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Fishery Bulletin 1 10(3) 
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Amphipod Chaetognath Copepod 
Crab Euphausiid Misc Pollock Pollock Pollock Pollock 
<60 mm 60-200 mm >200 mm No length 
Prey category 
Figure 4 
Diet of walleye pollock (Theragra chalcogramma ) sampled in the eastern Bering Sea, 1982-2006 
(excluding 1983 and 1984). (A) Average percent frequency of occurrence ( %FO ), percent body 
weight (%BW), and partial fullness ( PF ) of ten prey groups are shown. (B) The %FO, %BW , 
and PF of prey pollock between 60 mm and 200 mm standard length from predator pollock 
stomachs and the percentage of stations where cannibalism occurred for the same years. 
Standard error bars are shown for %FO , %BW, and PF. 
amount that occurred was also related to location and 
its associated bottom depth and temperature, and the 
abundance of age-1 prey pollock, but was not related to 
the presence of the cold pool. Mueter et al. (2006) also 
found no evidence that the presence of the cold pool 
was related to total predation mortality (by multiple 
species of predators) on age-1 pollock, as estimated by 
a multispecies virtual population analysis; instead total 
predation mortality of age-1 pollock was related to the 
abundance of adult pollock and the spatial association 
between juveniles and adults. 
The spatial overlap variable between predator and 
prey pollock in this study was a measure of horizontal 
overlap and did not account for potential differences in 
vertical distribution. Age-0 pollock are found above the 
thermocline in the summer, and several studies have 
examined the hypothesis that water column stratifica- 
tion separates them from cannibalistic adults during 
the summer (Bailey, 1989; Swartzman et al., 1994). In 
the summer, the majority of prey pollock available to 
large fish are age-1 pollock, which are often found near 
the bottom (Duffy-Anderson et al., 2003). The spatial 
