Wrasse and lumpfish used as biological sea lice control in salmon farming raise significant welfare concerns as their own welfare has been largely neglected relative to their utility function.
Cleaner fish welfare represents a case where the welfare of one species has been systematically neglected in favor of its utility for another. Wrasse and lumpfish deployed in salmon cages face multiple welfare challenges: inappropriate temperatures and densities, inadequate refuges and substrates, competition stress with salmon, and lack of species-appropriate food. High mortality rates indicate severe welfare compromise. The same evidence for fish sentience that motivates salmon welfare concern applies to cleaner fish. Welfare-consistent salmon aquaculture requires addressing cleaner fish welfare alongside salmon welfare, including provision of appropriate refuges, density limits, and mortality monitoring.