ML051300288

Annual Environmental Protection Plan Operating Report

ML051300288
Person / Time
Site:	Millstone
Issue date:	04/28/2005
From:	Price J Dominion Nuclear Connecticut
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
05-110
Download: ML051300288 (14)

Text

Dominion Nuclear Connecticut, Inc.

Millstone Power Station gJ Dominion, Rope Ferry Road Waterford, CT 06385 APR 2 8 2005 U.S. Nuclear Regulatory Commission Serial No.05-110 Attention: Document Control Desk NSS&L/DF RO Washington, DC 20555 Docket No. 50-423 License No. NPF-49 DOMINION NUCLEAR CONNECTICUT, INC.

MILLSTONE POWER STATION UNIT 3 2004 ANNUAL ENVIRONMENTAL PROTECTION PLAN OPERATING REPORT In accordance with Section 5.4.1 of the Environmental Protection Plan (EPP), Dominion Nuclear Connecticut, Inc. hereby submits the Annual Environmental Protection Plan Operating Report, describing implementation of the EPP for the previous year. transmits information for the period January 1, 2004, to December 31, 2004.

Should you have any questions regarding this report, please call Mr. Paul Blasioli, Environmental Services, at (860) 447-1791, extension 0417.

Very truly yours, J. e Price Sit ice President - Millstone

,::j 06

Serial No.05-110 Docket No. 50-423 License No. NPF-49 Page 2 of 2 Enclosure (1)

Commitments made in this letter: None.

cc: U.S. Nuclear Regulatory Commission Region I 475 Allendale Road King of Prussia, PA 19406-1415 Mr. G. Wunder Project Manager U.S. Nuclear Regulatory Commission One White Flint North 11555 Rockville Pike Mail Stop 08-B-1A Rockville, MD 20852-2738 Mr. S. M. Schneider NRC Senior Resident Inspector Millstone Power Station

Serial No.05-110 Docket No. 50-423 License No. NPF-49 Enclosure I Millstone Power Station, Unit 3 Annual Environmental Protection Plan Operating Report January 1, 2004 - December 31, 2004

Annual Environmental Protection Plan Operating Report January 1 - December 31, 2004 Millstone Unit 3 Environmental Protection Plan Dominion Nuclear Connecticut, Inc.

Millstone Power Station Rope Ferry Road Waterford, Connecticut 06385 April 2005

2004 Annual Environmental Protection Plan Operating Report (AEPPOR)

1. Introduction This report covers the period January 1, 2004 through December 31, 2004.

During 2004, Millstone Power Station Unit 3 (MP3) operated at a capacity factor of 88.5%; this included a 37-day refueling outage (3R09 4/3/04 - 5/9/04). The capacity factor from the end of the refueling outage until the end of 2004 (cycle

10) was 98.5%.

As required by the MP3 Environmental Protection Plan (EPP), this AEPPOR includes:

• summaries and analyses of the results of environmental protection activities, a list of EPP noncompliances,

• a list of all changes in. station design or operation -which involved a potentially significant unreviewed environmental question, and a list of non-routine reports, describing events that could have'resulted in significant environmental impact.

2. Environmental Protection Activities 2.1 Annual National Pollutant Discharge Elimination System (NPDES) Report of Ecological Monitoring (EPP Section 4.2)

Paragraph 5 of the Millstone Power Station (MPS) NPDES permit requires continuation of biological studies of supplying and receiving waters, entrainment studies, and intake impingement monitoring. These studies include analyses of intertidal and subtidal benthic communities, finfish communities,- entrained plankton, lobster populations, and winter flounder populations. Paragraph 7 of the permit requires an annual report of these studies to the Commissioner of the Connecticut Department, of Environmental 'Protection (DEP). The report that fulfills these requirements for 2004, Annual Report 2004 - Monitorina the Marine Environment of Lonq Island Sound at Millstone Power Station, Waterford.

Connecticut (Annual Report), presents results from studies performed during construction and operation of.MPS, emphasizing those of the latest samplingyear. Changes'to' the biological communities noted in these studies are summarized in' the Executive Summary section of the Annual Report, which is attached as' part of this report.

2004 AEPPOR Page 1 of 3

Table 1. MP3 NPDES Data Summary, Jan. 1 - Dec. 31, 2004.

