Farmed Salmon Sea Lice Management

Sea lice are ectoparasites that cause significant welfare harm to farmed Atlantic salmon and threaten wild salmon populations near farm sites.

Key Facts

Sea lice (Lepeophtheirus salmonis and Caligus species) attach to salmon skin and gills, causing lesions, scale loss, and physiological stress.
Severe sea lice infestations cause open wounds on the head and back that allow secondary bacterial infection.
Treatment options include chemical treatments, thermal delousing, mechanical removal, and biological control using cleaner fish.
Thermal delousing — exposing fish to 34-degree water briefly to dislodge lice — causes stress and mortality if poorly calibrated.
Cleaner fish species (wrasse and lumpfish) eat sea lice from salmon but themselves have significant welfare needs that are often unmet.

Welfare Considerations

Sea lice management in salmon farming creates a welfare dilemma within a welfare problem. The lice themselves cause significant harm; the treatments used to remove them also carry welfare costs. Thermal and mechanical delousing cause acute stress and mortality when improperly applied. Cleaner fish — used as biological control — are often housed poorly and discarded after a single season without adequate welfare consideration. Addressing sea lice welfare comprehensively requires both lice prevention strategies and humane treatment methods that minimise welfare costs to both salmon and their cleaner fish.

What You Can Do

Choose certified farmed salmon from producers with documented sea lice management welfare standards.
Advocate for cleaner fish welfare standards including appropriate housing, diet, and end-of-life management.
Support research into sea lice vaccines and genetic resistance that could reduce treatment necessity.
Reduce farmed salmon consumption where welfare-certified alternatives are unavailable.