Aquaculture

Sea Lice and Salmon Welfare: An Ongoing Crisis

Welfare analysis of sea lice infestation in Atlantic salmon farming -- the most significant welfare challenge in salmon aquaculture.

Key Facts

Sea lice (primarily Lepeophtheirus salmonis and Caligus species) are ectoparasites causing severe welfare harm in farmed salmon
Heavy lice burdens cause open lesions, secondary infections, and chronic stress in affected fish
Sea lice reproduce rapidly on fish farms and are a vector for disease transmission
Chemical treatments including emamectin and hydrogen peroxide stress fish and have welfare implications
Mechanical removal using thermal delousing causes burn injury and acute stress in treated fish
Biological control using cleaner fish (wrasse and lumpfish) is widely adopted but raises its own welfare concerns
Cleaner fish welfare is poorly studied -- many wrasse die before fulfilling their functional role
2025 lice pressure remains high despite extensive industry investment in control measures

Welfare Significance

Sea lice infestation is the dominant welfare crisis in Atlantic salmon farming. Fish with heavy lice burdens experience chronic pain from open wounds and the stress of repeated treatment. The treatment methods themselves -- thermal baths, hydrogen peroxide, and mechanical brushes -- cause acute pain and injury. Fundamental changes to production systems, including closed containment, offer the most welfare-effective long-term solution.

What You Can Do

Advocate for closed containment salmon aquaculture as a welfare and environmental improvement
Support research into welfare-conscious lice control methods that do not cause treatment stress
Choose ASC-certified salmon and ask retailers about lice management welfare provisions
Support mandatory welfare reporting for sea lice burden and treatment frequency in salmon farms