Fish migrating from the sea to the Dijle river (or vice versa) are obstructed by a weir in the city of Mechelen which is designed to prevent tides from entering further inland. To mitigate this problem, fish-friendly weir management was implemented, the effect of which was measured in this study with acoustic telemetry. In 2015, 26 individuals of five fish species - European eel (Anguilla anguilla), common carp (Cyprinus carpio), flounder (Platichthys flesus), roach (Rutilus rutilus) and wels catfish (Silurus glanis) - were captured, tagged and tracked in the areas up- and downstream of the weir. 3 wels catfish tagged for the 2014_demer study were also detected. Results of the evaluated weir passages by fish showed that 21 of 29 fish were able to pass the weir at specific hydrological conditions and weir management options. The number of passages differed between species, but happened always in the periods that higher passage could be expected following their lifestyle. The study indicates the importance and benefits of a fish-friendly weir management.

This dataset was collected using infrastructure provided by VLIZ and INBO funded by the Research Foundation - Flanders (FWO) as part of the Belgian contribution to LifeWatch. 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.