Atlantic salmon aquaculture produces over 2.5 million tonnes annually, but intensive farming conditions create significant welfare challenges including sea lice, crowding stress and slaughter welfare concerns.
Salmon welfare has emerged as one of the most significant farmed animal welfare issues numerically: billions of individual fish are farmed annually. The evidence for salmon sentience has grown substantially — they show learned fear responses, preferential avoidance of noxious stimuli, and physiological stress markers comparable to tetrapods. Crowding at high stocking densities suppresses immune function and increases aggression-related injury. Sea lice infestations cause genuine suffering — behavioural evidence shows lice-infested fish perform unusual scratching behaviours and exhibit elevated cortisol. Treatment methods themselves carry welfare costs: hydrogen peroxide and warm water treatments cause significant stress and mortality. Slaughter welfare is inconsistent — many farms still use CO2 immersion, which causes prolonged distress before unconsciousness. Pre-slaughter stress (crowding, air exposure) compromises both welfare and meat quality. Genetic selection for rapid growth rates has created fish with cardiovascular problems analogous to fast-growing broiler chickens.