . 33 Figure 13. Algal Community Overlap Gaccard's Coefficient of Community) and Number of Species Shared Between Replicate Pairs, March 1991 . . . . . . . . . . . . . . . . . . . . . . . 37 Figure 14 Algal Community Overlap paccard's Coefficient of Community) am! Number of Species Shared Between Replicate Pairs, October 1991 . . . . . . . . . . . . . . . . . . . . . . 38 i
K Figure 15. Stunted and Denuded Omndrus Zones Observed in March 1991 . . . . . . . . . . . 45 Figure 16. Sparse and Denuded Omndrus Zones Observed in June 1991. . . . . . . . . . . . . 46 Figure 17. Stunted and Denuded Omndrus Zones Observed in October 1991 .......... 47 Figure 18. Sparx, Stunted, and Denuded Owndrus Zones Observed in December 1991 ... 48 n g I
E a LIST OF TABLES Table 1. AlgalIndicator Species used for Quantitative Community Analysis . . . . . . . . , . 10 Table 2. Faunal Species Richness at the Efiluent, Manomet Point, and Rocky Point Stations in March and October 1991 ............ .... ................. 14 Table 3. Faunal Densities at the Efiluent, Manomet Point, and Rocky Point Stations in March and I October 1991 . . . . . . . . . . . . ............................. 15 Table 4. Fifteen Most Abund e.it Species at the Emuent Station in March and October 1991 18 Table 5. Fifteen Most Abundant Species at the Manomct Point Station in March and October 1991 ................................................ 19 Table 6. Fifteen Most Abumiant Species at the Rocky Point Station in March and October 1991
...................... ...... ...... .............. 20 Table 7. Community Parameters for the Effluent, Manomet Point, and Rocky Point Stations in g M ar ch 1991 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............. 22 5 Table 8. Community Parameters for the Effluent, Manomet Point, and Rocky Point Stations in October 1991 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 Table 9. Species Groups Resulting from the Inverse Cluster Analysis with Bray-Curtis and Group Average Sorting . . . . . . . . . . . . . . .. ........... .......... 29 Table 10. Dry Weight Biomass (g/m2) for Omndrus crispus, Phyllophora spp., The Remaining Benthic Species, Epiphytes, and Total Algal Biomass at the Emuent, Manomct Point, ami Rocky Point Stations in March 1991 ............................ 40 m
Table 11. Dry Weight Biomass (g/m2) for Owndrus crispus, Phyllophora spp., 'the Remaining g Benthic Species, Epiphytes, and Total Algal Biomass at the Efiluent, Manomet Point, and Rocky Point Stations in October 1991. . . . . ...................... 41
.I.6 t
1 I iii B
I EXECLTlWE
SUMMARY
l His report represents results of quantitative data collected in Mar h and October 1991 at established stations in the vicinity of the Pilgrim Nuclear Power Station (PNPS) and qualitative transect surveys conducted in the thermal effluent in March, June, October, and December of 1991. These investigations represent the most recent phase of the long-term efforts to monitor the effects of the thermal effluent on the benthic communities adjacent to the PNPS. A viriety of analytical techniques were used to a"ess ammunity structure. Specific data on algal biomass, dominant fauna, species diversity, and faunal densities were analyzed along with overall community relationships. i-QUANTFTA TIVE STUDIES Faunal Studies A total of 107 species of benthic invertebrates were found in the 1991 samples. The majority of species consisted of crustaceans (34), followed by mollusks and polychaetes (30 each). In comparison witti the previous year, species richness increased at the Eftluent station, with a record high observed in the fall. At the reference stations, no such trend in species richness was observed. The faunal a community at the Eftluent station was also characterized by a very high number of " unique" 4. es (22) found in only one replicate. I Total densities recorded at the three stations were very high in March, due in large part to high I counts of the blue mussel, Afyrilus edulis. The Effluent station was highest in total density (about 500,000 individuals par m2), whereas the Rocky Point station was lowest (about 160,000 ind viduals per m2). In L October the mussel counts dropped dramatically, causing a sharp decline of total densities at all three stations. Density at the Effluent station was highest (108,000 individufs per m2); the lowest densities were recorded at the Rocky Point station (43,000 individuals per m2). In March, the 15 highest ranked species at each station accounted for 96 to over 99% of the total density at each station. Tne percentage of the 15 dominant species in September was lower, ranging from 87% to 93%. De lower percentage of the 15 most abundant species in the fall is the result of the decrease in the mussel populations. The absence of a true dominant in the benthic communities caused changes in the community structure, most noticeably at the Effluent station where the five most abundant -
, species each contributed about 10% to the total fauna. In March, Afytilus edulis alone represented almost 75% of the fauna at that station. A total of 18 to 23 species comprised the 15 highest ranked species at all three stations in March and October. Most of these dominant species were amphipods (11 species in March,12 species in October), followed by gastropods (4 species in March and October). Afytilus edulis I '
I
I was the only bivalve among the dominants during both seasons. Other phyla represented among the dominants were I tunicate (March and October),1 isopod (March), and 2 echinoderms (March). Overall, the diversity of the dominant fauna in terms of represented phyla was much greater in the spring than in the fall. Species diversity indices were obscured by the high density of Mytilus edults in March, but almost identi:al with and without mussels in October. When the mussels are removed from the analysis, the spring diversity values are within the range expected in near coastal benthic communities. For example, Shannon's H' ranged from 2.04 (Efnuent) to 3.88 (Rocky Point) in spring and from 3.40 (Rocky Point) S to 4.22 (Effluent) in the fall. The abundance of the mussels in October was so low t " their removal from the analpis caused the diversity index to decrease. Community analysis by clustering or similarity techniques indicates that the Efnuent station was very different from the reference stations in the spring and in the fall split into two replicate groups that each joined one of the reference stations. With NESS, the spring Ef0uent samples formed a cluster that was dissimilar from all other 1991 samples. Similarity analysis by species for both March and September revealed that dominance patterns
=
influenced the way the species groups joined. For example, most of the species tnat comprise the lists of highest ranked dominant species tend to cluster together, while the rare or infrequently encountered species comprise other groups. Algal Studies g No additions to the cumulative algal lists were made as a result of the analysis of the March and E October 1991 samples. The rock and cobble substrata found at the Efiluent, Manomet Point and Rocky g~ Point stations were heavily populated with red algae, especially Irish moss (Gondrus crispus) and I Phyllophora spp. Epiphytic algal species were observed at all stations, with Gondrus and Phyllophora serving as primary hosts. Algal community overlap measures the sin.ilarity in algal species composition between stations. Community overlap between the three stations was high, indicating that they were very homogeneous with regard to shared species. In March 1991, the range in percent overlap of replicate samples was lower at the Efiluent station (19.7%) than at either the Manomet Point (25.0%) or Rocky Point (21.7%) stations, evidence that individual samples at the Effluent station were more similar to one another than the samples from the reference stations. At all stations, range of percent overlap between replicates was less in October than in March, with the largest decrease occurring at the reference stations. Community overlap between the two reference stations was higher in October than it had been in March, whereas the 2 B
1 overlap between either of the reference stations and the Effluent station declined from March to October. These results indicate that the replicates from each station were more homogeneous and that the Ef0uent station differed more from the reference stations in October than in March. Total algal biomass was highest at Manomet Point in both March and October; the lowest total algal biomass values were found at the Ef0uent station in March arid at Rocky Point in October. biomass of Gondrus crispus was highest at Manomet Point in March and October; it was lowest at the Efnuent station in March and at Rocky Point in October Phyllophora spp. biomass was highest at Rocky Pi 't in March and at the Efnuent station in October; it was lowest at Manomet Point in March and at Rocky Foint in October. The highest biomass of benthic algal species other than Gondrus and Phyllophora for l both spring and fall was found at Rocky Point. The highest biomass of epiphytic algae was found at Manomet Point in March and at Rocky Point in October. Analysis of variance (ANOVA) for total algal biomass showed a significant difference among the three stations in March that the ScheN test attributed to the total algal biomass at the Effluent station being significantly different from the mean bio nass at the control stations and from Manomet Point; by October, this difference had disappeared. Contributing to the variation in total algal biomass were differences in biomass values of epiphytic algae among the three stations significant enough, in both seasons, so that the Scheffe test could attribute them to the difference in epiphytic algal biomass at I- Manomet Point and Rocky Point. In addition, epiphytic algal biomass at the Ef0uent station, in March, g was different from the mean biomass at the control stations and from the biomass at Manomet Point. In W October, analysis of variance showed significant differences in Gondrus and Phyllophora biomass values among the three stations that were so slight that Scheff6's multiple comparison test could not distinguish I the source of the variation. QUALITATIVE TRANSECT SURVEYS The qualitative transect studies performed to evaluate the Chondrus crispur community in the thermal plume area indicate that in 1991 the denuded and stunted areas rema:ned in the condition typical of full or nearly full operation of the plant. The Gondrus denuded and stunted areas encompassed 1320.5 m2 and 225 m 2 , respectively,in the March 1991 survey, in June, folloi , two months of non-operation of the plant, the denuded zone had decreased slightly to 1265 m2 but the stunted zone had l. disappeared and was replaced by a region the divers described as a sparse zone, an area typined by normal looking Gondrus plants that are thinly distributed. The area of the denuded zone continued to decrease to 1030 m2 in October and then increased slightly to 1200 m2 in December. The stunted zone (283 m2) reappeared in October and then decreased in area by December to 183 m2 3 g 1
i i 1.0 IhTRODUCTION This report represents a continuation of the long-term (18 yr) algal and faunal studies at Pilgrim Nuclear Power Station (PNPS) that are intended to monitor the effects of the thermal effluent. The program has essentially remained unchanged for the last ten years. Quantitative benthic algal and faunal sampling is conducted during the spring and fall at two reference sites, Rocky Point ar,d Manomet Point, and at a site offshore of the effluent canal (Figure 1). Qualitative SCUBA surveys of algal cover in the eftluent thermal plume are conducted quarterly during March, June, September, and December. This Semi Annual Repon includes quantitative data from samples that were collected in March and October 1991 and qualitative observations recorded in March, June, October, and December 1991. Work was performed under BECo Purchase Order 68003, in accordance with requrements of the PNPS NPDES Permit No. MA 0003557. 2.0 MLTHODS 11 FIELD SAMPLING ne sampling sites are the same locations that have been sampled since the beginning of the monitoring program, approximately 10 years ago. The stations are located by the following established procedures. Line-of-sight positions are established using highly visible structures located on the shore g as reference points. The Rocky Point station is located by lining up the microwave relay tower with the B PNPS red and white off-gas stack. De Eftluent ss tion, located approximately 120 m offshore, is g identified along the center line between the two discharge jetties, ne Manomet Point station is located 3 by lining up the two southernmost telephone poles on top of Manomet Point. Line-of sight positioning, combined with lead-line depth checks (10 ft. MLW) ensures station relocation to within a radius of 20 E to 30 m of the original station position. The field team deploys a temporary huoy to mark the station locations. All sampling is done by SCUBA-equipped biologists operating from a small boat. For the quantitative algal and faunal studies, five replicate samples delineated by a metal quadiant that measures 0.33 m on a side (0.1089 m2) are taken from the surface of rocks at each station. Upon entering the water, the divers descend to the bottom and locate suitable rocks for phcement of the quadrant. Divers assess algal and faunal cover and select rocks that are considered typical for the station. .All quadrate samples are taken within 10 m of *he designated station location. All attached flora and fauna within the quadrant are scraped from the rock. and drawn through an airlift device into a 0.5-mm mesh bag (Figure 2). Field labels with station, collection date, and 4 E
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Figure 2. Suctionl ift Device Uscu by Divers to Collect Benthic Santles. 6
l 5
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replicate number are placed in semple bags before sample collection. After sample collection, the sample bag is closed with a rubber stopper and placed in a large catch bag and a new bag is attached to the airlift, ne divers then locate the next suitable rock and repeat the sampling process. After the five replicates are collected at a station they are delivered to a biologist on the boat for pr0 cessing. While the vessel is anderway to the next station, the contents of each bag are transferred to e l-gal plastic jar, labeled, and preserved with 10% buffered formalin. Approximately 100 g of Borax is added to each jar as a buffering agent to prevent softening of calcified shells. For the qualitative transect survey, SCUB A observations are made alorg the axis of '.he discharge canal. A line is extended across the mouth of the discharge canal (Figure .'8) A weighted ceritral transect ^ line (CTL), marked at 10-m intervals, is then attached to the center of this line and deployed along the central axis of the canal to a distance of 100 m offshore. Using a compass, divers extend a 30 m measuring line, marked at 1-m intervals, perpendicular to the CTL. A diver swims along this third line, recording changes in algal cover from the CTL through the denuded and stunted Chodrus areas to where
- the algal cover becomes normal.
4 According to procedures established by Taxon (1982) and followed in subsequent years, the 4 { - distinction between " denuded" and " stunted" zones is based on the growth morphology of Chondrus crispus. The denuded zone is defined as that area where Chodrus occurs only as stunted plants restricted I to the sides and crevices of rocks. In this area, Chondrus is found on the upper surfaces of rocks only f where the microtopography of the rock surfaces creates small protected areas .n the stunted ,zby, Chondrus is found on the upper surfaces of the rocks but is noticeably interior in height, density, and 4 frond development compared to unaffected areas. In 1991 the divers included a distinction between a ! stunted zone and a sparse zone. The sparse zone is an area with normal looking Chondrus plants which
- are very thinly distributed. The normal zone is considered to begin at the point where Gondrus height and density are fully developed. The dive team must keep in mind while taking measurements that the shallow depths nonhwest of thn discharge canal preclude normal Gondrus growth. In addition to l observing algal cover, the divers record any unusual occurrences or events in the area and note the
} location of any distinctive algal or faunal associations. 2.2 LAllORATORY AN ALYSIS In the laboratory, the algal and fauncJ fractions of the samples are separated by washing the animals off the algae onto a 0.5-mm-mesh screen. The animals are preserved in a solution of 70% ethanol, ne algal fraction is preserved in a 10% formalin solution. The faunal samples are labeled y > 1
I g Dischargo Canal , Barrier f4et )
- - J,
. s al
,.
- 5l
>*Q ...
ie % , . 300 , o. . o oc Etfluent une W . . ., W 3 Wolght Marke at 10 - meter intervals
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.. # Measurtnc L.ine (30 meters marked off at 1 ~ meter intervals)
,, 4)
Trarnect une - ,
... e, g Diver Safety Une Mchw gg y I
_ .e me I E ! I I Figure 3. Design of the Qualitative Benthic Transect Sampling Program at Pilgrim Station. 8
.I.
I and stored in 16-oz glass or plastic jars until sorting. Algal samples are labeled and stored in 1-gal plastic jars until sorting. Each replicate sample is processed separately. The algal component of each sample is examined, using both dissection and compound microscopes, to identify all species of macroalgae and, in addition, record the presence or absence of 38 indicator species. Imponant algal references used to identify and confirm names are Taylor (1957), Parke and Dixon (1976), and SouQ (1976). TMrty-seven of the indicator species were originally chosen by Taxon in September 1978, having been carefully selected from a list of the several hundred algal species recorded from the PNPS study sites between 1974 and ; 199 (Taxon,1982). One species (Cadophora spp.) was added in 1988 (BECo,1988). The indicator l species include members of each of the major algal families from a variety of habitats, including all of , the dominant species within the study area, the majority of the macrophytic species, and the most common epiphytic species (Table 1). Herefore, the indicator species comprise the most substantial part of the algal community as measured by both percent cover and biomass, although they constitute only a small fraction of the flora inhabiting the study area in terms of the number of species. Dry-weight biomass of all macroalgae in each sample is reported as total biomass and for four I separate algal fractions: Chondrus crispus, Phyllophora spp., epiphytic species, and the remaining benthic species. Each fraction is weighed on a Mettler balance after being dried for 72 h in an oven set I. at 80*C. A 25% aliquot of the faunal fraction of each sample is processed and the remaining 75% of the sample is archived. Prior to sorting, the 25% aliquot is stamed with a saturated alcoholic solution of Rose Bengal for at least 4 h, but no longer than 48 h to avoid overstaining. He samples are examined under a dissecting microscope and each organism or fragmern thereof removed. Invenebrates are soned to major taxonomic groups, such as polychaetes, crustaceans, bivalves, gastropods, echinoderms, and other miscellaneous phyla. The blue mussel Mytilus edulis is left with the residue and counted during the sorting process. Final identification is to the lowest possible taxon (usually to species). During identification, the counts af each species are recorded. A new reference collection for the PNPS program has been developed from the 1990 samples and will serve as a voucher collection for subsequent identifications. The samples are archived for a minimum of three years after collection. I I I
I Table 1. Algal Irxlicator Species used for Quantitative Community Analysis. l Chlorophyta(Greca Algs) Rhodor lyta (Red Algv) lli Bryopsis plumosa Ahgeltla plicata
- Otactomorpha linum
- Antithamnion americanum
- l C. melagonium* bonnemaisonia hamifera*
Cadophora spp.*# Callophyllis cristata Enteromorphaflexuosa* Rhl:oclonium riparfum* Ceramium rubrum
- Owndrus crispus *
}
Uhu lactuca* Corallina o.ficinalis* 1 Cystoclonium purpureum
- Phaeophyta (Brown Algae) Gracilaria tibuhlar Gymnogongrus crenulatus l Chordariaflagell{forir.ls Membranoptera alata* n Desmarestia aculeata* P ria palmata D. viridis *# Irys runens* g Lwninar'1 digitata . pl. ora truncatc* g; L. saccharina P. p.,eudoceranoides*
Sphacelaria cirrosa*# P.traillii g Plumaria elegans l Polyides rotundus
- Polysiphonia elongata P.Jibrillosa*
P. harveyi* P. nigrescens* ' P. urceolata* Rhodomela confenvides* Spermothamnion repens
- I
- Species found in 1991 samples.
# Species present in March 1991 but absent in October 1991.
I I I 10
,5,
I 23 DATA ANALYSIS Ali faunal data are kept on specially designed project data sheets to facilitate computer entry. Data are entered into a spreadsheet format on a personal computer. The software used is Quattro Pro8 Some basie data summaries and calculations can be made while the data are in this form. Following data entry and reorganization in the spreadsheet, a hard copy of the raw data is generated and verified against the original coding sheets. All entry errors are corrected at this point. Data files are then transferred to the Woods llole Oceanoor. ' ic Institution (WHOI) VAX computer for analysis. Analytical software consists of a suite of prop ' veloped specifically for the analysis of benthic data. In addition to a variety of data-management and modification utilities, these programs include PRAREl and COMPAH. PRAREl summarizes the data for each sample, calculates a variety of diversity-related indices, and generates a rarefaction curve. COMPAH is a multivariate classification package that allows a wiJe variety of user-specified options for similarity indices and clustering strategies, including both normal (i.e., by station) and inverse (i.e., by species) analyses. The individual species composing the fauna at each station are rank ordered by abundance. The most abundant species is listed first, followed in order by less abundant forms. The percent contribution I of each species to the total fauna is denoted by a decreasing total percentage starting with the most abundant species and ending with the most rare. Basic statistical treatments include calculation of means I of abundances per station and extrapolation to density per m2 j Species richness is interpreted by using ajackknife procedure in combination with pooled species 5 data to evaluate the contribution of rare species in the communities (Heltshe and Forrester,1983). This procedure takes into account that random samples are not necessarily r aresentative of a population. The
~
jackknife estimate of species richness is a function of t',e number of so-called " unique" species present t at a station, that is those that are present in one and only one replicate out of five. W jackknife estimate of species richness ($) is expressed as: l . i = S+ .I" k n a where S represents the pooled species numbers at each station, n is the number of replicates, and k is the number of unique species. The variance of estimated species richness (var ($)] is also calculated to measure the spatial distribution of unique species. y 11 I s- _ -
I Measures of diversity calculated for each sample and station include the Shannon Wiener information (H') and evenness (l') indices and rarefaction curves constructed according to the method of Hurlben (1971). Shannon's H'has been shown to be r hiased estimator and for small samples will underestimate true populathn information (Smith and Grassie,1977). Hurlbert's expected species index of diversity is an unbiased estimator and is thus particularly useful when small and unequal sample sizes must be compared. ! He measure of similarity developed by Grassle and Smith (1976), the Normalized Expected Species Shared (NESS), combined with group average sorting is used for cluster analysis. NESS is based on the expected number of species shared between random samples of size m drawn from a population, and is sensitive to the less common species in the populations to be compared. For the present analyses, m was set at 200. He Bray-Curtis similarity measure, combined with group average sorting, is also used (Boesch, 1977). These values are calculated for stations (normal) and species (inverse). For the latter, data are analyzed using numbers of individuals. In order to evaluate patterns in the station and species similarities, a nodal analysis is performed using the results of the similarity analyses described above. This procedure is especially useful when evaluating the combined spring cnd fall data. Nodal analysis is a method of relating normal and inverse classineations to aid in the interpretation of cluster analyses. He methoi uses two way tables tnat show replicate groups on the vertical side and species groups on the horizontal side. His technique is used to measure constancy and fidelity. Constancy is a proportion derived from the number of occurrences - of a species group i' a replicate group as compared with the total possible occurrences. Fidelity is the a degree of restriction of a species group to a replicate group. E For the algae, community overlap was calculated using Jaccard's cos fficient of community (Grieg-Smith,1964) to measure the similarity in algal species composition among the Eftluent, Manomet Point, and Rocky Point sta: ions. Jaccard's coefncient provides a mathematical evaluation of the similarity between two replicates or stations using only species occurrence and does not consider differences in their abundance. Comparison of means in a single classi6 cation Model I ANOVA (Sokal and Rohlf,1969), for each season separately, were performed to determine whether there were any differences among stations in rJgal biomass. Sources of variation were among stations (df= 2) and within stations (df= 12); Fmy
= 3.89. When the ANOVA determined a significant difference in algal biomass among stations then Scheff6's multiple comparison test (Sokal and Rohlf,1981, p.256) was performed to determine where 12 5
I the difference occurred. Scheffd's test allows comparison between a pair of stations, for example, the two reference stations, or between one station and the mean of the other two, for example, the Effluent station versus the mean of Rocky Point and Manomet Point. 3.0 RESULTS 3.1 OUANTITATIVE FAUNAL h10NITORING - 3.1.1 Systematics j ] Since the sampling effon in April 1990, a total of 138 specbs have been identified,107 of which ^; were found in samples taken in March and October 1991. He largest taxonomic group were the crustaceans, contributing 34 species (32 %), followed by polychaetes and mollusks contributing 30 species - (28%) each. The other groups, such as nemeneans, echinoderms, and anemones, were represented by . few species that together accounted for the remaining 12% of the fauna. A species list can be found in Appendix A. In comparison to 1990, the number of species was slightly lower in 1991, mostly due to
< a reduced number of polychaetes and mollusks. ! Some 10 species were added to last year's species list. This slight increase in the total number of species found since the spring of 1990 agrees well with the expectations outlined in the previous I annual report (BECo,1991b).
- i. 3.1.2 Species Richness -
, Species richness values for all three stations in spring and fall 1991 are listed in Table 2. Data l are presented as total species per replicate for each station, with a mean value over all replicates at each station and a cumulative total representing pooled species numbers at each station.
In the spring of 1991, the highest number of species was found at Rocky Point (total: 78, average per replicate: 48.6). Manomet Point had the lowest number of species (total: 62, average per replicate: 38.8). The Effluent station was intermediate with 72 species total (average per replicate: 43.2). The fall samples were characterized by an increase in the number of species that was most distinct at the Effluent station with a total of 93 species (average per replicate: 59.4). Rocky Point was intermediate with 74 species (average per replicate: 46.8), and Manomet Point was lowest wim 70 species (average per replicate: 47.8). The number of species at the Effluent station is the highest ever reported for this station.