Selected water quality parameters for Unit 3(1).

max discharge discharge discharge discharge avg max max SwS flow (max) pH range temp. range temp. (avg) AT FAC TRC FAC 1gpd) (OF) (OF) (CF) (ppm) (ppm) (ppm)

Jan. 1357 8.1-8.2 47.9-65.3 56.1 18.1 0.13 0.03 0.23 Feb. 1357 8.1-8.3 50.7-56.3 53.2 17.3 0.15 <0.03 0.21 Mar. 1357 8.1-8.3 52.5-58.9 54.4 15.1 0.20 0.04 0.20 (2)

Apr. 1357 7.4-8.3 38.5-56.2 44.0 1.3 <0.03 0.24 May 1357 8.1-8.3 44.0-74.6 62.0 9.8 0.11 0.04 0.20 June 1357 8.1-8.3 70.3-81.3 75.7 13.1 0.16 0.04 0.20 July 1357 7.9-8.3 76.8-86.2 81.2 15.5 0.16 0.04 0.19 Aug. 1357 7.7-8.0 82.1-89.9 84.7 15.5 0.08 0.06 0.20 Sep. 1357 7.7-7.9 81.5-91.0 84.8 15.7 0.11 0.05 0.17 Oct. 1357 7.8-7.9 73.2-84.3 78.1 16.0 0.14 0.04 0.22 Nov. 1357 7.8-7.9 64.6-79.6 69.9 16.8 0.22 <0.03 0.19 Dec. 1357 7.7-7.9 57.1-76.7 63.6 17.7 0.13 <0.03 0.21 Notes:

' Parameters are measured at MP3 discharge (DSN 001 C), except for TRC, which is measured at MPS discharge (quarry cuts; DSN 001), and SWS FAC (service water system; DSN 001 C-5).

(2) For April 2004, no MP3 circulating water chlorine injection occurred, due to the scheduled refueling outage.

Abbreviations Used:

Temp. = Water Temperature AT = Delta-T (difference between discharge and intake water temperature)

FAC = Free Available Chlorine TRC = Total Residual Chlorine SWS = Service Water System 2004 AEPPOR Page 3 of 3

Attachment to 2004 Annual Environmental Protection Plan Operating Report January 1 - December 31, 2004 Executive Summary Section of "Annual Report 2004 - Monitoring the Marine Environment of Long Island Sound at Millstone Power. Station, Waterford, Connecticut" dated April 2005

ANNUAL REPORT 2004 Monitoring the Marine Environment of Long Island Sound at Millstone Power Station, Waterford, Connecticut

~,,

& mIio Millstone Environmental Laboratory-April 2005 omnn

Executive Summary EcIgrass MPS thermal discharge. These changes are not widespread, and remain restricted to approximately Historically, eelgrass has ranged to far western 150 m of shoreline on the east side of the power plant reaches of Long Island Sound (LIS), but over the last discharge to LIS.

century has become restricted to the easternmost third Seasonal shifts in occurrence of annual algal of the Connecticut coastline, where it remains as a species were noted at Fox Island-Exposed (FE) locally important habitat former. Near Millstone during 2004. These shifts included abbreviated Power Station (MPS), eelgrass shoot density, seed- season for cold-water species (e.g., Monostroma bearing shoot abundance, shoot length, standing stock grevillel, Spongomorpha arcta, and Dumontia biomass, and distribution were monitored during contorta) and extended season for warm-water summer months from 1985 to 2004 at three locations species (e.g., Grinnellia americana, Dasya (Jordan Cove, JC; White Point, WP; and Niantic baillouviana, and Bryopsis hypnoides). Similar shifts River, NR). Short-term declines in eelgrass have been observed in most years since Unit 3 began abundance were directly associated with fouling and operation (1986), with the exception of the extended overgrowth of eelgrass on three occasions; once by shutdown of all MPS reactors from March 1996 to blue mussels at NR in 1992, and twice by blooms of June 1998 when seasonality of these species at FE green algae (Cladophora spp.) at WP in 1991 and during the recent shutdown period was more typical 2004. Analysis of long-term trends indicated some of other sites.

degree of decline in most of the above parameters at Thermal effects on dominant species abundance and all three areas. Two populations to the east of MPS distribution patterns were also evident at FE in 2004 and near the fringes of the thermal plume (JC and and most apparent in the low intertidal zone.

