Welfare of Farmed Atlantic Salmon During Sea Lice Treatment

Sea lice are the dominant health and welfare challenge in farmed Atlantic salmon, and the treatments used to control them carry their own significant welfare costs.

Key Facts

Sea lice infestations affect over 80% of Norwegian salmon farms in any given year
Hydrolicer treatment uses high-pressure water jets to remove lice, causing scale loss and internal haemorrhaging
Thermolicer treatment uses warm water to remove lice; temperatures above 34 degrees Celsius cause thermal shock and brain damage
Chemical treatments including azamethiphos cause neurological effects in salmon at effective doses
Cleaner fish including wrasse and lumpfish are used as biological control but face high mortality of 50-80% in some farms
Functional vaccines against sea lice are in development but none are yet commercially available

Welfare Considerations

Sea lice treatment in salmon farming represents a welfare dilemma in which the disease itself causes suffering, but the treatments used to control it also cause significant acute welfare harm. Mechanical treatments including hydrolicer and thermolicer expose fish to intense physical stress that frequently causes injury and in some cases death. The welfare calculus requires honest assessment of treatment harm against the harm of untreated infestation. Better-designed treatment equipment, lower treatment temperatures, and investment in biological and genetic resistance approaches represent the welfare-positive direction for the industry.

What You Can Do

Choose ASC certified salmon that includes lice management performance standards
Advocate for sea lice treatment welfare standards in aquaculture certification schemes
Support research into sea lice vaccines and genetic resistance breeding
Ask seafood retailers what lice treatment methods their salmon suppliers use
Reduce consumption of conventionally farmed Atlantic salmon from high-lice-pressure regions