Cleaner fish (wrasse and lumpfish) are used to control sea lice on salmon farms. Their welfare is frequently overlooked despite their significant use.
Cleaner fish welfare represents an emerging area of aquaculture ethics. These animals are deployed as living tools to control sea lice, yet their own welfare needs are largely ignored. Wrasse are complex, socially intelligent fish with strong territorial instincts; housing them in salmon pens at high density causes stress and suppresses the very cleaning behaviour they are deployed to perform. Lumpfish are cold-water pelagic fish that fare poorly in the conditions optimised for salmon. High mortality rates suggest welfare is compromised. As fish sentience science advances and regulatory attention to aquaculture welfare increases, cleaner fish welfare is likely to receive greater scrutiny. The most welfare-positive approach combines biological control with other methods to reduce cleaner fish dependence.