(A) The endemic range of Cottus rhenanus in green modified from Kottelat and Freyhof (2007), updated with validated distribution data from the Netherlands (NDFF, 2022) and Belgium (Waarnemingen.be, 2022). Country borders are indicated with a solid line. The location of the study area is indicated by a red frame. (B) The River Meuse (dashed dark blue line), River Geul and tributaries (solid light blue lines) on Dutch territory are depicted with only the names of rivers and tributaries that are included in this study. Dams and weirs are represented by a red hexagon.