466 



Fishery Bulletin 88(3), 1990 





o 

 a: 



LJ 



100- 150- 200- 250 

 149 199 24 9 299 



10 0- 15 0- 20 0- 25 0- 

 14 9 19 9 24 9 29 9 



SIZE CU\SS (mm) 



(ZZ) 



(ZZ) 



rTTTTI 



ALL OTHER PRE^|• 

 OITHONA SP 



UNIDENT COPEPODIDS <1 5mm 

 ALL CALANUS SPP 

 ACARTIA LONGIREMIS 

 PSEUD0CAL6NUS COPEPODIDS 

 PSEUDOCALANUS SP 

 COPEPOD NAUPLII 

 INVERTEBRATE EGGS 



10 0- 15 0- 20-0- 25 0- 

 14 9 19.9 24 9 29 9 



SIZE CLASS (mm) 



Figure 2 



The diet of larval pollock in the Gulf of Alaska in June 1987, 

 t)y size class, in terms of %N, %l'OL, and %IRL 



Diet as a function of size 



Small unidentified calanoid copepodids(i.e.. <1.5 mm) 

 were the primary prey {IRl) for larvae 10.0-14.9 mm 

 SL, followed by P^eudocalanus sp. (Table 2, Fig. 2). 

 Copepod nauplii, which ranked as a major food item 

 for only this size class, was third in importance, fol- 

 lowed by Oitiwna sp. and Acartia longiremis. 



For larvae 15.0-19.9 mm SL, the same two prey 

 items dominated the diet, but Paeudocalanus sp. was 

 the most important item and small (unidentified) cala- 

 noid copepodids were second (Table 2, Fig. 2). Inverte- 

 brate eggs, A. hngiremis. and Oitfuma sp. ranked third 

 through fifth. 



For fish 20.0-24.9 mm SL, Pseudocalanus sp. con- 

 tributed twofold more to the diet than any other item 

 (Table 2, Fig. 2). Small calanoid copepodids, inverte- 



brate eggs, and yl. longiremiH were second, third, and 

 fourth most important prey, followed hy Pneudocalanus 

 copepodids. 



Pseudocalanus sp. continued to he the dominant prey 

 for the largest size class that was examined, 25.0-29.9 

 mm SL, comprising over 52% of the diet, with small 

 calanoid copej>odids ranking second in importance 

 (Table 2, Fig. 2). These were followed by Calunuji mar- 

 shallae. a species whose only major contribution to the 

 diet was in this size class, Oifhoua sp., and Psrudo- 

 calanus copepodids. 



Considering adult and copepodid forms together, 

 Pseudocalanus sp. was the principal prey for ail sizes 

 of larvae and early juveniles (Table 2, Fig. 2). The con- 

 tribution of Pseudocalanus sp. adults and all Calnnus 

 spp. increased directly in relation to fish size. On the 



