Migrating fish species are worldwide in decline due to several global changes and threats. Among these causes are man‐made structures blocking their freshwater migration routes. Shipping canals with navigation locks play a dual role in this. These canals can serve as an important migration route, offering a short cut between freshwater and the sea. In contrast, the navigation locks may act as barriers to migration, causing delays and migration failures. To better understand these issues for downstream migrating fish, we studied the behaviour of European eels (Anguilla anguilla) in the Albert Canal at two scales. The mid‐scale contained a 27‐km canal pound confined by two navigation lock complexes, in which we released and tracked 86 silver eels. The small scale was a 200 × 150 m area just in front of the most downstream complex of the canal pound, where we analysed the behaviour of 33 eels in relation to the flow field resulting from a computational fluid dynamics (CFD) model. This paper discusses the factors influencing fish behaviour, and the relation between these behaviours on both scales. On the mid‐scale, migration efficiency resulted from a combination of intrinsic behaviour and flow in the canal pound. Also on the small scale, intrinsic behaviour influenced the success to pass the navigation lock. Increasing the flow would create more attraction and passage opportunities and hence facilitate migration through shipping canals, but only if this flow guides the fish through safe passage routes.

中文翻译：

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欧洲鳗（安圭拉安圭拉）下游迁移路线上的运输运河：机遇还是瓶颈？

由于若干全球性变化和威胁，世界范围内的鱼类迁移正在减少。这些原因包括人造结构阻碍了它们的淡水迁移路线。具有导航锁的运输运河在这方面起着双重作用。这些运河可以作为重要的迁移路线，为淡水和海洋之间的捷径提供了捷径。相反，导航锁可能会成为迁移的障碍，从而导致延迟和迁移失败。为了更好地了解下游鱼类迁移的这些问题，我们研究了欧洲鳗鱼的行为（Anguilla anguilla）分为两个比例。中档有一个27公里的运河磅，由两个导航锁定系统限制，我们在其中释放并跟踪了86条银鳗。小规模位于运河下游最下游综合体的前面，面积为200×150 m，我们在其中分析了33鳗鱼相对于计算流体力学（CFD）模型产生的流场的行为。本文讨论了影响鱼类行为的因素，以及这两种行为之间的关系。在中等规模上，迁移效率是由于内在行为和运河磅流共同作用的结果。同样在小范围内，内在行为会影响通过导航锁的成功。