This is an acoustic telemetry dataset published by the Research Institute for Nature and Forest (INBO). It contains animal (fish) tracking data collected by the Permanent Belgian Acoustic Receiver Network (https://lifewatch.be/en/fish-acoustic-receiver-network) for the project/study 2015_dijle, using VEMCO tags (V7, V13) and receivers (VR2AR, VR2W). In total 26 adult individuals of five local wild fish species (Anguilla anguilla, Cyprinus carpio, Platichthys flesus, Rutilus rutilus, Silurus glanis) were captured, tagged and released in 2015, to study the effect of a specific barrier on their upstream/downstream migration in the Dijle basin. ... : 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 ...