FY 1986

Variability of the environment and selected fisheries resources of the eastern Bering Sea ecosystem

Incze, L.S., and J.D. Schumacher

In Variability and Management of Large Marine Ecosystems, K. Sherman and L.M. Alexander (eds.), American Association for the Advancement of Science, 109–143 (1986)

The commercial harvest of fish and invertebrates from U.S. waters of the eastern Bering Sea shelf ecosystem comes primarily from south of 60°N, with an average yield from this area exceeding 4 metric tons km yr. More than 70% of the total harvested biomass is comprised of a single species, walleye pollock (Theragra chalcogramma). Three species of benthic crab account for a small proportion of total harvest by weight, but are economically important and show marked fluctuations in abundance over periods of a few years. Spatial and temporal patterns of abundance of these four species are examined, emphasizing the occurrence of particularly strong year classes. Interannual variability in recruitment of these species is discussed with respect to prominent, variable features of their biotic and abiotic environment. Contrast is provided by two congeneric species of crab exhibiting markedly different recruitment patterns. The principal physical variables are sea temperature, horizontal, and vertical mixing (particularly during spring), and mean transport over periods of one or more months. The biotic variables for which we have data related to these species are zooplankton abundance during spring and changes in abundance of major predators in the ecosystem. The number of years of observation is insufficient to assess the real importance of any of the proposed mechanisms; however, the environmental and organismal changes are marked and well suited to further study.