The ecology of eulachon (Thaleichthys pacificus) in Twentymile river, Alaska

Abstract

The ecology of eulachon (Thaleichthys pacificus) was studied at Twentymile River, a tributory of Turnagain Arm located in southcentral Alaska. In 2000 and 2001, we investigated the environmental factors associated with the migration of adult eulachon and downstream drift of larval eulachon. We assessed run timing, freshwater duration, length, weight, age, presence or absence of teeth, fecundity, and gear selectivity for dip and gill nets. Catch per unit effort of migrating adult fish were correlated with water temperature, tide height, river discharge, light intensity, and the density of bald eagles (Haliaeetus leucocephalus). Water temperature, river discharge, tide height, and light intensity were related to downstream drift intensity of larvae. Radio telemetry was used successfully to study the migratrion movements of adult eulachon. Clusters of the upstream limits of migration identified four common spawning areas in both years.