FY 1995

Sea-ice conditions and the distribution of walleye pollock (Theragra chalcogramma) on the Bering and Chukchi Sea shelf

Wyllie-Echeverria, T.

Can. Spec. Publ. Fish. Aquat. Sci., 121, 131–136, In Climate Change and Northern Fish Populations, R.J. Beamish (ed.) (1995)

The Bering Sea Shelf is a large shallow shelf that is seasonally ice covered and supports large commercial fisheries. Sea ice occurs on the shelf for a period of up to 8 months. Its maximum southern extent varies as much as 30% interannually. The pattern of ice cover depends primarily on wind speed and direction, and secondarily on thermodynamics. Sea ice profoundly affects the underlying pelagic and benthic habitats. Pelagic species from the North Pacific dominate the outer shelf domain during the open-water season. This area is the object of multi-national fishing efforts focused on harvesting historically abundant resources of walleye pollock (Theragra chalcogramma). A hypothesis is presented that species utilization of the shelf will vary with ice cover. Benthic and pelagic species will respond differently to an open water outer shelf. I compare abiotic and biotic variability and demonstrate pollock can occupy areas further north during years of reduced ice cover.