Salmon escapes from aquaculture net pens affect both escaped fish welfare and wild salmon populations through competition, disease transmission, and genetic dilution of wild stocks.
Escaped farmed salmon face acute welfare challenges. Released suddenly from the dense, structured environment of net pens into open water, they are disoriented, vulnerable to predation, and lacking the foraging skills and genetic fitness of wild salmon. Many die quickly from starvation, predation, or failure to adjust to natural thermal variation. Escaped fish that survive and enter rivers face further stress — attempting to spawn without the conditioning of a full wild life cycle. From a wild animal welfare perspective, disease spread from escaped farmed fish creates suffering in wild populations, and genetic introgression from farm-origin fish reduces adaptive fitness in subsequent generations. Prevention through better net pen design and technology serves both farmed fish welfare and wild population protection.