Wrasse and lumpfish used as cleaner fish to control sea lice in salmon farms have distinct welfare needs that are increasingly recognized in advanced husbandry protocols.
Cleaner fish welfare represents an overlooked dimension of salmon aquaculture ethics. Introducing millions of wrasse and lumpfish annually to sea pens as biological pest control creates a substantial welfare responsibility that the industry has historically neglected. The high mortality rates that were once considered simply a production cost are increasingly recognized as indicators of inadequate welfare provision. The mismatch between lumpfish pelagic behavior and net pen structures, and between wrasse thermal tolerance and Norwegian winter temperatures, creates chronic welfare compromise that improved husbandry can partially but not completely address. Monitoring and reporting cleaner fish mortality as a welfare metric, alongside salmon welfare indicators, is an important step toward accountability.