Abstract The European eel (Anguilla anguilla (L.)) is critically endangered after a multi-decadal decline. Anthropogenic disruption to downstream migration, including at water control structures such as pumping stations, is thought to be one of the contributing factors. Some pumping stations only operate during floods and river water drains through sluice gates under the influence of gravity (‘gravity sluice’ hereafter) at all other times. Gravity sluices are considered a safe downstream passage route for downstream migrating silver eels, but it is not known if eels approach or pass through them. This novel study aimed to understand the timing, passage routes and fine-scale behaviour of downstream migrating silver European eel (n = 7) immediately upstream of a pumping station with a gravity sluice using acoustic telemetry. During the study, three eels passed through pumps (42.9%) despite only operating for 8% of the time that the gravity sluice was open, two passed through the gravity sluice (28.6%) and the remaining two retreated upstream (28.6%). Long passage delays (up to 21 days) were observed and eels were detected retreating back upstream (up to 10 times) prior to passing downstream. It is recommended that operational changes are implemented to make the gravity sluice a more attractive downstream passage route for downstream migrating silver eels and thus reduce passage through hazardous pumps.

中文翻译：

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带重力闸的泵站银欧洲鳗（安圭拉安圭拉）的下游通道

摘要 欧洲鳗鱼 (Anguilla anguilla (L.)) 在经历了数十年的衰退后，已处于极度濒危状态。人为干扰下游迁移，包括在泵站等水控制结构，被认为是促成因素之一。一些泵站仅在洪水期间运行，其他时间在重力影响下通过闸门（以下简称“重力闸”）排出河水。重力闸被认为是下游洄游银鳗的安全下游通道，但不知道鳗鱼是否靠近或穿过它们。这项新颖的研究旨在使用声学遥测技术了解位于带有重力闸的泵站上游的下游迁移银鳗 (n = 7) 的时间、通道路线和精细尺度行为。在学习期间，尽管重力闸打开的时间只有 8%，但仍有 3 条鳗鱼通过了泵 (42.9%)，其中 2 条通过了重力水闸 (28.6%)，其余两条退到了上游 (28.6%)。观察到长时间的通过延迟（最多 21 天），并且检测到鳗鱼在通过下游之前向上游撤退（最多 10 次）。建议实施操作变更，使重力闸成为下游迁移银鳗更有吸引力的下游通道，从而减少通过危险泵的通道。观察到长时间的通过延迟（最多 21 天），并且检测到鳗鱼在通过下游之前向上游撤退（最多 10 次）。建议实施操作变更，使重力闸成为下游迁徙银鳗更具吸引力的下游通道，从而减少通过危险泵的通道。观察到长时间的通过延迟（最多 21 天），并且检测到鳗鱼在通过下游之前向上游撤退（最多 10 次）。建议实施操作变更，使重力闸成为下游迁移银鳗更有吸引力的下游通道，从而减少通过危险泵的通道。