lOOr 



FIGURE 2— Percent biomass of 

 stomach contents by taxa per 5-cm 

 length group of Bering Sea walleye pol- 

 lock, summer 1974, 



CO 



<50 



o 



III 



FISH 



SHRIMP 



DIGESTED MATTER 



EUPHflUSIIDS 



AMPHIPOOS 



COPEPODS 



519 20-24 25-29 30-34 35-39 40-44 45-49 50' 



LENGTH (cm) 



100 



80-- 



60 



5 

 O 



40 



20- 



0^ 



DIGESTED MATTER 



FISH 



EUPHAUSIIDS 



AMPHIPOOS 



COPEPODS 



1 52'» 25-34 35-44 

 LENGTH (cm) 



Figure 3. — Percent biomass of stomach contents by taxa per 

 10-cm length group of Bering Sea walleye pollock, spring 1977 



stomachs collected in summer 1974. and the per- 

 centage of amiphods as food biomass tended to 

 increase with increasing pollock size. Other food 

 organisms that appeared in the diet are listed in 

 Table 2. 



The analysis of stomach contents by weight-per- 

 centage masks the behavioral aspects of pollock 

 feeding due to size differences in food organisms. 

 More information can be obtained from the data 

 when analyzed as grams of food organisms per fish 

 for each length class (Tables 3, 4). From this 

 analysis it appears that larger pollock tended to 

 exclude smaller food items from their diet. As the 

 pollock grew larger they fed more on euphausiids, 

 amphipods, and fish. 



306 



Table 2. — Proportion of taxa observed in walleye pollock 

 stomachs in the eastern Bering Sea. 



Taxa 



Fish 



Copepods 

 Euphausiids 

 Amphipods 

 Chaetognaths 

 Cephalopods 

 Mollusks 

 Ostracods 

 Larvaceans 

 Annelids 

 Shrimp 

 Cumacean 

 Nemerteans 

 Mysids 

 Crab 



Unidentified 

 Digested 

 Total 



Table 3. — Grams of food organisms per fish mot including fish 

 with empty stomachsl in each size class, Tenyo Mam, spring 

 1977. 



Data on the species composition offish in pollock 

 stomachs were available from the summer cruise 

 of 1974 [Oregon). Fish ingested were identified 

 from the stomachs of 27 pollock ranging in fork 

 length from 26 to 57 cm (mean = 40 cm). Of the fish 

 ingested, 89^/f by weight and 39^f by number were 



