Escaped farmed salmon interbreed with wild populations, causing genetic changes that reduce wild salmon fitness, creating a welfare concern that spans both farmed and wild fish.
The welfare interaction between farmed and wild salmon operates at multiple levels. Wild salmon that contract sea lice from farm sites experience the same skin damage and physiological stress as farmed fish — the welfare harm crosses the cage boundary. Wild salmon that hybridize with escaped farmed individuals produce offspring with reduced fitness — lower survival rates, impaired predator avoidance, and altered migration behavior — creating diffuse but real welfare costs across wild populations. The solution — closed containment aquaculture that eliminates the connection between farm sites and wild water — addresses both the welfare and conservation dimensions simultaneously. The higher cost of closed containment systems is a legitimate production challenge, but the externalized costs of open-cage escape and sea lice transmission are real costs borne by wild fish populations.