Entrainment 



lobster larvae were found in ichthyoplankton (IP) samples of the cooling water at Units 1 and 2 

 discharges from 1977 to 1985. Because lobster larvae distribution in the water column is patchy, large 

 volumes of water must be sampled to collect them. Thus, begirming in 1984, we initiated a special lobster 

 larvae entrainment study, these samples filter much larger volumes of cooling water (4000 m ) than do 

 the IP samples (400 m''). This sampling effort, focusing on lobster larvae in the cooling waters was initiated 

 in anticipation of Unit 3 start-up. 



The timing of lobster larvae collected in entrainment samples corresponded to the developmental stage 

 of egg masses carried by berried females. In May, the number of berried females collected in traps was 

 high and the development of the eggs indicated that hatching was imminent. In June, the number of 

 berried females carrying ripe eggs declined and by July the low number of berried females caught indicated 

 the completion of the biennial spawning cycle. Although the hatching process and stage duration is 

 temperature dependent (Templeman 1936) and most intense at temperatures of about 20 "C (Hughes and 

 Mattheissen 1962), the larval phase is completed in 25-35 d under normal conditions. In general, since 

 1977, larvae were collected from mid-May through late-June. 



Scarratt (1964, 1973) provided estimates of lobster larvae survival between stage I and IV for a 

 Canadian lobster population. In our study, most of the larvae collected were Stage I and presumably 

 hatched nearby (Table 14; 88% in 1984; 87% in 1985). 



Table 14. Summary of 1984 and 1985 lobster larvae entrainment studies 



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