Relation of Water Temperature to Bacterial Kidney Disease in Coho Salmon (Oncorhynchus kisutch), Sockeye Salmon (O. nerka), and Steelhead Trout (Salmo gairdneri)

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Abstract
Juvenile coho salmon (O. kisutch), sockeye salmon (O. nerka) and steelhead trout (S. gairdneri) were infected by i.p. injection of a suspension of the causative organism of bacterial kidney disease at 7 experimental temperatures from 3.9-20.5.degree. C. In coho salmon and steelhead trout, percent mortality was maximal (78-100%) in the range of 6.7-12.2.degree. C. As the temperature increased above 12.2.degree. C, mortality declined progressively; at 20.5.degree. C it was only 8-14%. The 2 highest temperatures had some suppressing effect on the disease, which was greatest at 20.5.degree. C. In sockeye salmon this was not apparent, as percent mortality was essentially 100% at all temperatures from 6.7-20.5.degree. C; this species appeared to be highly susceptible to the disease agent. Temperature also influenced the mean number of days between infection and death. This interval was shortest in all 3 species of salmonids at the higher temperatures, varying from 21-34 days at 15.0-20.5.degree. C. It increased progressively as temperature decreased below this range; at 6.7.degree. C it varied from 60-71 days among the 3 spp.