CANNIBALISM ON EGGS BY WALLEYE POLLOCK THERAGRA-CHALCOGRAMMA IN SHELIKOF STRAIT, GULF OF ALASKA

A strong density-dependent relationship has been observed for the walleye pollock Theragra chalcogramma population in the Western Gulf of Alaska. It has been suggested that this relationship may be attributed in part to egg cannibalism by the adult spawning stock. This hypothesis was examined by collecting stomach samples of walleye pollock from the main spawning area over 5 yr. Eggs were prevalent in many stomachs, especially in those from the older age classes. The mean number of eggs in the stomachs was not related to the overall amount of food in the stomach but was linearly related to the density of eggs in the water column. Total egg consumption was estimated for 3 years (1986, 1988, and 1989) and was found to be only a small (<1) percentage of the total egg production. Even during a year (1981) of peak adult abundance, the total calculated egg consumption was less than 3% of the total egg production. A passive filtration model provided estimates similar to those observed in the field. We conclude that egg cannibalism alone would not account for the high egg mortalities observed.