Restoration of sterlet populations in the Austrian Danube

The sterlet (Acipenser ruthenus) is the smallest species of the Danube sturgeons and lives during its whole life cycle only in freshwater without the need to migrate to the Black sea. Sterlets still are 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 a symbol for diverse human impacts on aquativ ecosystems and their negative effects on the biota. The Austrian population of the sterlet is threatened with extinction with only very few specimens remaining. With their extremely low densities they undergo a critical limit for self-reproduction. From a population dynamic point of view at least 500 to 1.000 adult mature fish in a Danube stretch of about 30- 50 km length are needed to build a minimal viable population. The main objective of the project is to breed autochtonous sterlets with innovative methods and release them into wild. The release of genetic autochthonous juvenile sterlets will support the wild population by reaching the required population size for a sustainable natural reproduction. Target areas for the release are the two free- flowing sections of the Austrian Danube in the regions called „Wachau” and „Nationalpark Donauauen“, the latter including the Morava river at the Austro- Slovakian border. These areas offer suitable habitat diversity and have a high importance to the longterm success of the measures. Different LIFE Projects in these areas have already taken place. They already have and will further increase habitat quality by great scale river revitalization work. The breeding station will be located in the heart of the Austrian capital Vienna at an island of the Danube River which is frequented regularly by stakeholder groups.