Wrasse and lumpfish are used as cleaner fish in salmon farms to eat sea lice, but their welfare is among the most neglected in any commercial fish species. Understanding the problem is the first step toward meaningful improvement.
Cleaner fish represent one of the most acute and overlooked welfare failures in modern aquaculture. The combination of alien environmental conditions, inadequate refuge, thermal stress, aggressive interactions with salmon, and starvation when lice densities are insufficient creates a lethal cocktail for a majority of deployed animals. The extreme mortality rates — accepted as an operational norm by much of the industry — would trigger immediate regulatory intervention if they occurred in the salmon themselves. Wild-caught wrasse experience stress from capture operations using fyke nets and transport before deployment. Farmed lumpfish, while avoiding wild capture stress, face industrial rearing conditions and cage deployment that produce comparable mortality. The welfare problem is compounded by the biological control rationale: cleaner fish are deployed to reduce the welfare impact of lice on salmon, but at the cost of severe welfare harm to the cleaner fish themselves. Addressing this requires investment in cleaner fish welfare research, mandatory welfare standards, and innovation in alternative lice control methods that don't require biological sentinels.