Wrasse and lumpfish are deployed in salmon farms to eat sea lice as biological control. These cleaner fish have their own welfare needs that are frequently neglected in commercial operations.
Cleaner fish welfare represents a hidden welfare crisis within salmon aquaculture. Deployed to solve the sea lice welfare problem for salmon, wrasse and lumpfish face inadequate conditions that cause extremely high mortality. Wrasse are territorial fish that require shelter structures; without them they are stressed by the open water salmon cage environment and susceptible to salmon aggression. Temperature mismatches cause mortality as wrasse cannot tolerate the cold northern waters where salmon farms operate in winter. Lumpfish are not yet well-understood in terms of their welfare needs. The regulatory gap for cleaner fish welfare has begun to close in Norway, where minimum standards are being developed. The welfare cost of cleaner fish must be integrated into the overall welfare assessment of salmon production systems.