Wrasse and lumpfish are used as biological sea lice control agents in salmon farming. Their welfare is a significant but often overlooked concern within the salmon aquaculture welfare landscape.
Cleaner fish welfare represents a hidden welfare problem within salmon aquaculture's already complex welfare landscape. Wrasse and lumpfish are introduced into salmon cages primarily as a tool to address a salmon welfare problem (sea lice), but their own welfare is rarely considered systematically. Wrasse are highly territorial, curious fish with complex social behaviours in the wild — in salmon cages they are frequently eaten by the salmon they are meant to serve, lack shelter structures, and experience aggressive interactions with large conspecifics. High mortality rates mean that millions of small fish suffer and die annually as a by-product of salmon welfare management. Lumpfish are cold-water adapted and struggle in warmer cage conditions. Regulatory requirements for cleaner fish welfare — including minimum survival rates, shelter provision, and appropriate feeding — are increasingly being proposed by welfare organisations. Better biological lice control should ideally reduce total suffering in the system, not transfer it from salmon to smaller fish.