Flussabwärts gerichtete Fischwanderung an mittelgroßen Fließgewässern in Österreich

Questions concerning the impact of hydropower plants on downstream migration of fish have traditionally focused on
diadromous species and are gaining importance worldwide. In Europe, in this regard mainly studies have been performed considering Atlantic Salmon and European Eel, whereas e.g. the potential effects on native potamodromous freshwater fish fauna
largely remain unknown. Fish are critical biological indicators regarding the good ecological status or potential of rivers as
codified in the European Water Framework Directive. Therefore, the primary objectives of this project are to systematically assess
the extent of downstream migration of fish and to record the degree of damage of selected native fish species during turbine
passage. The investigations are carried out at hydropower plants with Kaplan turbines in medium-sized water bodies
( mean flow > 100 m³/s) with different target species. The selected species are the index species of two important water regions; the Hyporhithral (European grayling, Thymallus thymallus) and the Epipotamal (Nase, Chondrostoma nasus). The information gained in this study will be used to describe the population dynamics of selected fish species in middle-sized Austrian rivers considering the impacts of turbine passage. This is of special relevance, as protective measures such as racks upstream of turbines to screen fish on medium to large power plants entail substantial costs, with smaller life stages still not be hindered to enter turbines during downstream migration.