Atlantic salmon farms are a likely source of Tenacibaculum maritimum infection in migratory Fraser River sockeye salmon

• Published in: Canadian journal of fisheries and aquatic sciences Vol. 79; no. 8; pp. 1225 - 1240
• Main Authors: Bateman, Andrew W., Teffer, Amy K., Bass, Arthur, Ming, Tobi, Kaukinen, Karia, Hunt, Brian P.V., Krkošek, Martin, Miller, Kristina M.
• Format: Journal Article
• Language: English
• Published: 1840 Woodward Drive, Suite 1, Ottawa, ON K2C 0P7 Canadian Science Publishing 01.08.2022; NRC Research Press; Canadian Science Publishing NRC Research Press
• Subjects: Aquaculture; Atlantic salmon; Background levels; Bacterial diseases; Bacterial infections; Baseline studies; Differential equations; Diseases; Empirical analysis; Environmental aspects; Farms; Fish diseases; Fishes; Infections; Islands; Migration; Oncorhynchus nerka; Risk factors; Rivers; Salmo salar; Salmon; Salmoniformes; Sockeye salmon; Tenacibaculum maritimum; Canada; British Columbia Canada; Fraser River
• ISSN: 0706-652X; 1205-7533
• DOI: 10.1139/cjfas-2021-0164

Juvenile sockeye salmon (Oncorhynchus nerka) in British Columbia migrate past numerous Atlantic salmon (Salmo salar) farms from which they may acquire infectious agents. We analyse patterns of molecular detection in juvenile sockeye for the bacterium Tenacibaculum maritimum, known to cause disease in fish globally and to cause mouthrot disease in farmed Atlantic salmon in British Columbia. Our data show a clear peak in T. maritimum detections in the Discovery Islands region of British Columbia, where sockeye migrate close to salmon farms. Using well-established differential equation models to describe sockeye migration and bacterial infection, fit to detection data, we assessed support for multiple hypotheses describing farm- and background-origin infection. Our best models (with 99.8% empirical support) describe constant background infection pressure, except around Discovery Islands salmon farms, where farm-origin infection pressure peaked at 12.7 (approximate 95% CI: 4.5 to 31) times background levels. Given the severity of associated disease in related species and the imperilled nature of Fraser River sockeye, our results suggest the need for a more precautionary approach to managing farm–wild interactions in sockeye salmon.