- 13
l I! Table 2. Faunal Spccles Richness at the Efiluent, Manomet Point, and Rocky Point Stations in March and Octota 1991. Effluent hianomet Point Rocky Point Spring Fatt spring Fall Spring Fatl No. Species / Replicate 47,35,44, 65, 60, 60, 42,42,39, 46,44,48, 50,51,51, 39,46,49, 53,37 61, 51 35,36 53,48 43,48 58,42 hican 1 Standard Deviation 43.2 i 7.36 59.4 1 5.13 38.8 1 3.27 47.8 1 3 35 48 6 i 336 46 8 i 7.33 l 5 No. Species / Station 72 93 62 70 78 74
.' wkknifed Estimate 95.8 120.5 77 0 86.3 101.8 95.3 Species Richness ($)
Variance ($) 42.24 30.36 0.96 2.!6 11.84 8 96 l 8 In order to assess the rare species that might be present at the stations but were not found because of the relatively small area sampled, the jackknife estimate of Heltshe and Forrester (1983) was calculated (see Section 2,3), resulting in an estimated species richness value ($). In March 1991, the estimated species richness was highest at Rocky Point, lowest at Manomet Point, and intermediate at the Effluent station; i.e., the estimated species richness showed similar patterns to the actual number of species found in the samples. In October 1991, estimated species r!chness was highest at the Eftluent station, lowest at Manomet Point, and intermediate at Rocky Point. Again, the estimated and actual species richness values showed similar patterns. en Between March and October 1991, species richness increased a* the Eftluent station and Manomet E Point, but declined slightly at Rocky Point. He increase in species richness at the Eftluent station appears to be a continuation of a trend observed in 1990, whereas no seasonal or long-term pattern could be detected at the reference stations. 3.1.3 Faunal Density Faunal densities for each s -ti r; , pressed as mean number of individuals per replicate (extrapolated from the 25% aliquot that w er 4 yzed) and number of individuals per m2, are listed in Table 3. Densities of the mussel Myfilus edulls are listed separately, along with the densities of the remaining fauna, to demonstrate the often strong influence of the mussels on faunal densities. Overall, 14 I B, , = l l
r L densities droi. ped considerably between spring and fall 1901 at all three stations due to a sharp decline in the Mytilus edulis populations (Figure 4), ne most drastle decline in mussel denshy was found at the Effluent station (hlmost 400,000 individuals per m2 in Merch, about 5000 individuals per m2 in October). At the reference stations, mussels declined from 120,000 to about 3500 indisiduals per m2 a Manoms Pois and from almost 100,000 to about 1500 individuals per m2 at Rocky Point. He changes in densities for the remaining fauna were, in comparison, minor. Densities of two additionvl species are shown in Figure 4. Jassafalcata, which has historically been the most abundant amphipod at all stations, exhibited a sharp decline in dernity in October 1991 at the Efiluent and Rocky Point stations but increased at Manomet Point. Overall, Jarsafalcata has declined steadily at the Effluent and Rocky Point stations since September 1990 and appears to have been replaced by other amphipods (see ; Species Dominance, Section 3.1.4 below) contrast, the gastropod I.acana vincta, increased markedly in abundance in the October 1991 samples , .I three stations when compared with the very low spring densities. Table 3, Frunal DensMes at the Effluent, Manomet Point, and Rocky Point Stations in March and October 1991, I Density Station Seawn Total Fauna Mytilm c,fulis Remaining Fauna Mean ( *) No. No, Mr.an ( R) No. No. Mean ( *) No. No. inJiv./ Rep. Indiv./m2 Indiv./ Rep. Indiv./m' Indiv./ Rep. Indiv./m2 Spring 59.341 517,631 41,945 385,368 14,396 132,263
" ' " ' " ' ' " ' - ' ' ~ ~ ' ' ' -""''~ - " " " ~ " " ~ " " ' ' "'~~'
EFF Fall 11,747 107,871 570 5.23B 11,177 102,533 Spring 20,534 168.660 13.014 127,839 6,620 60,821 gp . . . _ . . _ . _ .. . Fall 9,966 91,511 375 3,445 9,591 88.056 Spring 17,285 158,804 10,513 96,586 6,772 62,218
' ' ' ' ' ' " ' " ' ' ' ' ' ' ' ' " ' ~ ' ' ~ " '
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RP Fall 4.714 43,224 158 j 1,455 4,556 41,( l9 L,s.4,.3 =, -- - 15
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E 3.1.4 Species Dominance The fifteen numerically dominant species of each station in spring and fall 1991 are listed in Tables 4 through 6. A suite of 23 and 18 species comprised the dominants founj in the March and October samples, respectively. De October dominants included 12 amphipods, 4 gastropods, I bivalve (Afytllu3), and 1 , tunicate. Eleven of these species were among the dominants of all three stations,5 were among the dominants of two stations, and 2 species were among the dominants of only one station (1 at the Efiluent station, I at Rocky Point), nese data indicate that the faunal composition was very similar at all three stations, although the ranks of the dominants shared by three stations were very different at each station. In the spring, the top rankmg speeles at all three statiens were much more similai than in the fall. All stations were dominated by Afytilus cdulls and lassafalcata, ene or two species of Cony >hlum, and lacuna vincia. A similar tendency could be observed in 1990, when the suite of dominants was quite similar at all stations in the spring, but differed in the fall (aside from Afytilus which remained the top ranking species in the fall of 1990). The sharp dedine of Afytilus in the fall of 1991 resulted in a very different community structure in that a true dominant was not nresent at any station. Instead, the stations were characterized by four or five I- :pecies occurring at high abundances. At the Effluent station,1 r amphipods and the snailIAcuna vincta each contributed roughly 10% of the total faurn, whereas Afytilus represented only about 5%. Only 7 of the I spring dominants at this station were also among the fall dominants. The diversity of the dominant fauna in terms of represented phyla reported in the spring was no longer seen in the fall when altnost all dominants were amphipods (12 out of 15 species). At the reference stations, the community structure resembled more the communities normally seen in this project, i.e., one species clearly dominating and all others contributing only minor percentages of the total fauna. At Manomet Point, the two most abundant species were Lacuna vincta and lassa falcata with each contributing about 20% to the total fauna. The lower ranking species represented between 1 and 10% of the total fauna. The most abundant speeles at Rocky Point was the amphipod De. tamine thea (34% of the total fauna); the second and third ranking species lacuna vincta and Caprella penantis contributed roughly 20 and 10%, respectively, of the total fauna. The differences in the composition of the dominant fauna at both reference stations between spring and fall was much less then at the Effluent station: 13 of the spring dominants at Manomet Point and 12 at Rocky Point were also among the fall dominants of those statiora. I 1 17 I I
Il Table 4. Filleen Most Aburdant Speci:s at the Efiluent Station in March and October 1991, g l__ ITIT UINT Sp % 1991 hil1991 Meas hssed of was haem l Nunder pee Wai/ed Nunder of Replasu lame pee Emfie l Sem*ma $$ec are Iteplu mas dIama l Mynlus adula (Bo olve) 10,486 0 74 45 Carrella per.anas ( Anthip<di 3750 l).12
/ausfakau (Ant hi puJ) 2,137.4 15.1l Denamuw Ara ( Anthind) < ' .s i1,71 CorepAium Nt/msum 6!).4 436 Collm/vus latiiscu!w ( Any hind) 320.R Il.22 (Amphip<d)
Cerephium acusum ( Airthipcd) 447.8 3.18 !ausfalc 14 (Anth ird) 294.6 1031 5 lacund wicsa (Osstrtynd) 142 6 1.01 luuna swsa (OsantoJ) 271.4 9.49 Caperlia pesantis (Arrrhiyd) 60 8 0 43 MytJus tJuhs (bshe) 142.6 4 99 Calliordw Larsucular 18.0 0. 8 ) Coreptuum saberndatum ( AnchipoJ) 129.8 4.54 (Amphipod) Daiswne shra (Anthind) 17.2 0.12 Peworr** WrmiJ ( A"t ipod)h 107.0 3 74 Cre.+ratulus lacwas 14.2 0.10 Compheum acuium (Ant hi ndi 105 4 3.69 (Nemertean) Idara phosphorra (1wyd) 13.2 0 09 Corephium honath (Amphird) 93.4 3.27 m Aswrids forbesi (Echintderm) Ia.4 0,08 Carrella bararv (Amphipod) 76 4 2+7 Photor manusa (Polysheets) 1C3 0.01 Martita lunata (Gennyd) 10 4 2 46 Eulalia vertin (iblychaete) 9.4 0.07 luk,>roctrw angulpes ( Anyhipcd) 66.2 2.32 Molgula sp. (Turiste) 7.2 0.05 Am/AiAtw mHcua ( Anyhind) 53.0 1 65 E Strongylocentrosus 6.8 0.05 Pleur.smtes glaber ( Anyhirtd> 50.4 1.76 E Jrcebachicaris /Ethinnderm) TUTAL OF 15 $PIrlES 13,995.4 99.37 TOTAL OF 15 $PEct!3 2488.2 87.14 REM AINING IDfRTIE!ED 89.5 0 63 RD1 AINING IDENTirlED F AUN A . 75 370.2 12.no FAUNA . 57 $PECIES $PECIES TOTAL IDEffr! TIED 14,085.2 100.00 TOTAL IDENTIFIED T AUN A - 90 2858.4 100 N FAUN /. 72 $PECIE$ ; $PICILS I I I 18 g g 5
E Table 5. Fifteen Most Abuislant Species at the Marxur.ct Point Statior in March arx! (ktolo 1991. . O 1 i I MANOMIT IUlNT 5$ % 1991 I all 1991 I Mcan Nunh: fusse of West.fal 5euna Mena Nund.ee pw twess of uctsar.r.d I'auas pit Reli46e $pe6 W Rspl e _ 8ta kes Myrefus eJ bs (bshe) 3.478 6 6 7.16 Lacaw incw (Gastnycd) $72.2 23.34 i Jassa fakau (AnthipoJ) 827.0 16.11 Jansefakssa (Anth ip4) 490 6 20.01
= Coropkum ocusum ( Anthipcd) 2M6 3.91 Carrella penanas (CaprilhJ) 232 8 9.50 bcuns sucsa (Ossa.nvoJ) 133.0 2.59 Deiamtw # Ara (Anthinds 196.2 8.00 Convpluum h<etui ( Anphip4) 127.8 2 49 Margansas umbibcabs (Gatnymt) 164 6 6.71 Margarfus umbehcabs (Gastripal) 76 4 1 49 Cervpluum scusum (Anphird) 161.0 6.57 Moltula sp. Uunicats) 46 4 0 90 Mysilus eJubs (hahe) 93 8 38)
JJosse pAosphorra (Anchipm!) 35.0 0 68 CcerpMum beesus (Anthindi 93 4 3.51 I Cauiopia* lariiscuhu ( Ant hi rdi 13.4 0 46 Pirusymus glaber ( Arrphird) 8).2 3.39 Desanuns sAsa (AmphipW) 18 8 0.37 Colboreus larisuulus (Anthind) 59.0 2 41 Caperlia penanns ( Arnphip<4) 15 8 0.37 1sca ryrocerus anguipes (Anit hi pW) 36.2 1 48 fachyrocena anguipes ( Arnphipal) 18 0 0.35 Carrena Lacerts ( Anytund) 32 5 1.34 Amphisor rubricasa ( Arnplc.p4) 16.2 0.32 Molgula sp. (Tunkste) 30.8 1.26 Pleus>=urs glaber ( Anthir d) 15.2 0.30 M str#4 Junau (Gestny # 26.2 1.07 Ponscarneia facimis ( Anthipod) 14.6 0 26 Ponsoprasia se.crmas ( Anthipal) 15.2 1 01 I TOTAL Or 15 srEclE3 5.G49 8 98.38 TOTAL or 15 stEctr3 2.298.0 93.75 REMAINING IDFVrtrlLD F AUN A . 83.8 1.62 REM AINING IDENTirlLD F AUN A . 153 6 6.25 47 $PLCir3 54 $PECIES TOTAL IDENTIT?ID FAUNA 62 4,133.6 100 00 TUT AL IDENTir1ED r AUN A - 69 2451 6 100 (0 I hPECILS $PLCir3 I l I I I 5
- - -- E
l k A90 6 Fiftecil Most Abundant Species at the Rocky Point Station in March and October 1991. l ROCKYIW(T I
$pring 1991 I~all 1Y91 Maan Pmedd Wea Pined d Nuadet kjemifu4 Nundies knewafuut pre Fauna pes Iouse Sta'we Itgla. ate sva we Eglame Mynk <Juhs(b ahe) 2,628.2 60 82 Driamine aAra (Ant h t 4) 394.4 34.30
/assafakasa ( Anyhipc4) 431.8 10 m) locuna nacia (Osstnpod) 217.8 l$.94
~
CompAlum acuram ( Anthipod) 260 4 6 03 Caperum p<nanas ( Ant hi p4) 126 2 10 97 locma wncsa (Gastnyod) 225.6 5.22 CoropA.um bmedi(Ant hi rd) 76.0 6.61 Molgu.'s sp. (Twsste) 75 8 1.75 Mynfus edula (Baelve) 39.5 3 44 Mergeruss umkhcahs (Onetnyod) 75.4 1.75 Margows umkficahs (Gastron4) 30 4 2 64 CoropAlum bontli (Arnphipod) 73.4 1.70 ConyAlum acun.m (Ant hi N4) 24.2 2.10 Mistrua lunasa (Gastnyad) 69.2 1 60 Onobs aculse (Gastnt(4) 23.0 2.00 Onoha scul<a (Gestnpod) $3.2 1.28 Caunysus tardscuk (AnthipoJ) 21.6 l 88 PenJof ra'ta ia'rmis (Anphipod) $4 6 1.26 AmpAtthor ruhdcuta ( Anphind) 19 4 1.6 d hchyrocerus anguipes (Anyhipc4) 53.0 1 23 Amsotrwis inermis ( Anthipod' 17.4 1.51 5swntylocenswsus droebacounests n.4 1.14 Marrua luna,a (Gastn.gud) 17.0 l .48 (hhinodenn) Deramine aAre (Arnphipod) 39.6 0.92 Mc4t ufa er. (Tunicste) 15 6 1.36 Carrt#4 ymansis ( Anth tc4) 2f 2 0 68 Pirurymass gleber ( Anyhird) to S 0 94 IJoses phospliores (Isopaf) 23 8 0.55 hchyrocerus anfuires (Arnchipod) 10.0 0.87 g , TCrrAL OF 15 SPECIES 4,144.6 95.93 TUTAL OF 15 $PEfif3 1,04).3 43.73 RI%IAINING ' 'ENTIRED F AUN A - 176.6 4.07 R111 AINING IDENTIFIED FAUN A - 106.7 9.27 63 $PECIEa 60 SPECIES TOTAL IDD4TITIED FAUNA 78 4,321.2 100 00 TOT AL IDENTIFIED FAUN A - 75 1850.0 100 a)
$PECIES $PECTES I
E I 20 I
.B
l 3.1.5 Species Diversity Diversity-related community parameters for hiarch and October 1991 are presented in Tables 7 and 8, respectisely. In the spring, the lowest diversity was observed at the Efileent station with a Shannon-Wiener index of 1.34 (mussels in:luded). De highest Shannon-Wiener index was calculated for Rocky Point at 2.49. When mussels were excluded from the analysis, allll' values increased by a factor of approximately 1.5. Iturlbert's rarefaction method revealed similar results; the number of expected speeles per 5000 individuals increased roughly 1.5-fold when mussels were excluded. The analysis of the October 1991 samples produced very different results. Due to the very low mussel counts at all stations (see abeve), the Shannon-Wiener indices with and without mussels were almost identical for each station, differing by 0.1 or less. A very striking difference to previous yers, aho caused by the low mussel abundances, is the slight decrease ofIt' w hen mussels are escluded. The highest diversity was found at the I.f fluent station (11'=4.30), and the lowest diversity was found at Rocky Point (11'= 3.50). Diversity at hianomet Point was intermediate (11'= 3.68) and most similar to Rocky Point. These values are considerably higher than the corresponding sprin;; values, but are within range of the diversities found in the fall samples from the previous year (mussels excluded). With llurthert's rarefaction method, the ranking of the two reference stations is reversed with Rocky Point showing more expected species per 5000 individuals (72.1) than hianamet Point (59.9). Diversity measured with rarefaction at the Efiluent station is still the I highest at 73.6 expected species per 5000 individuals, and it is very simi'ar to Rocky Point. Diversities measured in October 1991 are expressed as curves in Figure 5. Only stations with Afyrilus included are shown in this figure bees.use of the negligible difference caused by the absence of mussels from the analysis.
- I I
I i \. ( l I 21 I
v.w. _ Table 7. Community Paranxters for the Emuent, .Manomet Poire, and Rocky Point Stations in Mardt 1991. ( spec == per Sper=s per sb am=- Ever===s Simtre Densey Taal Wo. Spmes per 5:=== rer Srmes F U1 e 5'JO trativ. 1000 indsv. 2500Imirv. 5000 Indiv. Womer (IT) (Imlim3 %er=s 100 lai. e 25.9 34.5 134 0.217 72 6.- *.'2.0 16.7 E m uent 517.631 42.4 51.9 2.04 0332 71 9.7 22.2 30.4 Wdhout Myrdas 132.271 33 3 41.6 1.82 2J06 62 10 3 20.0 25.2 Manomet Point 188.660 46.6 55.7 2.85 0.480 61 15.7 27.8 34.7
%ht Myritar 60.821 47 7 57.9 2.49 0 393 78 15 3 28.5 35 8 Rocky 1% int 158.504 60 4 69 9 3 88 0 619
" 21.6 37.7 47.0 Wahout Myr#ar 62,218 i
U Table 8. Commurday 1% meters for the Emuest, Manomct Point, armt Rocky Point Stations in October 1991.
~
Specum per semes per Shans==- Evenness Twal No. Species per Species per Species ger ' Starke Density 2500 Indiv. 5000inJrv. Wwmer (If1 y) Si ma 300 Indiv. 500 Imire. 1000 ladsv. I (Indim7 06~ r 49 3 62.0 73.6 430 93 23.9 40 6 E m ocnt. 107.871 61.8 73 3 4.22 0.648 23.4 40 2 48.9 Without Myrdar 102.533 92 40.5 S t .6 59.9 3.68 0(A) f 91,511 70 18.8 32.7 Manomer Point 51.1 59 3 3 58 0587 69 18.1 32.1 40 0 Wdhout Myrdas 88.056 61 3 72.1 3.50 0.564 74 20.6 38 3 47.4 Rocky fbint 43.284 60 8 71.6 3.40 0.550 20.0 37.8 46 8 Wthout Myrdas 41.829 73 E N E E M E E E E E E M E E E E E E W
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?.1 A Community Analysis Similarity Analysis by Stat!:s Similarity between statims was raeasured with two clustering methods, liray Curtis and NESS (Grusle & Smith,1976; Boesch,1977). Figures 6 and 7 show the dendrograms resulting from the analysis l of the spring and fall 1991 data combined. With Bray-Curtis, the two main dusters in the dendrogram represent the two seasons (Figure 6)jokin.g at a low similarity level of 0.21. Within the spring data, there are three large clusters consisting of a mixture of Manomet Point and Rocky Point samples, the remaining three Rocky Point samples, and all Efiluent samples, respectively. He similarity among the individual Eftluent replicates is the highest of all spring clusters, but the group of Effluent samples joins the two reference samples at a relatively low similarity level of 0.44. In the fall half of the dendrogram, four clusters can be distinguished. They c.msist of all Manomet Point samples, three Efiluent samples, al' Rocky Point samples, and the remaining two Efflurnt samples, respectively. The laiger Eftluent clusterjoins the Mr.nomet Point cluster at the 0.58 lesel, whereas the small Ef0uent cluster joins the Rocky Point cluster at the 0.52 level. Similarity among samples forming a cluster is eenerally lower in the fall tien in the spring, but all fall samples join at a level simile to that foand in the spring (0.44).
With NESS, which is mare sensitive to rare species than Bray-Curtis, the samples group differently in some places (Figure 7). V'hile the fall samples form one large cluster, the spring samples are split into two very dissimilar clusters, one consisting of all samples from the two reference stations (left side of the dendrogram) and the other consisting of the Ef0uent samples (right side et the dendrogram). The very low similarity of the Eftluent station and the re:erence stations in the spring was already shown in the previous report (BECo,1991b), and in this combined dendrogram is even more conspicuous because the spring samples as from *he Eftluent station join all ot!.er samples taken in spring and fall 1991 at a low level of 0.50, whereas g the fall samples join the spring samples frem the reference station *, at a rnuch higher level of 0.74. That means that the spring Ef0uent samp!es are the rnost dissimilar of all regardless of season. Within the fall cluster, the Eftluert samples are split in'a two groups as in the Bray Curtis analysi'.. One group joins one of the reference stations similar to the pattern seen in the Dray-Curtis dendrogram. The smaller Ef0uent cluster does not join the other reference station as seen in the Bray-Curti:. dendrogram (Fig. 6), but r ther joins all remaining fall samples at the 0.79 level. Thu main differences between the Bray-Curtis and NESS dendrograms are as follows: (1) He reference stations Eroup by station with NESS, but form a mixed cluster and one with the remaining Rocky Point samples with Bray-Curtis; (2) the spring Ef0aent cluster joins the spring referene station clusters with Bray-Curtis, but joins only the combined spring and fall samples with NESS; (3) the fall Effluent samples are 24 I a
E .I 3 .. _ I "- w. I
.36
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Figurc 6. Similarity Analysis Based on Dray-Curtis and Group Average Sorting, Spring and Fall E 1991 Data Combined. 25 I
I I 3 u-I u. N-I u. 1, ,. . I 6 m 7$ = W 5 m 80 = w m 641 aa "r _._
=- p- .d,
_L _L g
,, ,,1
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E Figure 7. Similarity AnrJysis Basal on NESS and Group Average Sorting, Spring and Fall 1991 Data Combined. I I 26 5 m
split into two clust' , that each join one of the reference stations with liray Curtis, but the smal!er Ef0uent cluster joins all other iall samples with NESS. Both methods clearly point at seasonal differences in similarity, and both methods show that the Ef0uent station is more similar to the reference stations in October 1991 than it has been since September 1990 (see Figure 10 in BECo,1991a). I Similarity Analysis by Species he Ofty most abundant species of the combined spring and fall 1991 samples were analyzed with Bray-Curtis. He dendrogram is shown in Figure 8, ar..! a list of species groups (clusters) is provided in Table 9. The dendrogram shows two main groups of clusters joining at a similarity level of 0.13 and a single species (the polychaete 1%olve mlnum) joining all other species at the very low level of 0.W. The two main groups ccasist of non-dominant species (left side of the dendrogram) and dominant species (right side of the dendrogram). Within these two main clusters, a total of thirteen species groups was identiGed. Groups 1, 4,5,7, 8, and 9 consist of species occurring in low abundances throughout the area during both seasons. I Groups 2,3, and 6 include species that generally occurred in low abundances, but were occasionally found among the dominants. Groups 10,11, and 12 consist of species that were usually among the dominants at I each station during both seasons. Group 13, the single species joining the other 49 species at a very low similarity level, was a spring dominant at the Ef0uent but otherwise was rare or absent. Nodal Analysis To better understand the results of the similarity analyses, the sample groups and species groups were compared in a nodal analysis. Two measures were calculated: constancy, which shows the frequency of occurrences of a species group in a sample group compared to its frequency at all samples combined; and i fidelity, which shows how restricted or faithful a species group is to a sample group. De highest possible constancy value is 1.00, indicating that all species of a species group occurred in all samples of a sample group; the lowest possible value is 0, indicating that none of the species in a species group occurred in any of the samples of a sample group. Fidelity values are between 0 (all species of a species group are evenly distributed over all sample "oups) and > 3 (all species of a species group occurred in only one sample group). The results of the nodal analysis are presented in Figures 9 through 12. In Figures 9 and 10, the dendrograms shown in Figures 6 and 8 are used. The species groups are listed in Table 9, and the sample groups are the ones described in Section 3.1.6. Figure 9 show s the constancy diagram, with the species groups along the y axis and the sample groups along the x-axis. Figure 10 shows the corresponding Odelity diagram. Here are two questions that car be 2, I
' Il (( f i'lli J
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1 . Figure 8. Similarity Analysis of the Fifty Most Abundant Species, Sprint, ud Fall 1991 Data Combined. Using Bray-Curtis and Group Average Sorting. E E E E E E E E E E E W W W W W g g g
I Table 9. Species Groups Resulting imm the Invene Cluster Analysis with 11 ray-Curtis and Group Average Sorting. Group 1 Group 9 5 Proboloides holmes! Phoxocephalus halbolli Ophbpholls aculeata 5 Anomia simple.t Gtoup 10 Lamellidoris aspera ischyrocerus anguipes Caprella nr. septentrionalis Caprella linearis E Pontagenela inermis Gtoup 2 Corophlwn tuberculatwn Asteriasforbesi Amphitht>e rubricata E Hiatella arctica Crepidula plana Crepidulafornicata hiirrella lunata Nerels pelagica Idotea phosphorea E Petricola pholadiformis biofgula sp. Tellina agills Onoba aculea Group 11 l- Pleusymtes glaber Corophium acutum Group 3 Corophlwn insidlJswn ofytilus edulis Fabricia sabs la Corophlwn bonelli E Afargarites umbilicalls idotea balthica Group 4 Group 12 Cerebrandus latteus De.xamine thea Phyllodoce maculata Caprella penantis Oligochaeta Jassafalcata Anemone lacuna vincta Erichsonellafillformis Collioplus laevisculus E Group 5 Group 13 Polygordius sp.1 Pholoe minuta I Group 6 Nicolea zostericola Amphlpholls squamaa Strongylocentrows droebachtensis Harmothoe Imbricata Group 7 Polydora socialis
. Polydora giardi Group 8 1hrbonilla elegantula E. Eulalla viridis I
29 I
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AJ _ O.94 l' , 1 2 3 4 5 6 7 e Spring > c Fall r ,! W Sample Groups g, Figure 9. Constancy Diagram for Spcxies Groups and Sample Groups in 1991. Clustering is with E Iltay-Curtis and Group Average Sorting. , 30 I
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Station Groups I l l Figure 11. Cortstancy Diagram for Species Groups and Station Groups iri 1911. Clustering is with Hray-Curtis arx1 Group Average Sorting.
,, i es E_..~~~_,.-.,.__-.___.___________,_________.________________ _ . . _ _ _ _ _ . _ _ _ _ _ _ . _ _ _ _ _ __
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Figure 12. Fidelity Diagram for Species Groups and Station Groups in 1991. Clustering h with Bray-Curtis and Group Average Sorting. 33
I answired with the help af these two measures: (1) why was the E10uent station 50 dissimilar te the refstence suGto in the spring (especially visible in the NESS dendrogram where k appeared as the most dissimilar stathn of b9th seasons)7 and (2) why do the fall samples from the Ef 0uent station split into two dissimilar clusErs? To answer the fits: question, those species groups have to be identi0ed that have constancy Rhd/or Odtlity values in sampla group 3 (spring Ef0uent samples) differing consideraNy from the vaines with all other sampo groups. new species groups are group 11 among the dominants (including ifyrilua rdulls) ana groups 6 and 8 tmaag the non-dominants. Both groups 6 and 1I eshibit a much lower constancy and fiJelity in sample group 3 than in any other sample group, whereas species group 8 hat much higher cc nstancy and fidelity values in ahis species group than in any other. h forrnsMon of the two tall Ef0uent clusters (sample groups 5 and 7) is chie0y caused by differences in constancy and fWlity of species groups 1 and 9 Caat eshibit a pstchy di!tribution. Abundances , of the species forming group 1 are generatiy higher in sarnple group 5 (3 Efiluent fall samples) than in sample group 7 (2 Ef0uent fall samples). Species group 9, which consists only of the amphipod Phmoaphalus holbolli, is less abundant in sample group 5 than in sample group 7. Figur3s 11 and 12 show constancy and fidelity diagrams that resulted from t. compar hon of the species g groups listed in Table 9 and 6 sample groups, each consisting of all replicates of oie station from one season. W This analysis was perfoimed to detect those species that caused the clear seasoral break in both the tiray-Cartis and NESS dendrograms (Pgures 6 P.ad 7). Fom species groups showed :imilar seasonal differencu, at all stations: groups 8 ar,d 13 had higher constancy and fidelity values in all spr.ng samples (sample groups M), whereas species groups 2 and 10 had higher constancy and fidelity values in the fall (sample groups 4-6). Species group 10 is the ordy group that includes dominant species, whereas all other groups responsible for the seasonal differences consist of non40minant species. In addition, there are statien specific seasonal differences in constancy and fidelity of other species groups that may have contributed to the overall seasonal differences. I I I I I 4 l B
~l
l B l 3.2 OUANIIM11YJiALGAL 140NUDRING I 3.2.1 Systematics No additions to the cumulhilve algal species list presented in Semi Annual Report No.16 (BECo, 1980) were made as a result of the analyses of the hiarch or October 1991 samples. 'The 27 species found in 1991 samples are indicated in Table 1. 3.2.2 Algal Community Description The habitats and associated algal and faunal communities found at the hianomet Point, Rocky Point, ance Eftberd subtidal stations are typical of shallow, exposed areas in western Cape Cod Bay and have been we9 Gc.cuvnted by Grocki (1981) and Davis and hicGrath (1984). The rocky subst ata characteristic of all three stations are coveicd w:Ja Anu macroalgal communities typically dominated by two species, Chondrus crispus and Phyllophora spp, in 1991, ria mt realgae moderately colatet.d the rock and cobble substrata found at all three stations. Two-thirds of the species collected in hiarch and threcquarters of the species collected in October belonged to the Rhodophyta (red algae). In addition to the dominant species Chondrus crispus and Phyllophora spp., other benthic rhodophytes included Corall!na oficinalls, present in all hiarch replicates, Polysiphonia urceolata and Rhodomela cortfenvides, prer.ent in all October replicates, as well as Ahrifelria plicata and Polyldes rotundus. Epiphytic thodophytes found in all h1 arch and October replicate I samples were Ceramlum rubrum, Cystoclonium purpurcum, and Spermothamnion repens. Other species collected in all March and October samples were the chlorophytes (green algae) Chaetomorpha linum, C. I melagonium and Rhl:oclonium riparfum; and the phacophyte (brown alga)Desmarestia aculeata. Three alga species seca in the March samples were absent in the fall collections, the chlorphyte Cladophora spp., and the phaeophytes Desmwestia viridis and Sphacelaria cirrosa. Blomass of Chondrus crispus was highest at Manomet Point in March and October. Iliomass of Phyllophora spp. was highest at Rocky Point in hiarch and at the Effluent station in October. The highest biomass of the remaining benthic species was at the Rocky Point station in both March and October. Manomet Point had the highest blomass of epiphytic algae in March but the lowest in October. Gracilaria tlkvahlac, an indicator of warm water, was not collected in any of the replicate samples in either March or October 1991. Ilowever, Gracilarla was observed by the divers within the discharge canal during all four seasons; Gracilaria, within the denuded zona, extended out to 40 m on the transect line in March, and was densest within the discharge canal in October. No Ianinarla, a cold water indicator, was !c an at the Effluent station at any season; Laminaria was observed at both reference stations in March and at Rocky Point in October, 1 5
- ' ' - " - ' - ' - -' ----m._ _ _ _ _ - - _ _ . , _ _ _ , _ _ _ _ _ _ _ . _ . _ _ _ _
I 3.2.3 Algal Community Overlap Community overlap was calculated for htarch and October 1991 using Jaccard's coefnelent (Grieg. Smith,1964) to provide a mathematical evaluation of the similarity in algal composition between pairs of replicates or staions. Jaccard's coefficient us s only species occurrence and is not induenced by differences in abundance. Species occurrence records of the 27 indicator species found m 1991 (Table 1) were und for these calculations. Comparisons between replicate samples for each station for htarch and October 1991 are presented in matrix form in Figures 13 and 14. Overall, the similarity of all three stations was high, ranging from 81.5% to 88.5% in h1 arch and from 83.3% to 90.5% in October, indicsting a high degree of homogeneity in algal species present at all three stations. In h1 arch, community overlap between the Efnuent station and both hianomet Point and Rocky Point was higher (88.5% and 84.6%, respectively) than between the two reference stations (81.5%), indicating that the algal comrnunities at the reference stations were more similar to the algal community at the Efnuent station than they were to each other. 110 wever, the situation had reversed by the fall when community overlap between the Ef0uent station and both hianomet Point and Rocky Point was lower (83.3%, in both cases) than between the two reference stations (90.5 %), indicating that the algal communities at the reference stations were more similar to each other than they were to the Ef0uent - station. Community overlap between hianomet Point and Rocky Point increased from htarch (81.5%) to g October (90.5%), showing that the algal communities at hianomet Point and Rocky Point were more similar W to each other in October;han in March. Concurrently, from htarch to October, overlap between the Efnuent Station and each of the reference stations decreased, evidence that by me fall the Effluent station was less timilar to the reference stations than it had been h1 arch. The range in percent overlap between replicates at the Effluent station was slightly higher in htarch (19.7%) than in October (16.8%), suggesting that the replicates were more similar in the fall than in the spong. A much larger seasonal difference was seen at the reference stations. At both the hianomet Point and Rocky Point stations the range in percent overlap between replicates was much greater in h1 arch (25.0% and 21.7%, respectively) than in October (15.8% at both s:ations), a trend also seen in 1990. This indicates that in Oc*ober the replicate samples from the reference stations were much more similar to each other than those taken in hiarch. I I 36 B W
mM M M M M M M M M M M M W W W W W M-N1 2 3 4 5 e 1 2 3 4 5 e E N E ' I 37 18 39 37 I 21 23 21 ?!
