Salmon Lice and Welfare in Open-Net Aquaculture

Salmon lice infestations are the most significant animal welfare and environmental problem in open-net salmon aquaculture, causing chronic skin damage and pain in farmed fish while spreading to wild salmon populations.

Key Facts

Salmon lice (Lepeophtheirus salmonis) can cause lesions penetrating to the skull of severely infested fish
Norway produces over 1.4 million tonnes of farmed Atlantic salmon annually, the largest in the world
Chemical treatments for lice have increasing resistance problems, leaving many farms without effective control methods
A single farmed salmon can carry more than 1,000 lice, far exceeding welfare thresholds of 0.5 mature female lice per fish
Laser systems, warm water treatments, and biological controls using cleaner fish are among the alternatives to chemical treatments

Welfare Considerations

Salmon lice represent one of the best-documented animal welfare crises in aquaculture. Heavy infestations cause chronic pain through skin erosion, with lesions that can expose underlying tissue and bone. Welfare indicators including abnormal swimming behaviour, reduced feeding, and elevated cortisol are well-documented in heavily infested fish. Chemical treatments cause acute physiological stress during application. Biological control using wrasse and lumpfish as cleaner fish raises additional welfare concerns for these cleaner fish, which are often poorly managed.

What You Can Do

Choose ASC-certified salmon which includes lice control welfare standards in its requirements
Advocate for closed-containment aquaculture systems that eliminate sea lice exposure to both farmed and wild fish
Support research into lice-resistant salmon strains and biological control methods that reduce chemical use
Reduce farmed salmon consumption and choose wild-caught Pacific salmon as a lower-welfare-impact alternative