Feeding and growth of seasonal cohorts of larval walleye pollock (Theragra chalcogramma) in Auke Bay, Alaska

Abstract

Larval walleye pollock, Theragra chalcogramma (Pallas), typically occur in the water column in synchrony with peak densities of prey. A primary objective of this investigation was to examine and compare growth rates of larval pollock. The growth rate of a synchronous cohort (hatched 10-14 May, 1986) was found to be significantly higher (P<0.05) than that of an earlier cohort (hatched 15-19 April, 1986) . Synchronous cohorts are larvae that occur simultaneously with the maximum densities of herbivorous copepods. Growth rates were determined by otolith analysis. Prey densities and water temperature were implicated as causes of the observed differences in growth. Prey densities were approximately 3 times higher for the synchronous cohort than the early cohort. Additionally, the early cohort experienced water temperatures 2-3°C colder than the synchronous cohort. Results suggest that synchronous larval walleye pollock have higher growth rates and may have higher survival rates.