The feeding ecology of chum salmon fry (Oncorhynchus keta) in northern Prince William Sound, Alaska

Abstract

A two year study of the feeding ecology of early outmigrating chum salmon fry, Oncorhynchus keta, in northern Prince William Sound, Alaska, demonstrated harpacticoid copepods and chironomid insects to be dominant food taxa with calanoid copepods, polychaete larvae, cladocerans and cirripeds also contributing. Examination of the IRI (Index of Relative Importance) values for harpacticoids and insects revealed fluctuating seasonal patterns. Low IRI values for harpacticoids and/or insects coincided with higher IRI values for calanoids, polychaetes, cladocerans and cirripeds. ANOVA analyses and t-tests results on stomach contents demonstrated spatiotemporal variations in diet. Early outmigrating chum fry inhabited tidal mudflats, rocky beaches and vertical rocky outcrops where harpacticoids and insects were prevalent. CTD data and plankton tows indicated that tidal advection supplied pelagic prey from Unakwik Inlet to Jonah Bay. Fluctuating IRI values by prey taxa suggest an opportunistic rather than selective feeding behavior for chum fry based on prey availability.