Wrasse and lumpsucker fish are used as biological control agents for sea lice on farmed Atlantic salmon. Their own welfare needs are frequently inadequately met in sea cage production.
Cleaner fish welfare represents a hidden welfare cost within salmon aquaculture. Wrasse and lumpsuckers deployed into sea cages face an environment radically unsuitable for their needs. These small fish are exposed to predation by salmon during cage introduction and suffer ongoing injury from larger fish. Without adequate shelter structures, wrasse experience chronic stress and predation injury. Their species-specific dietary needs for algae and invertebrates are unmet by the pelleted salmon feed available in cages. High mortality rates - often exceeding 50% within 3 months - reflect the severity of the welfare mismatch. The welfare cost to billions of cleaner fish is a welfare consequence of salmon sea lice management that receives far less attention than the lice themselves.