Improving welfare standards for cleaner fish deployed in salmon aquaculture requires attention to their specific biological needs for refuge, diet, and species-appropriate housing.
Cleaner fish welfare improvements require recognition that these species have behavioural and environmental needs that differ significantly from salmon. Wrasse without appropriate hiding places in salmon cages suffer chronic stress from lack of refuge in a predator-dominated environment. Inadequate diet beyond lice availability causes malnutrition. Cold winter water temperatures in northern sites are outside the thermal tolerance of some wrasse species. Species-appropriate housing, adequate diet supplementation, and thermal management represents the minimum welfare standard for cleaner fish used as biological pest control. The investment required is modest relative to the welfare benefit for millions of individual fish.