\ .E 2 73.9 N. 17 16 15
.I g
2 84.0 ?! 19 19 g l E 3 78.3 77.3 9 17 0 3 100.0 84 0 21 21 84.0 82.6 84.0 Iq h 4 82.6 66.7 86.4 17 h 4
= z 5 81.0 71.4 83.0 81.0 84.0 82.6 84.0 75.0 5
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Percent Overlap Percent Overlap U I 2 3 4 5 E 4 19 MP RP EFF I 19 16 21
@ 7
~x 2 82.6 17 21 19 j MP 22 23 b a n O {f 3 69.6 77.3 17 18 o RP 81.5 22 $k" 5
4 91.3 91.3 70.8 20 $ EFF 88.5 84.6 Z i D 5 82.6 82.6 85.7 83.3 B Percent Overtap Percent Overlap
)
i Figure 13. Algal Community Overlap Gaccard's Coefficient of Community) and Number of Species Shared Between Repl March 1991. A, Manomet Point Station; B, Rocky Point Station; C, Efiluent Station; D, Station Overlap.
I 2 3 4 5 1 2 3 4 5 15 15 15 15 1 17 17 16 17 1 b \ b 2 83.3 18 17 17 j 2 81.0 17 17 18 j 73.9 73.9 16 18 3 78.9 94.7 17 17 g 3 g I D 4 83.3 89.5 85.0 17 4 80.0 89.3 72.7 16 y a Z z 88.2 94.4 89.5 94.4 5 77.3 85.7 78.3 76.2 5 A - B Percent Overlap Percent Overfan M i 2 3 4 5 7 x 1 16 17 17 17 j MP RP ETF 2 84.2 17 17 17 *
.g MP 19 20 g us nB $,
3 94.4 89.5 18 18 g RP 90.5 20 {j t Ze 4 89.5 85.0 94.7 18 $ EFF 83.3 83.3 D 5 94.4 89.5 100.0 94.7 Percent Overlap
, C Percent Overlap Figure 14. Algal Community Overlap Gaccard's Coefficient of Community) and Number of Species Shr. red Between Replicate Pairs, Octolar 1991. A, Manomet Point Station; B, Rocky Point Station; C, Effluent Station; D, Station Overlap.
E E E E E E E M M E W W W W W M M M M
3.2.4 Algal liiomar.s Owndrus crLspus Chondrus crispus biomass was measured at the Ef0uent, hianomet Point, and Rocky Point stations in htarch and October 1991 (Tables 10 and 11, respectively). In hiarch, the range of individual biomass values was highest at Rony Point (2.75 to 277.33 g/m2), followed by the Ef0uent station (0.46 to 146.24 g/m2 ), and hianomet Point (82.44 to 217.75 g/m2). At the Effluent, hianomet Point, and Rocky Point stations, mean Chondrus biomass was 21%,46%, and "l5% of the total algal biomass, respectively. The hianomet Point station had the highest mean biomass value for Chondrus (161.75 g/m2), followed by Rocky Point (112,75 g/m2), and the Effluent station (52.22 g/m2). An ANOVA showed no significant differences among any of the stations when mean Chondrus biomass values were compared (at p=0.05). In October, the raage of individual biomass values was greatest at Manomet Point (140.18 to 375.46 g/m2), followed by the Eftluent station (2.48 to 216,83 g/m2), and Rocky Point (0.00 to 175.52 g/m2). hiean Chondrus biomass was 17%,41 %, and 18% of the total algal biomass, respectively, at the Ef0uent, hianornet Point, and Rocky Point stations. The Manomet Point station had the highest mean biomass value for Chondrus (238.50 g/m2 ), followed by the Ef0uent station (90.09 g/m2), and Rocky Point (81.17 g/m2). An I ANOVA showed a signincant difference among the three stations in Chondrus crispus blomass (F,=4.78; 1%=3.89); however, this difference was so marginal that Scheffd's muluple comparison test was unable I to show any difference between means. The Scheffe test indicated that for Chondrus biomass, the Effluent station was not different from the reference stations whether considered separately or together and that the two reference stations were not different frorn each other. Between March and October the mean biomass of Chondrus mereased at the Ef0uent station and
~
Manomet Point and decreased at Rocky Point. Phyth>phora spp. Phyllophora spp. biomass values for March and October are given in Tables 10 and 11, respectively. I in March, the range of individual biomass values was greatest at the Rocky Point station (13.31 to 210.96 g/m2), followed by the Ef0uent station (19.19 to 214.63 g/m2), and Manomet Point (57.74 to 159.55 g/m2). Phyliophora spp. were 51% of the total algal biomass at the Ef0uent station,30% at Manomet Point, and 41 % at Rocky Point. Rocky Point had the highest mean biomass value for Phyllophora spp. (131.07 g/m2), followed by the Effluent station (127.82 g/m2), and Manomet Point (105.77 g/m2). No significant differences existed between the stations in March 1991 when comparing Phyllophora spp. biomass (at p=0.05). I 39 I I - - - - . -
I TABLE 10. Dry Wdght Blomus (g/m') for Chondnu enspur, Phyllophorn spp., 'Ihe Remaining Benthic Spects, Epiphytes, and Total Algal Blomus at the Effluent, Manomet Folnt, and Racky Point Stations in March 1991. CAos4rus cenpr Phy#ophora spp. Remaining Benthk Epiphytk Spe . All Species frotal) Algae Statbn/ un Reptkate Bbre?' Percent Bbmass Percent Bbmass Pertent Biomass P m ent Bbmaas g 75.35 46.63 16.37 15.61 5.48 254.86 EFF1 7.9N 2.81 214.63 19.19 12.02 69.86 43.81 20.84 13.07 159.46 EFF 2 49.57 31.09 48.88 87.49 29.24 57.65 19."' 7.80 2.61 299.18 EFF 3 146.24 0.22 161.11 78.32 35.43 17.22 8.72 4.24 205.72 EFF 4 0.46 156.70 52.99 63.80 21.58 18.36 6.21 295.69 EFF 5 56.82 19.22 127.82 51.34 54.67 21.96 14.27 5.73 248.98 R EFF 52.22 20.97 , 35.55 43.70 9.74 61.60 13.72 448.82 MP1 183.97 40.99 159.55 28.69 12.76 3.55 25.52 7.11 359.03 l MP2 217.75 60.65 10.1 00 144.13 47Al 17,99 5.94 58.20 19.22 302.76 MP3 82.44 27.23 57.74 17.62 23.32 7.12 69.95 21.35 327.63 MP4 176.62 53.91 41.22 12.22 &3.54 24.78 337.18 W MP3 ' 147.98 43.89 64.44 19.11 105.77 29.79 27.80 7.83 59.76 16.83 355.08 R MP 161.75 45.55 4 05 22.40 6.82 15.33 4.67 328.37 RP 1 277.33 84.46 13.31 181.30 56.75 59.39 18.59 15.42 4.83 319A6 RP 2 63.34 19.83 16.02 46.08 16.22 18.91 6.66 284.12 RP 3 173.59 61.10 45.53 59.56 102.27 29.82 33.69 9.82 342.96 RP 4 2.75 0.80 204.26 B RP 5 46.73 13.90 210.96 62.74 60.13 17.88 18.45 5.49 336.26 g 131.07 40.68 50.05 18.02 20.36 6.32 322.23 X RP 112.75 34.99 EFF: Emuent; MP: Manomet Poir.t; RP: Rocky Point; R Mean bionuss I I E I \ 40 l l 5
=
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TAllLE 11. Di,v Weight Blornass (g/m') for Chondrus crispus, Phyllophora spp., ne Itesnalning Benthic Spedts, Epiphytes, and Total Algal Blomass at the Effluent, Manomet E Poir.t, and llocky Poirit Statioru in October 1991. I Statbn/ Chondrus crbrus PhyHophora spp. Remainlet llenthk Spairs Epiphytk Specks (Totall All Algae I __ Replkste Bbman Penent 4.77 Bbman 470.84 Pucent 62.03 Bbmau 4.87 Penent 0 64 Bbmau 247.13 Penent 32.56 Bbmau 759.01 EIT 1 36.17 64.83 9.64 2.32 117.32 28.06 415.21 EIT : 19.09 4 60 269.16 EIT 3 2.48 0.46 408.14 75.08 33.97 6.25 99.05 18 22 543.64
$3.16 122.00 29.91 14 2 3.58 54.44 13.35 407.87 EIT 4 216.83 EFT 5 175.89 32.65 250.16 46.44 42.41 7.87 70.23 13.04 538.68 I R EIT MP1 90.09 375.46 16.91 74 65 304.06 79.87 57.06 15.88 21.10 3.49 3.96 0.69 117.63 44.15 22.07 8.78 532.88 502.97 44.02 324.42 48.57 7.89 1.18 41.59 6 13 667.94 MPO 194 04 26,94 436.51 59.56 17.81 2.43 81.06 11.06 732.84 MP3 197.46 49.11 4 68 0.98 53.33 11.15 478.17 MP4 1 R$ .34 38.76 234.82 MP5 140.18 26.f' 323.87 61.39 7.34 1.39 56.18 10 65 527.57 48.10 8.24 1.42 55.2.5 9.49 ' 581.90 I
R MP 238.50 40.99 279.90 2.37 85.19 19.29 140.91 31.90 205.17 46.45 441.74 RP 1 10.47 0.00 0.00 159 64 31.90 163.40 32.65 177.45 35.44 500 49 RP 2 34.65 436.15 I RP 3 90.70 20.80 112.27 25.74 82.07 18.82 151.11 36.23 145.14 29.96 80.97 16.71 82.80 17.09 484.43 RP 4 175.52 29.27 76.56 17.35 88.77 20.12 146.79 33.26 441.24 RP 5 129.16 115.76 25.12 111.22 24.14 152.66 33.13 460.82 R RP B1.17 17.61 EFT: Effluent; MP: Manomet Point; RP: Rocky Point; R: Mean tsionan l I I ,y 4i I . _
l in Oaober, the greatest range of individual biomass vdues was at Manomet Point ((79.87 to 436.51 g/m2), followed by the Eftluent station (122.00 to 470.84 g/m2), and Rocky Point (76.56 to 15944 g/m2). Phyllophora spp. maJe up approximately one-half of ^e tota. algal biomass at the Eftluent and Manomet Point stations (57% and 48 %, respectively), but only or ,uar,er of the total biomass at Rocky Point (25.0%). He Effluent station had the highest mean biomass for Phyllornora spp. (304.06 g/m2), followed by Manomet ! Point (279.90 g/m2), and Rocky Point (115.76 g/m2). An ANOVA slowed a significant difference among the three stations in Phyllophora spp. biomass (F,= 4.15; 1% = 3.89). liowever, just as in the case with Chondrus, this difference was so slight that the Sch:ffe's multiple wmparison test was unable to show where this difference occurred; the Scheffe test showed that the reference stations were not different from each other and that the Eftluent station was not different from the reference stations. He typical scannal increase of Phyllophora spp. biomass from spring to fall (llECo,1987a) diJ occur at the Effluen* station and Manomet Point where the mean biomass more than doubled; however, at Rocky Point, mean biomass decreasal, so that Rocky Point which had had the greatest Phyllophora biomass in March had the least in October. Bioman of Rewpr%g denthic Species
%e categery called " remaining benthic species" excludes Chondrur crispus, Phylirrhora spp., and algal epiphytes, t,at does include Chaetomorpha linum C. melagonium, Rhicoclonium riparfum, Ahgeltla plicata, and Polyldes rotundus at all stations during both seasons, and Phycodrys rubens at all stations in the spring and the Effluent station in the fall.
Biomass data for the remaining benthic species for March and October 1991 are traented in Tables l 10 and 11. In both March and October, Rocky Point had the greatest range of biomass values (79.87 and 82.43 g/m2, respectively), followed by the Effluent statior. (34.43 and 37.54 g/m2, respectiveyj and Manomet Point (30.94 and 14.32 g/m2, respectively). In March, the percentage that the remainitty t.Ahic species contributed to the total algal biomass was greatest at the Effluent station (22 %), intermediate at ku(.y Point (18%), and least at Manomet Point (8%); in October, Rocky Point had the largest percentage of remaining l benthic species (24%), followed by the Eftluent station (4%), and Manomet Point (1%). The highest mean biomass values occurred at Rocky Point in both spring and fall (58.05 and i11.22 g/m2, respectively); the Eftluent station had intermediate biomass values during both seasons (54.67 and 21.10 g/m2, respectively) and Manomet Point had the smallest values (27.80 and 8.24 g/m2 , respectively). To avoid statistical redundancy and permit a meaningful ANOVA for the total algal biomass, an ANOVA for biomass of the remaining benthic species is not presented here. Purtherrnore, in October, an l c l I l
==
I examination of the variance (the F,,,,-test) calculated from biomass values for the remaining benthic species showed that the data were not homogeneous (s',,,ls2 =45.97; F,. my = 15.5; F,.,"*%37.00), even at P < 0.10 and, therefore, could not be used in an ANOVA as they do not satisfy one of the basic assumptions for an ANOVA. Epiphytic Algal Biomass Biomass values of epiphytic algae in Mar- and October 1991 are given in Tables 10 and 11. In March 1991, mean epiphytic biomass values were highest at Manomet Point (59.76 g/m2), followed by Rocky Point QO.36 g/m2), and the Efauent station (14.27 g/m2). In October, mean epiphytic biomass values were highest at Rocky Point (152.66 glm2), followed by the Efnuent station (117.63 g/m2), and Manomet Point (55.25 g/m2). Epiphytic algal biomass at the Effluent station was less than that at Rocky Point in March and October (30% and 23%, respectively), llowever, the relationship in epiphytic algal biomass between the Effluent station and Manomet Point changed dramatically from spring to fall, revuung from 76% less at the Effluent station in March to 133% more in October. The percent contribution of the epiphytic species to the total algal biomass at Manomet Point was greatest in March (16.83%) but least in October (9%). At the I Effluent station and Rocky Point, the epiphytic species contribute a small and similar percentage to the total algal biomass in March (5.73% and 6.32% , respectively) but were a large contributor in October (22% and I 33%, respectively). There was a significant difference among the three stations in epiphytic algal biomass in March (F,= 16.52; F.mm=3.89) and October (F,=4.48; Femu3.89). Schefffs multiple coraparison test attributed the ANOVA results in both seasons to a significant difference in epiphytic algal biomass at Manomet Point and Rocky Poht. In addition, in March, the epiphytic algal biomass at the Efiluent station was significantly different from the mean biomass at the reference stations and from the biotaass at Manomet Point though not significantly different frr.a the Rocky Point station biomass. Total Algal Biomass Values for total algal biomass for March and October 1991 are given in Tables '.0 and 11. The Effluent station had the lowest mean biomass value (248.98 g/m2) in March and an intermediate value (532.88 g/m2) in October. Manomet Point had the highest mean biomass value in both March and October (355.08 and 581.90 g/m2, respectively). In March, tctal algal biomass at the Effluent station was 30% less than at Manomet Point and 23% less than at Rocky Point; in October, total algal biomass at the Effluent station was 8% less than at Manomet Point and 16% greater than at Rocky Point. Total algal biomass increased from 43 I I _
1 l I! spring to fall at all three stations, by 43 % at Rocky Point, M% at hianomet Point, P.ad 114% at the Effluent ' station. In hiarch, an ANOVA showed a signi0 cant difference among the three stations in total algal biomass (F,=5.78; F.mq= 3.89) Scheffd's multiple comparison test showed that total algal biomass at the Effluent station was significantly different from the mean biomass at the reference stations and from the biomass at Manomet Point but was not signi0cantly different from the Rocky Point station biomass, nor werc the two reference stations different frc:n each other. In October, an ANOVA showed no significant differences among the three stations in total algal biomass. 13 OUALITATIVE TRANSECT SURVEY Qualitative transect examinations of the acute impact zone were initiated in January 1980 and quarterly surveys were begun in 1982. Four surveys were prformed during 1991 (March 28, June 27, October 4, and , D cember 26), bringing the total number of surveys conducted since 1980 to 44. Results of surveys l l conducted from 1980 through 1983 were summarized in Semi-Annual Report No. 22 (BECo,1983). A summary of the surveys conducted between 1983 and 1988 is presented in Semi-Annual Report No. 35 (BECo,1990a), along with a review of the four sutwys performed in 1989. ResuMs of the four 1990 surveys are in Semi-Annual Report No. 37 (BECo,1991a). Detailed results of the March and June 1991 surveys are in Semi-Annual Report No. 38 (BECo,1991b). Thb repo" summarize' the March and June 1991 surveys and incorporates new data from the October and December 1991 surveys.
"gures 15,16,17, and 18 show the results of transect surveys performed by SCUBA divers. The denuded zone is essentially devoid of Gondrus crispus, the stunted zone contains Oondras that is smaller s
and less desse than that growing under normal conditions, and the sparse zones are those in which normal l Jooking Gondrus is sparsely distributed. The distinction between stunted and sparse zones was initiated this year by the divers. A large boulder that is nearly exposed at mean low water, and that is used as a landmark by both the Science Applications International Corporation (S AIC) and the Massachusetts Division of Marine Fisheries dive teams, is plotted in each figure. This boulder serves as a visual fix for the proper placement of the transect line and ensures consistency among the surveys. 3.3.1 March 1991 Transect Survey I The extent of the denuded and stunted areas mapped on March 28,1991 immediately offshore from l PNPS is shown in Figure 15. The Gondrus denuded zone extended approximately 94 m offshore along the central transect line and was asymmetrically distributed, extending 8 to 13 m northwest and 3 te 4 m southeast 44 E a
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=
I of the baseline. The denuded zone covered an area of 1320.5 m2, and was 5% larger than in December 1990. Dense assemblages of Cystoclonium purpureum and a species tentatively identified as Gracilaria tikvahlae were growing near the 40-m mark on the transect line. To the northwest, Membranoptera alata, an alga not seen during the two previous surveys, was living near patches of Ulva lactuca. Dense patches of mussels (Mytilus edulls) had settled on several rocks between the 70 to 80-m marks and within 8 m of the baseline. The stuntd zone (225 m2) was 25% larger than in December 1990. I 3.3.2 June 1991 Transect Survey Results of the divers' survey taken on June 27, 1991 are shown in Figure 16. The denuded zone extended 85 m along the transect line,9 m less than in March, and was slightly asymmetrically distributed around the transect line with more area northwest of the line than southeast of the line. The area of the denuded zone (1265 m2) had decreased slightly from that seen in March 1991 Within the discharge canal there was dense coverage of the red, fibrous alga, Cvstoclonium purpureum and patchu of Ulva lactuca and Codiumfragile. Ulva was present within the denuded zone from the jetties to the 70-m mark, north of the transect line. No true region of stunted Chondrus growth was observed. Two areas north of the denuded I zone contained sparsely distributed but normal looking Gondrus; the southern boundary was clearly delineated by moderate coverage of normally growing Gondrus and increased algal diversity. I 3.3.3 October 1991 Survey Figure 17 shows the results of the transect survey conducted on October 4,1991. The denuded zone extended to the 86-m mark on the transect line. He asymmetry of the denuded zone around the transect line I with more area denuded of Gondrus north of the line (52%) than to the south (48%) vrac less pronounced than in the March or June surveys. The greatest lateral enent of the denuded zone was 7 m from the transect line at the 65-m mark. He area (1080 m2) of the denuded zone was IM less than that found in June. Within the discharge cr.nal, there was thick coverage by a purple-colored, fibrous alga, probably Cystoclonium purpureum, and a green, filamentous alga, Gracllaria. Beyond tne discharge canal, algal species density and diversity was lower north of the transect line than south. Within 10 m north of the transect line most rock surfaces were b:tre with a scattering of individual (stunted) Chondrus plants. Corallina appeared as small patches within parts of this region but very few additional species of algae were observed. Further to the north, more than 10 m from the transect line, the flora consisted of Fucus spp. and denser arrays cf Gondrus. The Gondrus denuded zone was more clearly delineated on the southern side of the transer t line than on the north and ran roughly parallel (5 m offset) to the line; bare rock characterized much 49 I I
I of the 5-m stea, beyond which Gondrus and several other algal species densely covered all rock surfaces. Mussel shell patches were present within 5 to 8 m of the transect line at the 55-m,75-m, and 95-m marks along the line; these areas corresponded to juvenile mussel beds noted in the March 1991 survey. No Lanunaria was observed in the area. The stunted zone (283 m2), absent in June, reappeared. The stunted zone was very asymmetrically distributed with 95% (269 rn2) of the area north of the transect line. The northern region was characterized by two bulges to the northweet at the 45-m and 65-m marks and reached 14 m and 15 m away from the transect line, respectively. To the south, the stunted zone appeared only as a narrow band, I m wide at the most, from the 45-m to 65-m marks. 3.3.4 December 1991 Transect Survey The results of the divers' survey performed on December 26,1991 are mapped in Figure 18. De denuded zone extended out to the 87 m mark on the transect line. The asymmetry of the denuded zone around the transect line was more pronounced than in either June or October with the boundary extending out to 10 and 11 m north of the transect line but only 5 m to the south. The area (1200 m2) of the denuded zone was 11% greater than in the Wtober survey and only slightly less (5%) than it had been in June. The density of Gracilaria and Cystoclonium purpureum within the discharge canal was much lower than in October; 65% of the rock surfaces were bare. Iseyond the. canal, Corallina was the predominant algal species within the Gondrus denuded zone. As in earlier surveys the Gondrus denuded zone was more clearly delineated on the southern side of the transect line than on the north with most rock surfaces within 5 to 6 m of the transect line bare. Beyond this 6-m region, healthy Gondrus plants and other algal species em occurred but coverage was less plush and diversity lower than in October. The mussel shell debris seen in l October had disappeared. No Laminaria was present within the survey area. De stunted zone was confined to the northwestern side of the denuded zone where it extended out to 19 m from the transect line at the 65-m mark. The area (183 m2) of the stunted zone was 32% smaller than the northern portion had been in October. The Gondrus plants within the stunted zone were not only stunted in appearance but were sparsely distributed. South of the denuded zone a narrow band, at the most 2 m in width, of healthy but sparsely distributed Gondrus, occurred from the 33- to 73-m mark on the transect line. I I I 50 a!
"i
l l
4.0 CONCLUSION
S 4.1 FAUNAL STUDIES l e Species richness was lowest at Manomet Point and highest at Rocky Point in March 1991, whereas it was highest at the Ef0uent station and lowest at Manome' Point in. October 1991. I Species richness increased markedly at the Effluent station and to a lest:r extent at h*anomet Point between spring and fall. it decreased si'phtly at Rocky Point. i 4 I e Faunal densitigs were highest at the Effluent station, intermediate at Manomet Point, and I lowest at Rocky Point in both the spring and the fall. Dertsities dropped drastically in October due to a sharp decline in the mussel populations. o Dominant species were much more similar among stations in March than they were in October. The decline in mussel density allowed for occupation of the free space by groups of species : hat were different for each station. The commanity structure changed between j March and October in thv. true dominants were no longer present in October. At the Ef0uent station, the diversity of the dominant fauna observed in the spring among the lower ranking i species had disappeared in the fall when almost all abundant specics were amphipods. I o Snecies diversity was lowest at the Effluent station and highest et Rocky Point in the s;; ring, whereas it was highest at the Effluent station and lowest at Rocky Point in the fall. Ahhough I the Shannon-Wiener indices were relatively high in the fall, they were within range of H' measured in previous years, as well as the spring of 1991, when mussels were excluded. l I i o Similarity among stations showed clear seasonal differences Additiona.tly, the Efauent station showed some unu;ual similarity patterns throughout We year. In Mech, the Efiluent station was very dissimilar from the teference stations, but all replicater of that station were very
-g similar. In October, the repl'ntes of the Efiluent station split up into two group 2 that each 3 showed high similarity with one of the reference studons. Analysis of the combined spring i
and fall data reveded that the Effluent station was dissimilar from di other 1991 stations regardless of the season. (2 ALGAL STUDIES
-I o Algal communi ties consisted re.ostly of red algae, including the dominant species Chondrus
< erispus and Phyllophora spp. Several species of green wt brown a.lgae were also collected.
