Cleaner fish — wrasse and lumpfish — are used in salmon aquaculture to control sea lice. Their welfare in this role is poorly understood and often inadequate.
Cleaner fish deployed in salmon cages as a biological sea lice control measure face extreme welfare challenges. They are small fish placed in cages dominated by much larger, faster-moving salmon. Mortality rates are very high — driven by predation, crushing, outcompetition for food, and disease. Wild-caught wrasse removed from their reef habitat experience severe social disruption in addition to physical welfare harms from capture. Lumpfish farmed for the industry spend their lives in sterile hatchery conditions before being killed by the salmon farm environment. The welfare of cleaner fish has been largely invisible in the sea lice management debate — the salmon industry views them as tools rather than animals requiring welfare consideration.