Background The Danube is the longest river in the European Union, originating in the Black Forest and flowing through Germany, Austria, Slovakia, Hungary, Croatia, Serbia, Romania, Bulgaria and Ukraine before emptying into the Black Sea. One of the most important tributaries of the River Danube in the Lower Austrian foothills is the River Ybbs. The mouth of the Ybbs long provided excellent natural habitats and conditions for fish, including islands, gravel banks and branches. However, the river has been reworked four times since 1891 with a massive reduction in quality habitat. The Melk power station has had a notable environmental impact in the Nature 2000 site “Niederösterreichische Alpenvorlandflüsse”. Its dams have interrupted the natural river dynamics of the Danube, preventing fish living downstream from reaching their traditional spawning grounds in the river’s tributaries. At the power station, 39 fish species have been recorded, of which 11 are Annex II species and 5 are endemic to the Danube basin. Despite the cutting off of the fish from their spawning grounds, the beneficiary estimated that the recolonisation potential was promising. It managed to bring together all the key stakeholders to work together on this project, including Verbund - Austria Hydro Power AG, which contributed around 35% of the total costs. Objectives This project aimed to restore the natural dynamics of the River Danube and its most important tributaries in the Lower Austrian Alpine foothills. This had the overall aim of increasing the numbers of fish and plants that live in these areas and specifically of seeing the Danube fish once more using gravel beds in the tributaries for spawning. One strand of work would involve restoring conditions at the mouth of the Ybbs to provide improved habitats for many species of plants and animals. The project intended to try a new approach, involving only the minimum intervention necessary to allow the two rivers to naturally restore advantageous conditions. The other strand would be to establish a fish bypass around the Melk power station, enabling fish to migrate once again up the Danube past the station. It sought to create a river continuum of 22 km on the Danube and 13 km on the Ybbs. The project was planned in the context of complementing the work of two other LIFE Nature projects which together are targeting over 90 km of the river. Results The project has succeeded in reconnecting many fish species with their natural spawning grounds and in providing important new spawning grounds for endangered fish species at the mouth of the Ybbs. The area also shows signs of becoming a valuable breeding site for wetland birds. The fish bypass was constructed as similar to a natural channel as possible. A 2 km long channel with an average width of 12 m was dug. The bed was sealed with clay and enhanced using pebbles, rocks and wood. Selected combinations of plants and trees - including 5 000 willows - were planted alongside to provide optimal habitat conditions. An innovative water-supply technique provides a normal flow of 1 500 litres per second and ensures a minimum of 700 l/s using a vertical slot and pumps in case of water shortage in the Danube. Monitoring revealed that fish were able to use the bypass in a natural way to swim around the section of river affected by the power station. The number of fish species migrating through the channel was 42, exceeding expectations and including the endangered zingel (Zingel zingel), streber (Zingel streber) and schraetzer (Gymnocephalus schraetzer). However, the actual number of individual fish using the channel was below expectations and it is assumed that it will take some time for fish to ‘learn’ to use this new route. Further information on the project can be found in the project's layman report (see "Read more" section). To restore the mouth of the river Ybbs, the project purchased 3.8 ha of private agricultural land, excavated 80 000 m3 of earth and relocated 800 m of cycle path - land was also provided by the national and local authorities. Once water was allowed to flow into the redeveloped area, natural forces took over the shaping of the channels and banks. Monitoring showed that the new mouth of the Ybbs has already turned into a nursery for common Danube fish and highly protected species such as the asp and Danube roach. Important bird species, such as the endangered common sandpiper (Actitis hypoleucos) and kingfisher (Alcedo atthis) were seen to breed in the area, which can also provide suitable stopover or even breeding places for waders. The beaver (Castor fiber) was also seen several times in the project site. The project provides an excellent demonstration of retrofitting a fish byway to power plants. It also tells a very positive story in terms of the natural maintenance of the project’s interventions at the mouth of the Ybbs. Further information on the project can be found in the project's layman report (see "Read more" section).