Intensive Salmon Farming and Open-Net Cage Welfare

Open-net cage Atlantic salmon farming raises significant welfare concerns relating to stocking density, sea lice, disease, and the welfare implications of fish unable to escape their environment.

Key Facts

Global Atlantic salmon aquaculture produces over 2.5 million tonnes annually, primarily in Norway, Chile, Scotland, and Canada
Open-net cages allow interaction with the wild marine environment — including sea lice, wild fish contact, and escaped farmed fish
Stocking densities in Scottish salmon cages are regulated at a maximum of 25 kg/m3 but average densities may be lower
Sea lice infestations affect nearly all Scottish salmon farms annually, requiring repeated treatment interventions
Salmon welfare assessment is increasingly standardised using operational welfare indicators including fin condition, lice counts, and behaviour
Scotland has developed a Salmon Interactions Working Group to address welfare, environmental, and regulatory concerns

Welfare Considerations

Open-net cage salmon welfare is affected by multiple concurrent stressors: stocking density limiting normal swimming and escape from conspecifics, sea lice causing skin damage and chronic immune stimulation, treatment procedures causing additional acute stress, and the inability to escape from any of these conditions. The welfare of fish in open-net systems is fundamentally constrained by the open-cage design — fish cannot move away from lice pressure, water quality fluctuations, or aggressive conspecifics. Land-based RAS (recirculating aquaculture systems) offer greater welfare control but are significantly more energy-intensive. Improving welfare within existing open-net systems requires continuous monitoring, rapid treatment response, and lower stocking densities than current regulations permit.

What You Can Do

Choose Scottish salmon certified under RSPCA Assured which sets welfare-specific standards above legal minimums
Support the Aquaculture Stewardship Council (ASC) certification which includes welfare metrics in its salmon standard
Reduce salmon consumption or choose alternative omega-3 sources including plant-based algae oil supplements
Support research into land-based RAS salmon production that provides better welfare control with reduced environmental impact