Observations of Eulachon, Thaleichthys pacificus, in the Elwha River, Olympic Peninsula Washington

Abstract

This paper summarizes a pilot study conducted in spring 2005 that documents, for the first time, eulachon, Thaleichthys pacificus, in the Elwha River. General morophometrics of the Elwha eulachon are comparable to those found in other northwest systems. Eulachon abundance in the Elwha appears much lower than in other northwest rivers with documented eulachon runs. Theories for fish presence in the Elwha include straying, and reestablishment of a remnant stock. The local historic observations of eulachon in the Elwha (but not other Olympic Peninsula rivers) up until the mid 1970's, combined with the severely degraded habitat of the lower Elwha River, indicate that the Elwha eulachon are a remnant population. Upcoming dam removals will restore riverine sediment processes, including delivery of sand gravel size material suitable for eulachon spawning to the now severely sediment starved lower river. Dam removals are therefore anticipated to have restoration benefit to eulachon and may play a role in regional...