Differential infestation of juvenile Pacific salmon by parasitic sea lice in British Columbia, Canada

• Published in: Canadian Journal of Fisheries and Aquatic Sciences
• Main Authors: Brookson, Cole B., Krkošek, Martin, Hunt, Brian P.V., Johnson, Brett T., Rogers, Luke A., Godwin, Sean. C.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 2020
• Subjects: Aquatic Science; Ecology, Evolution, Behavior and Systematics; Canada; Pacific; British Columbia; Sockeye; Keta; Fraser River; Oncorhynchus gorbuscha; Pink salmon
• Online Access: http://dx.doi.org/10.1139/cjfas-2020-0160; https://cdnsciencepub.com/doi/full-xml/10.1139/cjfas-2020-0160; https://cdnsciencepub.com/doi/pdf/10.1139/cjfas-2020-0160

Fraser River Pacific salmon have declined in recent decades, possibly from parasitism by sea lice (Caligus clemensi and Lepeophtheirus salmonis). We describe the abundance of both louse species infesting co-migrating juvenile pink (Oncorhynchus gorbuscha), chum (Oncorhynchus keta), and sockeye (Oncorhynchus nerka) salmon over 5 years in the Discovery Islands and Johnstone Strait, British Columbia. The generalist louse, C. clemensi, was 5, 7, and 39 times more abundant than the salmonid specialist, L. salmonis, on pink, chum, and sockeye salmon, respectively. Caligus clemensi abundance was higher on pink salmon (0.45, 95% CI: 0.38–0.55) and sockeye (0.39, 95% CI: 0.33–0.47) than on chum salmon. Lepeophtheirus salmonis abundance was highest on pink salmon (0.09, 95% CI = 0.06–0.15). Caligus clemensi had higher abundances in Johnstone Strait than in the Discovery Islands. These results suggest differences in host specialization and transmission dynamics between louse species. Because both lice infest farmed salmon, but only C. clemensi infests Pacific herring (Clupea pallasii), conservation science and management regarding lice and Fraser River salmon should further consider C. clemensi and transmission from farmed salmon and wild herring.