Crowding stress in farmed Atlantic salmon is one of the most significant and modifiable welfare challenges in commercial aquaculture, with well-documented effects on physiology, behaviour, and immune function.
Crowding stress in salmon farming is a fundamental welfare challenge that interacts with virtually every other welfare variable — water quality, disease susceptibility, sea lice treatment efficacy, and slaughter outcomes. The economic incentive to maximise biomass per cage volume runs directly against welfare, making regulatory limits and third-party certification essential counterweights. The evidence is consistent: lower stocking densities produce healthier, calmer, faster-growing fish with better welfare. Some of the most progressive salmon producers have voluntarily adopted lower densities and found that improved welfare outcomes compensate economically through reduced disease costs and improved feed conversion. This makes crowding reform one of the most tractable welfare improvements in aquaculture.