Aquatic Animals

Sea Lice in Salmon Aquaculture: Welfare and Ecology

Sea lice infestations are one of the most serious welfare and ecological problems in Atlantic salmon farming, causing painful lesions, stress, and contributing to wild salmon population decline.

Key Facts

Sea lice cause open lesions, scale loss, and osmotic stress in salmon
Heavy infestations can kill young fish within days
Chemical treatments to control lice are themselves physiologically stressful
Escaping sea lice from farms infest wild salmon and sea trout
Cleaner fish such as wrasse and lumpfish are widely used but have their own welfare issues

Welfare Considerations

Salmon with heavy lice burdens display stress behaviours, reduced feeding, and immune suppression. Treatment with chemicals, heat, or mechanical methods is acutely stressful and sometimes fatal. The use of cleaner fish introduces a secondary welfare concern — wrasse in particular suffer high mortality, poor enrichment, and inadequate veterinary care in most farms. Welfare-positive approaches include closed containment systems and selective breeding for lice resistance.

What You Can Do

Choose salmon with lower-impact aquaculture certification
Support research into closed containment salmon farming
Advocate for mandatory welfare monitoring of cleaner fish
Reduce salmon consumption to lower demand on intensive systems
Support wild salmon conservation organisations