The goal of this research is to get knowledge about the different routes the silver eels are taking from their hinterlands, into the Rhine-Meuse estuary and finally entering the sea. Moreover fish passage success on the way to the sea by several pumping stations is also investigated. The results of this research will give us insights how migration routes could be optimized for silver eel and how mortality (by non-eel friendly pumps) of the eels during the route could be reduced.