- Community overlap between stations was higher between the Effluent station and both t reference stations than between the two reference stations in the spring. Ilowever, in
[. October, commur,ity overlap between the Efficent station and both Manomet Point and Rocky Point was lower than between the two reference staticas, indicating that in the fall the Effluen s'ation differed more from the reference stations than in the spring.
.I
'I t
I
- higpn biomass of Ozondrus increased at all stations between March and October in March, Chondrus biomass was highest at Manomet Point and lowest at the Ef0uent station. In October, Manomet Point still ranked highest, whereas Chondrus biomass was lowest e Rocky '
Point. Phyllophora biomass, in March, was highest at Rocky Point and lowest at Manomet Point, whereas in October, the Efauent station had the greatest Phyllophora spp. biomass and Rocky Point the least. B: tween March and October, Phyllophora biomass increased at the Ef0uent station and Manomet Point but declined at Rocky Point. Biomass of the remaining benthic species was highest at Rocky Point and lowest at Manomet Point during both seasons. Epiphytic algal biomass, in March, was highest at Manomet Point and lowest at the Efnuent station, whereas in October, it was highest at Rocky Point and lowest at Manomet Point. ' Total algal biomass increased from March to October at all three stations, by 43% at Rocky Point,64% at Manomet Point, and 114% at the Ef0uent station. 4.3 OUALITATIVE TR4NSECT SURVEYS I
- The area of the Chondrus denuded and stunted zones increased slightly from Decembe 1990 to March 1991, a period when the plant was in full operation. Between March and June the l
area of the denuded zone and total affected area decreased, reflecting the shutdown of the g l plant from May through July. The area of the denuded zone and total affected area centinued g l to decrease through October but increased by the time of the December transect. The area of the denuded zone varied only moderately over the year; it was greatest in March (1320.5 m2) and least in October (1080 m2). 5.0 LITERATURE CITED Boesch, D.F.1977. Application of numerical classi6 cation in ecological ir.vestigations of water pollution. U.S. Environmental Protection Agency, EPA Report 600/3-77-033. I14 pp. Boston Edison Co.1980. Marine Ecology Studies related to the operation of Pilgrim Station. Semi-Annual y' Report No.16. Boston, MA. = Boston Edison Co.1983. Marine Ecology Studies related to the operation of Pilgrim Station. Semi-Annual g Report No. 22. Boston, MA. E Boston Edison Co. 1986. Marine Ecology Studies related to the operatien of Pilgrim Statien. Semi-Annual g Report No. 27. Boston, MA. 3 Boston Edison Co.1987a. Marine Ecology Studies related to the ope,ation of Pilgrim Station. Semi-Annual g) Report No. 30. Boston, MA. 3 l Boston Edison Co.1988. Marine Ecology Studies related to the operation of Pilgrim Station. Semi-Annual Report No. 32. Boston, MA. ) Boston Edison Co.199%. Marine Ecology Studies related to the operation of Pilgrim Station. Semi-Annual l Report No. 35. Boston, MA. I 52 i a
=
I Boston Edison Co.1990b. Marine Ecology Studies related to the operation of Pilgrim Station. Semi-Annual Report No. 36. Boston, MA. Boston Edison Co.1991a. Marine Ecology Studies related to the operation cf Pilgrim Station. Semi-Annual Report No. 37. Boston, MA. Boston Edison Co.1991b. Marine Ecology Studies related to the operation of Pilgrim Station. Semi Annual Report No. 38. Boston, MA. Davis, J.D. and R. A. McGrath 1984. Some aspects of nearshore benthic macrofauna in western Care Cod Bay. In D:vis, J.D. and D. Merriman (eds.), Observations on the Ecology and Biology of Western Cape Cod Bay, Massachusetts. Lecture Notes on Coastal and Estuarine Studies. Springer Verlag, NY, 228 pp. Grasste, J.F., and W. Smith.1976. A ,imilarity measure sensitive to the contribution of rare species and its use in investigation of variation in marine benthic communities. Oecologia 25: 13-22. Grieg-Smith, P.1964. Quanticative Plant Ecology. Second Edition, Butterworths, Washington 256 pp. Grocki, W. 1984. Algal investigations in the vicinity of Plymouth, Massachusetts. In: Davis and Daniel Merriman (eds.): Observations on the ecology and biology of western Cape Cod Bay, Massachusetts. Lecture Notes on Coastal and Estuarine Studies. 228 pp, Springer Verlag, NY. ,I Heltshe, J.F., and N.E. Forrester. 1983. Estimating :p..ies richness using the jackknife procedure.
- Biometrics 39: 1-11.
Hurlbert, S.H. 1971. The nonconcept of snecies diversity: a critique and alternative parameters. Ecology 52: 577-586. I Newell, R.D.1979. Biology of Intertidal Animals. Marine Ecological Surveys Ltd.,Faversham, Kent. 781 PP-B Parke, M., and P. Dixon.1976. Checklist of the British marine algae 3rd revision. Journal of the Marine Biological Association of the United Kingdom 56: 817-843. Smith, W., and J.F. Grassle. 1977. Sampling properties of a family of diversity measures. Biometrics 33: 283-292. Sokal, R.R., and F.J. Rohlf. 1969. Biometry. Freeman Press, San Francisco 776 pp. I South, G.R. 1976. A checklist of marine algae of eastern Canada. Ist Revision. Journal of the Marine Biological Association of the United Kingdom 56: 817-843. 3 Taylor, W.R.1957. Marine Algae of the Northeastern Coast of North America. 2nd Edition. University f5 of Michigan Press, Ann Arbor, MI. 590 pp. Taxon. 1982. Benthic studies in the vicinity of Pilgrim Station. In: Marine Ecology Studies Related to I Operation of Pilgrim Station. Semi-Annual Report No.19. 53 I
i I
- APPENDIX A. LIST OF SPECIES IDENTIFIED AT TIIB FFFLUENT, MANOMLT POINT, AND
- ROCKY POINT STATIONS IN 1990/1991 (*: PRESENT IN SPRING 1991)
Smaller PhJ14 Dorvilleidae
*Alelodorvillea sp.1 CNIDARIA
*Hallclystus auricola Nephtyidae Metridium senile *Nephrys caeca
- Anemone Nephrys longosetosa I PLATYHELMINTilES
- Accel Nephrys picta Nereididae I NEMERTEA
' Turbellaria Neanthes succinea
*Nerels pelagica Nercis zonata I *Cerebratulus facteus
*Nemertea
*Tetrastemma vittatum Orbiniidae
*Naineris quadricuspida l *SIPUNCULOIDEA Paraonidae
*Aricidea catherinae
-3 bandida g Pectinarildse
- OLIGOCHAETA Pectinaria granulata POLYCHAETA Pholoidae Anipharetidae *Pholoe minu'o Asabellides oculata Phyllodocidae Arenicolidae Eteone longa
. Arenicola marina *Eulalia viridis Eumida sanguinea Capitellidae *Phyllodoce (Analtides) macidata
. *Capitella capitata Mediomastus californiensis Polygordiidae
*Polygordius sp.1 Cirratulidae Caulleriella bloculata Polynoidae Gaeto:one setosa *Harmothoe extenuata Gaeto:one sp.1 *Harmothoe imbricata Cirratulus cirratus *Izpidonotus squamatus
. .l *Dodecaceria corallil
*Iharyx acutus Sabellatildae g
;E
*Sabellaria vulgaris Cossuridae
*Cossuro longocirrata I
I A1 I
Sabellidae AMPHIPODA
*Fabricia sabella Ampitholdae Potamilla neglecta *Ampithoe rubricata .
?Pseudopotamilla rentformis Aoridae Sigalionidae Unciola irrorata
*Sthenelab boa Calliopidae Spion1dae *Calliopius laeviusculus Polydora cornuta
*Polydora giardi Corophildae
*Polydora socialis *Corophium acutum K Polydora websteri *Corophiwn bancill l Prionospio steenstrupi *Corophium insidiosum E~
Spiofillcornis *Corophiwn tuberculatum
*Spio thulini g Dexaminidae 5 Syllidae *Dexamine thea
*Autolytus alexandri g
*Autolytus cornutus Gammatidae l Autolytusfasciatus *Gamarellus angulosus
*Autolytus prismaticus Gammarus oceanicus a Exogone hebes Marinagammarus stoerensis l
*Syllides longocirrata Syllis (1)posyllis) cf. hyalina 1schytoceridae
*lschyrocerus anguipes Terebellidae *Jassafalcata Nicolea venustula
*Nicolea ostericola Phoxocephalidae Polycirrus eximius *Phoxocephalus holbolli
*Polycirrus phosphorius Pleustidae E -
Cnnstag.ca *Pleusymtes glaber U ISOPODA Pontogenelidae Yoteidae *Pontogenela inermis
*1dotea phosphorea
*Idotea bathica Stenotholdae l
*Metopella angusta n Janiridae *Probolcides holmesi
*Jarra marina g CAPRELLIDEA 3 Limnoridae Caprellidae IJmnoria lignorum *Caprella linearis g
*Caprella penantis l
*Caprella nr. septentrionalis Caprella unica A2 I
E-
I CUMACEA Lacunidae
*Diastylispolita
- Lacuna vincta g *Diastylls sculpta J DECAPODA Lamellidorididae
*Lamellidoris aspera l
- Cancer borealis l Cancer Irroratus Littorinidae
*Carcinus maenas
- Littorina littorea
*Crangon septemspinosa Littorina satatills
*Eualus puslolus
*Pagurus acadianus Nassariidas
*Pagurus longicarpus *Nassarius trivittatus Mollusca Naticidae
*Lunatia heros GASTROPODA Acmaeidae Omalogyridae
*Acmaea testudinalis *Omalogyra atomus
.g 5 Aeolidiidae Pyramideltidae Aeolidia papillosa *Odostomia dealbata
.g Doto coronata *Odostomia gibbosa E *Turbonilla elegantula Calyptraeidae
> *Crepidulafornicata Rissoidae
*Crepidula plana *Almnia pseudoarcolata
*0noba aculea Cerithiidae Bittium alternatum Trochidae Margarites helicinus Columbellidae *Margarites umbilicalls
*Anachis transiirata
*Mitrella lunata BlVALVIA Coryphellidae Anomiidae Coryphella rufbranchiata
- Anomia simplex Coryphella salmonacea Anomia squamula Cratenidae Cardiidae
*Cratena pilata *Cerastoderma pinnulatum Diaphanidae .
Hiatellidae
*Diaphana minuta *Siatella arctica
*Hiatella striata
!l' W- Facelinidae
*Facelina bcstoniensis Lyonsiidae Lyonsta hyalina I A-3
I Mactridae Tuniratta Spisula solidissinsa POLYCLINIDAE My\dae Amaroucium constellatum
*htya arenarla MOLGULIDAE Mytilidae 'Afolgula sp.
Afodiolus modiolus
*hiytilus cdulis Petricolidae
*Petricola photadiformis Tellinidae
*hiacoma balthica ]
hiacoma tenta l
*Tellina agills g Thraciidae g
*7hracia septentrionalis g Veneridae g Gemma genuna l
*hiercenaria mercenaria POLYPLACOPHORA Lepidochiton ruber
*Ischnochiton ruber I
Echinodermata ASTEROIDEA
*Asteriasforbest Henricia sanguinolenta ECHINOIDEA E
*Strongylocentrotus droebachlensis E OPHIUROIDEA g
*Amphipholis squamata E
*0phlopholis aculeata I
I A-4 i a.
I FINAL SEMI ANNUAL REPORT Number 39 (Volume 2 of 2) q on
-. h BENTIIIC ALGAL AND FAUNAL MONITORING AT TIIE I- PILGRIM NUCLEAR POWER STATION (IMPACT ON BENTillC COMMUNITIES)
January-December 1991 LI to BOSTON EDISON COMPANY Regulatory Affairs Department Licensing Division 25 braintree 11111 Office Park Braintree, Massachusetts 02184 I g From SCIENCE APPLICATIONS INTERNATIONAL CORPORATION I 89 Water Street Woods IIole, MA 02543 (508) 540-7882 I 1 April 1992
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- I; 7
I I I I I B I l I I i-I I I I I I
s B TABLE OF CONTENTS EXECI' 'E
SUMMARY
........................................... 1 I NTRODU CTI ON . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1 M ETI l O DS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 H A C K G ROUND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 QUANTITATIVE FAUNAL COMMUNITY STUDIES . . . . . . . . . . . . . . . . . . . . . . . . . 6 Species Richness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 j Fa unal Densi ty . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 l
..- Species Diversity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 I I Similarity Among Stations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Discussion-Faunal Studies ..................................... 14 16
)
[ QUANTITATIVE ALG AL COMMUNITY STUDIES . . . . . . . . . . . . . . . . . . . . . . . . . 17 !
- y Algal Community Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 _
Algal Community Overlap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 l Alga l Blom ass . . . . . . . - . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 l Discussion-Algal Studies ...................................... 20 ; QUALITATIVE TRANSECT SURVEYS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 i C ONC LUS IO NS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
- Quantitative Faunal Stu dies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 I Quantitative Algal Community Monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . .
Qualitative Transect Surveys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 28 LITERATURE CITED . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 LIST OF TABIES
~ Table 1. Algal Community Overlap in Percent Between Station Pairs for the Period 1983-1991
........................................................ 19 LIST OF FIGURES Figure 1. Location cI Benthic Sampling Sites near Pilgrim Station .................. 5 Figure 2. Monthly PNPS Capacity Factor and Circulating Pump Activity Piotted for the Period 1983 Through 1991 ............................................ 7 E
l I
._ , .- - - , . - - - - - - - - - - - - - - - , - - - - - - - - - - - . - - - . , - -- - . - - - - - - , , - - - - - - - - - . - - - - - - , - - -- ----.---r--- ------m.-- - - , .--r:------ - - - - - ----- ----------- ------------ - - ----- - - - -- - - -
I-I I I' I_ i I g . I I I - 5 I I I I I
?
Figure 3. Species Ridmiss for the Period April 1983 Through Septesnber 1991 Plotled vith Monthly PNPS Capacity Factor (M DC) . . . . . . . . . . . . . . . . '. . . . . . . . . . . . . . . . . . . . . 8 Hgure 4. Total Faunal Densities (Individuals per m8) for the Period April 1983 Thrt, ugh October i 1991 Plotted with the Monthly PNPS Criparity Fector (MDC? . . . . . . . . . . . . . . . 10 l Hgure 5. Total Faunal Densities, excluding 3ff tilus edulis Ondividuals per m2), for the Period April i 1983 Through October 1991 Plotted with the Monthly PNPS Capacity Factor (MDC) 11 , Figure 6. Shannon Wiener Dive.rsity (11') Iridex for Data Excluding Afytilus edulis for the Perion April 1983 Through October 1991 Plotted with the Monthly PNPS Capacity Factor (MDC) ................................................... 13 Figure 7. Dendrogram Showing Results of Cluster Analysis of Data Using NESS Sinnkarity and Group Average Sorting, Spring and Fall 1991 Data Combined . . . . . . . . . . . . . . . 15 Figure 8. Seasonal Fluctuations in Total Mean Algal Blo.nass at the Manomet Point, Rocky Point, and Effluent Stations During Spring and Fall Sampling Periods for the Collections Between April 1983 and October 1991 Plotted wl;h the Monthly PNPS Capacity Factor (MDC) 21 Hgure 9. Seasonal Fluctuations in Total Mean Phyllophorn Biomass at the Manomet Point, Rocky i Point, and Effluent Stations During Spring and Fall Sampling Periods for the Collections Between April 19&3 and October 1991 Plotted with the Monthly PNPS Capacity Factor (MDC) ................................................... 22 Eg.tre 10. Seasonal Fluctuations in Total Mean Chondrus Blomass at the Manomet Point, Rocky Point, and Effluent Stations During Spring and Fall Sampling Periods for the Collections Between April 1983 and October 1991 Plotted with the Monthly PNPS Capacity Factor (M D C) . . . . . . . . . . . . . . . . . . . . . . . . . . ............ ............ 23 Figure 11. Area of the Denuded and Stunted Zones in the Vicinity of the PNPS Effluent Canal Picited with the Monthly PNPS Capacity Factor (MDC). No area measurements were made in September and December 1987, all of 1988, and March and June 1989 because of lack of definitive demarcations of denuded and stunted zones . . . . . . . . . . . . . . . . . . . 24 Figure 12. Results of the 1991 Qualitatise Transect Surveys of the PNPS Acute Impact Zone off the discharge Canal. A, March; B, June; C, October; D, December ............. 26 I I I if l I -
I EXECUTIVE
SUMMARY
This volume of the semiannual report summarizes the potential impacts caused by the PNPS on t the benthic communities in the vicinity of the Pilgara Nuclear Power Station. Field and laboratory studies are detailed in volume 1 of this report. De cooling water that circulates through the plant is v. armed and discharged through a canal into ; the nearshore waters of Cape Cod Bay, his discharged wret includes three sources of potential impact on the benthic communities: 1) warming of ambient waters,2) chemical discharges (mainly Cl), and 3) increased current vr.locities resulting in scouring of the bottom. Species composition and community I structure may be t. hanged to varying degrees depending upon climate and local oceanographic conditions. Scouting has a diract physical impact that actually removes benthic organisms and prevents recolonization. In its extreme, the bottom scouting results in rock surfaces that are completely denuded and devoid of macroscopic marine life. The following observations were recorded as part the 1991 l Benthic Monitoring Program and compared with data from recent years. Total number of species observed at the Effluen, station were not related to plant operation, but may be related to habitat modification caused by changes in mussel populations. Total faunal density fluctuations are strongly influenced by mussel populations. Unusually high mussel populations were observed in the vicinity of the discharge canal and at the Effluent station in June 1990, but declined sharply in 1991. Mussels msy have migrated to the site in response to higher temperatures from the thermal discharge or by the currents. Species diversities declined at all stations in 1990 and remained low in the spring 1991 samples. However, species diversity increased markedly in the October 1991 sarr.ples. PNPS did not appear to have any negative impact on species diversity in 1991 because the - station with the highest diversity in October was the Effluent station. Typically, the Effluent station exhibits a different clustering pattern in the -imilarity analysis 1 during periods of plant operation. This pattern disappeared after the long 2-% yect shutdown and returned by the September 1990. This trend has continued in the 1991 samples. De Effluent station differs structural!y from the two reference stations. In 1990, two species, one anemone (Metridium senile) and an amphipod (Corophlum tuberculatum) were dominant at the Effluent station in the fall, but rare or absent elsewhere. In the spring 1991 a gastropod (7hrbonilla elegantula) and a predatory polychaete (Eulalia viridis) were iraportant at the Effluent station, but rare elsewhere. In the fall 1991 samples, two different groups of Effluent samples were defmed in the cluster analysis. This difference appears to have been caused by the distributi ons of an amphipod (Phoxocephalus holbolil) and another group of five invertebrates represented by species group 1 (Table 9 i., volume 1). l I
I A composite assessment of all benthic community parameters including species richness, diversity, and density taken together with community composition indicates that subtle alterations in the Effluent station are probably the result of PNPS operation. In the October 1991 samples, the species richness and diversity values were actually highest at the Ef0uent station indicating an enhancement of benthic community parameters. 'Ihe reasons for this enhancement are not clear, but depart from a more typical _ pattern where these parameters are generally reduced at the Efnuent station. In March 1991, the number of algal species shared (overlap) between the reference staons was lower than between the Effluent and reference stations, thus the community at the Effluer.t station was , more similar to those at Manomet Point and Rocky Point stations than the two reference stations were to each other, only the fourth time this pattern has been seen since 1983. By October 1991, the (overlap) between the reference stations was higher than between the Eiduent and reference stations, a return to the more typical situation. Thus, in 1991, the algal community at the Effluent station was more similar to those at the reference stations in March than in October. Algal biomass did not follow the typical seasonal decline during the winter months. From September 1990 to March 1991 total algal biomass increased at the Effluent station and at Manomet Point and decreased only slightly at Rocky Point. Total algal biomass increased at all three stations during the summer of 1991, reaching levels not seen since the power plant resumed operation in March 1989. The warm-water alga, Gracilaria tibuhlac, was observed at the Effluent station during all four surveys; g Laminaria, a cold-water species, was seen only at the reference stations. g The size of the denuded zone of the acute impact area was similar to that observed during 5 previous times of full power plant operation. Area of the denuded zone is mainly in0uenctd by circulating water pump operation and the slight decrease in affected area seen from the March to Octobec surveys may be explained by the three-month outage in May, June, and July 1991. Typically, the denuded zone decreases in area during the spring, a time of abundant algal growth; this pattern was ob. served in 1991. The algal community at the Effluent station was different from those at the Manomet Point and Rocky Point stations in 1990. The warm-water alga, Gracilarla rikvahiae, was observed at the Effluent station during the April, June and December surveys of 1991 (the absence of Gracilaria in September might be correlated with the low operating capacity of PNPS the preceding month). I I !- S I
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'. I . INTRODUCTION The Benthic Monitoring Program at the Pilgrim Nuclear Power Station (PNPS) began in 1972, and has continued to the present time with occasional modifications. The study was continued in 1991 under BECo Purchase order 68003, as required by NPDES Perm!t No, MA0003557 issued by the U.S. EPA and Massachusetts DWPC. He objectives of the prol, ram are to identify and assess any impact of the operation of PNPS on the nearshore marine epibentLic community. Benthic communities are excellent indicators of environmental perturbations because most of the organisms are sessile and are unable to migrate away from sources of disturbance. It is possible, therefore, to correlate changes in the benthic community, such as density or diversity, with changes in environme. ital conditions. PNPS is a base-load, nuclear-powered electrical generating unit designed o produce 670 megawatts of electrical energy under full operational conditions. The i.tation is cooled by water that is withdnwn from Cape Cod Bay. The cooling water is then returned to the Bay via a discharge canal that is designed to dissipate the heat from the water through rapid mixing and dilution. Two circulating pumps produce a combined water flow of approximately 20 m' per see at full operational capacity. The cooling system at PNPS includes three sources of potential impact on the benthic community: 1) warming of ambient waters,2) chemical discharges (mainly Cid, and,3) increased current velocities resulting in scouring of the bottom. Increasing temperature may stress the community so that species composition and community structure change; the extent of such change depends upon season of the year and the influence of local oceanographic conditions. Increasing current directly affects the benthos by actually I removing benthic organisms and preventing recolonization; intense bottom scouring may cause the rock surfaces to become bare and devoid of macroscopic inarine life. Operational conditions at the PNPS have provided an opportunity to assess long-term trends associated with the impact on the benthic community. Plant operations have included years of nearly full operatior. as well as times when there were complete shutdowns, sometimes for prolonged periods. The longest outage in the history of the plant began in April 1986 and continued until march 1989. During this period the benthic community associated with the effluent canal and nearby areas immediately offshore were subjected to reduced current velocity as the use of circulating pumps was restricted to one or none. In addition, the discharge water remained at ambient temperature. As a consequence, the benthic community normally affected by these effluent parameters recovered, so that by 1988 there was essentially no difference bety.een the control stations and the areas near the discharge canal. Studies conducted since the power plant has returned to operation were designed to assess the impact of plant operation on a benthic environment that had returned to near ambient conditions. j I
i INTRODUCTION The Benthic Monitoring Program at the Pilgrim Nuclear Power Station (PNPS) began in 1972, and has continued to the present time with occasional modifications. The study was continued in 1991
< under BECo Purchase order 68003, as required by NPDES Permit No. M A0003557 issued by the U.S. >
{ EPA and Massachusetts DWPC. The objectives of the progra;n are to identify and assess any impact of the operationof PNPS on the nearshore marine epibentiiic community. Benthic communities are excellent indicators of environmental perturbations because most of the organi2ms are sessile and are unable to migrate away from sources of disturbance. It is possible, therefore, to correlate changes in the benthic comm'enity, such as density or diversity, with changes in environmental conditions. PNPS is a base-load, nuclear-powered electrical generating unit designed to produce 670 megawatts of electrical energy under full operational conditions. He station is cooled by water that is withdrawn from Cape Cod Edy. The cooling wa'er is then returned to the Bay via a discharge Gaal that is designed to dissipate the heat from the water through rapid mixing and dilution. Two circulating pumps produce a combined water flow of approximately 20 m' per see at full operational capacity. The cooling system at PNPS includes three sources of potential impact on the benthic community: 1) warming of ambient waters,2) chemical discharges (mainly Cid, and,3) increased current velocities resulting in scouring of the bottom. Increasing temperature may stress the community so that species composition and community structure change; the extent of such change depeads upon season of the year and the influence of local oceanographic conditions. Increasing current dirxtly affects the benthos by actually g B removing benthic organisms and preventing recolonization; intense bottom scouring may cause the rock surfaces to become bare and devoid of macroscopic marine life. Operational conditions at the PNPS have provided an opportunity to assess long-term trends associated with the impact on the benthic community. Plant operations have included years of nearly full operation as well as times when there were complete shutdowns, sometimes for prolonged periods. He longest outage in the history of the plant began in April 1986 and continued until march 1989. During this period the benthic community associated with the effluent canal and nearby areas immediately offshore weie subjected to reduced current velocity as the use of circulating pumps was restricted to one or none. Ir, addition, the discharge water remained at ambient temperature. As a consequence, the benthic community normally affected by these effluent parameters recovered, so that by 1988 th.:re was essentially no diEerence between the control stations and the areas near the discharge canal. Studies conducted since the power plant has returned to operation were designed to assess the impact of plant operation on a benthic environment that had returned to near ambient conditions. I ' I
l I Voh.me 2 of the Semi-Annual Report summarizes impact findings in relation to the Benthic Monitoring Program, it discusses overall trends in the data presented in Volume 1 and in previous reports in an effort to summarize the effects associated with PNPS operations on the benthic community. Volume 2 places particular emphasis on the effects of full plant operation following periods of prolonged ar.d short plant shutdowns. METIIODS ne present design of the benthic monitoring program includes quantitative and qualitative approaches for determining the presence and extent ofimpacts a sociated with the PNPS. Specifications for methods and procedures follow guidelins established by the Pilgrim Administrative Technical Committee (PATC) and adopted by BECo as modified in 1981 (BECo,1987). The quantitative studies were designed in order to compare benthic community parameters at three stations: 1) a surveillance station located approximately 120 m offshore from the mouth of the discharge canal (Effluent station),
- 2) a control or reference station located 0.25 nmi NW of the discharge canal (Rocky Point station), and
- 3) a reference station located 2 nmi SW of the discharge canal (Manomet Point station)(Figure 1). Algal and faunal community analyses performed on data collected from these stations are compared for spatial and temporal (seasonal) variability. Differences between the Effluent and reference stations are then examined for potential impacts associated with PNPS operation.
