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

Juvenile coho salmon (Oncorhynchus kisutch), sockeye salmon (O. nerka), and steelhead trout (Salmo gairdneri) were infected by intraperitoneal injection of a suspension of the causative organism of bacterial kidney disease at seven experimental temperatures from 3.9 to 20.5 °C. In coho salmon and steelhead trout percent mortality was maximal (78–100%) in the range of 6.7–12.2 °C. As the temperature increased above 12.2 °C mortality declined progressively; at 20.5 °C it was only 8–14%. The two highest temperatures had some suppressing effect on the disease, which was greatest at 20.5 °C. In sockeye salmon this was not apparent, as percent mortality was essentially 100% at all temperatures from 6.7 to 20.5 °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 three species of salmonids at the higher temperatures, varying from 21 to 34 days at 15.0–20.5 °C. It increased progressively as temperature decreased below this range; at 6.7 °C it varied from 60 to 71 days among the three species. Key words: bacterial kidney disease, temperature, salmonids, Corynebacterium, coho salmon, sockeye salmon, steelhead trout