Pathogen Screening of Naturally Produced Yakima River Spring Chinook Smolts; Yakima/Klickitat Fisheries Project Monitoring and Evaluation, 2004-2005 Annual Report.

Abstract

In the spring of 2004 naturally produced smolts outmigrating from the Yakima River Basin were collected for the sixth year of pathogen screening. This component of the evaluation is to monitor whether introduction of hatchery produced smolts would impact the prevalence of specific pathogens in the naturally produced spring chinook smolts. Increases in prevalence of any of these pathogens could negatively impact the survival of these fish. Since 1999 the Cle Elum Hatchery has been releasing spring chinook salmon smolts into the upper Yakima River to increase natural production. In 1998 and 2000 through 2004 naturally produced smolts were collected for monitoring at the Chandler smolt collection facility on the lower Yakima River. Smolts were collected from mid to late outmigration, with a target of 200 fish each year. The pathogens monitored were infectious hematopoeitic necrosis virus, infectious pancreatic necrosis virus, viral hemorrhagic septicemia virus, Flavobacterium psychrophilum, Flavobacterium columnare, Aeromonas salmonicida, Yersinia ruckeri, Edwardsiella ictaluri, Renibacterium salmoninarum and Myxobolus cerebralis. Of these pathogens, only R. salmoninarum was detected in very low levels in the naturally produced smolts outmigrating in 2004. To date, only bacterial pathogens have been detected and prevalences have been low. There have been small variations each year and these changes are attributed to normal fluctuations in prevalence. All of the pathogens detected are widely distributed in Washington State.