He Effluent station is located far enough offshore of the discharge canal that the most scouring g effects present in the nearfield discharge area are moderated by dilution, wave action, and long-shore 5 currents, he site, therefore, is believed to experience only subtle effects on community structure and g species composition. In contrast, the nearfield discharge area itselfis heavily impacted with considerable E bottom scouring as evidenced by the algal denuded zone. In order to study this acutely impacted area, a qualitative diver transect study has been designed to map the effects on algal communities. Divers perform quarterly transect surveys to measure the extent of denudation and stunting of the algal flora in the nearfield discharge area. The focus of these studies is the commercially important red alga Oondrus crispus (Irish Moss), a species common to western Cape Cod Bay. Divers swim along a measured transect line in Se nearfield discharge area. i e divers note the boundaries of the denuded, stunted, and normal Gondrus zones. Variations in the size of these zones are recorded over time as a means of determining the area most severely affected by PNPS operations. Detailed descriptions of field methodologies are presented in the first volume of this report. I 4 1 5'
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I BACKGROUND PNPS operational conditions from 1983 through 1991 provide an opportunity to assess the degree of impact of the cooling water discharge on the benthic community and on the length of time it takes for this community to recover when the plant is shut down. Figure 2 depicts the annual maximum dependable capacity (MDC) factor and circulating water pump operation of PNPS since 1983. He MDC is a measure of reactor output that approximates *hermal loading to the marine environment. A maximum MDC value of 100% represents the highest allowable change in ambient temperature for water discharge to Cape Cod Bay (18'C AT). The cumulative capacity factor from 1973 to 1991 was 47.4%, but from 1983 to 1991 was only 38.0%. Dunng the life of the plant, power output has varied greatly. The most productive years were 1978 (74.6%),1979 (82.5%),1983 (80.3%),1985 (84.4%), and 1990 (72.3%). Dese very productive years frequently have been followed by low output years, with the most extensive period of no output lasting from April 1986 to March 1989. During times of plant shutdown or variable power outputs, only one of the two or none of the circulating seawater pumps may operate (Figure 2). During the shutdown that began in April 1986, oae circulating pump operated much of the time, but there were extended g periods when no pumps were in operation. 5 The longest power outage ended in March 1989 with the resumption of electrical generation and the operation of either one or both circulating pumps. The longest consecutive period of time that both pumps have been operating since March 1989 has beca 12 months, from May 1990 through April 1991. Since then, the plant was shut down for three months, from May through July, for refueling and part of November. 5 QUANTITATIVE FAUNAL COMMUNFIT STUDIES Species Richness ne number of species collected at each station has been plotted over time as a measure oflong-term species richness patterns (Figure 3). In terms of potential impact from Ge effluent discharged from PNPS, one obvious effect should be a reduction in numbers of species at the Effluent station during times of plant operation. At the same time, the numbers of species at the reference stations should remain consistently higher. Until 1987, this pattern was typically observed during periods when the level of operation of the plant was high. Ilowever, during the extended power outage, and especially from March 1987 to September 1988, the Effluent station exhibited lower numbers of species regardless. Following this period, the number of species at the Effluent station increased and all three stations were 6 i E.
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E essentially the same. By the fall of 1990, the number of species at the Ef0uent station had again been reduced in relation to the two reference stations. Beginning in 1990 the number of species present at the ! Effluent station increased to 72 in h1 arch and Sen to 93 in October. Both totals represent the highest species richness ever recorded at the Efiluent station. In fact, the 93 species recorded frorn the Effluent ! statlun in October represents the most species ever recorded at any of the truce gations. Among the
. control stations, the total number of species found at the Rocky Point station gradually declined from 80 species in both 1990 samplings to 73 in the October 1991 samples. At Manomet Point, the total number of species declined sharply from a high of 74 in September 1990 to 62 in March 1991, increasing to 70 in October.
These long-term results suggest that the numbers of species present at the Effluent station are not necessarily related to the operation of the PNPS. One very obvious correlation between the long-term trends in numbers of species is with the density of the blue mussel Myrilus edulls. During 1987, mussel populations were very low at all statione, then gradually increased to unusually high population levels in Septernber 1988 (see below for qualitative observations on dense mussel populations in June 1990 and i March 1991). %Is result correlates very well with the low counts of species at all stations that were observed in March 1981 and highs recorded in September 1988. In contrast, the major decline in rnussel populations observed between the March and 01ober 1991 collecting dates correlates very well with enhancM species richness and diversity at the Effluent station. Mussel density alone, however, does not
,& ovide a full explanation as for high species richness and diversity at the Effluent station because t Manomet Point and Rocky Point e:.hibited similar declines in mussel densities, yet species richness and diversity did not increase as dramatically. Based upon species numbers, the Efiluent statlan has historically had lower numbers of species than the references stations. This trend has not been consistent since the plant returned to full operation 1989. Thus, in terms of species richness, ti.e thermal discharge i
does not appear to be adversely impacting the Effluent station. Faunal Density Re total faunal densities from 1983 through 1991 are shown at all three stations (Figure 4). Total densities have fluctuated widely duilng this interval, largely because of periodic ma.;s settlements of blue mussels. When mussels are removed from the density tanul&tions, total densities are typically much lower (Figure 5). There does not appear to be any seasonal correlation with totai density at any station. Long-term variation in individual non mussel species have not been investigated.
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I The biology of Mytilus edulis includa initial larval settlement on Olamentous red algae followed, after a perk >d of growth anci deve!opment, by migration to sites of secondary attachment. The migration of these " plantigrade" juveniles is probably more important than the initial settlement and may explain the unusually hnse populations that were observed in the ef0uent canal area in June 1990 as part of the qualitative transect surveys. He mussels were mostly small, but were observed to be so thick that the algae were completely buried by the masses of mussels. His population had been considerably reduced in September and was completely gone in December. His reduction in mussel population was probably caused by starfish predation, many individuals of which were observed to be associated with the mussels In 1991, densities of Mytilus edulls remained relatively low at both hianomet Point and Rocky Point in htarch, while they increased at the Ef0uent station to one of the highest levels ever recorded. In October 1991, however, densities dropped to their lowest levels since 1986 and 1987, resulting in very low total faunal densities at all three stations (Figure 4). Historically, mussel populations at the Ef0uent station have been both higher and lower than the reference stations at hianomet Point and Rocky Point. No consistent pattern can be discerned from the g data. It is likely that both the presence and absence of mussels strongly in0uence the density, richness, a and diversity of the benthic communities at these stations. Populations of larger mussels would create habitat by providing space within the byssal threads, while their absence would provide space for other colonial organisms to settle and grow and likewise provide additional habit at. hiass settlements of juveniles orobably reduce species richness because habitat space for settlement and other activities such as feeding would be decreased. b 5 Species Dnersity Species diversity is a measure of the relationship between the number of species (richness) and their abundance in the communit'/ . Species diversity has been calculated in this program both with mussels included and excluded because their high numbers sometimes obscure potential patterns. Two measures of diversity have been prese.nted in the BECo reports, ne first is the Shannon-Wiener (H') index, with its associated evenness fPielou's l'), and the second is llurlbert's rarefaction (See volume 1 for details). Long-term summaries of #' values are provided in Figure 6. Typically, a seasonal pattern is evident, where low diversity values in the spring are followed by higher values in the fall. This pattern l we observed, with few exceptions, more or less regularly from 1983 through 1989. In the 1990 g l 5 12 I l 'n sa
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6"U 'i"l"6' 'u 'i"h"6"L" S" k"6"u ' S" k"6"u 'i" h" 6"L"i" 6"6 L" 1990 i"6"6"L"i"&"6' 1991 1986 1987 1988 1989 1983 1984 1985 CJ Manomet Point M Ebsp Point MDC A Emuent Figure 6. Shannon-Wiener Di1rersity (It') Inder for Data Excluding MytBas edulis for the Period April 1983 Throu Plotted with the Afonthly PNPS Capacity Factor (3tDC).
samples, however, species diversity increased at both Manomet Point and Rocky Po;nt between spring I, and fall, but de:reased at the Effluert station. His latter result corresponded with a decrease in the tota! number of species at the same sution (BECo,1991). In 1991, species diversities dropped at all three stations in March. Diversities were very low at the Eftluent station. In Octaber, however, H' increased to 4.3 at the Efauent station, the second highest value ever recorded at the station (Fig. 6). This was also the first time that the Effluent station was observed to have higher diversities than either of the control stations. Similarity A.mong Stations Cluster analysis was used to compare the community structure at each of the stations between seasons for 1991 (Figure 7). Historically, the benthic assemblage at the Effluent station has differed stneturally from the Manomet Point and Rocky Point stations (e.g., DECO, 1985, 1986, 1987, 1988, 1989). His difference has been evident in ae sitnitarity or cluster analysis. These results have suggested that a subtle farfield impact of the PNPS discharge affects the overall faunal composition at the Effluent station. As evidence for this long-term observation, the Effluent station bee ame indistinguishable g from the controls at the end of the 2 % year shutdown period in (BEco,1990). The structure of the E community did not immediately change following the sh . awn; it took nearly two years before the stations became similar enough in the analysis for the replicates from the controls to mix with the Effluent station (BECo,1990). Dere is thus a lag effect evident in the impact of the PNPS operation on the benthic community structure. A plant shutdown does not produce an immediate change in clustering patterns, in the spring of 1991, the similarity analysis indicated that the Effluent samples joined the reference stations at a very low level of similarity, indicating that the faunal assemblage was considerably different (Figure 7). This difference was attributed to the presence of two species groups that were abundant at the FTuent station, but rare elsewhere (See volume 1 of this report). De fall 1991 samples were unusual in that the samples from the Efiluent station were divided into two groups that joined with different clusters of reference station samples (Figure 7). The basis for these clustering pattern can be attributed to the variable distribution of individual species such as the amphipod 8%awcephalus holbolli. I 14 i 1 5
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I I i 15 l t i
i Ths community ana'pis ha consistently indicated that during normal periods of PNPS operation, the Ef0uent station differs from the reference stations at Manomet Point and Rocky Point. These differences disappeared in late 1989 after the plant had been off line for 2-% years. The community patterns are now reestablished. The differences in the faunal assemblages at the Ef0uent station are unusual in 1991 because the fall samples exhibit elevated benthic community patameters (diversity, richaca, nuinbers of spedes) over the reference stations. When these data are taken into account, the effect of the PNPS on the benthic community in Fall 1991 is more one of enhancement than one of diminishment. One possible explanation for the increase in cornmunity parameters at the Ef0uent station is that the brief plant shutdown in 1991 (May4uly) occurred during the maximal time of larval availability leading to successfv! settlement at a site of reduced species richness. I Discuulon-Faunal Studies l1 Results of the 1990 and 1991 quantitative benthic faunal studies indicate that the Efnuent station differs structurally from the two reference statiora. These differences include traditional beathic community parameters, such as species diversity and density, as well as overall community composition g ws 'evealed by cluster analysis. Further inspection of the 1990 and 1991 data indicated that in September a 1990, two species (Aferridlum sende and Corophium tubercdatum) had become dominant at the Ef auent station thht were either not important or were entirely absent at the reference stations, in 1991, other groups of species were apparent that provided the Ef0u;nt station with a different overall faunal assemblage from the controls. In the spring 1991 samples a gastropod (Thrivmilla elegantula), and a predatory polychaete (Eulalla viridis) were important at the Ef0uent station, but rare elsewhere. In the b fall 1991 samples, two different groups of species were denned in the cluster analysis, including an g amphipod (Phoxocephalus holbolll) and another group of five invertebrates. The results of the 1991 benthic community studies supported the conclusions reached in the 1990 report (BECo,1991) that the benthic communities at the Ef0uent station differed from those of the reference stations. Near the end of the long 2-% year power outage at the plant, the Eftluent station and reference stations became essentially indistinguishable from one another (BECo,1990). After a full year of renewu! plant operation, some changes began to emerge in the structure of benthic communities near the discharge canal (DECO,1991). No one single benthic parameter was cited as evidence of PNPS having an impact on benthic communities, but when all were taken together, a cumulative impact was evident. Those trends observed in the 1990 samples are again evident in 1991. An interesting twist, 16 I I a
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I , l however, is that the benthic community a' the Eftluent station appears to have enhanced species richness and civersity that tre higher than either Manornet Point and Rocky Point instead of being lower. Faunal communities that are associatal with thermal discharges and under some stress, are believed to be chrracterized by low densities, few species, and elevatid diversities (Imgan and Maurer, 1975). Species that dominate lh such an environment tend to be opportunists or pioneers. At the Pilgrim Sta:lon, benthic communities located offshore of the discharge canal da not appear to be subjected to estreme stress, although low levels of potential stress we, apparently present in the September 1990 samples, as evidenced by depressed density, diversity, and richness (BECo,1991). In the October 1991 samp!cs, howcver, this trend reversed, with ar. enhancement of the cornmunity. He data en faunal density suggest that mussel density can subtly impact other commtmity parameters by influencing which species are able to settle or become associated with the different stations. The impact of PNPS operation on benthic communities in the farticld is thus difficult to predict. The pattern of lower benthic parameters at the Effluent station and highet ones at the reference stations l was reversed la the 1991 samples. QUANTITATIVE ALGAL COMMUNITY STUDIES Algal Community Description
- De algal cornmunity at the Effluent station is dominated by the red macroalgae, Omndrus crispus i and Phyllophora spp. These species are also dominant at the Manomet Point and Rocky Point stations, u Less abLndant but nonetheless importa.nt algst species are those that indicate en effect upon me community by the th:rmal efiluent nf PNPS. nese important spec.a .nclude Gracilaria tibuhlae, a warm-water species (BECO,1982), and lemharia spp., a typical cold water alga, prevalent alor.g the 1 northeast coast of the United States. Gracilaria tihuhlac does not occur at the reference stations but
( occurs regularly at the Eftluer.t station durmg normal c.perational years of PNPS. Gracilaria tibuhlar abundance decreased drastically during 1986 and the species was entirely absent from the denuded zone during 1987, the sec(md year of the nearly three year power outage. Conversely, Laminaria spp. was present within the area that had formerly beer. the acute impact zone bring all four observation periods in 1987,1988, and in March and June of 1989. The disappearance oflaninaria spp. by September 1989 and the reappearance of Gracilarta tibuhlar coincided with the retum of PNPS to operational status. During 1991 Gracilarla was observed by the divers within the discharge canal area during all four seasons. Ianinaria spp. was only observed at the reference stations. I n g I
I Algal Community Oscriap Table 1 presents algal community overlap values (i.e., the percentage of shared species) between pairs of stations from 1983 through 1991. In general, the Manomet Point and Rocky Point statiora have been more similar to each other (higher percentage overlap) than either have been to the Efiluent station. One exception to this pattern occurred in the fall of 1985 while the plant was in full operation; three exceptions to this pattern occuired in the spring, once during the extended shutdown period in 1988, and twice while the plant was in full operation, in 1983 and this past year in March 1991. The exceptions to the general pattern appear not to be correlated with power plant operation and may depend upon meteorological and oceanographic variability in Cape Cod Bay (DECO,1989) for those years and seacons. In addition, the nearly three year power shutdown of PNPS from April 1986 until March 1989 did not cause any marked changes in the dominant algal species composition, indicating that PNPS operrtions have had little effect on species composition. As in most previous years, the overlap values for the various station pairs in 1991 (Manomet Point vs. Rocky Point, Manomet Point vs. Efiluent, and Rocky Point vs. Effluent) were not very different; the March and October overlap values had ranges of 7.0% and 7.2%, respectively. The small g range in overlap values seen for most sampling periods indicates a relatively homogeneous algal species a distribution among all three stations. In 1991, species overlap between the reference stations was typical of levels observed prior to 1990 when unusually high overlap was seen. Algal filomass The March 1991 samples were similar to the March 1990 samales in that algal biomass failed to follow the typical seasonal decline during the winter months. Ratl er, at the Effluent station and at g Manomet Point the mean values for total algal biomass increased from September 1990 to March 1991 (Figure 8), and the biomass at Rocky Point ordy decreased very slightly. During the summer of 1991, total algal biomass increased at all three stations, reaching levels not seen since the powet plant resumed operation in March 1989. This may be related to the three-month shutdown of the plant from May through July. The summer increase in biomass at the Effluent station and Manomet Point was due to an l increase in biomass of the red algae Otondrus crispus and Phyllophora spp. la addition. at the Effluent station the biomass of the epiphytic species associated with the red algae increased dramatically (> 800%). At Rocky Point, however, the increas in total biomass resulted solely from biomass increase of the remaining benthic species and the epiphpes; biomass of both species of red algae actually declined. I 18 E E
5 l Table 1. Algal Communtly Overlap in l'ercent Between Station l' airs for the l'eriod 1983-1991. Overlap (% ) Year Season . MP vs. RP MP vs. EFF RPvs.EFF Spnng 81.0 85.2 81.0 1983 Fall 77.8 67.9 73.0 Spring 76.0 68 0 70.4 1 1984 Fau 84.0 73.1 71.0 l ( $pring 88.0 77.0 75.0
- 1985 Fau 65.5 73.1 88.9 Spring 90.9 76.9 80,8 I 1986 Fall Spring 84.0 77.2 70.4 66.7 77.8 70.8 1987 Fall 80 0 80.0 76.0 Spring 88.9 81.5 82 5 I 1988 Fall Spring 82.8 81.5 89.7 76.9 85.7 80.0 1989 l3 Fall 87.0 85.2 74.1 Spring 96.3 88.9 92.6 1990 l Tall 96.0 80.8 84.6
( Spring 81.5 88.5 84.6
^
l 1991 l Fall 90.5 83.3 83.3 lI ll I 19 l lI
Disctmlon-Algal Studies By the end of 1991, PNPS had been tu operation for nearly three years, except for a three-month hiatus from May through July in 19)1 and a few other brief interruptions. Measures of similarity between station pairs (Jaccard's coefficient of community) show that h the spring of 1991 the Ef0uent station was more similar to the reference stations than the reference stations wm to each other, a situation seen in only four sampling periods since 1983. By (ktober 1991, the reference stations were again more similar to each other than they were to the Ef0uent station, the more typical condition. Tnis change, with the reference stations becoming nore similar to each other and less similar to the Ef0uent station in the fall is caused, in part, by the nuniber of species occurring at the reference stations in the fall being lower than in any of the other 1991 samnles. Of 27 species observed in tne spring 24 species were present at the Ef0uent station r; d Rocky Point and 25 species occurre1 at Manomet Point. Ilowever, in the fall, of 24 species recorded, all 24 species were present ;f the Ef0uent and only 20 species at each of the reference stations. De effect of power plant operation upo*: the algal commimity has been confined primarily to changes in species composition rather than biomas1. His pattern was repeated in the 1991 samples. g Biomass values for the major algal categories failed to show any differences among stations for eitt.er a season that would indicate a signincant effect of PNPS at the Ef0uent station (Figures 8-10). The impact g of PNPS on the algal communities of the Ef0uent station is reDected in the presence or absence of several 5 less dominant species, probably because of differences in ecological requirements of the different species, g For example, the warm-water species Gracilaria tibuhit's is found only at the ef0uent station during g times of triermal discharge and the cold-water species Iominarla spp. is found only at the reference g stations. 5 QUALITATIVE TRANSECT SURVEYS Results of the qualitative transect surveys irom 1983 through 1991 are presented in Figure 11. The total acute impact area (denuded, stunted, and including sparse in June and December) is plotted with the area of the denudal zone only and the monthly PNPS capacity factor (MDC). The di'ference between the denuded and total acute impact zones represents the stunted zons (and included a sparse zone in June and December 1991). A lag time in recovery response by the acute impact tone to the 1984 PNPS power outage was reported in Semi-Annual Report No. 27 (BECO,1986). Evidence of this slow recovery included a decrease in the area of the total acute impact zone that began in mid-1984 (5 months after the cessation of power plant operations) and continued thrwgh mid-1985. Between December 1984 and 20 5
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December 1985, the total impacted area (denuded and stunted rones combined) was the smallest recorded betweer.1983 and 1986, indicating a delay in recovery of this area in response to the absence of thermal discharge in 1984. His phenomenon reversed itself under normJ PNPS operating conditions, so that only 6 to 9 months after the resumption of thermal eftluent discharge the site of the acute impact zone began to increase between September and December 1985. These results confirmed a delay period of about 6-9 morahs between the causal factor (cessation or resumption of thermal eftluent discharge) and associated response (decrease or increase of the acute impact zone size). Ir 1987, increased recolonization of the denuded and stunted zones by Chondrus crispus made zone boundaries difficult to distinguish (no areal differences could be discerned from September 1987 through June 1989). As in summer 1984, the considerable decrease of the denuded area of the acute impact zone from December 1986 to June 1987 was mostly the result of the shutdown of the circulating water pumps from late march to early September (BECO,1988). Apparently, water current scouting is a greater stress to algal colonization than increased water temperature. Scouring denudes the substratum, whereas elevated temperature results in stunted growth (Bridges and Anderson,1984). In 1988, the circulating water pump activity was low, resulting in little thermal loading and scouring effect. Results of the 1988 transect surveys showed such a increase in recolonization of the formerly denuded and stunted zones by Omndrus, in response to the continuing outage, that the divers I were unable to detect boundaries of these zones, and no area measurements could be made. In March and June 1989, divers were still unable to detect boundaries of the denuded or stunted zones, and no area measurements were made (BECO,1990). In September and December, presumably in response to increased PNPS operations and the resultant scouring of the acute impact zone, boundaries began to be redefined and area measurements were made of the total impact zone. During 1990, the boundaries between the stunted and denuded renes became more clearly defined, and areal measurements of both zones were made (Figure 12). The areas of the denuded and total acute impact zones in June 1990 were the highest seen since 1983. He dramatic increase in total affected area that occurred between April and June 1990 had not been seen before in the 1983-1990 period. He typical pattern seen prior to 1990 was that during the spring, with warmer temperatures and increased sunlight, algal growth flourishes, and the impact area declines even in years when the power plant is operating at high capacity. The pattern seen in 1990 was anomalous and permitted no ready explanation. 25 i
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In 1991, the boundaries of the acute impact rone remained well4enned, except that in June therc was no true stunted zone ist only an area described by the divers as " sparse", that is, where the algal plants grew normally but were thinly distributed. I rom March to June, ec total s%ted area and the Chondrus denudal zone decreased in area, a return to the typical pattern seen before 1990. This decrease in area continued through 'he October survey, perhaps aided by the May through July power plant outage. There was a slight increase in affected area in December. CONCLUSIONS Quantitatise Faunal Studies I e Total number of species observed at the Ef0uent station is not related to plant operation, but may be related to habitat modification caused by changes in mussel populations. The total number of species at the Efauent station in the fall 1991 samples was the largest ever recorded at any of the stations. e Total density Ductuations are strongly induenced by mussel populations, g Unusually high mussel populations were observed in the vicinity of the dir, charge B canal in June 1990. Mussels may have migrated to the site in response to higher temperature from the thermal discharge or by the currents. Greatly reduced densities in fall of 1991 are attributed to declines in mussel density.
- Species diversities declined at all stations in 1990, preclu<!!ng any obvious effects of PNPS on area wide species diversity patterns, in 1991, however, species I diversities were low in the spring, but greatly elevated in the fall, especially at the Ef0uent station.
e Community analysis using cluster analysis indicates that by September 1990, the Ef0uent station differed structurally from the two reference stations. Two species, one anemone and an amphip(xl were dominant at the Ef nuent station, but rare or absent elsewhere. This trend continued in 1991, with changes in abundances of individual species or grmps of species being directly responsible for the different clustering patterns.
. e A composite assessment of all benthic community parameters including species richness, diversity, and density taken together with community compositica
!ndicates that subtle alterations in the Ef0uent station are probably the result of PNPS operation. In some years the.<e impacts result in higher densities and reduced species richness and diversity. In the fall of 1991, however, species richness and diversity were the highest ever recorded at the Eftluent station.
27
Quantitathe Algal Community Monitoring
- In October 1991, the algal community at the Eftluent station differed more from the Manomet Point and Rocky Point stations than in March.
- ne number of algal species shared (overlap) between the reference r.tations was lower, in March 1991, than that between the Effluent and reference stations. A return to the more typical pattern was seen in October when the overlap between the reference statiens increased and became greater than that betw een the Eftluent station and both reference stations.
- Algal biomass increased from September 1990 to March 1991 at the Efiluent g station and Manomet Point, a generally atypical pattern, and one similar to snat 5 observed in 1990. The expected seasonal increase in biomass between March and October occurred at all three stations.
Qualitative Trannt Surveys
- The size of the denuded zone of the acute impact ares was similar to that observed during earlier times of full power plant operation. Area of the denuded rone is mainly influenced by circulating water pump operation and the slight decrease in affected area seen from the March to October surveys may be explained by the three-month outage in May, June, and July 1991. Typically, the denuded zone decreases in area during the spring, a time of abundant algal growth; this pattern was observed in 1991.
- De warm-water alga, Gracilarla tibuhlac, was observed at the Effluent station during all four seasonal surveys; it was not observed at the reference statiors.
LITERATURE CITED Boston Edison Co.1982. Marine ecology studies related to operation of Pilgrim Station. Semi-Annual Report no.19. Boston Ma, Boston Edison Co.1985. Marine ecology studies related to operation of Pilgrim Station. Semi Annual g Report no. 25. Boston Ma. e Boston Edison Co.1986. Marine ecology studies related to operation of Pilgrim Station. Semi-Annual E Report no. 27. Boston Ma, 3 Boston Edison Co.1987. Marine ecology studies related to operation of Pilgrim Station. Semi-Annual Report no. 29. Boston Ma. Boston Edison Co.1988. Marine ecology studies related to operation of Pilgrim Station. Semi Annual Report no. 31. Boston Ma. 28 5
=
I Itoston ikilson Co.1989. Muine ecology studies related to operation of Pilgrim Station. Semi Annual TReport no. 33.11oston hia.
. Boston !!dison Co.1990. hiarine ecology studies related to operation of Pilgrim Station. Semi Annual Report no. 35. Boston hia. .l Doston Edison Co.1991. hiarine ecology studies related to operation of Pilgrim Station. Semi Annual Report no. 37. Boston hia, i Bridges, W. L. and R. D. Anderson.1984. A brief survey of Pilgrim Nuclear Power Station hiarine Ecology Study Prytam. Lecture Notes on Coastal and Estuarine Studies 11:263-271.
