Table 31. Annual mean length 2ind percent length-frequency distribution by 5-cm size 



intervals of winter flounder impinged at MNPS from October 1976 through 

 September 1985. 



The occurence of many fish in spawning condition at MNPS may have been partly related to behavior. 

 The enviromnental cues used by winter flounder to successfully return to the Niantic River from distant 

 areas for spawning are not known. Beverton and Holt (1957) and McKeown (1984) noted that currents 

 are among the important factors in guiding oriented migration of demersal marine fishes. If adult winter 

 flounder move along the shoreline in search of a particular estuary, then the intake currents at MNPS 

 may attract individuals seeking to enter the river for spawning. Also, the larger numbers of males impinged 

 than females may be related to their generally smaller size and therefore lower sustained swimming speeds 

 (Beamish 1966; Tcrpin et al. 1977), which would have allowed fewer of them to escape from the intake area. 



Fish return sluiceways 



A fish return sluiceway was installed at MNPS Unit 1 and put into operation in mid-December of 

 1983. A sluiceway was constructed at Unit 3 and has been in operation since the start of commercial 

 operations in late April of 1986. Survival studies completed before (NUSCo 1981b) and after (NUSCo 

 1986b) installation of the Unit 1 sluiceway indicated that future impingement mortality of winter flounder 

 at MNPS would most likely be less than 20% (Table 32). Data restricted to only colder months, when 



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