WP; <1.5 km from the MPS discharge to U1S) Seasonally high abundance of Hypnea muscifonnis, a exhibited more gradual declines over the 20-year species observed for the first time in 2001, and study period suggestive of regional causes unrelated expanded populations of Sargassum filipendula, to MPS operation. Thermal input to these nearby Corallina officinalis, and Gelidium pusillum now study sites was minimal under three-unit operation characterize the lower shore community at FE.

(<10 C above ambient conditions), and decreased Polysiphonia spp. maintained a perennial population since the effective retirement of Unit I in late 1995 at FE in 2004, but occurred as a summer annual at that reduced total MPS cooling water flow by about sites unaffected by MPS. The heavy blue mussel set 25%. Heavy, often sudden, eelgrass losses were observed regionally in 2004 was particularly documented on five separate occasions between 1985 pronounced at the FE site.

and 2001 at sites in the Niantic River, located well Higher Ascophyllum growth at Fox Island-New (FN, beyond the influence of the MPS thermal plume. the study population nearest the MPS discharge) than at Since 2001, eelgrass population health in the river has other sites was observed in 2003-2004, as in many shown some signs of improvement based on previous study years since Unit 3 began operation in expanded distribution and increases in shoot density 1986. Natural influences of other factors such as and biomass. Research on eelgrass populations ambient temperature conditions, nutrients and light, elsewhere in the northeastern U.S. has associated also played an important role in Ascophyllum growth at similar declines with anthropogenic influences, such FN.

as nutrient loading from surface run-off and The rocky intertidal monitoring program has also groundwater sources. These influences, coupled with documented regional patterns and modifications to increases in regional water temperature and waterfowl shore communities unrelated to MPS operation. These grazing, may factor strongly in observed declines in include the introduction to the region of two exotic red this study. algae, Grateloupiatunrturu in 2004 and Antithaamnion pectinatum in 1986, decreases in barnacle abundance Rocky Intertidal in recent years, and a long-term increase in abundance of the common brown rockweed, Fucus vesiculosus.

Rocky intertidal monitoring studies during 2004 continued to document ecological changes to the shore community near to, and associated with, the Executive Summary v

Benthic Infauna evident. For examiiple, Acrnira catlherinaeand 7Taryx spp. abundance returned to levels observed prior to The objective of the benthic infaunal monitoring Unit 3 operation within a few years after Unit 3 start-program is to measure infaunal species composition up; however, the opportunistic mollusk Nucula and abundance and to assess whether observed annulata is maintaining a population level above the changes are related to construction and operation of two-unit operational period. The sediment param-MPS. This report includes data from the period eters, grain size and silt/clay content, remained 1980-2004, with focus on 2004 data. elevated thrcugh 2004, but are approaching pre-Unit The analysis of data indicates measurable impact at 3 operational levels.

three stations Effluent (EF), Jordan Cove (JC), and Sediments and infaunal community characteristics Intake (IN) in the immediate vicinity of MPS. All at the more distant reference site of Giants Neck changes in benthic community structure are (GN) have exhibited changes that were not related to associated with corresponding changes in sediment operation of MPS. Mean grain size has been composition. variable, while silt/clay was relatively consistent, with Prior to start-up of Unit 3 and construction of the no long-term trends in either parameter. Infaunal second quarry cut in 1986, the sediments at the EF community composition at GN has generally been site were of medium size and the benthic community dominated by three taxa (TYaryx spp., oligochaetes was dominated by polychaetes. Following startup of and Acnira cathIerinae). Acnira catherinae, Unit 3, the increase of water flow removed fine to common at GN in the early monitoring years, has medium sediments, leaving coarser sediments with declined in abundance, while Tharyx spp. and low silt/clay levels. Community structure became oligochaete abundances have increased over the oligochaete-dominated. Following shutdown of Unit entire study period. The GN station has been I in 1995, water flow from the discharge was reduced valuable in validating periodic area-wide shifts in and sediment characteristics again became similar to species abundance and community structure in the pre-Unit 3 operational period. As a result, response to natural factors not impacted by oligochaete abundance has significantly decreased. construction and operation of MPS. Population The high settlement of Mytilus edulis in 2004 resulted increases of Mytilus edulis in 2004 described above in high community abundance when compared to were also observed at GN. Similar to pulses of the previous years. opportunistic polychaete Mediomastus ambiseta that Dredging and erosion from cofferdam removal at occurred during 1983-88, 1994, and 1998-99 at all the Unit 3 intake (1983-1985) resulted in changed sampling stations, the area-wide increase of Mytilus sedimentary characteristics (primarily increased edulis suggests a natural event rather than an effect of silt/clay content). Following construction comple- MPS operation.

