trast, in a seasonal 1 -yr study of food of adult walleye 

 pollock off Hokkaido Island, Japan, the rate was 

 much higher, particularly during the winter months 

 when up to 80% of the stomachs were empty (Maeda 

 et al. 1981). In an eastern Bering Sea study (Bailey 

 and Dunn 1979), generally few walleye pollock had 

 empty stomachs in summer 1974 (results similar to 

 those of my study); however, a much higher percent- 

 age offish had empty stomachs there in spring 1977 

 than in my study. 



The diet of small walleye pollock varied widely from 

 season to season in the percent volume of each food 



type (Fig. 2). Euphausiids were the predominant 

 food of small walleye pollock in winter and spring 

 (34% and 78%, by volume, respectively) but con- 

 stituted <7% of the stomach contents in the summer 

 and fall. Conversely, mysids were the predominant 

 food in the summer and fall diets (36 c /< and 22%, by 

 volume, respectively) but were much less important 

 in the winter and spring (<5%, by volume). Copepods 

 were also an important food (11%, by volume) in the 

 summer but were insignificant (<1%) in other 

 seasons. 

 For each season, the diet of intermediate-sized 



SMALL WALLEYE POLLOCK 

 < 250 mm SL 



INTERMEDIATE-SIZED WALLEYE 

 POLLOCK 250 - 349 mm SL 



to 



30 



20 



10 







40 

 30 

 20 

 10 

 



40 

 30 

 20 



10 

 



srszs* 



78 



SPRINC 

 n = 12 



SPRINC 

 n = 31 



-P^"":"'f:";:;^ [| 



40 - 

 30 - 

 20 

 10*— 



SUMMER 

 n = 74 





SUMMER 

 n = 35 



FALL 

 n = 67 



L, ,,,:;>:■ ::■:-:■' 



FALL 

 n = 48 



WML 



 ■*- 



d? 



WINTER 

 n = 51 



dr 



/ 



# 



i 





# 



£ 







4=3= 





WINTER 

 n = 47 



P 7 



& 



T 



S^A* 





^5- 



$ 



£ 



J? 



/ 



£ 



<? 



4? 



P^T- 





/ 



n$g*ji 







FIGURE 2. — Mean percent volume of majorfood categories in stomachs of small and intermediate-sized walleye pollock by season of year, Auke 

 Bay and Fritz Cove, southeastern Alaska, 1979-80. (Figures do not include empty stomachs or those with only a trace of food.) 



641 



