assessment of Units 1 and 2 environmental impact and is providing an 

 extensive time series of data important for 3 Unit impact assessment. 



Entrainment studies have determined the natural variability, season- 

 ality, densities, and species composition of entrained ichthyoplankton 

 (Table 4) . This information has identified fish populations likely to 

 have the greatest potential for entrainment impact. These populations 

 include anchovies, sand lance and winter flounder which generally have 

 represented over 80% of the fish larvae entrained and cunner and tautog 

 comprising over 80% of the fish eggs entrained. 



The extensive offshore ichthyoplankton program of the mid-1970's 

 provided information on ichthyoplankton spatial distribution in the 

 Millstone area. From this information we have been able to identify the 

 primary spawning areas of important taxa. The Niantic River appears to 

 be the primary local spawning area for anchovies and winter flounder 

 based on the high density of anchovy eggs collected in the river (1974 - 

 1975) and the abundance of small winter flounder larvae. Although 

 spatial distributions have been identified, additional offshore informa- 

 tion on the net export of larvae out of the Niantic River and the import 

 of larvae from adjacent areas of Long Island Sound would provide a 

 perspective as to what portion of the ichthyoplankton population is 

 entrained . 



Estimated annual entrainment of eggs and larvae is determined from 



sample densities and cooling water volume. The estimates have been 



large for dominant taxa (Table 5) and we have assumed a "worst case" of 



i 

 100% mortality in lieu of conducting entrainment mortality studies. 



Entrainment mortality studies at other sites have indicated that many 



eggs and larvae survive (Cannon et al. 1977, Ginn et al. 1977). The 



30 



