Original title: Environmental factors influencing downstream migration of European eel (Anguilla anguilla L.) in a free-flowing river system
Researchers tracked 39 adult eels as they moved down a free-flowing Belgian river. Away from the tidal zone, eels began migrating when river flow rose above its seasonal average, and pauses were linked to lower flow. They tended to move during the first part of the night and around the new Moon. Near tidal water, the tides played a larger role in when they moved.
Imagine walking home along a river path while the weather and daylight keep changing. A dry stretch may make the walk slow, and the tide can push against you or carry you along. In this paper, the walk is the eels' journey downstream: river flow, night-time darkness, the Moon, and tides all shape when they move or pause.
European eels are critically endangered, and reaching the sea is part of their migration. For people managing river barriers, the findings suggest timing water releases for high flow, dark nights, and early night hours could help more eels pass downstream.
The abstract reports results from 39 eels tracked in one free-flowing Belgian river system. It does not establish whether the same patterns hold in other rivers or whether the suggested timing strategies at water-control structures increase eel escapement in practice.
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Environmental factors influencing downstream migration of European eel (Anguilla anguilla L.) in a free-flowing river system — Hanna Jaspaert, Pieterjan Verhelst, Jan M. Baetens — Movement Ecology — doi:10.1186/s40462-026-00700-7
Abstract licence: CC BY
Explanation generated by Synthesis from the abstract — it is not the original paper.