Logan, D.T. and D. hiaurer. 1975. Diversity of marine invertebrates in a thermal effluent. Journal of _ the Water Pollution Control Federation 47:515-523. I I l
)
pl 29
I I ICHTHYOPLANKTON ENTRAINMENT MONITORING AT PILGRIM NUCLEAR POWER STATION JANUARY-DECEMBER 1991 Volume 1 of 2 (Results)
,5 5
Submitted to Boston Edison Company I I by Marine Research, Inc. Falmouth, Massachusetts I April 4, 1992 E B l
4 il j lI il l 1 TABLE OF CONTENTS SECTIOl{ 1%QE i I EXECUTIVE
SUMMARY
1 II INTRODUCTION 2 i f III METHODS AND MATERIALS 3 i IV RESULTS AND DISCUSSION 7 ] l A. Ichthyoplankton Entrained - 1991 7 ! B. Multi-year Ichthyoplankton Comparisons 14 C. Lobster Larvae Entrained 18 V HIGl! LIGHTS 20 !I APPENDICES A and B (available upon request) lI c il I I E I 1 g-5
l LIST OP FIGURES f.lGURE EAGI Entrainment campling station in PNPS discharge i 1 canal. 4 2 Location of entrainment contingency plan samp-ling stations, C-1 through C-13. 6 3 Dominant species of fish eggs and larvae found in PNPS ichthyoplankton samples by season. I cent of total and sumned monthly means for all species are also shown. Per-8 4 Mean monthly densities per 100 m8 of water in the PNPS discharge canal for the eight numer-ically dominant egg species and total eggs, I 1991 (dashed line). F611d lines encompassing shaded area show high and low values over the 1975-1990 period. 22 5 Mean monthly densities per 100 m8 of wat)r in the PHPS disenarge canal for the eleven numeri-cally dominant larval species and total larvae, 1991 (dashed line). Solid lines encompassing shaded area show high and low values over the 1975-1990 period. 26 LIST OF TABLES IADLE PAGI I 1 Species of fish eggs (E) and larvae (L) ob-tained in ichthyoplankton collections from the Pilgrim Nuclear Power Station dischutgo canal, January-December 1993. 30 2 Species of fish eggs (E) and larvae (L) col-
+'cted in the PNPS discharge canal, 1975-1991. 33 LIST OF APPENDICEc APPENDIX A* Densities of fish eggs and larvac per 100 m8 of water recorded in the PNPS discharge canal by species, date, and replicate, January-December 1991.
B* Hean monthly densities and range per 100 m8 of water for the dominant species of fish eggs and larvae entrained at PNPS, January-December 1975-1991.
*Available upon request.
11
i SECTION I EXECUTIVE SUMMAllY I PHPS ichthyoplankton sampling was completed twice por month in January, February, October-December, weekly from March through September except that sampling occurred only twice in June due to circulating water system shutdown. Numerical dominants among the 34 species represented in the g catch by season included American plaico, sculpin, rock gunnel, and sand lance during winter-carly springs tautog, cunner, and mackerel during late spring-early summer; and rockling, hake, cunne', and windowpane during late summer-autumn. Comparisons between 1991 monthly mean densities per 100 m8 of water and those recorded over the 1975~1990 period suggest that Atlantic cod eggs were uncommon in February along with rockling, hake, and labrid eggs in June and July. In contrast, Atlantic mackerel eggs and larvae were found to be abundant in 1991 tor the i fourth consecutive year. Rock gunnel and sculpin larvae were relatively abundant in February. The distribution of tautog and cunner larval densities was unusual as they were both absent in July yet relatively abundant in September. No lobster larvae were obtained in the 1991 collections. Only eleven have been taken in 18 years of-sampling. No unusually high densities warranting contingency sampling lI were observed in 1991. I
- I
I flECTION 11 1RIRQDilCIIDH I. This report summarizes results of ichthyoplankton entrainment sampling conducted at the Pilgrim Nuclear Powc.r Station (PNPS) j discharge canal on a regular basis from January through December 1991. Work was carried out by Marine Research, Inc. (MRI) for l Boston Edison Company (BEco) under Purchaso order No. 68006 in compliance with environmental monitoring and reporting requirements of the PNPS HPDES Permit (U.S. Environmental Protection Agency and Massachusetts Division of Water Pollution Control). In an effort to condense the volume of material presented in this report, details of interest to some readers may have been omitted. Any questions or requests for additional information may be directed to Marine Research, Inc., ralmouth, Massachusetts .irough DECO. I 5 E I I I I 2 E
5 l SECTIOiL111 liGiQDS AND MATLillALS I Entrainment samplit.g at PHPS was scheduled twice per month during January, February, October, November, Doctmber, and weekly March-September. Although weekly esampling was scheduled ior June, PNPS began a refueling outage in May which resulted in both circulating water system pumps being out of service for much of Junct samplec were obtained on two occasions with a single CWS pump operating. All samples were collected in triplicate from rigging mounted approximately 30 metera f rom the headwall of the discharge canal (Figure 1), at low tido during dayliqht hours. A 0.333-mm mesh, 60-cm diameter plankton not affixed to this rigging was streamed in the canal for 8 to 12 minutes depending on the abundt. .2 of plankton and detritus. In each case, a minimum of 100 m8 of water was samplod. Exact filtration volumes were calculated using a General Oceanics Model 2030R digital flowmoter mounted in the mouth of %e net. All samples were preserved in 10% Formalin-scawater solutions and returned to the laboratory for microscopic hnelysis. A l detailed description of the analytical procedures may be found in MRI (1988).*
- Marine Research, Inc. 1988. Ichthyoplankton Entrainment Monitor-ing at Pilgrim Nuclear Power Station January-December 1987.
III.C.1-6-10. In: Marine Ecology Studies Related to Operation of Pilgrim Station. Semi-annual Report No. 31. Boston Edison Company. 3 4
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E HEADWALL ' OQg' ?,: g UNIT 1 INTAKC PNPS fit.,: ' 7Xt 4.n .@ l 3 e ICHT)'/QPt ^ IKTON 3 UNIT 1 STATIGt i i 100 METERS l g Figure 1. Entrainment sampling station in PNPS discharge canal. I 4
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m 7 When the Cape Cod Bay ichthyoplankton study was completed in 1976, a contingency sampling plan was added to the entrainment I
~
monitori.ng program. This plan was designed to be implemented if eggs or larvae of any dominant species proved to be " unusually abundant" in the PNPS discharge samples. The goal of this sampling plan was to determine whether circumstances in the vicinity of Rocky Point, attributable to PHPS operation, were causing an abnormally large percentage of ichthyoplankton populations there to be entrained or, alternatively, whether high entrainment levels simply were a reflection of unusually high population levels in ! Cape Cod Bay. " Unusually abundant" was defined as any mean density, calculated over throa replicates, which was found to be . 50% greater than the highest mean density observed during the same month from 1975 through 1990. The contingency sampling plan consists of taking additional u ns of r iplicates from the PNPS discharge on subsequent dates to ociitor the temporal extent of the unusual density. An optional I offshore sampling regime was also established to study the spatial distribution of the species in question. The offshore contingency program consists of single, oblique tows at each of 13 stations (Figure 2) on both rieing and falling tides for a total of 26 samples. Any contingency sampling requires authorization from 1 Boston Edison Compani. i J Y 5 M
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mm W s J SECTION IV RESULTS AND DISCUSSION A. Ichthyoplankton Entrained - 1991 , Population densities per 100 m) of water for each species listed by date, station, and replicate are presented for 1991 in Appendix A (available upon request). Ta'r.le 1 lists all species , represented in the 1991 collections, indicates the conths eggs _ and/or larvae of each species were found and, for the more common species, the months of peak abundance. Ichthyoplankton collections are summarized below within the
- three primary spawning seasons observed in Care Cod Bay: winter-early spring, late spring-early summer, and late summer-autumn.
Figure 3 shows the dominant species of eggs and larvae within each season for 1991. Winter-early sprina spawners (DecembeI-Aprill The beginning of this spawnir.g season is sampled at the end of the calendar year. The two December 1991 collections produced four Atlantic cod eggs (Gadus morhua) and 15 Atlantic herring larvae (Clupea harenaus). These counts resulted in respective monthly mean densities of 0.5 and 1.8 per 100 m2 of water. The number of species represented in the earlier collections of the winter-early spring spawners was fjve in
- January, increasing to eight in February, twelve in March, and fif teen in April. Eggs were re3 atively uncommon since specj cc =
I ' I
I I I I I. I. I' Figure 3. Dominant species of fish eggs and larvae found in PNPS ichthyoplankton samples by season. Percent of total and summed monthly means for all species are also shown. I I % 1 5 I I. I, Is I; 8 i l! t B
=1
Eg s Larvae Winter-Early pring Season Winter-Early Spring Season Decemoer-April December-April
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I contributing most to entrainment during th.i s period spawn demersal, adhesive eggs which are not generally subject to entrainment. They were in fact absent from the January and February collections. March samples contained small numbers of Atlantic cod, American plaice (Hiopoglossoiden plates-spides), and winter flounder (Pleuronectes americanus) eggs. Monthly mean. densities amounted to 0.3 per 100 m8 for both cod and plaice, 0.1 per 100 m8 for flounder. Since they are demersal and adhesive, winter flounder eggs are not typically entrained at PNPS. Their numbers in PNPS samples are there-fore not considered representative of numbers in the surround-ing area. Those that were taken were probably dislodged from the bottom by currents or perhaps other fish. The number of species represented by larvac generally in-creased with time during the winter-early spring period; five species were taken in January, eight were taken in February, ten were taken in March, followed by eleven in April. Numer-ical dominants included the rock gunnel (Pholis gunnellus), grubby (Myoxocechalus aenaeus), and sand lance (Ammodytes sp.). Rock gunnel represented 63% of the January total, 60% of the February total, 30% of.the March total, and 8% of the April total with monthly mean densities of 2, 46, 20, and 6 per 100 m8 of water, respectively. Grubby did not appear in the collections until February when they accounted for 12% of i the catch with a monthly mean density of 9 per 100 m3 Grubby I densities peaked in March with a mean density of 39 larvae per 10 B,
='
I 100 m 8 accounting for 59% of the month's catch. They declined to 13 per 100 m2 in April with a percent contribution of 19. Larval sand lance accounted for 2% of all larvae in January, 1% in February, 8% in March, and 55% in April; monthly mean densities were 0.1, 0.7, 5, and 38 per 100 in', respectively. I Late soring-early summer (May-Julyl May, June, and July collections contained 20, 39, and 15 -- species, respectively. Among these totals, 11, 12, and 13 species were represented by eggs. Numerical dominants included the labrids (teutog, Taqtaga onitis; cunner, Tautoao-labrus g.qlspersus) and Atlantic mackerel (Scomber scombrus). Assuming labrid-yellowtail eggs (Pleuronectes ferrugineus) were primarily labrid eggs, tautog and cunner contributed 33% of the total in May with a monthly mean density of 321 per 100 m2, 54% of total in June with a monthly mean of 607 per 100 m3, and 92% of total in July with a monthly mean of 219 per 100 m2 Mackerel contributed an additional 56% to the May egg total with a monthly mean of 538 per 100 m2 of water, 42% to the June total with a monthly mean of 473 per 100 m3, dropping to 4% of the July total with a mean of 0.2 per 100 m3 Larval collections consisted of 15 species in both May and June, falling to 6 species in July. Atlantic mackerel, radiated shanny (Ulvaria subbifurcata), winter flounder, and I. cunner were numerically dominant. Mackerel accounted for 12 and 86% of the May and June larval catch with respective
'I I
monthly mean densities of 7 and 200 per 100 m8 Larval mackerel were absent from the July catch. Radiated shanny contributed 33% to the May total with a monthly mean of 19 per 100 m 8 , dropping to 1% of the June total with a raean density of 2 larvae per 100 m8 They were absent in July. Flounder and cunner were also absent in July but accounted for 19 and 1% cf the May total and 1 and 7% of the June total, respec-tively. Corresponding monthly mean densities amounted to 16 and 2 per 100 m2 for flounder and 0.3 and 17 for cunner in May and June. I Late summer-autumn spawners (Auaust-November) Both the number of species represented each month and overall densities typically decline steadily through this season. During 1991, 18 species were represented in August, 13 were represented in September, dropping to 3 in October and 6 in November. Species represented by eggs amounted to 12 in August, 10 in September, 3 in October, and 2 in November. 5 Rockling and hake (EnchelvQDun ginbrius, Uronhvcis spp.), windowpane (Sc_ochthalmus aquosus), and tautog/ cunner were the numerical dominants among the eggs. Rockling and hake accounted for 40, 43, 70, and 82% of the four respective monthly egg totals with monthly mean densities of 48, 9, 1, and 0.4 per 100 m' of water.- Windowpane, assuming they acccunted for most of the grouped Paralichthys-Sconhthalmus eggs,' contributed an additional 29% to the August total with l I l u
l I a monthly mean of 35 per 100 m8 of water, 41S to the September total with a mean of 9 per 100 m8, and 18% to the October
.g
" total with a mean of 0.' per 100 m8 They were absent from the November collections. Tautog and cunner were present only in August and September when they represented 25 and 2% of all eggs with monthly mean densities of 30 and 0.4 per 100 m8 Late summer-autumn larval collection'; contained 13 species in August, 11 in September, 1 in October, and 4 in November. Seasonal dominants included cunner, rockling, tautog, and hake. Cunner appeared only in August and Septem-ber when they accounted 'Ior 63 and 37% of the larval catch with monthly mean dens' ties of 13 and 8 per 100 m8, respec-tively. Rockling added 12 and 17% to the respective August and September totals, as well as representing all of the small number of larvae taken in October; they were absent in November. Monthly mean densities were 2, 3, and 0.4 per 100 m8 during the three respective months. Tautog and hake contributed 6 and 5% to the August total, 20 and 16% to the September total with respective mean densities per 100 m3 of water of 1 and 1.in August. 4 and 3 in September. Both tautog and hake were absent fron the October samples, hake also from the November samples. A single larva? tautog was taken in November representino a mor.thly mean of 0.2 per 100 m8 I
I
. 13
I D. Multi-year Ichthyoplankton comoarisons Table 2 presents a master species list for ichthyoplankton collected from the discharge canal at PNPS and indicates the years each species was taken from J.h through 1991. The general period of occurrence within the year is also indicated for each species including the peak period for the numerical dominants. A total of 34 species was represented in the 1991 collections, below the overall average of 38 and equal to the low value of 34 observed in 1984 when Loth CWS pumps were out of service from April through August. No new species were added to the overall list in 1991. Monthly mean densities per 100 m8 of water were calculated for each of the 13 numerically dominant fish eggs or fish egg groups, those accounting for 99.3% of the 1991 egg total, as well as total eggs (all species combined) for each year from 1975 through 1991 (Appendix B, available upon request). To help compare values over the 17-year period, egg data were plotted in Figure 4. For this figure cod and pollock (Pollachius virens) eggs were combined with as the gadid-Glyntocechalug group, rockling and hake were combined l with the Enchelyopus-Urophycis-P_eprilus group, and labrids and yellowtail were combined with the labrid-Pleuronectes group. For each category chown, the highest monthly means obtained from 1975 through 1990 were joined by solid lines as were the lowest monthly means, and the area between was shaded, indicating the range of - these values. Monthly mean values for 1991 were joined by a dashed line. Appendix B and Figure 5 contain comparable data for the eleven numerically dominant species of fish larvae, those accoJnt-I E
=
ing for 96.1% of the 1991 catch, as well as total larvae (all species combined). Low values obtained for both eggs and larvae during AprO. through August of 1984 and 1987 were excluded from these figures and the following discussion because exceptionally low values were common then, probably due to low through-plant water volumes (see Impact section). Based on these data, egg densities for Atlantic menhaden ( Brevoor tig tyrannus), searobins (Prionotus spp.), Para 1ichthyji-SconhthalDus group, and American plaice were well within the range - of monthly mean densities observed over the previous 16 years. Among the numerically dominant larvae, fourbeard rockling, sculpins (My_Qyocephalus spp.), seannails (Liparis spp.), radiated shanny, sand lance, and winter flounder were also within the range of . monthly mean densities recorded over past years. Among the remaining eggs and larvae, the following observations were made:
- 1. Atlantic cod eggs were absent in February for the fourth consecutive year. Prior to 1988 they were taken every year in 8 February although not in high numbers (1 to 3 per 100 m) of
, water).
- 2. Atlantic mackerel eggs have been abundant in June during the past three seasons. In June 1991 (monthly meaa = 473 per 100 m2) their numbers declined compared with 1988 (2220 per 100 m2), 1989 (1013 per 100 m2), and 1990 (2081 per 100 m2);
however densities continued to rank well ahead of 1975-1987 when means ranged fror 3 (1976) to 277 (1986) per 100 m2 Mackerel larvae were also relatively common in iby (6.6 per 15 I I
I 100 m2) and June (200 per 100 m2) 1991. May's mean density surpassed all previous May values, 1979 being the previous high with 6.1 larvae per 100 m2 June's density ranked second, exceeded only by the 1981 value of 318 por 100 m).
- 3. In contrast f ourbeard rockling eggs and the hakes (combined with the Enchelvoppg-Urophycin-Eeprilus group) were uncommon in June and July 1991. Combining rockling and hake with the Enchelyoous-Urophycis-EppIi193 group showed respective monthly mean densities of 30 and 6 por 100 m 3 in June and July.
Previous low values were 10 for June (1982) and 21 for July (1986).
- 4. Similar results were obtained for labrid eggs. _ Combined with the labrid-yellowtail group which they no doubt dominate in summer, 1991 monthly means for both June (607 per 100 m3) and July (219 per 100 m) 8 ranked below all previous values for those me.nths. Previous low values were 733 per 100 m8 for June in 1980 and 452 per 100 m3 for July in 1986.
- 5. . Rock gunnel and sculpin larvao were abundant in February. For rock gunnel February 1991 (46 per 100 m2) ranked ahead of all previous February values,1985 snowing the previous high with -
l a mean density of 25 per 100 m3 For sculpin a mean density of 30 per 100 m3 in February 1991 exceeded all previous Febru-ary periods except 1988 with 41 per 100 m 2. Interestingly, in both high-density years shorthorn sculpin (Myoxocenhalug i Ftcornius) accounted for most of the sculpin larvae taken I Il 16 l 5
during February. In all other years they were uncommon or absent. I I 6. Larval tautog and cunner were both absent from the July 1991 collections, were within the normal range in August, and relatively abundant in September. Tautog were absent from
-g g July collections in only two previous years, in both cases (1984, 1987) when both CWS pumps were off (see Impact sec-tion). While not absent, they were uncommon in July 1975 (0.1 x per 100 m8) and 1982 (0.3 per 100 m8). The mean September density for tautog (4.2 per 100 m8 ) exceeded the previous high mean of 3.8 per 100 mi recorded in 1975. A single tautog larva was also collected .in November 1991 (density = 0.2 per I 100 m 2 ), the first time one has been recorded that late in the year. Cunner were absent from the July collections only one other year, 1987 when no CWS pumps were running. Their mean
- density in September 1991 (6.6 per 100 m3) exceeded the previous high (4.9 per 100 m3) recorded in 1980.
Although several of the above monthly mean densities exceeded all other corresponding means, no densities meeting the unusually
- high definition of the contingency sampling plan were encountered during 1991.
Ichthyoplankton populations sampled over a long time series
; typically display density variations of one order of magnitude, and u - two orders of magnitude are not unheard of (see Figures 4 and 5).
Variations in spawning stock size and condition, food availability, I il \ _-_--_ _ - _ _ _ - _ - - _ - _ - - - _ - - - -- -
E predator densities, and physical variables such as water tempera-ture and wind all contribute to the level of observed ichthyo-plankton densities. In many cases the 1991 monthly densities which I extended above or below all previous values at PNPS did so only slightly. In cases such as mackerel eggs which have been entrained in relatively high numbers for four years, the data probably reflect relatively strong stock biomass (NOAA 1991) . Likewise persistently low densities of Atlantic cod eggs noted from 1988 tnrough 1990 are consistent with a regional downturn in the size of the spawning population (NOAA 1991). I C. Lobster Larvae Entrained No larval lobsters (Homarus americanus) were found in the 1991 entrainment samples. Following is a summary of previous lobster larvae collections at PNPS, a total of 11 having been taken. 1990: 2 larvae - 1 stage I, June 26; i stage IV August 23. 1983-1989: none found. 1982: 1 larva - stage I on June 14.
- 1981: 1 larva - stage IV on June 29. 5 1980: none found.
1979: 1 larva - stage I on July 14. 1978: none found. 1977: 3 larvae - 1 stage I, June 10; 2 stage I, June 17. 1976: 2 larvae - 1 stage I, Jul'f 22; 1 stage IV-V, August 5. 1975: 1 larva - stage I, date unknown. 1974: none found. I
*NOAA (National Oceanic and Atmospheric Administration). 1991.
Status of the fishery resources off the northeastern United States g for 1990. NOAA Technical Memorandum NMFS-F/NEC-81. 5 18 R e l
i The lobster larvae collected in 1976 were obtained during a more intensive lobster larvae program which employed a 1-meter not, collecting relatively large sample volumes, in addition to the standard 60-cm plankton not (Marine Research 1977) .** Poth larvae taken in 1976 were collected in the meter net; none were found in the routine ichthyoplankton samples. I i : I . I I E
** Marine Research, Inc. 1977. Entrainment investigations and Cape Cod Bay Ichthyoplankton Studies, July-September 1976. III.C.1 71. In: Marine Ecology Studies Related to Operation of Pilgrim Station, Semi-annual Report No. 9. Boston Edison Company.
19
E SECTION Y HIGHLIGHTS E
- 1) Atlantic cod eggs were absent from the February 1991 collec-tions for the fourth consecutive year. Recent low densities are consistent with a regional downturn in the size of the spawning population.
- 2) In contract Atlantic mackerel eggs remained abundant in June 1991 as in June 1988, 1989, and 1990. Recent high egg counts probably reflect relatively strong stock biomass. May and June 1991 mackerel larval densities were also relatively high.
- 3) Fourbeard rockling, hakes, and labrid eggs were uncommon in June and July. In each case mean monthly densities for 1991 ranked below corresponding values observed during previous years dating back to 1975.
- 4) Rock gunnel and sculpi n larvaa were relatively abundant in February 1991. The February 1991 density for rock gunnel a
exceeded all previous February values while that for sculpin l exceeded every other February but one. Shorthorn sculpin contributed the majority of-larval sculpin during both high-raitking years. S)_ Larval tautog and cunner were be*h absent from the July 1991 collections. This occurred only two other years for tautog, in both cases when both CWS pumps were off. Similarly cunner were absent from the July catch only one other year, also when I both CWS pumps were_off. September 1991 mean densities for l 20 g i g l N l
both tautog and cunner exceeded all previous September values by a small margin. l
- 6) No lobster larvae were obtained in the 1991 ichthyoplankton
- collections.
- 7) No unusually high densities requiring contingency sampling were recorded in 1991.
I I I I I I I I I I I I 21 I
f' j I I I I
,i I
Figure 4. Mean monthly densities per 100 m8 of water in the I PNPS discharge canal for the eight numerically g dominant egg species and cotal eggs, 1991 (dashed line). Solid lines encompassing shaded area show E high and low values over the 1975-1990 period. Brgvoortia tyrannus Labridae-Pleuronectes I Gadidae-Glyptoceohalus Scomber scombrus Enchelyonus-Urochvcis Paralichthys-Scophthalmus Peorilus Hippoalossoides p]At;essoides l-Prionotus spp. Total eggs
- 5 I
I I I I 22
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I I I I I: Figure 5. Mean monthly densities per 100 m2 of water in the PHPS discharge canal for the eleven E numerically dominant larval species and 3 total larvae, 1991 (dashed line). Solid lines encompassing shaded area show high s and low values over the 1975-1990 period. Clunea harenaus Ulvaria subbifurcata Enchelv,qpng cimbrius Pholis aunnellus Myoxocechalus spp. Ammodytes sp. - Linaris spp. Scomber scombrug Tautoca onitis Pleuronectes americanus Tautocolabrus adspersus Total larvae en E_ I I I I I u g a w
i l l CLUPEA HARENGUS ENCHELYOPUS CIMBRIUS LARVAE LARVAE I. 10 1000 I. N-A ,-: ; n 100 r d f: *t ~o k, m
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- 1991
+191l I. J I
J I PLEURONECTES AMERICANUS LARVAE TOTAL LARVAE 1000: I~ 100; / . g b l i w i;4 2fs a . . 10 g _f f k
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!I I 29 I
Table 1. Species of fish eggs (E) and larvae (L) obtained in ichthy;plankto mllections frm the Pilgrim Nuclear Power Station discharge canal, January-Deceber 1991. Lines indicate peak periods for the mre abundant species. Secies Jan Feb _ Kar Apr Rif Jtp Jul Aug 3 Oct br Dec Atlantic menhaden Brevoortla IIrannt:s E -E- -E-L L Atlanticherring t h harSnate L L -L- L L -L-Bay anchovy Anchoa allchilli E E E Anchovy Mdjoa spp. L L L fourteard rockling Enchelvopu:; cinbrius E -E E- E E E E E L L- L L L Atlantic md Gadus m rhua E E E E E E 8 L L L L Silver hike Mluccius bilirrearis E E E E L L Poliock Pollachitti virens L L L Hakes Urophycis spp. E E E E L L L Goosefish Lophius gdcanu;i E E E Silversides Menidia spp. E L L L L Worthern pipefish SYnanathus fuscus L L L L Searobins Prionotu;; spp. E E E E EB M M M M M M M m M m M M M e m m m m
Table 1(continuedJ. Jul Atn Sap Oct Nov Dr Species Jan- Feb nir Atr Msv Jun E Grubby Myoxocephalus aenaeus '
-L L L L L L L longhorn sculpin H. octodeca: spinosus L L L L Shorthorn sculpin i;. scorplus L._tegis atlanticus L -L -L L-Seasnail L. g>hani L L Gulf snailfish L L Sap Stenotarus chrysops E E- E E E Wrasses Libridae U Tautoqa onitis L L- -L L L Tautog L L- -L L Cunner - Ia_ut_ogol_abr3:s adspersus L -L L L Radiotsishanny Ulvaria stbbifurcata Rock gunnel Etn[tsgunnellus L L- L L Cryptacanthodes m_gilatig L Wrymouth L L L L Sand lance M pittes sp. L Atlantic mcteml Sg_rtsI gggt;t -E E- E L L E E E Butterfish P_epr_i_13g triacanthus L
I
' ^ -
t Table 1 (cnntinmd). ~
~
Apr H
.r Jun Jul R:n !2_ vet fice M Jan Feb Mar S m ias E E
!allrath flounder Etroptri microstmm E
Fourspot flounder Paralichthys <dl_omar*n L L L E -E E E E E- E Windowpane Scochthalmr; rprgg;* L L L E E E E WiMaflounder Clyptomphalt cyngglag;u;; L 4 { American plaiw Himmlos&ds platewides E ~E E- E L L L l E E E Pleuronectes areri_canu;; M Wintar flounder L L- L L E E E E E Tellowtail flounder P. ferraies L L E Eogchoker Trinectes mentus
*Althrogh these eggs were not identified specificall=, they sere assuv,a to have oca:rrel as shows based on larval abutdana.
