Sea Lice Management in Salmon Farming

Sea lice infestations cause severe welfare harm to farmed Atlantic salmon, and treatments to control lice cause additional stress and injury — making this one of the most significant welfare problems in aquaculture.

Key Facts

Sea lice are external parasites that feed on salmon skin, mucus, and blood, causing open wounds
Infestations above threshold levels trigger mandatory treatment in most salmon-farming countries
Chemical treatments include hydrogen peroxide baths, emamectin benzoate, and azamethiphos
Mechanical treatments include laser lice removal, thermolicer (warm water exposure), and freshwater bathing
Each treatment event causes significant stress and can cause scale loss, thermal injury, and increased mortality

Welfare Considerations

Sea lice represent a compound welfare problem: the infestation itself causes chronic pain from open lesions, and the treatments used to control lice cause acute stress and sometimes injury. Chemical treatments expose salmon to substances that cause physiological shock; mechanical treatments involve crowding, temperature extremes, and handling. The ideal solution — developing salmon resistant to sea lice through selective breeding or vaccination — is being pursued but not yet available at scale. Until then, welfare-conscious management minimises treatment frequency and uses the least stressful methods.

What You Can Do

Support research into sea lice vaccines and breeding programmes that reduce treatment need
Choose farmed salmon from certified producers with documented sea lice management welfare standards
Advocate for treatment welfare impact to be reported alongside lice threshold compliance
Support closed containment aquaculture systems that eliminate sea lice as an alternative to net pen farming
Reduce farmed salmon consumption or choose certified welfare-conscious alternatives