Welfare of Animals in Marine Aquaculture Net Pens

Open-net marine aquaculture for salmon, sea bass, sea bream, and other species raises complex welfare challenges related to density, disease, parasites, and slaughter.

Key Facts

Global marine aquaculture produces over 30 million tonnes of fish per year
Sea lice infestations are the dominant welfare challenge in Atlantic salmon farming, causing skin damage and stress
Stocking densities in net pens can reach 25-40 kg per cubic metre for salmon
Mechanical delousing treatments (hydrolicer, thermolicer) cause acute stress and can injure fish
Crowding for harvesting is a major acute stressor before slaughter in net pen operations
Norway, Scotland, and Chile are the world largest marine net pen salmon producers

Welfare Considerations

Fish in marine net pens face a range of chronic and acute welfare challenges. Sea lice are perhaps the most significant, causing tissue damage, osmoregulatory disruption, and immuno-suppression, while treatments intended to control them can themselves cause significant welfare harm. Crowding, noise, boat disturbance, and predator netting failures add additional stressors. Breed selection and improved husbandry practices offer paths to improved welfare within existing net pen systems.

What You Can Do

Choose ASC (Aquaculture Stewardship Council) certified seafood
Support research into non-chemical sea lice controls such as cleaner fish and lasers
Ask seafood retailers about their supplier welfare standards
Reduce consumption of farmed salmon from low-welfare sources
Advocate for stocking density regulations backed by welfare science