Aquaculture Welfare: Salmon Sea Lice Management

Sea lice infestation is a major welfare and production problem in farmed salmon. Management approaches range from chemical treatments to biological controls with varying welfare implications.

Key Facts

Sea lice (Lepeophtheirus salmonis) are ectoparasites that feed on salmon skin and mucus
Heavy infestations cause significant welfare harms: open wounds, secondary infections, and physiological stress
Medicinal treatments include hydrogen peroxide baths and in-feed treatments such as emamectin benzoate
Biological control using cleaner fish (wrasse, lumpfish) is increasingly used as a welfare-positive alternative
Freshwater treatments (submerged barriers, freshwater flushing) kill lice without chemical residues
Sea lice from farmed salmon can infect wild salmon populations, affecting both welfare and conservation

Welfare Considerations

Sea lice management involves genuine welfare tensions. Allowing infestations to develop unchecked causes severe welfare harms to individual fish. Chemical treatments - while effective - involve bathing fish in substances that can cause their own stress and physiological responses. The development of cleaner fish husbandry has introduced a new welfare consideration: the welfare of wrasse and lumpfish used to control lice is often overlooked, despite these being sentient fish in their own right. Best practice integrates multiple management approaches, minimises chemical use, and provides genuine care for cleaner fish populations. Consumer demand for welfare-certified salmon creates market incentives for improved practices.

What You Can Do

Choose ASC-certified salmon that meets standards for sea lice management
Advocate for sea lice monitoring data to be publicly available for all salmon farms
Support research into non-chemical sea lice management methods
Reduce farmed salmon consumption and diversify to lower-welfare-impact protein sources
Follow Fish Welfare Initiative's work on salmon farm welfare standards