Survival of Rainbow Trout and Lake Trout after Sea Lamprey Attack

Abstract
Survival was significantly higher (P = 0.054) for rainbow trout Oncorhynchus mykiss (formerly Salmo gairdneri) than for lake trout Salvelinus namaycush when the fish were subjected in the laboratory to a single attack by a sea lamprey Petromyzon marinus. Of 77 rainbow trout, 40% died (35% by direct attack and 5% by secondary infection) and 60% survived; of 77 lake trout, 56% died (42% by direct attack and 14% by secondary infection) and 44% survived. The higher survival of rainbow trout probably resulted from their more aggressive feeding behavior in captivity, greater resistance to secondary infection, and better adaptation to water temperatures higher than 10°C. The location of sea lamprey attachment on the fish was not a factor in the mortality of either species. These results are the first to indicate that survival is higher for one salmonid than for another after a single sea lamprey attack.

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