The European eel (Anguilla anguilla) is a catadromous fish that spawns in the Sargasso Sea. As larvae, eels cross the Atlantic Ocean and reach the continental slope of Europe, where they metamorphose into post‐larval glass eels. These reach the continent, where some enter fresh water, some remain in marine waters, and others move between fresh and marine waters. After 5–25 years, as adult silver eels, they migrate back from fresh water to the Sargasso Sea to spawn and die. The glass eel stage is a critical step during which the eels cross the continental shelf and recruit to estuaries, where they facultatively transition to fresh water. Extensive research has been conducted to understand the behavioural mechanisms and environmental cues that aid and guide glass eels' migration. Glass eels follow odours and salinity gradients, they avoid light, and they change orientation and depth according to the tides. Recent work revealed that European glass eels also use Earth's magnetic field and lunar cues to orient. However, while we understand many aspects of their orientation behaviour, a unifying theory describing how glass eels migrate from the continental slope to fresh water is lacking. The goal of this review is to develop a comprehensive hypothesis on the migration of European glass eels, integrating previous knowledge on their orientation behaviour with recent findings on magnetic and celestial orientation. This review follows the journey of a hypothetical glass eel, describing the nature and the role of orientation cues involved at each step. I propose that, although glass eels have the sensory capacity to use multiple cues at any given time, their migration is based on a hierarchical succession of orientation mechanisms dictated by the physical properties of the environments that they occupy: (i) lunar and magnetic cues in pelagic water; (ii) chemical and magnetic cues in coastal areas; and (iii) odours, salinity, water current and magnetic cues in estuaries.

中文翻译：

---

关于欧洲玻璃鳗（安圭拉安圭拉）迁徙的综合假说

欧洲鳗鱼 (Anguilla anguilla) 是一种在马尾藻海产卵的河蟹。作为幼虫，鳗鱼穿过大西洋到达欧洲大陆坡，在那里它们变质成幼虫后的玻璃鳗。它们到达大陆，在那里一些进入淡水，一些留在海水中，还有一些在淡水和海水之间移动。5-25 年后，作为成年银鳗，它们从淡水迁移回马尾藻海产卵和死亡。玻璃鳗阶段是鳗鱼穿越大陆架并进入河口并在那里兼性过渡到淡水的关键步骤。已经进行了广泛的研究，以了解有助于和引导玻璃鳗迁移的行为机制和环境线索。玻璃鳗遵循气味和盐度梯度，它们避光，它们会根据潮汐改变方向和深度。最近的工作表明，欧洲玻璃鳗还利用地球磁场和月球信号来定位。然而，虽然我们了解它们定向行为的许多方面，但缺乏描述玻璃鳗如何从大陆坡迁移到淡水的统一理论。这篇综述的目的是对欧洲玻璃鳗的迁移提出一个全面的假设，将以前关于它们的定向行为的知识与最近关于磁和天体定向的发现相结合。这篇综述讲述了一条假设的玻璃鳗的旅程，描述了每一步所涉及的定向线索的性质和作用。我建议，尽管玻璃鳗具有在任何特定时间使用多种线索的感官能力，它们的迁徙基于由它们所处环境的物理特性决定的一系列定向机制：(i) 远洋水中的月球和磁力线索；(ii) 沿海地区的化学和磁性线索；(iii) 河口的气味、盐度、水流和磁力线索。