tion, the sediment characteristics became more consistent over time. The 2004 data continue to show Lobster Studies recovery of the infaunal community. The number of individuals and species richness at IN have increased The American lobster occurs in the Northwest over the study period, in particular abundance of Atlantic from Canada to Cape Hatteras and supports organisms more common in early years, such as one of the most active commercial fisheries in the Acmira catherinae. These trends, along with northeast United States. The local lobster population in concomitant decreases in abundance of opportunistic the vicinity of MPS has been studied since 1978 to species, such as Nucula annulata, indicate continued determine if power plant operation has contributed to recovery at the IN station. However, the persistence population changes beyond those expected from natural of other opportunistic species, such as Protodorvillea variability and the level of fishing activity. Several gaspeensis, indicates that the sedimentary environ- aspects of MPS operation could potentially impact the ment is disturbed and needs a longer time to local population of American lobster. In early summer, completely recover. after hatching from eggs, lobster larvae swim to the Following Unit 3 start-up in 1986, fine sediments surface to begin the 6- to 8-week planktonic phase of scoured from the MPS discharge were deposited in their life cycle and are susceptible to entrainment Jordan Cove, resulting in increased silt/clay content through cooling water systems. Juvenile and adult and changes to infaunal community structure at the lobsters can be impinged on intake traveling screens or JC monitoring site. Most of the sediments were be exposed to the heated effluent in the discharge area.

scoured within the first year of Unit 3 operation. Objectives of the lobster monitoring program at MPS Initial impact has lessened over time, but is still are to: 1) evaluate year-to-year, seasonal, and among-vi Monitoring Studies, 2004

station changes in catch-per-unit-effort (CPUE); 2) affecting lobsters in LIS, near their southern range of monitor lobster population demographics, including distribution in nearshore waters.

length frequencies, growth rates, sex ratios, female size at maturity, characteristics of egg-bearing females; and Fish Ecology Studics

3) monitor movements of lobsters collected in the vicinity of MPS. Lobster larvae entrainment studies The objective of the fish ecology monitoring have been conducted since 1984 to estimate the program at MPS is to determine whether operation of number of larvae entrained through the cooling-water the MPS electrical generating units has adversely systems. Impacts associated with recent plant affected the occurrence, distribution, or abundance of operations on the local lobster population were local fishes. Potential impacts include entrainment of assessed by comparing results of the 2004 study with fish eggs and larvae through the condenser cooling-those from 1978 to 2003. Emphasis has been placed water system, impingement of juvenile and adult fish on assessing long-term trends in the abundance and on intake screens, and changes in distribution or population characteristics of lobsters collected in the abundance attributable to the thermal discharge.

Millstone Point area. Trawl, seine, and ichthyoplankton monitoring programs Results of lobster monitoring from 1978 to 1999 were established in 1976 to provide the basis for indicate that the local lobster population was stable or identifying taxa potentially affected, as well as increasing. The lower abundance of lobsters observed information on long-term abundance trends used to from 2000 to 2004 were unrelated to MPS operations measure changes in the local populations.

and attributed to an increase in natural mortality This report summarizes data collected from associated with a shell disease affecting lobster monitoring programs during June 2003 through May populations from eastern LIS to the Gulf of Maine. 2004. MPS Units 2 and 3 were both operating during During 2004 the incidence of lobsters found dead in most of this report period, except for scheduled our traps and shell disease prevalence and severity refueling outages of 51 days and 37 days at Units 2 declined substantially. No significant long-term trends and 3 in fall 2003 and spring 2004, respectively. Unit were identified in the overall total CPUE of lobsters or I was effectively retired on November 4, 1995, which in the total CPUE at the three monitoring stations. The eliminated the potential impacts of that cooling-water CPUE of legal-size lobster has exhibited a significant system on fish and larvae in the MPS area. Detailed declining trend at the Jordan Cove and Twotree analyses on seven taxa most susceptible to MPS stations, but no significant trend in legal lobster CPUE operational impact from entrainment or thermal occurred at the station located near the MPS intakes. effects assessed the potential effects of MPS.

