A Survey of Pathogens Found in Eulachon Thaleichthys pacificus Captured from the Cowlitz River, Washington

Eulachon Thaleichthys pacificus are an important commercial and sport fish of the Northeast Pacific Ocean that supported large fisheries on the Columbia River from 1938-1989.  Large population declines have led to the Southern Distinct Population Segment of the species being listed as threatened under the Endangered Species Act in March 2010.  Development of effective management plans for the species are ongoing but have been hampered by a lack of basic biological information including pathogen susceptibility.  During the adult spawning migrations in 2011 and 2012, fish were collected from the Cowlitz River, a tributary to the Columbia River, and screened for nine bacterial and viral pathogens common to fishes in the region.  Only three out of the nine pathogens were detected: Flavobacterium psychrophilum (bacterial coldwater disease), Aeromonas salmonicida (furunculosis), and Renibacterium salmoninarum (bacterial kidney disease).  Among these, we found that F. psychrophilum was the predominant pathogen in sampled Eulachon.  These results indicate that more species may serveas reservoirs for these pathogens in the Columbia River than previously thought.  Further trials should be done to determine if these pathogens cause disease in Eulachon and to understand the dynamics of transfer between Eulachon and other species in the same habitats.