High stocking densities in open-net salmon aquaculture pens create chronic stress, disease risk, and behavioral restrictions that compromise the welfare of millions of fish in commercial salmon farming operations.
Salmon crowding in open-net marine pens creates conditions that are fundamentally incompatible with the behavioral and physiological needs of a naturally migratory, active species. In the wild, Atlantic salmon range across vast ocean areas, but in commercial pens they are confined to spaces where normal swimming and orientation behaviors are severely restricted. The resulting chronic stress response suppresses immune function, increasing vulnerability to the sea lice and pathogens that represent significant animal welfare and environmental problems in salmon aquaculture. Improving welfare requires meaningful reductions in stocking density, investment in environmental enrichment through current generators and resting refuges, more robust disease prevention strategies, and the development of welfare monitoring protocols that assess fish behavioral and physiological indicators rather than relying solely on mortality rates.