Furthermore, the combined CPUE of legal-size lobster Analyses of these species generally focused on at the three stations increased by almost 70% during comparing temporal trends over the past 28 years.

2004, when compared to catches in 2003. Similar Results from the fish ecology monitoring program results were reported for commercial lobster catches in during 2003-04 indicate that no long-term abundance our area during 2004, nearly doubling the catch of legal trends determined for various life stages of the seven lobsters reported during 2003. On the other hand, selected taxa could be directly related to the lobster catches remained depressed in other areas of operation of MPS. No significant long-term trends LIS; the commercial landings for the entire State during were detected for juvenile or adult silversides 2004 (about 0.7 million pounds) were the same as collected by trawl or seine. Similarly, no long-term reported in 2003. The long-term sustainability of the trends were identified in grubby larvae, juveniles or Connecticut lobster fishery may be threatened if the adults, cunner eggs or larvae, or tautog larvae.

condition of lobsters in western LIS does not improve. Atlantic menhaden larvae showed a significant If lobster recruitment in our area depends on larval increasing trend in abundance, as did juveniles taken production in western LIS and the population in by seine and trawl. Likewise, a recent stock assess-western LIS does not recover, catches in our area ment indicates that Atlantic menhaden abundance has would be affected in the future. increased in Southern New England waters. Since Long-term trends in some lobster population the late 1970s and early 1980s, cunner and tautog characteristics have been identified over the past 27 have become less abundant at the Intake trawl station, years (growth, female size at maturity, abundance and exhibiting a significant negative trend. However, this size characteristics of egg-bearing females), which occurred following the removal of the Unit 3 rock were related to natural increases in seawater cofferdam, a preferred habitat for these species. No temperature and not the operation of MPS. Increased significant trend was detected in the abundance of water temperature may also be responsible for the cunner or tautog at Intake in subsequent years.

increased susceptibility and transmission of diseases Executive Summary vii

Cunner abundance at the Jordan Cove and Niantic result, extensive studies of the life history and popu-River trawl stations has fluctuated without trend since lation dynamics of this important sport and 1976. Tautog, primarily juveniles, are increasing in commercial species have been undertaken since 1976.

abundance at the Niantic River trawl station and in Surveys of adult spawners are conducted each year in Jordan Cove catches by both trawl and lobster pot. the Niantic River during late winter and early spring.

Although tautog eggs exhibited a long-term negative Larval sampling is conducted at the plant discharges, trend in abundance, egg abundance and subsequent in Niantic Bay, and at three stations in the Niantic larval production have increased since 2000. Tautog River. Settled, post-entrainment age-0 juveniles are larval abundance during 2003-04 was nearly four collected at two sites in the river. Winter flounder are times larger than any previous value reported, likely also commonly taken in the year-round trawl moni-reflecting an increase in spawner biomass as a result toring program (TMP).

of decreased fishing mortality. The large numbers of Seawater temperature has potentially important tautog and cunner eggs entrained at MPS did not effects during spawning, egg incubation, and the appear to affect future recruitment or subsequent periods of larval development and first year settle-spawning stock biomass of these two fishes, because ment. Mean water temperature at the MPS intakes in the proportion of juvenile recruits relative to adults winter 2004 was cooler than the long-term average, has increased, and there has been a significant but was warmer than average during the other three increase in tautog in the Niantic River and Jordan seasons. The cool winter resulted in ice formation in Cove. This is supported by independent research, the Niantic River, which delayed the start of both the which showed that annual fecundity of tautog in adult spawning survey and larval sampling.

