Winter Flounder Studies 



Introduction 



This section summaiizes recent research on the 

 winter flounder {Pseudopleuronecte.s americanm) 

 and builds upon the data base previously assem- 

 bled by Northeast Utilities (NU) as part of envi- 

 ronmental studies for the Millstone Nuclear Power 

 Station (MNPS). Due to the local abundance 

 and importance of the winter flounder to the 

 Connecticut sport and commercial fisheries, this 

 species has been intensively studied since 1973 

 and considerable data have been collected on its 

 life history and population dynamics. A summa- 

 rization of the data, results, and conclusions for 

 all aspects of the work from 1 973 through early 

 1986 was included in NUSCO (1987). This time 

 frame represented the pre-operational period for 

 MNPS Unit 3, which began commercial operation 

 in late April of 1986. 



The population of winter flounder is composed 

 of reproductively isolated stocks which spawn in 

 specific estuaries and coastal areas from Nova 

 Scotia to New Jersey (Ix^bcll 1939; Perlmutter 

 1947; Saila 1961; Leim and Scott 1966). Most 

 adults enter natal estuaries in fall and early winter 

 and spawning occurs in late winter and early 

 spring. Females usually mature at age 3 and 4 

 and males at age 2 and average fecundity is about 

 500,000 eggs per female. Eggs are demersal and 

 hatch in about 15 days, depending upon water 

 temperature. The larval stage lasts ab(5ut 2 

 months, also depending upon water temperature. 

 Small larvae are planktonic and remain in natal 

 estuaries to a great extent, although some may be 

 carried out into open waters by tidal currents. 

 Some of these larvae may return to the estuary 

 on subsequent incoming tides, but the rest are 

 lost from the system. larger larvae maintain 

 some control over their position by vertical move- 

 ments and also may spend considerable time on 

 the bottom. Following metamorphosis, most 



demersal juveniles remain in the estuary in shallow 

 waters. Immature yearling (age 1) winter flounder 

 become photoncgative and though many remain 

 within the estuary, are usually found in deeper 

 water than age young-of-the-year (Pearcy 1962; 

 McCracken 1963). Many adults stay in estuaries 

 following spawning, while others disperse into 

 deeper waters. By summer, most have left shallow 

 waters as their preferred temperature range is 

 12-15''C (McCracken 1963). However, some re- 

 main inshore and may escape temperatures above 

 22.5°C by burying themselves in cooler bottom 

 sediments (Olla et al. 1969). Adults are omnivores 

 and as opportunistic feeders eat a wide variety of 

 algae and benthic invertebrates. They are sight 

 feeders and are usually active only during the day. 

 Additional details regarding winter flounder hfe 

 hi.story, physiology, behavior, and population dy- 

 namics may be found in Klein-MacPhce (1978). 



Because winter flounder stocks are localized, 

 our studies have focused on the population spawn- 

 ing in the Niantic River to determine if MNPS 

 impacts of impingement and entrainment have 

 caused or would cause changes in local abundance 

 beyond those expected from natural variation. 

 Operation of Unit 3 approximately doubled the 

 volume of cooling water used by MNPS and 

 some impacts could be expected to increase com- 

 mensurately. In assessing the impact of winter 

 flounder larval entrainment, our efforts have been 

 aimed at estimating the number of individuals 

 annually entrained and measuring changes at the 

 adult population level. The approach chosen to 

 carry out these two basic tasks consisted of a 

 combination of sampling programs and analytical 

 methods designed to provide a preliminary short- 

 term assessment capability and, ultimately, a long- 

 term assessment tool in the form of a compre- 

 hensive simulation model, which includes hydro- 

 dynamics and population dynamics submodels. 

 Short-term empirical assessment methods (Ilorst 

 1975; Goodyear 1978) and a preliminary 



Winter Flounder Studies 



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