Seabird responses to fluctuating prey availability in the eastern Bering Sea

Walleye pollock Theragra chalcogramma are important prey of piscivorous seablrds at offshore breeding colonies in the southeastern Bering Sea.The reproductive success of kittiwakes Rissa spp. is related to the abundance of juvenile pollock.It is proposed that poor pollock recruitment in recent years, as determ~ned by fisheries surveys, led to persistent kittiwake breeding failures in 1981-84.Declines in numbers of k~ttiwakes and other piscivorous seabirds at 2 colonies also may be related to the decline in pollock abundance.In contrast, planktivorous seabirds, which possibly compete with juvenile pollock for zooplankton, particularly copepods, might benefit from a low abundance of pollock.A conceptual model of food limitation and trophic interactions at several levels in the offshore pelagic food web of the eastern Bering Sea can be developed by relating relations between seabirds and their prey to ( l ) the high grazing efficiency of the herbivorous zooplankton community, which is dominated by large calanoid copepods, (2) estimates of a high annual loss of copepods, presumably to vertebrates, and (3) regional carbon budgets.The possibility that populations of several species respond to changes in pollock abundance should be considered in management decisions for the commercial pollock fishery