Declining Wild Salmon Populations in Relation to Parasites from Farm Salmon

• Published in: Science
• Main Authors: Krkošek, Martin, Ford, Jennifer S., Morton, Alexandra, Lele, Subhash, Myers, Ransom A., Lewis, Mark A.
• Format: Article in Journal/Newspaper
• Language: English
• Published: American Association for the Advancement of Science (AAAS) 2007
• Subjects: The Louse; Oncorhynchus gorbuscha; Pink salmon; Copepods
• Online Access: http://dx.doi.org/10.1126/science.1148744; https://www.science.org/doi/pdf/10.1126/science.1148744

Rather than benefiting wild fish, industrial aquaculture may contribute to declines in ocean fisheries and ecosystems. Farm salmon are commonly infected with salmon lice ( Lepeophtheirus salmonis ), which are native ectoparasitic copepods. We show that recurrent louse infestations of wild juvenile pink salmon ( Oncorhynchus gorbuscha ), all associated with salmon farms, have depressed wild pink salmon populations and placed them on a trajectory toward rapid local extinction. The louse-induced mortality of pink salmon is commonly over 80% and exceeds previous fishing mortality. If outbreaks continue, then local extinction is certain, and a 99% collapse in pink salmon population abundance is expected in four salmon generations. These results suggest that salmon farms can cause parasite outbreaks that erode the capacity of a coastal ecosystem to support wild salmon populations.