FISllKKV HULLETIN: VOL. 86. NO. 4 



myctophids, and 0.6% stichaeids. In terms of 

 percent by number and the percent of frequency of 

 occurrence, the fishes other than gadids (FOG in 

 Figure 2D) were more important than the cepha- 

 lopods. No gadids were found in either the 30-49 

 cm group or the 50-69 cm group of fishes; however, 

 they were the dominant prey (75% by weight, 64% 

 by number, and 73% by frequency of occurrence) 

 of Greenland haUbut >70 cm (Fig. 2D, lower left) 

 as in the other three depth groups (Fig. 2A,B,C, 

 lower left). Other food in this size group included 

 macrourids, cyclopterids, and pleuronectids. Even 

 though gadids did not occur in the two smaller size 

 groups, they were important in the Depth 4 group 

 as a whole (Fig. 2D, lower right). 



Trends in Fish Consumption 



The size of the walleye pollock consumed by 

 Greenland halibut increased dramatically with pred- 



ator size (Fig. 3). The relationship appears linear 

 with r^ = 0.835. Based on the age-length key for 

 walleye pollock (Halliday and Umeda 1986), the wall- 

 eye pollock eaten by Greenland halibut were approx- 

 imately age and age 1 for smaller size fish (<50 

 cm), age 1 and age 2 for medium size fish (50-69 

 cm), and age 3 and age 4 for the fish >70 cm 

 (Fig. 4). 



The importance of prey fishes in the diet of Green- 

 land halibut appears to be depth related (Table 2). 

 Clupeids disappear from the diet in waters >200 m 

 deep, while gadids are important in all depths but 

 occur most frquently (85%FO), and comprise most 

 of the diet both in number and weight (65% and 

 93%, respectively), in the area <200 m deep. Zoar- 

 cids appear in stomachs only in the area 200-600 

 m deep, and bathylagids start appearing at 200-399 

 m and increase in importance as the water depth 

 increases. Myctophids seem to be more important 

 in the area 400-599 m than in the other depths. 



500 

 450 



400- 



'§ 350- 



E 



-P. 300 



WALLEYE POLLOCK 



A A. A 



20 40 60 80 



Predator fork length (cm) 



100 



Figure 3.— Scatter plot of the fork length of walleye pollock that were consumed by Greenland 

 halibut of different sizes in the eastern Bering Sea. 



684 