M M M M M M M M M M M M M M M M M CS M
. % 5g m m m M M M M M M m M M m m m m M M E :
Table 2. S;ecies of fish eggs (E) and lauae (L) collacted in tne FNPS E;charga canal, 1975-1971. General pariMs of occurrence for y and larvae c:rbin along the right side; for the daninant species, pariods of paat abedance are alsr, stcc in parentheses. l Species _1.975 1975 1577 1978 1979 1930 1991 1932 1%) ^ *
- 1935 1989 1937 19M 1939 190 191 PeriM cf r ws J J Tet - J m Anguilla restraia J* J J J J J L L J NT - Jai Alosa spp. L L E/L E/L E/L E/L E/L E E/L E/L E/L E/L E/L E/L E/L 4-{Je}-(Crt}Dae Erevocrtia tLrannus E/L E/L E/L E/L L L L L L L L L L L Jan - W
- L L L L L L L CI E N hirenaus L L L L L L L L L L L L Jr - M bcrna spp. L L L E E E E E/L E E E E E Ja - M 3.nitebilli Apr - Jr '
L L L L L L E/L Omarus mordax L L L L L E/L Apr - Jul E/L E E E Fresne brome E/L E/L E/L E/L E/L E/L E/L E/L E/L E/L E/L E/L E/L E/L Efi, E/L hr(Jm)-(M)Dac Enchelvom gtbdus E/L E/L E/L E/L E/L E!L E/L E/L EjL E/L E/L 71:{hj - INi>c E/L E/L EjL E/L E/L E/L E/L E/L E/L Gadus m rtna E/L E/L L L E E E Mr - Jul Malanwrax"s amlefircs L E/L E/L E/L E/L E/L E/L E/L E/L E/L E/L E/L E/L Ny(Ny) - (JmiW wrixclusbilimaris E/L E/L E/L E/L E/L E/L E/L E/L L L L L L L L Jan - Ny L L L L L t. Micrmaius tonmd L L L L L Jan-J c . h , h - E/L E/L L L E/L E/L ibilachius yJi,r_e;s E/L E/L E E/L E E/L E/L E/L E/L E/L E/L E/L yr(Eug)-(%)W Urw hicis spp. E/L E/L E/L E/L E E/L E/L E/L E/L Sap Ophidiidae-Zoarcicaa L E E E E/L E/L E/L Pay - Cet Lophiusamricanus E E/L E/L E!L L E/L E!L E/L E/L E/L E/L J:1 L ! Stromiuratafo Jul Fundulus spp. i. E Jo E E. he. E litus Oct J [. tuialis L May - M E L L L L L L L Manidia snp. L L L L E/L E/L E/L L E My- @ M.renidia E/L E/L E L L L L L L L L L L L yr - Cet Sy m athus fuscus L L L L L L
*J = juvenile.
**W Lyst and Septaber; peaks = Kar&M3y and Mvmber-Decerber.
Table 2 (continued). . Spacies 1975 1976 1977 1978 1979 19N 1991 1932 1983 1924_ 1935 19?6 1987 19R3 19 9 l'M 17?! Period of he L Jm Sebastes norvMicus Eglonotusspp. E/L E E E E/L E/L E E/L E/L E/L E/L E/L E/L E E E my(Jun) - (b;lry C;Toxocaphalus spp. L L L L L L L L E/L L E/L L L L E/L L E/L Dncimr)-(yr)J21 H.aonaeus L L L L L 1 L L L L L L E/L Jan(Mar) - (4r}hl L L L L L L L L E/L L L Jn(Mar)-(AprjMay H. octohw0inosus L L L L L L L L L L L Fab - Apr
- 5. scc"plus Aspi4rheroidas renopternius L L L L Nr - Vr L L E L L L L E/L Apr - Jul Cyclopteru;; l_trpus L L L L L L L L L L !, L L L L Jan! Apr) - (Jmpal Liparis spp. L L L L L L L L L L L L L L L Mar (@:) - (J2 pal L. atlanticus L L L L L L L L L L L Jan(Feb) - (tippr L.cohani Centrepristis striata L L L L L L L L L L Jul - Oct L L L May - Eq CvncscionIglajis Stonetonus chrTsops L L L E L L J r - Jul .
L L JcI- b; Manticirrhus s.Ltatilis L2ridae E E E E E E E E E E E E E E E E E NriMy) - (b;)Sep Tautos onitis L L L L L L L L L L L L L L L L 1. My(Jm) - (b;)) . Taut &2clabrus aisparsus L L L L L L L L L L L L L L L L L May(Jm)-(b;)Oct L L L L L L L Jan - J m L3tsmus lgpretaeformis L Ulvaria subbifurcata L L '. L L L L L L L L L L L L L L Fab ( 4 r) - (Jm M L L L L L L L L L L L L L Jan(Fej - (yr}Jr Pholis y tnellus L L L L Cryptacant!nias ramlatus L L L L L L L L L L L E6 - Apr A.Tryivtts sp. L L L L E/L L L L L L L L L L L L L Jan[Mr) - (MI)J= L Jul - b; C,eblom gintral L L L E/L E/L E/L E/L E/L E/L E/L E/L E/L E/L E/L E/L yr(My)-(J:1):q war setebra E/L E/L E/L E/L E/L L E/L E/L L E E/L E/L L E/L Eay - Cet Feprilus tIJ_acantfrs E/L E/L E/L E E E/L E/L M M M M M mW W W W W m m m a m
M M M M M M M M M M M M M M M M M - - Table 2(continwi). Spacies 1975 1R6 1977 1978 1979 193t! 1921 IM2 1933 1934 1935 1936 1937 1933 175 1990 I??1 E Pericd of Wmm Jul - Oct l L E E/L E E Ettepus nicrostaras L L E/L E L Sep - M E/L Paralichthys dontatus E/L E/L E/L E/L E/L E/L E/L E/L E/L N37 - ert E/L E/L E/L E/L E/L E/L E/L E.oblonTr* E/L Apr(May) - (M)Oct E/L E/L E/L E/L E/L E/L E/L E/L Scephthalms aTrsm* E/L E/L E/L E/L E/L E/L E/L E/L E/L E/L E/L E/L E/L E/L 51r(May) - (Jm)b E/L E/L E/L E/L E/L E E/L Glyptocaph31us emcclassus E/L E/L E/L E/L E/L E/L E/L ! E/L ElL E/L E/L E/L E/L Jc(Mar) - (Jr}h
!!irtmlossoidas platassoidasE/L E/L E/L E/L E/L E/L E/L E/L E/L E/L E/L E/L Jc( A;r ) - (JI] An ;
L E/L E/L E[L E/L E/L E/L E/L E/L Pleu:Unectes anaric m s E/L E/L E!L E/L E/L E/L E/L E/L Feb(Apr)-(Marjh E/L rl/L E/L E/L E/L E/L E E/L E.ferrminees E/L E/L E/L Ntr-Ja L E/L
- E. putnri E May - M f E E E E E/L E/L E E Trinetas reculatic L Jul - A W Sphcereidas raculatus L 43 38 37 34 42 37 36 41 0 42 34 43 35 37 35 NTier of S;Mies** 41 36 l
if.
- Alt %rjh these ens were not idantifiad specifically, they rere assma? to tuve occurred as shown bred on tha occurrence of larvaa.
1975-1978 ayf tan speies of Liigtig for 1975-190.
**For canparative purposes three species of Fjgtocephalus ere assuni for
I I ! I i I I . l APPDiDIX A* I Densitiers of fist eggs and larvae per 100 m8 of water roovedad in the PNPS dis-charge canal by species, dato, and repli-cato, January-December 1991. I '
*This Appendix is available upon request.
I I I
- I I ,
I I - - - _ _ _ _ _ _ _ _ _ _ - - - - -
I I I I I APPC NX B* I Moon anth. m of sw.a 8
'fa s.' tics and rango por 100 t- dominant bpecies of
,.Jr'-e entrained at P14 PS ,
I fish c.:gg
+4 : - J January-ccw Jer, 19?J-1991.
I *This Appendix in available upon request. d 1 I I I I I I I. I I
' l 1 i I ICitTilYOPLANKTON ENTRAINMENT MONITORING AT PILGRIM NUCLEAR POWER STATION JANUARY-DECEMBER 1991 [ Volume 2 of 2 ! (Impact Perspective) ; 4 l I
. Submitted to Eoston Edison Company 130ston, Massachusotts bY
- Marine Research, Inc.
Falmouth, Massachusetts l I ' April 4, 1992 E I I E I I
I I I TABLE Or CONTfl{IS SECTIOli l' AGE I EXECUTIVE
SUMMARY
l II INTRODUCTION 2 III IMPACT PERSPECTIVE A. Contingency Sampling Plan 3 B. Ichthyoplankton Entrainment - General 6 C. Ichthyoplankton Entrainment - Specific 7 D. Potential Pump Effects 11 E. Lobster Larvae 20 IV llIGilLIGilTS 22 I " """^""' "" ' I I I I I I I I I
I I LIST or nGuitns PIGURE 1%QE 1 Numbers of eggs estimated to have boon entrained by PHPS in 1991 had it operated at full pump ilow by species or species group (dominants only) in-cluding all egg speclec combined. The period of occurrence observed in 1991 is also indicated. 8 2 Numbers of larvao estimated to have been on-trained by PNPS in 1991 had it operated at full I pump f2ow for each dominant species including all larvao combined. The period of occurrence ob-served in 1991 is also indicated. 9 3 Hean monthly densities per 100 m' of water for 1 total eggs and total larvae entrained at PNPS within four pump operation categories during I the April-July period of 1983-1991. Values for 1983,1985, 1990 are averaged (all pumps operating) as are 1986,1988 (1 CWS pump out of service). See text for details. 16 I I LIST OF TABLES TAD 12 1 lehthyoplankton densities por 100 m8 of water ' which reached the " unusually abundant" level in PHPS entrait1 ment samples, 1980-1991. 4 LIST OP PLATES PLATE 1 Plankton not streaming in the discharge canal at Pilgrim Station for the collection of fish eggs and larvae (lobster larvae are also recorded). I A single, six-minute collection can contain sev-eral thousand eggs and Jarvae representing 20 or more species. I I 11 I
SECU ON I 1MECUTIVE SU11tiARY Entrainment sampling at the Pilgrim Nuclear Power Station (PNPS) discharge canal was scheduled twice per month during l January, February, October-Decembert weekly March through Septem- l i ber. Sampling occurred only twice in June du.: to circulating water system shutdown. PNPS operated at 58% capacity in 1991; a i refueling outage resulted in sampling with only one of two circulating water system pumps in operation from May through July. Ichthyoplankton doncities meeting the " unusually abundant" criterion defined under the contingency sampling program were not recorded in 1991, the last occasion being in Fat,ruary and March
-1988. 13ased on full load flow capacity, total numbers of eggs which may have been entrained by PNPS in 1991 were estimated to range f rom 2.1 Idllion for Atlantic menhaden to 628.7 million for the labrid-yellowtail group. Corresponding values among the eleven
.I dominant larval species ranged from 2.0 million for Atlantic herring to 108.2 million for Atlantic mackerel. Recent declines in abundance of cunner, windowpane, yellowtail flounder, and winter flounder in collections around PHPS appear to be widespread and therefore unlikely to be directly related to entrainment of eggs and larvae. An analysis of egg and larval entrainment between years with differing pump regimes indicates that larval entrainment and perhaps even egg entrainment are directly related to water withdrawal rates. No lobster larvae were collected in PNPS entrainment samples in 1991. I
I SECTION II INTRODUCTION I This report addresses results of PNPS ichthyoplankton entrainment sampling in relation to potential impact assess.nent. Discussions are based on results presented in "Ichthyoplankton Entrainment Monitoring at Pilgrim Nuclear Power Station January-December 1991", Volume 1 - Results, Work was conducted by Marine I Research, Inc. (MRI) for Boston Edison Company (BECo) under Purchase Order No. 68006 in compliance with environmental monitor-ing and reporting requirements of the PNPS NPDES Permit (U.S. Environmental Protection Agency and Massachusetts Division of Water Pollution Control). In a continuing offort to condense the volume of material presented in this and related reports, details of interest to some readers may have been omitted. Any questions or requests for additional information may be directed to Marine Research, Inc., Falmouth, Massachusetts, through BECO. Plate 1 shows the ichthyoplankton sampling not being deployed I on station in the PNPS discharge canal. I. I I I l , l
-~~ ~ ' ~ ~ ~ ~ - _ _ _ _
s I I I
,]N 1
e ,%, _ . , - ~ ~ E g, g;;sMC:s a ~i3; b ~
.= N
+
- 2
- ( % % Y :."" N.>? %..a;% 'c n .gV,% .#Q " ' .-A .i .
~
$g;:yR5 v4 g }( & s t% er. z 3 e n Q .
, ~ , . .x u t j m
- y 7T - a
~ g% ; .;
g.d, g 339.3
.4 1 d't S
l _ ':: '
$O ,g s
c . J I E Plankton net streaming in the discharge canal at Pilgrim Station for the Plate 1. collection of fish eggs and larvae (lobster larvae are also recorded). I A single, six-minute collection can conta..a several thousand eggs and Tarvae representing 20 or more species. I I I I
t SECTION III 1111$CT PERSPECTIVE A. Continaency Sanpling Plan Ichthyoplankton densities in the PNPS discharge canal meeting the " unusually abundant" criterion, defined as exceeding by 50% the highest mean density over three replicates recorded during the same month from 1975 through 1990, did not occur in 1991. This compares with no occurrences in 1989 or 1990, tuo occasione in 1988, no occurrences in 1987 or 1986, four in 1985, six in 1984, one in 1983, eight in 1982, seven in 1981, and twelve in 1980 (Table 1). No specific events were recorded prior to 1980 primarily because
" unusually abundant" was not precisely defined early in the contingency plan.
In past years it was standard practice for DECO, in consulta-tion with regulatory personnel, to authorize the collection of an additional set of triplicate entrainment samples following the recording of an unusually large density at PHPS. In most cases the additional sets were taken within two days of the original. In all but three cases when this occurred mean densities dropped back to levels within the range established over previous years, indicating that the " unusual" density probably reflected the occurrence of a high-density ichthyoplankton patch in the Rocky Point crea rather , than a more widespread phenomenon. In the three cases where high densities persisted (larval Atlantic menhaden, Brevoortia tyrannus, June 1981; larval rock gunnel, Pholis gunnellus, April 1982; larval I ' I
. - - _ _ . _ _ . . _ _ - . . _ _ _ _ _ _ _ . _ . . . _ _ _ _ _ _ _ . - _ _ ~ _ _ _ . _ _ _ _ _ _ _ _ _ . _ _ . _ _ .
I: Table 1. Ichthyoplankt on densities per 100 m3 of water which reached the
" unusually abundant"* 1evel in PNPS ent rainment samples , 1980-1991.
" Unusually abundant" Previous high Species Month density (year) densit y Iyearl Brevoortin lyrannus June 74.2 (1980) 6.2 (1978)
Sept ember 1961.9 (1982) 1.4 (1979) a " 1065.8 (1982) October 37.8 (1980) 0.2 (1918) Enchelvopus Urerhycia September 71.3 (1980) 30.1 (1479) Peorilus Uronhvcis spp. September 152.8 (1980) 22.3 (19/8) I Labrid-Limanda 6 1abrid July 12917.0 (1981) 8116.8 (1975) Scomber scombrun May 15261.3 (1985) 572.0 (1980) , 1457.6 (1985) LARVAE , Brevoortia 1JInunus June 7.1 (1981) 4.2 (1980) 495.9 (1981) 1 34.7 (1981) " " g October 11.7 (1980) 1.8 (1976) g November 24.3 (1980) 3.2 (1978) r Enche1vonus cimbrius August 204.6 (1983) 36.0 (1980) , Urophycis spp. September 105.6 (1984) 22.3 (1981) Tautoga onitis August 21.6 (1984) 4.1 (1974) September 9.2 (1980) 4.8 (1975) Tautogolabrus adsnersna June 624.5 (1981) 378.8 (1977) July 296.5 (1980) 138.5 (1974)
- 2162.5 (1981) 296.5 (1980) l September 20.3 (1980) 1,5 (1975) j Ehplia gunnellus February 19.6 (1984) 7.4 (19/5) l 13.8 (1984) " "
g j 47.5 (1985) 19.6 (1984) 3'
- i. March 70.2 (1980) 36.9 (1915) l 210.5 (1984) 70.2 (1980) 415.2 (1984) '
April 74.0 (1982) 12.1 (1977) 74.7 (1982) " 34.0 (1982)
- 22.4 (1982) " "
23.5 (1982) " " 4 5
)I i Table 1 (continued). l
" Unusually abundant" Previous high j Species Mont h density fyear) density fyear) l LARVAE (continued) i Ammodvtes sp. January 31.1 (1980) 13.5 (1975) 104.4 (1985) 31.1 (1980) h ah2I scombrus June 2700.0 (1981) 128.0 (1975) i Myoxocephalus r,pp. febrw ry 79.2 (1988) 3;.4 (19PS) f
- March 153.6 (1980) 97.0 (197$)
l 308.3 (1988) 188.7 (1986) i April 303.o (1982) 53.1 (1981) g *" Unusually abundant" was defined as $01 greater than the previous high density ig observed during the sarue month 1975-1990, l iI i . lI 1
- I t
l I . l lE I -
1 rock gunnel, February 1985, additional entrainment sampling at about two-day intervals indicated that high densities continued for up to two weeks. Since no changes in PHPS operation occurred, it appeared in those situations that productivity was generally high relative to previous years. I B. Ichthyopl_ankton Entrainment - General Entrainment of ichthyoplankton at PNPS represents a direct, - negative environmental impact since fish eggs and larvae pass through the plant in large numbers each day and are subjected to elevatad temperatures, mechanical forces, and periodic chlorina-tion. When PHPS is not on line, increased temperature is not a f actor but ichthyoplankton may still be subjected to mechanical forces and periodic chlorination when circulating seawater pumps operate. Although survival has been demonstrated for some species of fish eggs at PNPS such as the labrids (45%; Marine Research 1978, 1982) and among larvae at other power plants (0-100% initial survival depending on species and size; Ecological Analysts 1981), I_ mortality is assumed to be 100% as a conservative approach to PNPS impact assessment. To place fish egg and larval densities entrained at PNPS, expressed as numbers per 100 m8 of water, in some perspective in relation to amounts of water utilized by PNPS, they were multiplied by maximum plant flow rates over each respective period of occurrence. This was completed for each of the numerically dominant species as well as total eggs and total larvae. Mean I e
E monthly densities were multiplied by 17,461.44, the full load ilow capacity of PHPS in 100 m 8 units per 24-hour day, then by the number of days in each respective month they occurred. Values for each month in which a species or species group occurred were then summed to arrive at a seasonal entrainment value in each case (Figures 1 and 2). Among the eight numerically dominant groups, numbers of eggs entrained ranged from 2,079,658 for Atlantic I menhaden to 628,704,386 for the labrid-yellowtail group (tautog, Tautogn onitis, cunner, Tautocolabrus adspersus, yellowtail flounder, Pleuronectes icIrqaineus). Corresponding values among the eleven dominant larval species varied from a low of 2,046,481 for Atlantic herring (ClupcA harcTgun) to a high of 108,184,098 f or Atlantic mackerel (ficonber scombrus) . For all eggs and all larvae combined, values amounted to 1,325,716,178 and 288,677,765, respec-tively. These numbers indicate the vast quant.ities of eggs and larvae which can be entrained by the circulating seawater system at PNPS during a year's time and are assumed to be lost to the local fish population. I C. Ichthyonlankton Entrainment - Specific The effects of entrainment on populations of Atlantic jdi menhaden, winter flounder (Pleuronectes americanus), pollock (Pollaching virens), cunner, rainbow smelt (OsmeruE mordaK), Atlantic silversides (Menidi_a menidia), and alewives (Alosa pseudoharengus) were assessed by Stone and Webster (1975) using flow rates for two units at Pilgrim Station. Using conservative E I .
t Number of Eggs Entrained - 1991 SPECIES AND PERIOD OF OCCURRENCE _ . . _ . _ _ _ _ _ _ _ _ r _ _ _. . _ . . _ _ . Brevoortia tyrannus (June-November) 2.079.658 l Enchelyopus-Urophycis-Peprilus (April-October) 85,810.755 Cadidae-Glyptocephalus (January-November) 4.012,639 i Prionotus spp. (June-September) 2.591,103-Labridae-Pleuronectes (May-October) 628,704,38 G Scomber scombrus (May-September) 539.263.398 i i ! Paralichthys-Scophthalmus,(May-October) 50.098.443 l ce f l Ilippoglossoides platesseides (April-June) 3.434,141 Total Eggs - 1,325.716,178}1 u .. _ _ m _ . ... .. ._._..>...o._i.s . ..2m_ ._ 4 . n . intr j l 1 10 100 1000 10000 1 l (Millions) { i { Figure 1. Numbers of eggs estimated to have been entrained by PNPS in 1441 had it operated at full p.rmp iIow i by species or species group (dominants 2nly) including all egn species comb i nc.f . The perimi ot { occurrence observed in 1991 is also indicated. l i i i i
- h. 8 t
3 i E M M
- i. -. .-. . .. -. ._. - -. - ___ . . _ _ _ _
t
~
aus. sua seu uma sus aus num aus aus esu sua sua sua sus uns um sus umsl use Number of Larvas Entrained - 1991 SPECIES AND PERIOD OF OCCURRENCE __ _ -._ ! Clupea harengus (April-May, November-January) ,M_ _ . _ _ _ . 2,046,481 55,370.230 Enchelyopus cimbrius (April-November) 44,379,993 Myoxocephalus spp. (February-June) 1.257.673 1iparis spp. (March-June) 3.849,374 Tautoga-onitis (June-September) 20.187.171 Tautogolabrus adspersus (June-September) 14,010,361 l Ulvaria subbifurcata (A! ril-July) s 37,694,011 Pholis gunnellus (January-May) 23.485,288 Ammodytes sp. (January-June) , 100,184,098 Scomber scombrus (May-August) , 10.696,354 Pleuronectes americanus (April-June)
~
m 8,67 7.765
. ~ . . . . . . . . - t u sa ins Total larvac . . . _ , . . . ~ . .
10 100 1000 1 (Millions) Figure 2. thunbers of larvae est iraated to have been ent reined by PNPS in 1991 had it operated at full pump flow for each dominant species includin,,all
~
larvae cenhined. The period of occurrence observed in 1991 is also indicated. f
I assumptions and ignoring density-dependent compensation among non-entrc.ined ichthyoplankton, no appreciable adverso impact on Indigenous nopulations was predicted to occur. Modeling studies E1l conducted on five species of larval fish which appear to be more abundant in western Cape Cod Bay than in the remainder of the Bay (tautog; scannail, Idparin upp. ; radiated shanny, Ulvarin gubbifur , cata; sculpin, Hyoxocephalus spp. ; rock gunnel) suggested that the percentage of original larval production contributing to entrain- 4 ment by pHPS Unit 1 was less than 1.0 (Marine Research 1978). For twelve additional categories of eggs and Jr rae (see Marine Research 1978) considered to be more widely distributed in Cape Cod l Bay, percentages contributing to entrainment were smaller, the highest being 0.12% (labrid-Eleuroncries eggs). If entrainment of ichthyoplankton at PNPS represented a significant source of mortality in western Cape Cod day, the losses might be reflected in finfish collections in the PNPS area. A review of indicec of relative abundance for some species based on e otter trawl and gill not sampling by Massachusetts Division of I l Marine Fisheries personnel (Lawton ut al. 1990; V.J. Malkoski, personal communication) does not indicate any long-term steady declines among Atlantic herring, pollock, or tautog. Several species, on the other hand, have displayed recent declines in abundance. These include cunner, windowpane (Scochthalmus auuosus), yellowlail flounder, and winter flounder. In these cases, however, commercial landings, stock assessment research, and I I other monitoring studies indicate that these declines appear to be 10 l 5
t widespread, extending all along the Massachusetts coastline (MDMF 1985, Foster 1987, Howe et al. 1908, NOAA 1991, Marine Research 1991). Therefore, thet specific declines appear to be the result of natural population variation probably coupled with overfishing. D. Potential Pump Eff,gntu
- PNPS was involved in a long-term outage which began in April 1986 and continued into 1989. During most of this period only one -
of two main circulating water system (CWS) pumps was operating (flow = 155,000 gpm, 9.78 m8 per second, compared with 31G,000 gpm or 19.56 m8 per second, when the plant operates with two pumps). Beginning in late March 1987, intermittent use of a single circulating seawater pump made it basically unavailable for entrainment sampling, 1 caving only one or occasionally two Salt Service Water System (SSWS) pumps in service, each with a capacity of about 2500 gpm, or 0.16 m8 per second. From May through early September 1987 sampling continued with only the SSWS pump (s) providing flow for entrainment sampling. This situation also occurred from April through late August 1984 altr.cugh two SSWS pumps functioned throughout that period. During periods when sampling was completed with only SSWS pumps, ichthyoplankton densities appeared to be exceptionally low, particularly among larvae. During recent years the apparent influence of different pump regimes on densities of ichthyoplankton have been compared over the months of April-August (see MRI 1988, 1989, 1990, 1991). Results R l
I strongly suggest that larvae and to a lesser extent eggs are entrained in direct proportion to plant pumping rates. With the 1991 data base in hand these analyses were continued to determine if the relationship between densities and pumping rates remained clear. The 1991 data set complicated the analysis becauce two CWS pumps were operating during April and August while only one operated during May, Junu, and July. This effectively reduced the data base for portions nf the analysis to three months rather than I four. To compare the response of ichthyoplankton to dif ferent pump regimes, densities per 100 m8 of water were compared for single SSWS pump periods (1987), two SSWS pump periods (1984), single CWS pump periods (1986, 1988), and two CWS pump periods (1983, 1985, 1990). Statistical comparisons involving these data were initially restricted primarily to the May through August time frame when sampling was possible and the stated pump schedules were consis-tently maintained; the 1987 data set forced the exclusion of April from the statistical tests because no sampling occurred in April as 1987 due to uncertainty concerning the pump use schedule at that 5 time. The 1991 data set reduced statistical treatment to May through July. April and August data from all years analyzed were included in graphical analyses however. 'Ihe 1991 data were simply divided, April and August averaged with two-CWS-pump years, May-July with one-CWS-pump years. Collections made between April and August 1989 did not fall clearly into any specific pump use category because the plant was returning to service, and Chs pump operation varied between one and two pumps. Only J'Ine and August I a
=
I 1989 were consistently sampled under one regime (all pumps in service). When collections were first made in 1984 using the relatively l low-volume SSWS pumps, an assumption was made that ichthyoplankton
,I would continue to be sampled in proportion to its abundance in the Rocky Point area since larval finhes, especially the small ones, show little directional swimming ability and pelagic eggs certainly drift passively. Results reported in the 1986 annual PNPS report (Marine Research 1987) indicated that April-August 1984 larval entrainment collections (2 SSWS pumps only) were so low that local populations did not appear to be inpacted in similar proportion by the SSWS pumps as by the CWS pumps. When 1987 larval data became dvailable, the limited infit ence of the SSWS p'.ps became more apparent. May -August larval densities for 1987 when only one SSWS pump was used were exceptionally low each month, even when compared with 1984. Egg densities in 1987 ranked lowest over the 1983-1987 period only for August.
