Salmon Sea Lice Treatment and Welfare

Sea lice treatments including chemical, biological and physical methods each have distinct welfare implications for both salmon and cleaner fish.

Key Facts

Sea lice (Lepeophtheirus salmonis and Caligus spp.) are ectoparasites that feed on salmon skin, causing wounds and immune suppression
Chemical treatments including hydrogen peroxide and azamethiphos baths are stressful and potentially injurious to salmon
Laser systems (Stingray, Hydrolicer) kill lice optically without touching fish but require fish to pass through confined spaces
Thermolicer systems use warm water to detach lice but cause thermal stress and potential scale loss in salmon
Freshwater treatments remove lice effectively but cause osmotic stress in salt-water acclimated fish

Welfare Considerations

Sea lice treatment represents one of the most significant welfare challenges in salmon aquaculture: the parasites themselves cause welfare harm, and the treatments to remove them also cause welfare harm. Every treatment decision involves balancing lice burden welfare costs against treatment stress welfare costs. The development of treatments with lower welfare cost - such as laser systems and improved biological control - is an important welfare research priority. Reducing lice burden through preventive management that delays or avoids treatment is the highest welfare outcome.

What You Can Do

Support research into sea lice treatment methods with lower welfare costs for salmon
Advocate for welfare assessment of different sea lice treatment methods to be required in aquaculture licensing
Choose certified salmon from producers with documented, welfare-conscious sea lice management
Engage with salmon producers about their treatment decision-making frameworks
Support development of alternative sea lice management approaches including breeding for resistance