6000 9000 



EGG ABUNDANCE INDEX 



I'ig. 5. I jnear relationship between tfie larval anchovy recruitment index and the egg abundance index, suggesting 

 density-dependent mortality in the early life history stages. 



bay anchovy larvae. However, Leak and Iloude 

 (1987) reported that in a field study the highest 

 anchovy mortality was during egg and yolk-sac 

 stages and estimated that mortality due to preda- 

 tion was two to three times higher than that at- 

 tributed to star/ation. Cannibalism by adults 

 may be a source of predation and because adult 

 abundance is directly related to egg abundance, 

 this would be a self-regulating mechanism. Causal 

 mechanisms for the compensatory mortality of 

 the early life history stages of anchovies in the 

 Millstone area are not known, but because com- 

 pensation was occurring at the same time as en- 

 trainment through MNPS, this would help miti- 

 gate the impact on the adult anchovy population. 



Sticklebacks 



The threespine stickleback and the blackspotted 

 stickleback are small, nearshore fishes. The 

 threespine stickleback is distributed throughout 

 the north polar regions and as far south as 



Chesapeake Bay in the Western North Atlantic; 

 the blackspotted stickleback is found only in the 

 Western North Atlantic from Newfoundland to 

 LIS (Perlmutter 1963). 



Threespine and blackspotted sticklebacks are 

 very similar in appearance and are not easily dis- 

 tinguished (Bigelow and Schroeder 1953). Because 

 of this similarity, the blackspotted stickleback was 

 not identified in MNPS collections until October 

 1981 (NUSCO 1982). Although Fitzgerald and 

 Wlioriskey (1985) found no size overlap between 

 these two species in Canada, the length frequency 

 of individuals collected at MNPS overlapped at 

 30 to 55 mm (Fig. 6). Thus, length frequency 

 could not be used to separate the species in earlier 

 years and the data for the two species were com- 

 bined. 



Sticklebacks were collected in all sampling pro- 

 grams, but were only abund£int in impingement 

 samples from fall through spring. During the 



272 



