Salmon escapes from net pen aquaculture affect both the escaped fish and wild populations, with welfare and conservation consequences that have prompted regulatory responses in major producing countries.
Farmed salmon escapes represent both an environmental and individual welfare problem. Escaped fish are adapted to farm conditions — net pens with regular feeding, high densities, and no predators — and are poorly equipped to survive independently in the marine or river environment. Their welfare after escape is likely poor: they face starvation, predation, and the physiological stress of navigating environments for which they have no behavioural preparation. Additionally, their presence in rivers disrupts wild fish populations through competition, disease transmission, and genetic introgression. Preventing escapes through robust net pen design, real-time monitoring, and rapid response to damage is therefore both a conservation and welfare imperative. Recapture efforts after escapes can recover some fish and prevent some of the ongoing welfare costs of life in an unsuitable environment.