TABLE 2. Conlinued. 



Many researchers have found that impingement 

 rates were directly influenced by cooling-water 

 flow (ConEd and PASNY 1977; Lawler, Matusky 

 and Skelly Engineers 1980, 1987). The estimated 

 total number offish impinged each year by MNPS 

 was compared to annual cooling-water volume 

 (Fig. 2). Annual impingement at Unit 2 from 

 1976 to 1982 appeared to be related to cooling- 

 water flow. In 1983, cooling water flow was low 

 while the number offish impinged was high; Unit 

 2 was at full power during the winter of 1983, 

 but was shutdown from June through November. 

 Except for anchovies, the more abundant fishes 



were usually impinged in greater numbers during 

 the winter; this accounted for the differences noted 

 between catch and flow in 1983. In the fall of 

 1983, there was a noticeable reduction in daily 

 impingement at Unit 2 after the summer removal 

 of a cofferdam surrounding the Unit 3 intake. 

 The cofferdam existed when Unit 2 began oper- 

 ating and it provided a reef-like habitat in the 

 vicinity of the Unit 2 intake that may have at- 

 tracted fish. Analyses of daily monitoring data 

 revealed a significant (p<0.01) reduction in the 

 average number of organisms impinged at Unit 2 

 after the removal of the cofferdam (NUSCO 



Fish Ecology Studies 263 



