Salmon Lice Treatment and Fish Welfare

Treating salmon for sea lice infestations is one of the most welfare-compromising aspects of salmon farming, with both the infestation and treatment causing significant harm.

Key Facts

Sea lice are parasitic copepods that graze on salmon tissue, causing wounds, stress and secondary infection
Lice infestations from farms increase infestation pressure on wild salmon populations in adjacent waters
Chemical treatments including hydrogen peroxide and azamethiphos baths cause acute stress and sometimes mortality
Mechanical treatments including laser systems and warm water cause trauma and thermal stress
Biological control using cleaner fish — wrasse and lumpfish — causes welfare concerns for the cleaner fish
Closed containment and in-tank lice control systems avoid lice entirely but have economic and scaling challenges

Welfare Considerations

Sea lice management exemplifies the welfare dilemma at the heart of intensive salmon farming: the infestation causes suffering, and the most common treatments also cause suffering. Welfare-conscious production prioritises prevention through biosecurity and early detection over reactive treatment. The welfare costs borne by the cleaner fish used in biological control — which die at high rates and are often not counted in welfare assessments — represent an additional and often overlooked concern.

What You Can Do

Support aquaculture certification schemes that require documented lice management welfare protocols
Advocate for cleaner fish welfare to be included in salmon farm welfare assessments
Encourage investment in closed containment systems that eliminate lice as a management challenge
Support research into lice-resistant salmon genetics and low-stress treatment methods
Choose salmon from farms with documented low lice burdens and minimal treatment use