Background The sterlet (Acipenser ruthenus) is the smallest species of the Danube sturgeons and resides for its whole lifecycle in freshwater without the need to migrate to the Black Sea. Sterlets are still present in very small quantities in the Upper Danube whereas the large anadromous sturgeon species became extinct in the last century due to overfishing and migration barriers. Sturgeons are an indicator of human impact on aquatic ecosystems and the species they host. The Austrian population of the sterlet is threatened with extinction as only very few individuals remain. Their extremely low densities mean that they are at the critical limit for self-reproduction. Objectives The LIFE Sterlet project will apply innovative methods for breeding autochthonous sterlets ahead of releasing them into the wild. The release of genetic autochthonous juvenile sterlets will support the wild population by reaching the required population size for sustainable natural reproduction. Target areas for the release are the two free-flowing sections of the Austrian Danube in the Wachau and the Danube National Park regions, the latter including the Morava river at the Austro-Slovakian border. These areas are home to suitably diverse habitats that offer the greatest chance of sustaining populations of the sterlet in the long term. Furthermore, the project aims to identify sensitive habitats in the project areas and provide recommendations for their conservation. The LIFE project will complement other LIFE projects that have been carried out on the Austrian Danube and have improved the project areas. Expected results: Creation of a genetic database including a hatchery and wild stocks; Establishment of a rearing container and hatching of 300 000 eggs per year over five years; Annual release of at least 10 000 juveniles in every project area over five years; Establishment of a population of at least 4 000 reproducing adults in the Danube National Park - Morava system and 2 000 specimens in the Wachau area; and Development of a management plan for protecting identified key habitats, restoring new habitats, managing populations, developing release strategies and evaluating protection status through international participation (DSTF, IGB- Berlin, ISS 8, WSCS).