Maturity Condition of Pelagic Walleye Pollock from the Aleutian Basin of the Bering Sea

Abstract

Maturity condition of pelagic walleye pollock Theragra chalcogramma in the winter Aleutian Basin was examined from GSI (gonadosomatic index) changing trend and observations of gonads collected through midwater trawl samplings conducted during December, 1988 to February, 1989. Throughout the whole survey period female GSI values increased gradually and rapidly reached the highest level around late February while those of males remained unchanged. Spawning female and spermatozoa-releasing male pollock occurred during late February in the southeastern waters of the Aleutian Basin. Assuming that pollock migrate eastward in the Aleutian Basin during winter and spawn in the southeastern Aleutian Basin, spawning was suggested to begin late in February in 1989.