Wrasse and lumpfish used as cleaner fish to control sea lice on farmed salmon have emerged as a welfare concern of their own, with millions dying annually in conditions poorly suited to their biological needs.
The welfare of cleaner fish has been called the salmon farming industry welfare problem within a welfare problem. Deploying millions of small fish into an environment optimized for a different species, with extremely high mortality rates, represents a significant welfare concern that has only recently received attention. Wrasse have complex needs — specific substrate, territorial space, temperature requirements — that are not met in salmon farm pens. The high mortality rates are not merely production failures but welfare harms experienced by individual animals with demonstrated behavioral complexity. The move toward purpose-bred lumpfish rather than wild-caught wrasse improves sustainability but does not resolve welfare challenges if conditions remain unsuitable. Industry welfare codes for cleaner fish represent progress, but mortality data suggests implementation has not yet closed the welfare gap.