Salmon Aquaculture Welfare: Sea Lice, Crowding, and Slaughter

Atlantic salmon farming is among the largest and most welfare-significant forms of aquaculture. Sea lice infestations, crowding, and slaughter methods are central welfare concerns.

Key Facts

Global Atlantic salmon aquaculture production exceeds 2.5 million tonnes annually
Norway, Chile, Scotland, and Canada are the largest producing nations
Sea lice infestations cause chronic skin lesions and are the most significant welfare issue in salmon farming
Standard stocking densities allow up to 25 kg of fish per cubic metre of cage volume
Slaughter methods include carbon dioxide stunning, percussion, and live bleeding
Welfare improvements including lice monitoring, lower densities, and cleaner fish are being adopted

Welfare Considerations

Sea lice feed on salmon skin and mucus, causing open wounds, secondary infections, and chronic pain. Heavy infestations are associated with reduced feeding, abnormal swimming behaviour, and elevated stress hormones. Treatment involves chemical bath immersion or mechanical removal — both acutely stressful. Crowded net cages restrict natural swimming and social behaviour. Carbon dioxide stunning used in many facilities causes prolonged distress before unconsciousness. Cleaner fish (wrasse and lumpfish) used to remove lice face their own welfare challenges, including high mortality in salmon farming environments.

What You Can Do

Choose salmon from lower-density, lice-managed or land-based (RAS) farms when possible
Support RSPCA Assured or equivalent welfare-certified salmon products
Reduce farmed salmon consumption given the current state of welfare in most operations
Advocate for mandatory welfare monitoring and reporting in salmon aquaculture licensing