eastern LIS is nearly twice that reported in more The A-mean trawl catch-per-unit-effort (CPUE) of southerly waters. This relatively high reproductive fish larger than 15 cm in the Niantic River during the capacity likely buffers entrainment losses. 2004 adult winter flounder spawning season was 1.7, American sand lance larvae exhibited a significant a decrease of 0.5 from 2002 and 2003 and the third long-term decrease in abundance since 1976, but this lowest CPUE of the time-series. The Jolly stochastic was likely due to large-scale ecological effects (e.g., model was applied to spawning survey mark and increases in abundance of its major predators). recapture data to estimate the absolute abundance of Densities of both anchovy eggs and larvae also the Niantic River adult spawning population. Only showed significant negative trends. The bay anchovy 201 fish were marked in 2004, the fewest of the time-appears to be experiencing a regional decline in series. Based on the mark-recapture data, the initial abundance. A sharp drop in abundance was measured overall abundance estimate of winter flounder larger over the past decade in Narragansett Bay and than 20 cm that were present in the Niantic River populations declined dramatically in Chesapeake Bay during 2003 was 4.2 thousand. Annual female after 1993. The bay anchovy is an important forage spawner abundance estimates since 1976 ranged from species for striped bass and recent increases in striped a low of 2 thousand in 2001 and 2004 to 75 thousand bass abundance along the Atlantic coast may have in 1982, with corresponding total egg production contributed to the reduced numbers of bay anchovy. estimates of about 1.7 to 44.8 billion. Historically, Trends in abundance of many of the fishes collected abundance of Niantic River winter flounder spawners over the past 28 years may also be affected by peaked in the early 1980s and decreased thereafter.

increasing seawater temperatures as suggested in This decline was attributed to stock and recruitment recent scientific literature. Fishes more commonly effects (i.e., decreased per-capita recruitment at high found in the New York Bight, such as spotted hake stock sizes), a general winter warming trend, and and black sea bass, are now becoming increasingly increased rates of exploitation. Niantic River CPUE common in LIS. Based on increasing trends in was significantly positively correlated with several abundance or the lack of decreasing trends not other winter flounder abundance indices from attributed to natural causes, MPS has had minimal throughout Southern New England and abundance effect on local fish assemblages. currently remains low throughout the region.

To provide some perspective on Niantic River win-Winter Flounder Studies ter flounder stock size estimates, annual exploitation rates were determined using annual recreational and The local Niantic River winter flounder population commercial landings data of winter flounder in LIS.

is potentially affected by the operation of MPS, The calculated exploitable biomass of Niantic River particularly from entrainment of larvae through the winter flounder represented approximately 2% of the cooling-water systems of the operating units. As a entire winter flounder resource in LIS during the past two decades.

viii Monitoring Studies, 2004

I Z Winter flounder larvae in 2004 were moderately taken in the lower river navigational channel abundant in the Niantic River and Bay. While the particularly low. However, this abundance decrease aggregate abundance of winter flounder larvae in the was much less when CPUEs were calculated for fish Niantic River decreased in 2004 from 2003, taken only in the upper portion of the river. The abundance was nevertheless equal to or greater than relative distribution of age-l fish in Niantic River and aggregate abundance estimates made since 1999. Bay may have also changed over the years, possibly Abundance in Niantic Bay was the seventh highest of due to environmental factors, such as bottom the time-series, which began in 1983. In the river, composition.

more Stage I larvae were found than expected from Age-0 abundance indices were either not signifi-the relatively low adult spawner abundance. This cantly correlated or were negatively correlated with finding suggested a potentially important density- the abundance of female adult spawners 3 to 5 years dependent compensatory mechanism in that reduced later. Conversely, positive correlations were found egg predation by sevenspine bay shrimp occurring between age-l abundance indices and these older under low egg densities resulted in higher egg fish. However, there was much scatter in these survival and more Stage I larvae. relationships and none of the early life stages were Rates of larval growth and development were posi- considered to be a reliable predictor of potential tively correlated with water temperature, but other future year-class strength. Unknown processes not factors such as density and prey abundance most related to MPS operation occurring after juvenile likely affected growth as well. Despite cooler than winter flounder leave shallow nursery waters in the average water temperatures during winter 2004, fall of their first year of life seem to be operating such growth rates of larvae in both the river and bay were that fewer adults are produced from more abundant above average and greater than expected. The 2004 year-classes of younger fish. The older juvenile life larval mortality rate was higher than the long-term stage (ages-I and 2) may be where a bottleneck is average, despite faster larval growth rates. Density- occurring in winter flounder population dynamics.

