Author(s): Stijn Bruneel; Lore Vandamme; Pieterjan Verhelst; David Buysse; Ine Pauwels; Johan Coeck; Kaat Thienpont; Sam De Visscher

Linked Author(s): Ine Pauwels

Keywords: Elver; Anguilla anguilla; Upstream Migration; PIT-telemetry; Fish Pass; Eel Ramp; Weir; Turbine; Migration; Hydraulic Conditions; Dijle; Belgium

Abstract: The successful upstream migration of the critically endangered European eel (Anguilla anguilla) remains severely challenged by man-made barriers, such as the watermill-turbine complex at Rotselaar on the Dijle river. This study details an investigation into the passage efficiency and movement behavior of upstream migrating elvers (juvenile European eel, Anguilla anguilla) at the Rotselaar watermill-turbine complex on the Dijle river in Flanders, Belgium. This site provides an ideal set -up to study the behavior of elvers near barriers as the river Dijle splits up in two river arms. One arm, the weir arm, ends at an unpassable weir over which large amounts of water can be released during peak discharge events. The other arm, the passage arm, ends in a weir with turbine but has a fish pass and an eel ramp just before via which elvers can move passed the site. PIT-telemetry was employed to track elvers, including local (inland river Dijle) and translocated (coastal river Yser) fish, released in 2024 and 2025. The study focused on assessing the functionality of the built fish pass, the experimental eel ramp and the potential issues entailed by the functioning of the weir (unpassable weir arm) and weir with turbine (passable passage arm). The overall detection rate on the site for elvers released

DOI: https://doi.org/10.64697/iahr.proc.ise2026.abs.149

Year: 2026