Cleaner Wrasse Welfare: The Forgotten Fish of Salmon Farming

Cleaner wrasse are small reef fish deployed in salmon sea cages to eat sea lice. Their use as biological pest control raises profound welfare questions — including evidence that wrasse may pass the mirror self-recognition test.

Key Facts

Wrasse species (primarily ballan, goldsinny, and corkwing) are used as cleaner fish in Norwegian and Scottish salmon farms
Over 50 million cleaner wrasse are deployed annually in Norwegian salmon farms alone
Wrasse clean sea lice from salmon by picking parasites from the skin — reducing the need for chemical treatments
Ballan wrasse (Labrus bergylta) showed signs of passing the mirror self-recognition test in a 2019 study
Wrasse are caught from wild populations or increasingly farmed — both routes raise welfare concerns
In salmon cages, wrasse are often squeezed by salmon, eaten, or prevented from accessing shelter and food
Wrasse mortality rates in salmon cages are extremely high — many individuals die within weeks of introduction
EU and Norwegian regulations have begun requiring welfare standards for cleaner fish, but implementation lags

Welfare Considerations

Wrasse welfare represents one of the most urgent and underappreciated welfare issues in aquaculture. The deployment of tens of millions of small fish into environments where they experience high mortality, physical injury from salmon, and deprivation of natural habitat constitutes welfare harm at enormous scale. The 2019 mirror test results for ballan wrasse — suggesting possible self-awareness — do not definitively establish sentience but significantly raise the moral stakes. Wrasse in salmon cages are deprived of the complex reef habitat they depend on: they need shelter structures, appropriate temperatures (they are cold-sensitive), and access to food beyond sea lice. In many cage deployments, these needs are inadequately met. The biological control rationale is genuine — wrasse do reduce chemical treatment needs — but this does not justify deploying them under conditions that guarantee suffering and rapid death. Improving wrasse welfare in cage systems and developing alternative sea lice controls are both urgent priorities.

What You Can Do

Ask salmon producers and retailers about their cleaner fish welfare standards and wrasse mortality rates
Support research into wrasse cognition and welfare to improve the evidence base for regulation
Advocate for mandatory welfare standards for cleaner fish use in salmon aquaculture certification schemes
Support development of non-biological sea lice control methods that avoid the welfare costs of wrasse deployment
Reduce salmon consumption from operations with poor cleaner fish welfare records