Variation in groundfish predation on juvenile walleye pollock relative to hydrographic structure near the Pribilof Islands, Alaska

Walleye pollock (Theragra chalcogramma) are an important forage fish in the eastern Bering Sea ecosystem. As part of an ongoing study of the processes affecting juvenile walleye pollock recruitment in the eastern Bering Sea, a concentrated effort has been focused on the hydrographic fronts near the Pribilof Islands, Alaska, as important nursery areas for these juveniles. D iel variation in the consumption of age-0 pollock by arrowtooth flounder (A therethes stomias) was examined from a series of collections at a station a t the tidal front located north of St Paul Island, Alaska. Age-0 pollock we re the primary prey of arrowtooth flounder throughout the day, but they wer e least digested in the late day, indicating a diurnal feeding pattern. A s imilar diurnal pattern was not seen in the vertical distribution of age-0 p ollock, suggesting that the feeding pattern exhibited by arrowtooth flounde r was based on their diel migratory behavior. Lengths of age-0 pollock cons umed by arrowtooth flounder were similar to those sampled with midwater tra wls. Walleye pollock cannibalism was examined along a transect that include d samples collected at the front and offshore of the front. Age-0 fish were the primary prey (by weight) at all locations. Adjacent cohort cannibalism was prevalent (age-0 pollock were 79% of the diet by weight) at the fronta l region. Estimates of age-0 pollock cannibalism rates were highest at the front for age-1 pollock and offshore for the adults. Prey selectivity analy sis indicated that age-0 pollock were more highly selected offshore than at the front. (C) 2000 International Council for the Exploration of the Sea.