The 350 km long Danube stretch in Austria is almost entirely integrated into a series of Natura 2000 sites despite being used by no less than nine hydroelectric power stations. The river still hosts many valuable freshwater habitats and species of European importance but, because of the hydropower stations, it is no longer possible for fish and other aquatic species to move up and downs stream.
The hydropower station "Ottensheim-Wilhering" has been in operation since 1975. It is located in the Natura 2000 site "Eferdinger Becken" in the southern stretch of the Danube in Upper Austria and until recently presented a major obstacle to fish migration, blocking off important spawning grounds situated along the river’s tributaries as well.
But today after 40 years, fish are once again able to swim past the power station. Thanks to the efforts of the Austrian hydropower company, VERBUND, and with the help of EU LIFE funds, a major semi-natural river of over 14.2 kilometres has been re-constructed around the power station The river stretch is now not only Europe's largest "fish migration aid", but also an important substitute for lost, river-like aquatic habitats of the Danube, and as such contains a variety of aquatic habitats for all life stages of typical Danube fish and other species.
The new river was built in only 14 months and was put into operation in May 2016. Just two months later an independent monitoring scheme found that over 5000 fish from the Danube had migrated through the new river. Altogether, 31 fish species were recorded, of which 7 are listed in the EU Habitats Directive, including the flagship species, "schrätzer" perch Gymnocephalus schraetzer. After the opening in 2016, 100 individuals from this rare species had migrated to the river bypass and, by the autumn, more than a 1000 young schrätzers had swum back down the river to the Danube. This means that the site is not only being used as a migration route but also as reproduction area for this rare species. This is a great success for the bypass river and for the preservation of the schrätzer perch.
The project is one of the networking activities in the LIFE project "Network Danube", whose overall aim is to reconnect Natura 2000 areas all along the Danube for fish. A significant step forward has been made towards achieving this goal thanks to the Ottensheim-Wilhering project.