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 remain 

 inshore and may escape temperatures above 22.5 °C by burying themselves in cooler bottom sediments 

 (OUa 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 their life history, physiology, behavior, and population dynamics may be found in Klein-MacPhee 

 (1978). 



Because winter flounder stocks are localized, NUEL studies have concentrated on the dynamics of 

 the population spawning in the Niantic River to determine if MNPS impacts of impingement and entrain- 

 ment have caused or would cause changes in local abundance beyond those expected from natural variation. 

 Preliminary field studies to estimate abundance of this population in 1973-74 were expanded in scope in 

 1975, when surveys using mark and recapture techniques were initiated. An adult abundance survey has 

 been completed each year through the present. In many years, studies of age structure, reproductive 

 activity, growth, survival, movements, early life history, and stock identification have been conducted. For 

 plant impact, impingement and entrainment estimates are available for each year. Data from many of 

 these studies have been used in a predictive mathematical population dynamics model developed by the 

 University of Rhode Island (Saila 1976). This model has formed the basis for all MNPS impact assessments 

 to date, including that for Unit 3 (NUSCo 1983c). However, a stochastic population dynamics model is 

 under development which should more realistically predict population-level effects over the expected 

 duration of MNPS operations. Increased knowledge of larval population dynamics and the stock-recniitment 

 relationship is necessary for the successful application of this model and has been the focus of recent efforts 

 at NUE1-. 



Tliis report includes a summarization of the data, results, and conclusions for various winter flounder 

 studies from 1973 through the winter 1986 adult abundance survey. Unit 3 began startup tests in fall 1985 

 and commenced commercial operations in late April of 1986. Therefore, no data from sampling programs 

 (other than the adult survey) after fall 1985 will be presented in this report. These data are from the 

 operational period for Unit 3 and will be included in future reports. Additional information on sampling 

 methodologies, program evaluations, and detailed results and analyses may be found in previous annual 

 reports and documents, including NUSCo (1975, 1976, 1977, 1978a, 1978b, 1979, 1980, 1981a, 1981b, 

 1982, 1983a, 1983b, 1983c, 1984, 1985, 1986a, 1986b). 



