Water level induced changes of habitat quality determine fish community composition in restored and modified riverbanks of a large alpine river

Bank habitats provide important functions for riverine fish. Yet, they have been heavily modified by land use, technical flood protection measures, and hydropower installations. Fish species requiring specific to complete their life cycle strongly declined therefore become target of river restoration measures. This study compared abiotic conditions fish community composition three bank habitat types in a large alpine river, comprising different degrees alteration the natural state (concrete profile, riprap, naturally restored riverbank). Significant differences characteristics such as bed material, water depth, turbidity, submerged vegetation, temperature were detected between sampling seasons. These level-dependent structural changes had strongest effect on distance-based linear modeling. Small specimens 3 13 cm TL juveniles most abundant areas, except Lota lota, which was man-made riprap. Target conservation mostly particularly critical young stages Chondrostoma nasus, Barbus barbus, Thymallus thymallus. Water level determined accessibility suitability habitats, with shallow, gravel-dominated flat angles being beneficial these species. The findings this evidence success structurally impacted rivers conservation. Fluctuating levels discharges typical should be better considered planning, light climate change, affecting timing amplitude discharge systems.