Arrowtooth flounder Atheresthes stomias diet and prey consumption near Kodiak Island, Alaska

Abstract

The arrowtooth flounder Atheresthes stomias (ATF) population in the Gulf of Alaska has increased dramatically over the past 25 years and the resulting ecosystem impacts are unclear. Arrowtooth flounder diet and prey consumption was studied to more accurately assess the predator-prey relationships of this key predator near Kodiak Island, Alaska. Temporal and ontogenetic diet trends were quantified from the analysis of 742 ATF stomachs sampled from annual bottom trawl surveys conducted in May and August from 2002 to 2004. Several significant dietary trends were found, most notably: 1) euphausiids decreased in dietary importance from May to August whereas the importance of capelin Mallotus villosus increased and 2) smaller ATF consumed more capelin and larger ATF consumed more walleye pollock Theragra chalcogramma and Pacific sand lance Ammodytes hexapterus. A bioenergetics model was used to estimate ATF prey consumption. Within the study area, the ATF population was dominated by large individuals ([great than or equal to] 50 cm total length) that accounted for> 75 % of the population's total prey biomass consumption. Arrowtooth flounder were significant predators and consumed an estimated 339 t of fish prey including Pacific sand lance and walleye pollock and 222 t of invertebrate prey such as euphausiids and shrimps.