Evidence of farm-induced parasite infestations on wild juvenile salmon in multiple regions of coastal British Columbia, Canada

• Published in: Canadian journal of fisheries and aquatic sciences Vol. 67; no. 12; pp. 1925 - 1932
• Main Authors: Price, M. H.H, Morton, A, Reynolds, J. D
• Format: Journal Article
• Language: English
• Published: Ottawa, ON National Research Council of Canada 01.12.2010; NRC Research Press; Canadian Science Publishing NRC Research Press
• Subjects: Agnatha. Pisces; Animal, plant and microbial ecology; Applied ecology; Aquaculture; Aquatic sciences; Biological and medical sciences; Comparative analysis; Control; Diseases and pests; Exploitation and management of natural biological resources (hunting, fishing and exploited populations survey, etc.); Fish stocking; Fisheries; Fishery management; Fundamental and applied biological sciences. Psychology; Lepeophtheirus salmonis; Management; Marine; Methods; Oncorhynchus gorbuscha; Oncorhynchus keta; Parasites; Parasitism; Salmon; Salmon fisheries; Vertebrates: general zoology, morphology, phylogeny, systematics, cytogenetics, geographical distribution; Canada; British Columbia; North America; Europe; America; British Columbia Canada; INE, Canada, British Columbia, Broughton Archipelago; INE, Canada, British Columbia, Georgia Strait; Salmonidae; Parasite; Reservoir; Host; Wild animal; Oncorhynchus gorbuscha; Oncorhynchus keta; Survival; Young animal; Infection; Vertebrata; Dynamics; Pisces; Rearing; Parasitism; Infestation; Strait of Georgia
• ISSN: 0706-652X; 1205-7533
• DOI: 10.1139/F10-105

Salmon farms are spatially concentrated reservoirs of fish host populations that can disrupt natural salmonid host-parasite dynamics. Sea lice frequently infect farm salmon and parasitize sympatric wild juvenile salmonids, with negative impacts on survival in Europe and Pacific Canada. We examined louse parasitism of wild juvenile chum salmon ( Oncorhynchus keta ) and pink salmon ( Oncorhynchus gorbuscha ) from three salmon farming regions in British Columbia (Finlayson, Broughton Archipelago, and Georgia Strait). We compared sites of low and high exposure to farms and included an area without farms (Bella Bella) to assess baseline infection levels. Louse prevalence and abundance were lowest and most similar to natural baseline levels at low-exposure sites and highest at high-exposure sites in all farm regions. A significantly greater proportion of the lice were Lepeophtheirus salmonis at high-exposure sites. Exposure to salmon farms was the only consistently significant factor to explain the variation in prevalence data, with a secondary role played by salinity. Our results support the hypothesis that salmon farms are a major source of sea lice on juvenile wild salmon in salmon farming regions and underscore the importance of using management techniques that mitigate threats to wild stocks.