Susceptibility of Salmonid Species and Hatchery Strains of Chinook Salmon (Oncorhynchus tshawytscha) to Infections by Ceratomyxa shasta

Nine salmonid species and nine hatchery strains of chinook salmon (Oncorhynchus tshawytscha) were examined for susceptibility to infection by Ceratomyxa shasta. All salmonid species tested were susceptible to infection by this myxosporidan, although no deaths occurred in the Atlantic salmon (Salmo salar). The level of resistance varied widely among the different species. A low prevalence of ceratomyxosis occurred in hatchery strains of chinook salmon from the Columbia River basin, while those chinook strains derived from outside this drainage system were highly susceptible to the parasite.