The goals of this study were to investigate the potential use of metomidate for one-step euthanasia of ornamental fish species representing commonly sold families in the ornamental fish trade and to determine a baseline euthanasia dose for most species tested. Metomidate hydrochloride, a rapid-acting, water-soluble, nonbarbiturate hypnotic related to etomidate, was tested at various concentrations and durations for euthanasia of species representing the following freshwater and marine aquarium fish families: Apogonidae, Ariidae, Blenniidae, Callichthyidae, Characidae, Cichlidae, Cyprinidae, Gobiidae, Gyrinocheilidae, Loricariidae, Melanotaeniidae, Osphronemidae, Pimelodidae, Poeciliidae, Pomacentridae, and Pseudochromidae. Fish in each trial were euthanized as a group (n = 1). Most groups contained 10–12 fish. Some higher doses required buffering. Euthanasia was considered successful if all fish in each group did not recover after 6 h in unmedicated water. All species immediately lost buoyancy and equilibrium, dropping to the tank bottom within 1 min and ceasing ventilation typically within minutes. However, reactivity to vibration, sound, or touch was noticeable for varying time periods afterward (8–66 min), so an additional 30 min of exposure after cessation of reactivity was included as part of the protocol. Although some species (Neon Tetras Paracheirodon innesi and Australian Rainbowfish Melanotaenia australis) were euthanized at a concentration of 40 mg/L metomidate for a total exposure time of 38 min, most species tested were successfully euthanized with metomidate at a concentration of 100 mg/L, with total exposure times ranging from 35–96 min. A few catfish species (Otocinclus sp. and Bronze Corydoras Corydoras aeneus) were refractory and recovered after 100 mg/L. However, Otocinclus sp. were successfully euthanized at 250 mg/L, and Bronze Corydoras were euthanized at 1,000 mg/L. Further studies are needed to provide additional data for these and other species and families, for different water chemistry conditions, and for various biological factors to fine-tune dosing regimens.

中文翻译：

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杀虫剂用于观赏鱼安乐死的初步研究

本研究的目标是调查灭蚁灵在观赏鱼贸易中代表常见销售家庭的观赏鱼物种的一步安乐死中的潜在用途，并确定大多数测试物种的基线安乐死剂量。Metomidate hydrochloride 是一种与依托咪酯相关的速效、水溶性、非巴比妥类催眠药，在不同浓度和持续时间对代表以下淡水和海水观赏鱼科的物种进行安乐死测试：Apogonidae、Ariidae、Blenniidae、Callichthyidae、Characidae、Cichlidae 、鲤科、Gobiidae、Gyrinocheilidae、Loricariidae、Melanotaeniidae、Osphronemidae、Pimelodidae、Poeciliidae、Pomacentridae 和 Pseudochromidae。每个试验中的鱼作为一个组被安乐死 ( n = 1)。大多数组包含 10-12 条鱼。一些更高的剂量需要缓冲。如果每组中的所有鱼在未加药的水中 6 小时后都没有恢复，则认为安乐死是成功的。所有物种立即失去浮力和平衡，在 1 分钟内下降到罐底，通常在几分钟内停止通风。然而，在之后的不同时间段内（8-66 分钟），对振动、声音或触摸的反应是明显的，因此在反应停止后额外的 30 分钟暴露被作为协议的一部分。虽然有些物种（Neon Tetras Paracheirodon innesi和澳大利亚彩虹鱼Melanotaenia australis) 以 40 毫克/升的灭鼠灵的浓度安乐死，总暴露时间为 38 分钟，大多数测试的物种都成功地用浓度为 100 毫克/升的灭蚁灵安乐死，总暴露时间范围为 35-96 分钟。一些鲶鱼物种（Otocinclus sp. 和 Bronze Corydoras Corydoras aeneus）是难治的，在 100 mg/L 后恢复。然而，Otocinclus sp。Bronze Corydoras 以 250 mg/L 成功安乐死，Bronze Corydoras 以 1,000 mg/L 安乐死。需要进一步研究为这些和其他物种和科、不同的水化学条件以及各种生物因素提供额外的数据，以微调给药方案。