Farmed Salmon and Sea Lice: A Persistent Welfare Crisis

Sea lice infestations are the leading welfare and economic challenge in Atlantic salmon farming, causing chronic pain, tissue damage, and significant mortality.

Key Facts

Sea lice (Lepeophtheirus salmonis) are parasitic copepods native to marine environments
Heavy infestations erode skin, expose underlying tissue, and can reach the skull
Chemical treatments including emamectin benzoate have generated resistant louse strains
Cleaner fish (wrasse, lumpsucker) are used as a biological control measure
Norway loses an estimated 50,000 tonnes of production annually to sea lice effects

Welfare Considerations

Salmon with heavy sea lice infestations experience chronic tissue damage, pain, and immunosuppression. The lesions created by lice feeding allow secondary bacterial and fungal infections. Chemical treatments — bath treatments and injected medicines — add further physiological stress. Cleaner fish themselves suffer high mortality in salmon cages, creating a secondary welfare problem. Closed containment systems eliminate the problem but require significant capital investment.

What You Can Do

Choose salmon certified to welfare standards with documented lice monitoring
Advocate for mandatory lice thresholds and public reporting in salmon farming
Support research funding for closed containment and recirculating aquaculture systems
Reduce farmed salmon consumption if welfare cannot be verified
Ask your supermarket to source from farms with transparent lice management records