Aquaculture and Wild Fish Interactions: Disease, Genetics, and Ecosystem Welfare

Aquaculture operations can affect wild fish populations through disease transmission, genetic introgression, and escapees — welfare considerations extend beyond farmed fish to wild populations in the vicinity.

Key Facts

Salmon farm escapes — numbering hundreds of thousands annually — can interbreed with wild Atlantic salmon reducing adaptive fitness
Sea lice from salmon farms infect juvenile wild salmon during their sea migration, causing significantly elevated mortality
Genetic introgression from farmed to wild salmon reduces the local adaptation that allows wild fish to survive in specific environments
Aquaculture effluent including feed, feces, and medications affects benthic communities and water quality around farm sites
Closed-containment and recirculating aquaculture systems eliminate escape and disease transfer risks but at higher capital cost
Wild fish population welfare near poorly managed farms is measurably worse through elevated parasite burden and disease exposure

Welfare Considerations

Aquaculture's welfare impact extends beyond its own fish to wild populations that interact with farm operations. Sea lice from salmon farms create parasitic burden for migrating wild salmon that reduces their survival and reproductive success. Escaping farm salmon that interbreed with wild populations reduce the genetic fitness of the offspring for specific river conditions. These are not abstract population-level concerns — they represent the welfare of individual wild fish experiencing elevated parasite burden and the diminished survival of wild salmon whose adaptive genetics have been diluted. Closed containment systems that prevent both escape and disease transfer represent a welfare improvement for wild fish populations as well as farmed ones.

What You Can Do

Choose salmon from closed-containment or recirculating aquaculture systems where available
Support aquaculture siting regulations that protect wild salmon migration routes from sea lice exposure
Advocate for stronger escape prevention requirements in open-net salmon aquaculture
Support research into closed-containment aquaculture systems that eliminate wild fish welfare impacts
Reduce consumption of open-net salmon from areas with documented wild fish population impacts