Salmon Sea Lice Treatment Welfare

Sea lice treatments including thermal delousing and mechanical removal cause significant acute welfare harm — welfare science is identifying the least harmful effective treatment combinations.

Key Facts

Sea lice are the most economically and welfare-significant parasites in Atlantic salmon farming
Thermal delousing involves brief exposure to 34 degree Celsius water to dislodge lice
Mechanical delousing uses high-pressure water to remove lice from fish surface
Both methods cause scale loss, physical injury, and acute stress
Non-medicinal treatments are used to avoid drug resistance but carry high welfare costs

Welfare Considerations

Sea lice treatment welfare is a genuine dilemma: untreated lice cause chronic tissue damage and immune compromise; treatments cause acute injury and stress. Thermal delousing in particular causes scale loss, fin erosion, and elevated cortisol for 24-48 hours post-treatment. Snorkel feeding systems that prevent salmon from swimming to the surface reduce lice burden without treatment stress. Cleaner fish (wrasse and lumpsucker) provide continuous low-level lice removal with lower welfare cost than batch treatments.

What You Can Do

Choose salmon from farms that use biological lice control as primary method
Support Fish Welfare Initiative research into low-welfare-cost lice management
Advocate for maximum treatment frequency limits in national aquaculture welfare codes
Ask retailers about sea lice management methods in their salmon supply chains