Cleaner fish — primarily lumpfish and wrasse — are used as biological sea lice control in salmon farms. Their introduction has raised significant welfare concerns for these small species deployed in challenging conditions.
Cleaner fish welfare has received growing attention as their use has scaled enormously. The welfare calculation is complex: their use reduces chemical treatment of salmon (a welfare benefit for salmon), but the deploying conditions currently cause extraordinarily high mortality in the cleaner fish themselves. Lumpfish are sentient animals with their own welfare needs that are poorly met in current deployment conditions. The absence of adequate shelter, inappropriate social densities, and the physical demands of continuous sea lice foraging in large salmon pens impose significant welfare costs. The welfare of cleaner fish must be weighed alongside the benefits they provide. Improving cleaner fish welfare through better shelter provision, appropriate density, and improved handling is both ethically required and likely to improve their lice control effectiveness.