Cleaner fish including wrasse and lumpfish are used to control sea lice on farmed salmon, but face significant welfare challenges of their own in this role.
Cleaner fish welfare represents a case where one animal welfare solution creates new welfare problems for another species. Wrasse and lumpfish were introduced to salmon cages as a biological alternative to chemical sea lice treatments, reducing welfare costs to salmon. But the cleaner fish themselves face poor welfare outcomes: mortality rates are often very high due to physical damage from salmon, inappropriate diet, inadequate sheltering substrate, and exposure to sea lice treatments that are toxic to them. Recognition that cleaner fish welfare matters — they are sentient animals with their own welfare interests — has prompted research into welfare-optimised husbandry and reduced reliance on wild-caught wrasse.