Upstream migration of fish at natural obstructions and fish passes efficiency in Southern Belgium.

Fragmentation of rivers by physical obstacles has resulted in the drastic range reduction or extinction of numerous diadromous and potadromous species of fish worldwide. In order to implement to partially or completely re-establish the free movements of fish in the entire watercourse, the Walloon regional government (Southern Belgium) initiated an integrated restoration project whose objectives are 1) To perform a complete inventory of all obstacles that may potentially interfere with the longitudinal connectivity and the free movements of fish, 2) To test, using radio telemetry, the ability of representative fish species (Salmonidae, Thymallidae, Cyprinidae, Esocidae and Cottidae) to clear different typologies of physical obstacles, 3) To determine the problematic sites that should be improved with priority. 4) To construct fish passage facilities and to examine their biological efficiencies. During our talk we will synthesize the results of ten years of research and define the different options for the future.