The disruption of longitudinal and lateral connectivity of rivers has led to ecological catastrophes such as the extinction of several diadromous fish species. River lamprey is an important indicator species for the integrity of ecosystems and connectivity within and between catchment areas. In the highly fragmented Scheldt river basin first restoration actions are undertaken, such as the building of nature-like bypasses. The migration patterns in the river catchment and their behaviour at a tidal barrier, lock-weir complexes and fish bypasses (passage timing and delay) in the upper Scheldt river show that the disrupted water management of the river and in consequence of its barriers and bypasses are one keys to (un)successful spawning migration in the catchment, beside spawning habitat deterioration.

The study was commissioned by the Vlaamse Waterweg NV. Data were exported from the European Tracking Network data portal (http://www.lifewatch.be/etn) developed by VLIZ using the ETN R package (https://inbo.github.io/etn/) developed by INBO. Field definitions can be found at https://inbo.github.io/etn/articles/etn_fields.html.