Acclimatisation with lice-infested salmon improves cleaner fish lice consumption

Securing the welfare and maximising lice removal efficacy of ~60 million cleaner fish used each year on salmonid farms is essential to develop a productive ethical industry with low salmon Lepeophtheirus salmonis levels. We tested whether ballan wrasse Labrus bergylta consumption differed depending upon they were acclimatised in cages either no Atlantic Salmo salar , without lice, or lice-infested salmon, prior deployment sea cages. After 1 wk, commercial densities stocked kept for further 3 wk. Each week, number was counted subset sampled gut contents physical welfare. Lice occurred less frequently guts (6% all dietary items) compared caprellid amphipods (76%). Ballan consumed more if pre-exposed (mean ± SE = 0.79 0.4 lice) not (0.15 0.1 p 0.003) (0.01 0.09 0.03). This did affect overall mobile loads which doubled over study period regardless acclimatisation strategy. Decline condition factor ( K ) increase specific damage time affected by If can be secured, could at scales as strategy improve biological control agents.