Experimental Exposure of Trout and Salmon from 12 British Columbian Stocks to the Myxozoan ParasiteCeratomyxa shasta

Abstract

Abstract Juveniles of 12 Pacific trout and salmon stocks were exposed to the infectious stage of Ceratomyxa shasta in water from the lower Fraser River. Seven tests were conducted in the fall and spring of 1984–1987, but three resulted in no or little infection, possibly because of annual and seasonal variations in parasite abundance. Of three trout stocks from the lower Fraser River drainage, two were resistant and one was moderately resistant to the parasite. More than 50% of steelhead Oncorhynchus mykiss (formerly Salmo gairdneri) from the central Fraser River drainage and a coastal bay became infected after exposure. Two stocks of chinook salmon O. tshawytscha from the central Fraser River drainage were moderately resistant. Two non-Fraser River stocks, including coho salmon O. kisutch, showed low resistance.