Salmon Sea Lice Biological Control: Welfare Benefits of Cleaner Fish

Cleaner fish including wrasse and lumpfish are used in salmon farms to control sea lice, offering welfare benefits over repeated chemical treatments when managed appropriately.

Key Facts

Cleaner fish species including ballan wrasse, corkwing wrasse, and lumpfish consume sea lice from salmon
Their use has significantly reduced chemical treatment frequency in Norwegian and Scottish salmon farms
Cleaner fish welfare in salmon pens is a growing concern — mortality rates can be high without appropriate management
Wrasse require hiding structures, appropriate water temperature, and species-specific nutrition in salmon pens
Wild-caught cleaner fish have their own conservation and welfare implications; aquaculture-produced fish are preferred

Welfare Considerations

Cleaner fish represent a positive welfare development for salmon when their own welfare is adequately managed. The welfare trade-off is real — replacing chemical treatments that stress salmon with cleaner fish that may themselves experience welfare problems if poorly managed. Best practice involves providing wrasse with hiding structures, appropriate feed supplementation beyond sea lice, temperature monitoring to prevent heat stress in warm surface waters, and regular welfare monitoring. Stocking density of cleaner fish relative to salmon should follow evidence-based ratios rather than simply maximizing fish numbers.

What You Can Do

Support research into cleaner fish welfare standards and best practice guidelines
Choose salmon from farms that use aquaculture-produced rather than wild-caught cleaner fish
Advocate for cleaner fish welfare standards as a component of salmon welfare certification
Engage with aquaculture welfare organizations about integrating cleaner fish welfare into salmon standards
Support development of alternative biological lice control approaches that reduce cleaner fish welfare risks