Farmed Salmon Sea Lice Management and Welfare

Sea lice infestations are one of the most significant welfare challenges in Atlantic salmon aquaculture, causing painful lesions and requiring treatments that themselves carry welfare costs for the fish.

Key Facts

Sea lice are parasitic copepods that attach to salmon skin, causing wounds, osmotic stress, and immune suppression
A single sea lice infestation cycle can kill smolts and cause severe lesion damage to larger fish
Treatment options include chemical baths, mechanical delousing, cleaner fish, and laser systems
Mechanical delousing using high-pressure water or thermal treatment causes acute stress and physical injury
Cleaner fish including wrasse and lumpfish used to eat lice often suffer high mortality on salmon farms
Closed containment systems physically prevent sea lice from reaching farmed fish but cost significantly more

Welfare Considerations

Sea lice infestations cause progressive welfare harm to farmed salmon. Early infestation causes skin irritation and altered swimming behaviour. Heavy burdens cause open lesions, secondary infections, and severe physiological stress from osmotic disruption. Treatment options present a welfare tradeoff: chemical treatments expose fish to toxic compounds and cause stress; mechanical removal using pressurised water or thermal baths causes acute pain and injury to fish whose scales and skin are damaged. Mortality rates during mechanical treatment can be significant. The use of cleaner fish introduces a separate animal welfare problem, as wrasse in particular suffer extremely high mortality in salmon farm conditions. Reducing reliance on open-net cage systems would address sea lice at their source.

What You Can Do

Choose farmed salmon certified under ASC standards with documented sea lice management and welfare monitoring
Support producers investing in closed containment systems that physically exclude sea lice from fish
Advocate for welfare standards limiting the use of mechanical delousing methods causing acute fish injury
Back research developing effective biological sea lice control with lower welfare costs than current methods
Reduce consumption of farmed Atlantic salmon from open-net systems with high sea lice management burdens