Mean densities per 100 m3 of water for total eggs and total larvac, May-July 1983-1991 were examined using a nonpP.rdmetTiC, single classification, Kruskal-Wallis test; data obtained on May 30, June 25, and August 19, 1987 .iere omitted because those samples were taken during brief periods of single cWS pump operation. For the Kruskal-Wallis test individual sa:.ipling dates were used. No significant dif ference was apparent among years for eggs (p = 0.05) but a very highly significant difference (p < 0.001) was found for larvae. Nonparametric rauJtiple comparisons among years for larvae I ' I
I showed no significant dif f erence (p = 0.05) among 1990, 1989, 1985, and 1983, years when the circulating water system operated at capacity for all or a portion of the season. No significant I dif ference was noted among 1991, 1988, or 1986, years when one CWS pump was out of service, although this three-year group was significantly different from the al1-pumps-operating group. However, the multiple range test was unable to separate 1985 (all pumps) from 1988 (one CWS pump), therefore a clear divisilon between the all-pumps and one-CWS-pump-0.S.S. group could not be shown statistically. Data sets from 1984 and 1987 clearly ranked below years when at least one CWS pump was in service. Statisti-cally significant differences were noted between 1984 (two ssWs pumps and 1987 (one SSWs pump), both years also differing from all other years. The summed ranks as well as results of the multiple comparisons (indicated by vertical bars) were as follows: h y July 19 M-1991 R) E SUM kMiK SUN 5 ECCS PC E _ UEAt PCMPS S 1989 - 2181 (ALL cr 1 C d 0.0.S.) 1990 - 77: (ALL) 1985 - 1074 (ALL) 1989 - 746 ( ALL or 1 CWS 0.0.S.) 1988 - 863 (1 GS 0.0.S. ) 1983 - 679 (ALL) 680 (ALL) 1985 - 640 (ALL) 1990 - 394 (All) 1988 - 558 (1 GS 0.0.S. ) 1991 - 333 (1CWS0.0.S.) 1986 - 489 (1CWS0.0.S.) 1987 - 302 (1SSWS) 1991 - 475 (1CWS0.0.S.) 1986 - 291 (1CWS0.0.S.) 1984 - $18 l (2SSWS) 1984 - 152 (2SSWS) 1987 - 189 l (1 SSWS) 10.01 n.s. Kruskal-WallisCoefficient 37.11*** 0.0.S. = Out of Service 14 Nl l
I l l'igure 3 presents the monthly means averaged within pump operation categories for the April-August time frame. Data for Hay-August 1990 were averaged with the corresponding data irom 1983 and 1985, the years of Iull operation. Data for April 1990 when only one CWS pump was in service were averaged with April 1986 and 1988. Similarly April and August 1991 were averaged with 1983 and 1985 when all pumps operated; May, June, July were averaged with i 1986, 1988, and 1990, periods with one CWS pump. Larval densities separated distinctly, particularly when sampling occurred orly with one or two salt service water pumps. Data for 1989 with mixed pump usage varied between the all and one CWS pump regimes but in a consistent manner. June and August with all pumps in service during each sampling period ranked above the other yects. May and July with two of five and one of four dates with all pumps in g service, respectively, showed monthly means which f c11 between the all and one CWS pump values. April, also having one of f our dates with all pumps operating, fell below the one CWS pump category but well above the twa SSWS pumps mean for that month. The fact that the overall Pay-July data set for 1990 larvae ranked significantly higher than 1983 and 1985, the other full-operation years, suggests that larvao were relatively abundant during the late-spring and early-summer of 1990. Similarly, that 1989 ranked just below 1990 and was not found to be significantly different from 1990, in spite of the six dates when one CWS pump was out of service, suggests that b general larvas were relatively abundant during that period. I r. concast , the low ranking of 15 .E
4 4 Fish Eggs Fish Larvae t i Mean Density /100 Cubic Meters I Mean Density /100 Cubic Meters l 10000:- - - -- - - - - - 1000 r--- - - - - - - - -- p- ., _ _s i
/ -.
? _, /'.=
7
/
j l\_ j N N, 100J' -' 1000 : N;si. g-- .4 i s. -
, /
/ '
./
j 10{
~ 100
!I :
V ! 4
., IL l;
)
/ x <
t V 10If 'g I I O.1 't [ i' t 1
'r - ,
f g _ . . _ , _ . . __n___...t_. > I 0.01 -- -
-'-------I I Apr May Jun Jul Aug Apr May Jun Jul Aug
- 1SSWS - 2 SSWS 1 CWS O.O.S. '~ 1SSWS - 2 SSWS 1C 1 0.0 S ALL -~ 1-2 CWS O.O.S. ALL -- t-2 CWS O O.S l PHPS Data. PNPS Data.
t l L_._.-_.__..._. _ __ --_ _ - - - - . - - rigure 3. Mean monthly densities per 100 m$ of water for total eggs and total larvae entrained at PNP 5 within four pump operation categories during the April-Augu t period of 1983-1991. See text for details. e EM M M M M m W W W M M M m me e m a m-
{ 'l larvae during the May-July 1991 period even among one CWS purnp periods suggests larvae were relatively uncommon then; a review of I the data indi~;ated that July catch rates were particularly low. The apparent reduced susceptibility of larvae to the SSWS pumps uns further indicated 1:y sampling on May 30, 1987 when collections were made while one CWS pump was placed into service for a short period. On May 28 no larvae were obtained while sampling under the influence of one SSWS pump. Two days later on May 30 a mean density of 132 larvae per 100 m' was obtained consisting of eight species. On June 4, again with only one DSWS E pump operating, two larval species with a combined mean density of 2 per 100 m' of water were taken. A comparison of the number of ichthyoplankton species recorded from May through July over the 1983-1991 period indicated that 1987 was clearly the lowest with 13 overall (22 with inclusion of the three dates when one CWS pump was in use); 1984 followed with 25. Numbers of species ranged from 29 (1986) to 34 (1989) during years when at least one CWS pump was in use. The low species count in a 1987 was due primarily to a scarcity of larvae. Only six species of larvae were recorded over the May-July period of 1987 compared with 16 (1984) to 30 (1985, 1989) over the other years. Numbers of egg species were somewhat more consistent with 12 being taken ir. 1987 compared with 14 (1987 and 1988) to 20 (1991) during the other years. Including May 30 and June 25 1987 when a single CWS pump was in service brought the 1987 totals up to 14 species of eggs and 14 species of larvae. I I
I The low densities of larvae in 1984 and the strikingly low densities in 1987 over the spring and early-summer period strongly suggest that ichthyoplankton populations near PNPS were not I impacted in similar proportion by the SSWS pumps as by the main circulating seawater pumps. A sharp decline in larval densities occurred between 1984 and 1987 values, suggesting that dropping from two to one SSWS pump eliminated entrainment of many larvae. The intermediate values for 1986, 1988, and 1991 when one CWS pump I was in service, ranking between 1984/1987 and 1983/1985/1990 suggests a direct relationship between pump flow and larva) entrainment. Values for 1989 with variable pump operation further support this conclusion (Figure 3). Apparently the relatively low flow of the SSWS pumps has very limited influence on drawing larvae into the intake embayment area and subsequently through the PNPS condensors. These results could reflect mainly physical flow effects acting upon free-floating larvae or perhaps an active larval swimming ability, permitting an increasing number of tnem to 5 avoid entrainment as pump capacity declines. For example, at some I point water entrained by the PNPS intake separates from the prevailing Cape Cod Bay current and enters the intake area. The area over which the flow separation occurs is presumably more widespread and the action rore forceful (the velocity higher) when two seawater pt perate than when only one seawater pump operates, or ev.o when one or twa SSWS pumps operate. Passive larvae and eggs should be entrained in proportion to their abundance, but more active larvae may swim, to the extent of their 18 5 t
l 6 ability, to remain within the Cape Cod Bay water mass. Also the more widespread the influence of a particular pumping rate, the higher the probability tht.t high-density ichthyoplankton patches will be entrained. The role which vertical diacribution plays may be of great importance as wels , as the smaller pumps probably draw water over a more restricted vertical profile, one which may not coincide with the presence of many eggs and larvae. Although no significant difference was detected among years for total eggs, years did rank in similar manner to the larvae. Notable exceptions occurred with 1988 (one CWS pump) which ranked third among the eggs and 1990 (2 CWS pumps) which ranked third among the fully operational years and fifth overall. The one SS% and two SSWS pump years (1984 and 1987) again ranked low. As mentioned for larvae, the high ranking of 1989 among the eggs taken from May through July, when one CWS pump was out of sarvice on six occasions, suggests that eggs were generally abundant during those months. Likewise the low ranking of 1986 eggs when only one CWS pump was out of service suggests egg densities were low that May-July period. It is important to keep in mind that all comparisons based on different pump cap & cities were made without knowledge of ichthyo-plankte, populations around Rocky Point. The observed rankings could have been due entirely, or in part, to differences in production among the nine years, although that would appear to be an extraordinary coincidence given the well-defined relationship between ichthyoplankton densities and PNPS flow. Perhaps, on the 19
I contrary, the f act that densities ranked according to pump capacity in spite of high inter-year variability suggests how strong this relationship may be. I E. L o b s t e r L a r_Yl LC I The scarcity of larval lobsters (liomarus anericanua) in PHPS entrainment samples is most interesting considering that, in 1980, 918 tons of legal-sized lobsters were landed in Plymouth County by - commercial lobstermen with-a value of four million dollars (Lawton et al. 1983). Among lobstermen working inshore waters, this increased to 1381 tons valuud at $6,8 million in 1985 (Hoopes 1986) and 1485 tons valued at $7.5 million in 1986 (Hoopes 1987). Over the next four years, following a drop to 1262 tons in 1987, landings rose steadily to 1454 tons in 1990. Value of those landings varied from $7.1 to $8.1 million (Hoopes 1988, 1989, 1990, 1991). Neuston sampling conducted in the northwest sector of Cape Cod Bay (Lawton et al. 1983; Matthiessen and Scherer 1983) also indicated that larvac were not particularly abundant there. To I_ support such a strong fishery it would appear young lobsters must arrive in the Plymouth area from other regions. Sampling around Rocky Point from 1974 through 1977 showed considerably more late-stage larvf e than young larvae (Lawton et al.1983) . That, coupled with the prevailing counterclockwise Cape Cod Bay currents, suggests that larvae may arrive from the north. Sampling at the mouth of the Cape Cod Canal also suggests that large numbers of larvae enter Cape Cod Bay from Buzzards Bay and perhaps the Canal I a m
i I itself (MatthieFSen and Scherer 1983; MatthicGsen 1984). Regard-less of source, larval lobsters appear to be especially uncommca in PNPS entrainment samples. Th.is is supported by Lawton et al. (1983) who caught only eight larvae in twenty nouston tows near shore around Rocky Point in 1975. In addition to their apparent scarcity in near-shore waters, larval lobsters' neustonic habits may reduce the probability of their antrainment since they would contact the PNPS int.ake skimmer wall which might prevent some from passing to the condensers. Reduced intake flow during the extended outage period covering the 1986-1989 larval seasons no doubt lowered the probability of lobster entiainment even further. I I I I-I I I 3 5 21 B
I SECTION IV lilGliLIGHTS
- 1) Ichthyoplankton densities in the PNPS discharge canal meeting the "ur usually abundant" criterion defined under the contingency sampling plan did not occur in 1991.
I
- 2) Total numbers of eggs and larvae which may have been entrained by PriPS in 1991 were estirc.Lted to range from 2.1 million for _
Atlantic menhaden eggs to 628.7 million for labrid-yellowtail eggs Lad from 2.0 million for Atlantic herring larvae to 108.2 ] million for Atlantic mackerel larvae.
- 3) Recent declines in cunner, windowpane, yellowtail floundu ,
and winter flounder appear to parallel more widespread declines and to be the result of natural population variation, probably coupled with overexploitation, rather than to be directly related to PNPS entrainment. _
- 4) Analysis of entrainment data collected from April through August 1983-1991 strongly suggests that larvae and to a lesser extent eggs are entrained in direct proportion to plant pumping rates.
I
- 5) No larval lobsters were collected in PNPS entrainment samples in 1991. The low numbers taken in discharge samples remains I surprising considering the strong commercial lobster fishery in the area.
22 a.
I I l SECTION V LITERATURE CITED Ecological Analysts, Inc. 1981. Entrainment survival studies. I Research Report EP 9-11. Submitted to Empire State Electric Energy Rasearch Corporation, New York. Foster, K.L. 1987. Status of winter flounder (PSmidopleuronectes I americanus) stocks in the Gulf of Maine, Southern New England, and Middle Atlantic areas. Woods Hole Lab. Ref. Doc. 87-06, National Marine Fisheries Service. 60p + appendix. Hoopes , T.B. 1986, 1985 Massachusetts Lobster Fishery C ?stics. Technical Series 20. Masssachusetts Department of Fisneries,
- g. Wildlife and Environmental Law Enforcement. Division of 3 Marine Fisharles. 17p.
1987. 1986 Massachusetts Lobster NShery Statistics. I Technical Series 21. Massachusetts Department of Fisheries, Wildlife and Environmental Law Enforcement. Division of Marine Fisheries. 20p.
. 1988. 1987 Massachusetts Lobster Fishery Statistics.
Technical Series 22. "assachusetts Department of Fisheries, Wildlife and E n v i r o r..< n t a l Law Enforcement. I Marine Fisheries. 17p. Division of 1989. 1988 Massachusetts Lobster Fishery Statistics. I Technical Series 23. Massachusetts Department of Fisheries, Wildlife and Environmental Law Enforcement. Division of Marine Fisheries. 17 p.
. 1990. 1989 Massachusetts Lobster Fishery Statistics.
Technical Series.23. Massachusetts. Department of Fisheries, Division of I Wildlife and Environmental Law Enforcement. Marine Fisheries. 22 p. 1991. 1990 Massachusetts Lobster Fishery Statistics. I Technical Series 23. Massachusetts Department of Fisheries, Wildlife and Environmental Law Enforcement. Division of Marine Fisheries. 22 p. Howe, A.B., T.P. Currfer, t L.S. Sass, and J.B. O'Gorman. 1988. Coastwide fishery resource assessment - coastal Massachusetts. Massachusetts Division of Marine Fisheries. 12p + appendix. I. Lawton, R., E. Koulcheras, P. Brady, W. Sides, and M. Borgatti. 1983. Distribution and abundance of larval American lobsters, I Homarus americanus Milne-Edwards, in the western inshore region of Cape Cod Bay, Massachusetts, p. 47-52. .in : M.J. Fogarty (ed.), Distribution and relative abundance of American 23 !I
I looster, HomargE nngrinanus, larvae: New England investiga-tions during 1974-1979. NOAA Technical Report NMFS SSRF-775. 64p. Lawton, R.P., B.C. Kelly, V. J. Halkoski, M. Borgatti, J.F. Battaglia, and D. Pichette. 1991. Annual report on monitor-ing to assess impact of Pilgrim Nuclear Power Station on marine fisheries resources of western Cape Cod Bay. (Charac-terization of the fisheries resources. ) Project Report No. 50 (January-December 1990) . III.A.1. 1-54. 1D: Marine Ecology 3 Studies Related to Operation of Pilgrim Station, Semi-annual report No. 37. Boston Edison Company. 3 s Marine Research, Inc. 1978. Entrainment investigations and Cape Cod Bay ichthyoplankton studies, March 1970-June 1972 and - March 1974-July 1977. Volume 2, V.1-44. 1D: Marine Ecology Studies Related to Operation of Pilgrim Station. Final E Report. July 1969-December 1977. Boston Edison Company. E
\
. 1982. Supplementary winter flounder egg studies conducted 3 at Pilgrim Nuclear Power Station, March-May 1982. Submitted g to Boston Edison Company. 4p.
. 1987. Ichthyoplankton entrainment monitoring at Pilgrim Nuclear Power Station January-December 1986, Volume 2 (Impact Perspective). 17p. ID: Marine Ecology Studies Related to Operation of Pilgrm Station. Semi-annual Report No. 29.
Boston Edison Company..
, 1988. Ichthyoplankton entrainment monitoring at Pilgrim Nuclear Power Station January-December 1987, Volume 2 (Impact Perspective). 17p. ID. Marine Ecology Studies Related to Operation of Pilgrm Station. Semi-annual Report No. 31.
Boston Edison Company.. 8 - 5
. 1989. Ichthyoplankton entrainment monitoring at Pilgrim Nuclear Power Station January-December 1988, Volume 2 (Impact g Perspective). 22p. ID: Marine Ecology Studies Related to g Operation of Pilgrm Station. Semi-annual Report No. 33.
Boston Edison Company..
. 1990. Ichthyoplankton entrainment monitoring at Pilgrim Nuclear Power Station January-December 1989, Volume 2 (Impact Perspective). 23p. ID: Marine Ecology Studies Related to g.
Operation of Pilgrm Station. Semi-annual Report No. 35. 3 Boston Edison Company..
. 1991. Ichthyoplankton entrainment monitoring at Pilgrim Nuclear Power Station January-December 1990, Volume 2 (Impact Perspective). 22p. In: Marine Ecologv Studies Related to Operation of Pilgrm Station. Semi-annual Report No. 37. E Boston Edison Company.. 5 24 5
1 l
1 I MDMF (Massachusetts Division of Marine Fisheries). 1985. Massa-chusetts marine fisheries assessment at mid-decade. Economic, environmental, and management probl2ms facing Massachusetts' I commercial and recreational marine fisheries. Boston. 31p. Matthiessen, G.C. 1984. The seasonal occurrence and distribution I of larval lobsters in Cape Cod Bay. p103-117. ID: J.J. Davis and D. Merriman (eds.), Observations on the Ecology and Biology of Western Cape Cod Bay, Massachusetts. Springer-l Verlag. 289p. and M.D. Scherer. 1983. Observations on the seasonal occurrence, abundance and distribution of larval lobsters I- (BQRanLE americaDMS) in Cape Cod Bay, p41-46. In: M.J. Fogarty (ed.) Distribution and relative abundance of American lobster, Homarus americarlun, larvae: New England investiga-I tions during 1974-79. NOAA Technical Report. NMFS SSRF -775. 64p. I NOAA (National Oceanic and Atmospheric Administration). Status of the fishery resources off the northeastern United States for 1990. 1991. NOAA Technical Memorandum NMFS-F/NEC-81. 130p. I Stone and Webster Engineering Corp. 1975. 316 Demonstration Pilgrim Nuclear Power Station Units 1 and 2. Boston Edison Company. I I I I I I I I 25 E
I y y I IMPINGEMENT OF ORGANISMS AT PILGRIM NUCLEAR POWER STATION (January - December 1991) l I I !
.I ann, Prepared by: dd 44 Q Lisv 6 n q Robert D. Anderson Senior Marine fisherles Biologist I
I
)
g ! Regulatory Affairs Department 1 Licensing Division Boston Edison Company I I ^ar" '"2 I i-I
3 E E E impinged species l~ E E E E E E
~- ' ~ ~ - - ~ . ___ -
I I Stdion ILile Eage 1
SUMMARY
l I_ 2 INTRODUCTION 2 _ 3 METHODS AND MATERIALS 5 I 4 RESULTS AND DISCUSSION 7 4.1 Fishes 7 4.2 Invertebrates 19 4.3 Fish Survival 23 g 5 CONCLUSIONS 25 I 6 LITERATURE CITED 27 I I I I I I ' I
r LISL0f._flGURES g Lt.gure Page 1 Location of Pilgrim Huclear Power Station 3 2 Cross-Section of Intake Structure of Pilgrim 4 Nuclear Power Station
. 3 Trends of Intake Hater Temperature, and Number 12 of Fish Captured by month from Pilgrim Station Intake Screens for the Five Most Abundant Species Collected, January-December-1991 5
4 Relationship of Pilgrim Station Circulating 15 Hater System (CHS) Pumps' Operation (Pump Flow) to Fish Impingement Rate for the Period 1986-1991. I I I I iI l I
I LISI_Of_lL&IES g nm i 1 The 300 foot long Pilgrim Station, concrete screenwash sluiceway is molded from 18" corrugated metal pipe, and meanders over breakwater rip rap. I 2 Fish survival testing is done at the end of the sluiceway where it discharges to ambient temperature irtake waters. I I I - I I I I I I
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LISLOI_ TABLES IAble EAge 1 Monthly Impingement for All fishes Collected from 8 Pilgrim Station Intake Screens, January-December 1991 2 Species, Number, Total Length (mm), Weight (gmD 9 and Percentage for All fishes Collected Fmm Pilgrim Station Impingement Sampling, January-I December 1991 3 Annual Impingement Collections (1981-1990) ior 10 . the 10 Most Abundant Fishes From Pilgrim Station Intake Screens During January-December 1991 4 Approxi.nate Number and Cause for Most Notable Fish 14 Mortalities at Pilgrim Nuclear Power Station, 1973- ~ 1991 5 5 Impingement Rates per Hour, Day and Year for All 17 Fishes Collected from Pilgrim Station Intake Screens During January-December 1991 I IV I I ,
I lable Eage 6 Impingement Rates Per Hour, Day and Year for 18 < All Fishes Collected from Pilgrim Station Intake Screens During 1973-1991 7 Monthly Means of Intake Temperatures ('F) Recorded 20 During Impingement Collections at Pilgrim Nuclear Power Station, 1982-1991 I 8 Monthly Impingement for All Invertebrates Collected 21 from Pilgrim Station Intake Screens, January-December 1991 9 Survival Summary for the Fishes Collected During 24 Pilgrim Station Impingement Sampling, January-December l 1991. Initial, One-Hour and Latent (56-Hour) Survival I Numbers are Shown Under Static (8-Hour) and Continuous l Wash Cycles I I I V I
SECIlotLI
SUMMARY
l Fish impingement rate averaged 6.27 fish / hour during the period January-December 1991, which is the highest rate since 1981 when there was also a large impingement incident. Atlantic herring (Clypen haremgyi huangui) accounted for 75.4% of the fishes collected. Atlantic silverside (Heald1A _ melidlA), Atlantic menhaden (Ereyoortia tyrannus), and winter flounder (Pleuronsiti perinnus) accounted for 8.7, 3.6 and 2.1%, respectively, of the fishes impinged. The peak period was July 22-25 when an Atlantic herring I impingement incident accounted for an estimated 4,200 of this species on the inteke screens. Initial impingement survival for all fishes from static screen wash collections was approximately 57%, and from continuous screen washes 50%. Delayed mortality data was incomplete do to failura of the screenwash survival pools, lost fishes or sampling in the screenhouse during portions of 1991. 1
- At 100% yearly (January-December) operation of Pilgrim Nuclear Power Station (PNPS) the estimated impingement was 54,925 fishes (784 lbs.). The PNPS capacity factor was 58% during 1991.
I The collection rate (no./hr ) for all invertebrates captured from January-December 1991 was 1.40+. Jellyfish and blue mussels (undetermined numbers), common starfish (hterias forbell). and sevenspine bay shrimp (Crarna leplenipinon) were most numeious, the latter species account'ng for approximately 25.4 and 22.31, respectively, of the enumerated invertebrates impinged. Mixed species of algae collected on intake screens amounted to 2,880 pounds.
I SECIl0H.2 IN18000CIl0B Pilgrim Nuclear Power Station -(lat. 41'56' I N, long. 70'34' H) is located on the northwestern shore of Cape Cod Bay (Figure 1) with a licensed capacity of I 670 MWe, The unit has two circulating water pumps with a capacity of approxi-mately 345 cfs each and five service water pumps with a combined capacity of 23 cfs. Water is drawn under a skimmer wall, through vertical bar racks spaced approximately 3 inches on center, and finally througi. vertical travel-ling water screens of 3/8 inch wire mesh (Figure 2). There are two travelling water screens for each circulating water pump. This document is a report pursuant to operational environmental monitoring and repo. ;ing requirements of NPDES Permit No. 0003557 (!!SEPA) and No. 359 (Mass. DWPC) for Pilgrim Nuclear Power Station, Unit I. The report describes im-pingement of organisms and survival of fishes carried onto the vertical trav-eiling water screens at Unit 1. It presents analysis of the rr itionships apong impingement, environmental factors, and plant operational variables. The report is based on data collected from screen wash samples during January-December 1991. I I i I I E M
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.I MEIBOQS_MD_BATERIALS I
Three screen washings each week were performed from January-December 1991 to provide data for evaluating the magnitude of marine biota impingement. The total weekly collection time was 24 hours (three separate 8-hour periods: morning, af ternoon and night). Two collections represented dark period sam-I pling and one represented light period sampling. collection period, all four travelling screens were washed. At the beginning of each Eight hours later, the screens were again washed (minimum of 30 minutes each) and all or-ganisms collected. When screens were being washed continuously, one hour col-
~I lections were made at the end of the regular samnling periods, and they repre-sented two light periods and one dark period on a weekly basis.
Water nozzles directed at the screens washed impinged organisms and debris into a sluiceway that flowed into a trap. The original trap was made of gal-vanized screen.(3/8-inch mesh) attached to a removable steel frame and it col-lected impinged biota shortly after being washed off the screens. A second
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trap was designed and used for sampling, in conjunction with sluiseway sur-vival studies, consisting of a section of half 18" corrugated metal pipe with 3/16-inch nylon, delta mesh netting attached. Impinged biota sampled by this trap were collected at the end of a 300' slutteway where initial, one-hour and latent (56-hour) fish survival were determined for static (8-hour) and contin-uous screenwash cycles. Plates 1 and 2 provide views of the beginning and end of this sluiceway structure which was constructed in 1979. I I I +
Variables recorded for organisms were total numbers, and individual total lengths (mm) and weights (gms) for up to 20 specimens of each species. A ran-dom sample of 20 fish or invertebrates was taken whenever the total number for a species exceeded 20; if the total collection for a species was less than 20, all were measured and weighed. Fielo work was conducted by Marine Research, Inc. Intake seawater temperature, power level output, tidal stage, number of circu-lating water pumps in operation, time of day and date were recorded at the time of collections. The collection rate (#/ hour) was calculated as number of organisms impinged per collecting period divided by the total number of hours in that collecting period. Beginning in 1990, if all four intake screens are not washed for a rollecting period then the number of fishes collected is increased by a proportional factor to account for the unwashed screens, as requested by the. Pilgrim Administrative-Technical Committee. Common and scientific names in this report follow the American Fisheries Society (1988, 1989 and 1991) or other accepted authority when appropriate. I I I I I E
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