PREY SELECTION BY AGE-0 WALLEYE POLLOCK, THERAGRA-CHALCOGRAMMA, IN NEARSHORE WATERS OF THE GULF-OF-ALASKA

Juvenile walleye pollock, Theragra chalcogramma, is the dominant forag e fish on the continental shelf of the Gulf of Alaska, yet little is k nown about the feeding habits of this important interval of pollock li fe history. The taxonomic composition and size of prey found in the st omachs of age-0 juveniles collected at three nearshore locations in th e Gulf of Alaska in September 1990 were compared to the composition an d size of zooplankton collected in concurrent plankton tows. The maxim um length of prey consumed increased dramatically over the length rang e of pollock examined (58-110 mm) from approximately 7 mm to 30 mm, du e mainly to the consumption of large euphausiids and chaetognaths by t he bigger individuals. The maximum width of prey changed little over t his size range although there was a general increase in prey width wit h increasing predator size. The minimum prey length and width did not change with increasing fish size. Juvenile pollock generally selected the larger prey sizes relative to what was available. Juvenile pollock showed a marked preference for adult euphausiids and decapod larvae a nd an avoidance of copepods and chaetognaths relative to the numbers c ollected in net tows. These results are discussed relative to the feed ing ecology of these juvenile fishes.