Abstract
Salmon farming is threatened by sea lice infestations, which impact fish health, compromise welfare and reduce market value. The use of lumpfish as cleaner fish offers a natural solution for sea lice control, but the delousing efficacy of lumpfish can be hindered by morphological deformities, particularly in the ventral suckers (suction cups) of the fish. Sucker deformities increase mortality rates, hamper welfare and impose a substantial financial burden. Deformed lumpfish, therefore, are typically removed before they are deployed in salmon pens, but this is done manually by visual inspection, which is laborious and time consuming, prompting the exploration of alternative exclusion solutions. We tested a novel automated separator designed to sort juvenile lumpfish based on sucker deformities, aiming at streamlining production in lumpfish hatcheries. The prototype, featuring two chambers and an air-driven rotating drum, was tested across five trials involving 293 juvenile lumpfish with varying sucker deformities. The separator was able to separate 78% of lumpfish with good functional suckers, and to exclude 79% of deformed individual. Sorting was swift and ~50% of lumpfish were sorted within 2 minutes. Binary logistic regression indicates that the probability of being sorted decreased significantly with the extent of sucker deformity and with lumpfish size. Around 22% of lumpfish with good functional suckers were not sorted by the separator likely due to behavioural avoidance, which warrants further study. Given the welfare and financial implications of having to exclude deformed lumpfish, the use of an automated separator as described here may contribute to increase the sustainability of lumpfish production for sea lice control in salmon farming.