[Interactions Among Marine Birds and Commercial Fish in the Eastern Bering Sea]
by
Richard R. Straty and Richard E. Haight
National Marine Fisheries Service
Auke Bay Fisheries Laboratory
Auke Bay, Alaska 99821
Abstract
The high primary and secondary productivity of the eastern Bering Sea makes it one of the greatest producers of commercial fish and largest congregating areas of marine birds in the world. The fish and birds are so interrelated that fluctuations in the abundance of one may well be responsible for changes in the abundance of the other. The seasonal and annual variation in the impact of birds on fish is a function of the life history, food habits, growth rate, and final size of the fish species of concern and of the distribution, abundance, and feeding habits of bird populations—plus the effects of the environment on these factors. Stages in the life history of some of the important commercial fish and shellfish of the Bering Sea directly or indirectly influenced by marine birds are identified.
The eastern Bering Sea is one of the world's richest fish-producing areas and is also one of the world's major congregating areas for marine birds. The large extent of the continental shelf and the climatic and oceanographic characteristics of the eastern Bering Sea combine to make this region extremely productive biologically. The distribution and abundance of plankton, benthos, and fish determine the distribution, time, and character of the migration of marine birds in the eastern Bering Sea (Shuntov 1961). Several studies have illustrated the close relation between marine birds and the biological properties of surface waters (Tuck 1960; Bourne 1963; Solomensen 1965). Spatial and temporal variations in the abundance of the fish families Clupeidae (herring), Gadidae (codfish), Osmeridae (capelin), and Ammodytidae (sand lance) are thought to be major determinants of the breeding seasons, breeding places, and movements of boreal seabirds (Ashmole 1971). The timing of breeding among larids and alcids is related to the seasonal changes in the surface waters inhabited by Ammodytidae and Clupeidae in the North Sea (Pearson 1968).
The eastern Bering Sea contains members of these and other fish families that are extensively exploited by man; the fish are also important as forage for other species of commercial fish, marine mammals, and marine birds. During some part of their life cycles, all fish species feed on plankton, nekton, benthos, or other fishes.
The incidental use or dependence of marine birds on commercial fish and the items on which the fish feed account for the major interaction between man and these two groups of animals.