Millions of wild-caught and farmed wrasse are deployed in salmon cages to control sea lice. Their welfare as working "cleaner fish" is an emerging and neglected area of aquaculture animal welfare.
Wrasse welfare in salmon aquaculture represents one of the most neglected welfare problems in the fishing industry. Tens of millions of fish are deployed as living pest control tools in conditions poorly suited to their biological needs. Ballan wrasse are temperate coastal fish that die in the cold, oxygenated water preferred by salmon — winter mortality can be extreme. They require refuge structures, correct diet, and appropriate social grouping that salmon cages rarely provide. Wild-caught wrasse experience capture stress and habitat disruption of their coastal nursery habitat. Mortality rates suggest most wrasse suffer significantly before dying in service conditions. The industry is expanding wrasse aquaculture to reduce wild capture pressure, but farmed wrasse face welfare challenges of their own in intensive production. Mechanical sea lice removal alternatives are developing but not yet fully replacing biological control.