Development of anaesthetic protocols for lumpfish (Cyclopterus lumpus L.): Effect of anaesthetic concentrations, sea water temperature and body weight

In recent years, use of lumpfish (Cyclopterus lumpus L.) as cleaner-fish to remove sea-lice have been chosen by many salmon farmers in Europe and Canada as an alternative to medical treatment, which has led to large scale production of lumpfish. At present, there is limited knowledge of how lumpfish respond upon anaesthesia, which anaesthetics and concentrations that are efficient and conditions for euthanasia. We have therefore tested and developed protocols for bath immersion for three commonly used anaesthetics metacaine (Finquel, buffered tricaine methanesulfonate, MS-222 and Tricaine Pharmaq), benzocaine (Benzoak vet) and isoeugenol (Aqui-S), determined concentration for normal and fast anaesthesia and evaluated safety margin for each condition. Also, a behavioral matrix has been developed. We have examined the effect of fish size (10–20 g, 200–400 g and 600–1300 g) and sea water temperature (6°C and 12°C). We found that 200 mg L-1 metacaine is an efficient dose for deep narcosis independently for fish size and temperature due to good safety margins with regards to both exposure times and doses. However, for many tasks lighter anaesthesia is sufficient, and then 100 mg L-1 metacaine can be used. Benzocaine is less efficient than metacaine, but can be used as anaesthetic of fish -1 for small fish (10–20 g) and 200 mg L-1 for medium sized fish (200–400 g). For larger fish (> 600 g), benzocaine is not suitable. Isoeugenol cannot be recommended for full anesthesia of lumpfish. The conditions for lethal doses varied with chosen anaesthetic, fish size and temperature. For small fish (10–20 g), exposure to 1600 mgL-1 of metacaine in 10 minutes it lethal. Guided protocols for non-lethal anaesthesia will contribute to ensure safe treatment of lumpfish according to an ethical standard for good fish welfare.近年来，欧洲与加拿大的众多三文鱼养殖者已选用圆鳍鱼（Cyclopterus lumpus L.）作为清洁鱼以清除海虱，作为药物治疗的替代方案，这推动了圆鳍鱼的规模化养殖。目前学界对圆鳍鱼的麻醉响应规律、高效麻醉剂与适用浓度，以及安乐死的操作条件仍缺乏足够认知。为此，我们针对三种常用麻醉剂——间氨基苯甲酸乙酯甲磺酸盐（metacaine，商品名包括Finquel、缓冲型三卡因甲磺酸盐MS-222及Tricaine Pharmaq）、苯佐卡因（Benzoak vet）与异丁香酚（Aqui-S），开发了浸浴麻醉操作方案，测定了常规麻醉与快速麻醉的适用浓度，并评估了各条件下的安全边际。此外还构建了行为学评价矩阵。我们还考察了鱼体规格（10–20 g、200–400 g及600–1300 g）与海水温度（6℃与12℃）对麻醉效果的影响。研究发现，200 mg·L⁻¹的间氨基苯甲酸乙酯甲磺酸盐可有效实现深度麻醉，且不受鱼体规格与温度限制，其在暴露时长与剂量两方面均具备良好安全边际。不过多数操作仅需轻度麻醉，此时可采用100 mg·L⁻¹的间氨基苯甲酸乙酯甲磺酸盐。苯佐卡因的麻醉效率低于间氨基苯甲酸乙酯甲磺酸盐，但可用于小型鱼（10–20 g）的麻醉，中型鱼（200–400 g）则需200 mg·L⁻¹的浓度。对于体型更大的个体（>600 g），苯佐卡因并不适用。异丁香酚无法用于圆鳍鱼的全程麻醉。致死剂量的适用条件因麻醉剂种类、鱼体规格与温度而异。针对小型鱼（10–20 g），在1600 mg·L⁻¹的间氨基苯甲酸乙酯甲磺酸盐溶液中暴露10分钟即可致死。本研究开发的非致死麻醉标准化方案，将有助于依照良好鱼类福利的伦理标准，保障圆鳍鱼的安全处置。