Monitoring the biodiversity and population ecology of fish in the Belgian Meuse River by the use of fishpasses. A 12-year study at the Visé-Lixhe dam Poster 6.2.20. pp 203-204

A 'Meuse Salmon 2000 ' project aiming at restoring an Atlantic salmon run in the Meuse River basin started in 1987 as a contribution of Wallonia to the European Year of Environment. In the course of this currently international programme, most dams (3-8 m in height) obstructing the canalised River Meuse in Belgium and The Netherlands have been fitted with modern fishways in order to defragmentate habitat and restore the free circulation of amphibiotic (Atlantic salmon, Sea trout, European eel) and holobiotic migratory fish species. Since 1990, a detailed investigation is being carried on at the Visé-Lixhe dam to scientifically register the fish ascending a small fishpass built in 1980 (at the same time as the barrage) and a big one constructed in 1998 to allow the upstream migration of large salmonids. Up till now, about 303,000 fish (biomass 12,000 kg) have been trapped in these fishways, belonging to 33 species (26 autochtonous + 7 allochtonous). Among the species recorded, we found several rare and/or endangered species such as Atlantic salmon (Salmo salar; reintroduction in progress), sea trout (Salmo trutta), river bleak (Alburnoïdes bipunctatus), nase (Chondrostoma nasus), barbel (Barbus barbus), wild carp (Cyprinus carpio), European catfish (Silurus glanis) and new aliens such as asp (Aspius aspius). During this study numerous data have been collected on the ecology (age and growth, reproduction, and recruitment, population dynamics) and behavioural ecology (migration periodicity in relation to water temperature and discharge) of the migratory populations of most representative species. Futhermore, biotelemetry techniques have been used to describe and analyse the behavior of migratory individuals confronted with a physical obstacle or a fishway entrance or caught in a fishway and then released above to allow them to moves further upstream.