Salmon farm escapes occur regularly, with millions of farmed salmon entering wild ecosystems. The welfare implications extend to both escaped farmed fish and wild populations.
Salmon farm escapes create welfare harms for multiple populations. Escaped farmed salmon are domesticated animals with reduced fitness for wild survival - they face predation, starvation from inability to compete effectively for food, and disease from exposure to pathogens they lack resistance to. Wild salmon populations affected by interbreeding with domesticated fish may lose adaptive traits honed over thousands of years to specific river conditions - reducing the fitness of entire wild populations over generations. Sea lice and diseases transmitted from farm escapees to wild fish create health welfare problems in wild populations. The welfare case for preventing escapes through better containment technology and siting is both a wild fish and farmed fish welfare argument.