Salmon Lice and Fish Welfare | Animal Welfare Hub

Sea lice infestation is the most significant and pervasive welfare problem in Atlantic salmon farming, causing chronic pain, secondary infection and mortality across the global salmon aquaculture industry.

Key Facts

Lepeophtheirus salmonis is the primary sea louse species affecting Atlantic salmon, causing skin lesions and tissue damage
Treatment resistance to multiple chemical treatments has developed in sea lice populations making control increasingly difficult
Cleaner fish including wrasse and lumpfish are deployed on salmon farms to eat lice, raising their own welfare concerns
Laser systems that kill lice with precision represent a promising non-chemical treatment option with potential welfare benefits
Scotland loses approximately 10% of salmon production value annually to sea lice-related mortality and treatment costs

Welfare Considerations

Sea lice cause chronic suffering in farmed salmon by feeding on skin, mucus and blood, creating open wounds that are painful and prone to secondary bacterial infection. High louse burdens can cause fish to rub compulsively against nets, causing further self-injury. Treatment is a major welfare event in itself — thermal delousing involves exposing fish to hot water, causing significant stress and sometimes mortality. Chemical bath treatments expose fish to biocides in contained spaces. Biological control using cleaner fish creates a second animal welfare issue, as wrasse and lumpfish are themselves sensitive species with welfare needs that are poorly met in most farm environments. The ideal welfare solution would be farm designs that prevent louse infestation rather than managing it after the fact.

What You Can Do

Choose salmon from land-based recirculating aquaculture systems that eliminate sea lice exposure
Engage with retailers about sea lice management methods in their salmon supply chains
Support research into lice-resistant salmon breeding and physical exclusion systems
Advocate for welfare standards for cleaner fish used in salmon farming to be developed and implemented
Reduce salmon consumption or choose certified alternatives where welfare evidence is strongest