FEEDING SELECTIVITY OF LARVAL WALLEYE POLLOCK THERAGRA-CHALCOGRAMMA IN THE OCEANIC DOMAIN OF THE BERING SEA

Feeding of larval walleye pollock was examined with respect to density and distribution of micro- and mesozooplanktonic prey (< 500 mu m) at 6 depths in the oceanic domain of the Bering Sea to determine if firs t-feeding larvae select among available prey and to assess their forag ing environment in comparison to other locations where walleye pollock spawn. At 30 m depth, walleye pollock larvae and copepod nauplii occu rred at maximum densities of 106.6 ind. 100 m(-3) and 26.3 ind, l(-1) respectively. First-feeding walleye pollock larvae (3.5 to 6.5 mm) fed exclusively on copepod nauplii and copepod eggs. Among copepod naupli i, larvae selected for Metridia sp. and Microcalanus sp. but against O ithona similis, even though the latter was the most abundant prey taxo n in the study area. Of the nauplii ingested by larval walleye pollock , there was evidence of selection for larger nauplii within Metridia s p., Microcalanus sp., and O. similis. In addition, larvae preferred St ages III to V of calanoid nauplii. Larvae at 30 m depth had the highes t incidence of feeding (97.5%) and number of prey items (4.6 larva(-1) ) ingested. Although the 30 m depth stratum provided best physical and foraging conditions, the overall low percentage of feeding larvae and low numbers of prey consumed suggest that foraging conditions for lar val walleye pollock at the time of sampling were below saturation feed ing levels.