Wrasse and lumpfish used as cleaner fish in salmon farming to control sea lice face significant welfare challenges, as their specific needs are often not met in commercial deployment.
Cleaner fish represent an interesting welfare paradox in salmon aquaculture. Deployed as a biological control to reduce chemical treatments and their welfare costs, cleaner fish are themselves often housed in conditions that compromise their welfare. Wrasse require complex habitat structure with hiding places, appropriate temperature ranges, and substrate for natural behavior — conditions rarely provided in salmon pen deployments. Lumpfish have welfare needs that differ substantially from wrasse and from salmon, requiring species-specific management. High mortality rates in both species indicate that welfare needs are frequently not met. The use of cleaner fish is net welfare positive if it reduces chemical treatment burden on salmon while cleaner fish welfare is adequately protected — but only with genuine commitment to meeting species-specific needs of both salmon and their biological control partners.