Cleaner fish including wrasse and lumpsucker are used to control sea lice in salmon farms, but their own welfare is often overlooked in this biological control context.
Cleaner fish welfare represents a case where animals with genuine welfare interests are deployed as biological tools with essentially no consideration of their own wellbeing. Wrasse are fish with demonstrable nociception, complex foraging behaviors, and habitat requirements that salmon pens cannot meet. Their welfare is compromised at every stage: capture from wild populations, transport with high mortality, and deployment in an alien environment where they face starvation, disease, and predation by salmon. The precautionary welfare principle applied to fish sentience means that treating millions of cleaner fish as disposable implements without welfare consideration is ethically problematic regardless of the welfare benefit to salmon from reduced sea lice burden.