The Wels catfish (Silurus glanis) is a large species of catfish native to wide areas of central, southern, and eastern Europe. In the Netherlands a native population exists as well as possible introduced populations in the Rhine-Meuse system. The population in the Netherlands is expanding and increasing while hardly any information is available on the habitat use, diet and migration patterns. In this project we aim to gain insight in these matters and whether they adapt their behaviour to the absence/precence of migratory fishes that congregate at the weir and hydropower station "Lith" in the river Meuse.