Stocking cleaner fish to control sea lice infestations in Atlantic salmon farms is widespread and is viewed as a salmon welfare-friendly alternative to current delousing control treatments. The escalating demand for cleaner fish (~60 million stocked worldwide per year), coupled with evidence that they experience poor welfare and high mortality in sea cages, requires that the lice removal effect of cleaner fish be substantiated by robust evidence. Here, we systematically ana lysed (1) studies that tested the delousing efficacy of cleaner fish species in tanks or sea cages and (2) studies of spatial overlap — and therefore likely encounter rate — between cleaner fish and salmon when stocked together in sea cages. Only 11 studies compared lice removal between tanks or cages with and without cleaner fish using a replicated experimental design. Most studies had insufficient replication (1 or 2 replicates) and were conducted in small-scale tanks or cages, which does not reflect the large volume and deep cages in which they are deployed commercially. Reported efficacies varied across species and experimental scale: from a 28% increase to a 100% reduction in lice numbers when cleaner fish were used. Further, our review revealed that the interaction of cleaner fish and salmon in sea cages has rarely been documented. While much of the evidence is promising, there is a mismatch between the current evidence and the extent of use by the industry. We recommend replicated studies in 9 key areas at a full commercial scale across all species that are currently widely used. More targeted, evidence-based use of cleaner fish should increase their efficacy and help to alleviate economic, environmental, and ethical concerns.

中文翻译：

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鲑鱼养殖中清洁鱼去除海虱：证据基础回顾

在大西洋鲑鱼养殖场放养清洁鱼以控制海虱侵扰很普遍，被视为对鲑鱼福利友好的替代方法，以取代当前的除虱控制方法。对清洁鱼的需求不断增加（全世界每年放养约 6000 万只），再加上有证据表明它们在海网箱中的福利不佳和死亡率高，需要强有力的证据来证实清洁鱼的虱子去除效果。在这里，我们系统地分析了 (1) 测试清洁鱼种在水箱或海网箱中的除虱功效的研究，以及 (2) 清洁鱼和鲑鱼在海网箱中一起放养时的空间重叠研究——因此可能的相遇率. 只有 11 项研究使用重复实验设计比较了使用和不使用清洁鱼的水箱或网箱之间的虱子去除情况。大多数研究没有充分的重复（1 或 2 次重复），并且是在小型水箱或网箱中进行的，这并不能反映它们在商业上部署的大容量和深网箱。报告的功效因物种和实验规模而异：当使用清洁鱼时，虱子数量从 28% 增加到 100% 减少。此外，我们的审查显示，在海网箱中清洁鱼和鲑鱼的相互作用很少被记录在案。虽然大部分证据是有希望的，但当前证据与行业使用范围之间存在不匹配。我们建议在 9 个关键领域以完整的商业规模对目前广泛使用的所有物种进行重复研究。更有针对性、循证地使用清洁鱼应提高其功效并有助于缓解经济、环境、