Cleaner fish used to control sea lice in salmon farms have their own significant welfare needs that are frequently inadequately met, creating a welfare challenge within a welfare solution.
Cleaner fish welfare represents a case of welfare harm embedded within a welfare solution. Wrasse and lumpfish are used to reduce sea lice burdens on farmed salmon, a genuine welfare benefit for the salmon. However, the welfare of the cleaner fish themselves is poorly managed in most operations, resulting in extremely high mortality rates that indicate widespread welfare compromise. Wrasse require shelter, species-appropriate food, and temperatures cooler than optimal for salmon, conditions rarely provided in salmon sea cages. Lumpfish need substrate for attachment behavior that is absent in open sea cage environments. Addressing cleaner fish welfare requires recognizing that using tens of millions of fish annually as biological pest control creates a welfare obligation toward those fish that is currently not being met by the industry.