and daily specific growth rates (SGR) were deter- 

 mined by: 



(log w^ - loggwr,) 

 SGR = 100 ,; _ , , (8) 



with t\ and f2 "= first and last days of 

 observation 



wt\ and u'?2 = weight at days t\ and 

 tj, respectively 



Annual entrainment estimates were calculated 

 from data collected at station EN in addition to 

 using these data to describe the abundance of 

 winter flounder in Niantic Bay. The estimates 

 were computed as the median density (number 

 per 500 m ) during the larval season times the 

 total number of 500 m units of seawater with- 

 drawn by MNPS during the same period of time. 

 A nonparametric method (Snedecor and Cochran 

 1967) was used to construct a 95% confidence 

 interval around each median and corresponding 

 entrainment estimate. 



Post-larval young-of-the-year studies 



A quantitative study of post -larval young- 

 of-the-year winter flounder in the Niantic River 

 began in 1983 (NUSCO 1987). Station LR has 

 been sampled every year and WA since late 1984 

 (Fig. 1). Each station was visited once every 

 week from late May through late September or 

 early October during daylight within about 2 

 hours before to 1 hour after high tide. A 1-m 

 beam trawl with interchangeable nets of 0.8- , 1.6-, 

 3.2-, and 6.4-mm bar mesh was used to catch 

 young winter flounder. Two tickler chains were 

 added in late June of 1983 to increase catch effi- 

 ciency as older and larger young apparently were 

 able to avoid the net without them (NUSCO 

 1987). In 1983, triplicate tows were made using 

 one of the nets, which was changed as young 

 grew during the season. Since 1984, two nets of 

 successively larger mesh were used during each 

 sampling trip to collect the entire available size 

 range of young. A change to the next larger mesh 



in the four-net sequence was made when young 

 had grown enough to become susceptible to it; 

 the larger meshes reduced the amount of detritus 

 and algae retained. Two replicates with each of 

 the two nets were made at both stations and the 

 nets were deployed in a random order. Distance 

 was estimated by letting out a measured line at- 

 tached to a lead weight as the net was towed at 

 about 25 m per min. Tow length was increased 

 from 50 to 75 to 100 m as the number of fish 

 decreased throughout the summer of each year. 

 For data analysis and calculation of CPUE, the 

 catch of both nets used at each station was 

 summed and standardized to give a density per 

 100 m of bottom covered by the beam trawl. 

 For comparisons among years, a moving average 

 of three weekly density estimates was used to 

 smooth the trends in abundance over time. 



The young winter flounder collected were mea- 

 sured in the field or laboratory to the nearest 0.5 

 mm in total length (TL). During the first few 

 weeks of study, standard length (SL) was also 

 measured because many of the specimens had 

 damaged caudal fin rays and total length could 

 not be taken. A relationship between the two 

 lengths determined by a functional regression 

 (NUSCO 1987) was used to convert SL to TL 

 whenever necessary. 



To calculate mortality rate, aU young were as- 

 sumed to comprise a single cohort. A catch curve 

 was constructed with the natural logarithm of 

 density plotted against time in weeks. The slope 

 of the descending portion of the curve provided 

 an estimate of the weekly rate of instantaneous 

 mortality (Z). Once Z was determined, weekly 

 survival rate (S) was estimated as exp(-Z) and 

 monthly as exp((-Z)(30.4/7)). 



Impingement of winter flounder at 

 MNPS 



The number of winter flounder impinged on 

 the traveling screens of MNPS Unit 2 was esti- 

 mated using techniques described in the Fish 

 Ecology section of this report. Length-frequency 



Winter Flounder Studies 



157 



