IMIS

Longitudinal and lateral connectivity of rivers is necessary for fish to successfully fulfill their life cycle. In Flanders, fish are obstructed in their essential free migrations by weirs, sluices, mills, pumping stations, …, which are needed to control the water level. The weir on the river Dijle upstream of Mechelen formed partially a physical barrier for the upstream migration of fish to the upstream part of the Dijle basin and the total of the Demer basin. An attempt has been made to resolve the shortcommings of the weir as migration obstruction, by the setting of a fish migration position. Results showed that 21 of 35 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. Next, a part of the receiver network of this study is maintained after the end of this study, to enable the tracking of large migratory species, such as eel and shad, which live and spawn, respectively, in the Scheldt river basin up to the rivers Dijle and Nete (confluencing in the river Rupel, which is a major tributary of the river Scheldt).