Effects of a Parasite, Eubothrium salvelini (Cestoda: Pseudophyllidea), on the Resistance of Juvenile Sockeye Salmon, Oncorhynchus nerka, to Zinc

Abstract

Most research to date on the tolerance of natural populations to physical and chemical stressors appears to have overlooked that parasites may themselves be stressors, and that they may be capable of modifying the resistance of the host to other applied stressors. Sockeye salmon (Oncorhynchus nerka) smolts trapped at the outlet of Babine Lake, central British Columbia, were subjected to 1 mg/ℓ dissolved zinc under laboratory conditions. Smolts infected with the intestinal cestode Eubothrium salvelini proved to be significantly more susceptible to zinc than were noninfected smolts. We recommend that future investigations of environmental effects, especially on wild populations, include consideration of the state of parasitism of the test organisms. Key words: Eubothrium salvelini, cestode, sockeye salmon, Babine Lake, zinc, toxicity