Larval survival was not calculated due to the low occurence of Stage II and III larvae relative to Stage IV 

 which may have been an influx from more distant hatching. Lund and Stewart (1970) indicated that larvae 

 produced from the western LIS population are responsible for the gradual recruitment of fourth and fifth 

 stage lobsters in middle and eastern LIS. Their hypothesis appears to be true given the number of fourth 

 stage larvae collected in our entrainment studies. 



Survival of lobster larvae after passing through the plant's cooling water system was observed in both 

 entrainment study years. In 1984, 2 stage IV, and in 1985, 2 stage I and 1 stage IV survived after passing 

 through the plant indicating that entrainment mortality is lower than the assumed 100%. Similar fmdings 

 at other power stations have been reported. CoUings et al. (1981) reported 14% survival for lobster larvae 

 (Stage II) collected at the Canal Electric Company, Sandwich, MA. 



In both of the lobster larvae entrainment studies (1984-85), and the IP samples collected since 1977, 

 more larvae were collected in night samples than in day samples (Table 14). While this may appear at 

 first to contradict the photo positive behavior of lobster larvae observed by many researchers (Fogarty 

 1983), a combination of factors may explain the contradiction. Diurnal vertical distribution is apparently 

 related to light intensity, and larvae tend to disperse from surface waters during night except under bright 

 moonlight (Templeman 1939). The fact that more larvae were collected at night when surface densities 

 have been reported to be lowest may result from a combination of this lobster larvae behavior and the 

 intake structure design. The intake structures have curtain walls which extend down into the water column 

 about 2 m below MLW. This means that cooling water is drawn from well below the surface. Therefore, 

 since lobster larvae disperse from surface waters during darkness, they are more susceptible to entrainment 

 at night regardless of tidal stage. 



Two 24 h samplings were conducted in 1985 to substantiate our initial fmdings of higher larval 

 densities in night samples and to determine peak diurnal abundance of lobster larvae in the cooling waters. 

 The numbers of larvae found on the two sampling dates were not significantly different; 19 larvae were 

 collected on 28 May and 17 were collected on 4 June (Table 15). 



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