. The Eastern Bering Sea Shelf : oceanography and resources / edited by Donald W. Hood and John A. Calder. Oceanography Bering also determine available prey. Although regional, seasonal, and yearly variations in prey densities must be important in determining food composition and feeding rates, these have not yet been well described in the eastern Bering Sea. Larval pollock (5-20 mm) have been reported by Clarke (1978) to undergo shifts in selection of prey sizes during ontogeny. The gut contents of small larvae (5-10 mm) consisted mainly of copepod eggs and nauplii. Larger larvae showed
. The Eastern Bering Sea Shelf : oceanography and resources / edited by Donald W. Hood and John A. Calder. Oceanography Bering also determine available prey. Although regional, seasonal, and yearly variations in prey densities must be important in determining food composition and feeding rates, these have not yet been well described in the eastern Bering Sea. Larval pollock (5-20 mm) have been reported by Clarke (1978) to undergo shifts in selection of prey sizes during ontogeny. The gut contents of small larvae (5-10 mm) consisted mainly of copepod eggs and nauplii. Larger larvae showed progressively increasing fractions of cyclopoid copepods, cala- noids, and larval euphausiids. Juvenile pollock (2-20 cm) presumably feed on a corresponding series of primarily zooplankton prey of increasing sizes, perhaps foraged from areas high in the water column. Although not well studied, important food items probably include copepods, amphipods, juvenile and adult euphausiids, eggs, and larval fishes. As adults (lengths 20-90 cm) pollock are general- ized predators that appear to follow a "diumally schooling-nocturnally active" behavior pattern, although freshly ingested food items can be found in the gut at any time of day. Large eyes are apparently adaptive for visual feeding, hunting at night, and foraging during low vdnter light intensi- ties. The sleek, fusiform body indicates capabili- ties of fast swimming speeds. A large mouth and abundant, fine needle-like dentition provide good apparatus for seizing and ingesting large, active zooplankton (primarily Thysanoessa spp. and Parathemisto spp.) and fish (mainly juvenile pollock) prey (Fig. 33-19). c 0) c o o o (0 E o (A 100 80 [D Pollock Hi Shrimp and crab Walleye pollock 541 I—I Euphausiids H Amphipods H Copepods. M CM CO to Fork Length (mm) Figure 33-19. Changes in prey selection with size (from Takahashi and Yamaguchi 1972). To place the role of pollock in the eastern Bering Sea food web in perspective
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