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Fishery Bulletin 97(4), 1999 



amphipods, mysids, crab larvae, and copepods were 

 relatively important prey. This was particularly true 

 for the relatively small size summer-spawned blue- 

 fish collected in the SNE in 1995; the diet of these 

 fish were dominated by copepods (Table 3). 



The diet of adult bluefish collected in the Georges 

 Bank region was dominated by butterfish, squid, 

 round herring, and Atlantic herring in both 1994 and 



1995 (Table 4). There were several commercially 

 important species consumed by adult bluefish on 

 Georges Bank in 1994. These included American pla- 

 ice, haddock, Atlantic cod, and several hake species. 

 A large component of the diet of adult bluefish from 

 Cape Hatteras to Montauk Point, NY, was bay an- 

 chovy. Butterfish, round herring, and squid were also 

 important prey of bluefish collected from this geo- 

 graphical region. The diet of bluefish from both re- 

 gions also included several other fish and inverte- 

 brate species (Table 4). Channeled whelk were preyed 

 upon by adult bluefish in the same region and year 

 that spring-spawned YOY bluefish were found to feed 

 on them. 



Net feeding 



Although there was evidence of net feeding, it did 

 not seem to bias diet indices. The percent occurrence 

 of several different prey found to be "fresh" and the 

 percent occurrence of these same prey found to be 

 "digested" was similar (Table 5). Only in spring- 

 spawned bluefish in the SNE region in 1995 were 

 there more fresh prey than digested prey in their 

 diet (30 fresh vs. 19 digested; Table 5). Spring- 

 spawned bluefish had more freshly eaten prey in 

 their diet (20—61%) than summer-spawned bluefish 

 (0-267^). 



Prey-type selectivity 



Spring-spawned YOY bluefish selected positively 

 icol/m) for bay anchovy in both 1994 (a=0.69, t-test 

 vs. 0.25, t=8.05, df= 154, P<0.001 )) and 1995 ( a=0.80, 

 ^test vs. 0.33, ^=6.40, df=74. P<0.001 ). However, YOY 

 bluefish avoided (a<l/m) butterfish, squid, and 

 "other" (determined for 1994 only) prey fish in 1994 

 (Mests vs. 0.25; P<0.001i and 1995 (^tests vs. 0.33, 

 P<0.05)(Table6). 



Prey-size relationships and selectivities 



There was a very weak but significant positive lin- 

 ear relationship between fish prey TL and YOY blue- 

 fish FL in 1994 (r2=0.10, P<0.0001, n=418) and 1995 

 (/•'-=0.02, P=0.027. ^=224) (Fig. 1). A positive linear 

 relationship also existed for fish prey TL and adult 

 bluefish FL in 1994 (^^=0.15, P<0.001, n=90) and 

 1995 (/•-=0.28, P<0.0001, n = lOO) (Fig. 2). Although 

 there was a significant increase in mean prey sizes 

 taken, juvenile and adult bluefish continued to take 

 small prey with increasing body size. 



Bay anchovy to bluefish FL ratios were higher in 

 the summer-spawned bluefish cohort than in the 

 spring-spawned cohort in 1994 and 1995. Additionally, 