dependence was examined by comparing mortality A stock and recruitment relationship (SRR) was and egg production estimates (a measure of Stage 1 determined for the Niantic River winter flounder larval stage abundance) at various monthly and population using adult CPLJE data. A February water seasonal water temperatures. Results of this analysis temperature parameter significantly improved the suggested that larval mortality decreased with model fit. At the request of the Connecticut Depart-decreasing egg production (i.e., density-dependency) ment of Environmental Protection, the SRR was and increasing spring water temperatures (i.e., an modified by adding a depensatory parameter (i.e., per effect of faster development). capita recruitment rate decreasing with decreasing Following larval metamorphosis and settlement, parental stock size). However, the data analysis densities of age-0 young in 2004 were twice as high showed that this parameter was not statistically at the lower river station than at the mid-river station. significant.

Overall, abundance of young was about average. The number of larvae entrained through the Mean lengths this year were larger than found in condenser cooling-water system at MPS is a measure almost a decade, which may have contributed to a of potential impact to winter flounder. As in previous lower than average mortality rate. High juvenile years, Stage 3 larvae predominated (53%) in mortality rates in some years reduced the abundance entrainment collections during 2004. Annual esti-of relatively large year-classes, whereas the lower rate mates of entrainment were related to both larval in 2004 should result in an average-sized year-class. densities in Niantic Bay and MPS operation. An The 2003-04 A-mean CPUE of 8.4 calculated for entrainment estimate of about 243 million was the young winter flounder taken during late fall and early fifth highest since 1976 and was related to above winter at TMP stations was the largest value found in average larval abundance in Niantic Bay and several years and consistent with high abundance of relatively moderate cooling-water demand. A spring the 2003 year-class, first indicated by beam trawl 2004 refueling outage at Unit 3 reduced potential sampling during summer of 2003. Although these entrainment by an estimated 199 million larvae.

two age-0 abundance indices were significantly Annual entrainment density (abundance index divided correlated and both can identify emerging strong or by total seawater volume) has varied without trend weak year-classes, their correspondence has since 1976, indicating that larval production and decreased during the past few years. availability in Niantic Bay remained relatively stable Fewer age-l juveniles have been taken during each despite increased water use during the 1986-95 period year of the Niantic River adult spawning population of three-unit operation and reduced cooling-water surveys since the early 1980s, with CPUEs of fish demand in 1995-97. Correlations between entrain-Executive Summary ix

ment estimates and abundance indices of post-entrainment age-O juveniles were positive, implying no entrainment effect, and that the more larvae available, the more that metamorphosed and settled in Niantic River and Bay. This was also demonstrated by a comparison of annual entrainment and juvenile year-class strength, which indicated that entrainment estimates were an index of emerging year-class strength and that this process was not the most important factor in determining juvenile abundance.

The potential impact of larval entrainment on the Niantic River stock depends upon the fraction of the annual winter flounder production entrained each year, which was determined in this study as equivalent eggs (termed production loss). Empirical mass-balance calculations showed that a large number of entrained larvae likely come from a number of sources in LIS besides the Niantic River. The Niantic River production loss of nearly 44% in 2004 was the second largest estimate and well above the long-term average of 15%. However, based on an apparent increase in egg survival noted in recent years, a factor that was not incorporated into this model, most production loss estimates since 1995 were likely conservatively high. Correcting the more recent esti-mates by using a higher egg survival estimate resulted in lower production losses, which fluctuated about the long-term mean.

To date, efforts of regulatory agencies to control fishing mortality have not resulted in large increases in abundance for winter flounder stocks across the region or in the Niantic River. Even so, the remain-ing small adult spawning stock in the river continues to produce relatively large numbers of larvae and young fish, which are a likely result of population compensatory mechanisms. The effective retirement of Unit 1 in late 1995 resulted in an immediate reduction of about one-quarter of the MPS cooling-water flow, which has permanently reduced potential plant impact, but has not resulted in stronger year-classes and subsequent enhanced recruitment to the spawning stock. Despite relatively good abundance of age-0 winter flounder (a post-entrainment life stage), significant recruitment to the adult spawning population has not occurred in recent years. This was due to unknown factors unrelated to MPS operation removing these fish from the population. Environ-mental effects, including changes to the Niantic River habitat, a warming water temperature trend, and interactions with other species (e.g., predation),

especially during early life history, also are important factors likely affecting the winter flounder recruit-ment process.

x Monitoring Studies, 2004