PROJECT DESCRIPTION
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 aimed to apply innovative methods for breeding autochthonous sterlets ahead of releasing them into the wild. The release of genetic autochthonous juvenile sterlets was aimed to support the wild population by reaching the required population size for sustainable natural reproduction.
Target areas for the release were 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 aimed to identify sensitive habitats in the project areas and provide recommendations for their conservation. The LIFE project was expected to complement other LIFE projects that have been carried out on the Austrian Danube and have improved the project areas.
RESULTS
The LIFE Sterlet project restored populations of sterlet (Acipenser ruthenus), an endangered fish species of the Sturgeon family, in the River Danube in Austria.
To stabilise the small sterlet population in the Austrian parts of the Danube, the project team releasing artificially-bred sterlets in the Danube upstream and downstream of Vienna. They established a rearing container with the aim of hatching around 300 000 eggs per year over five years. More than 238 000 young sterlets were released into the river during the project, and the number of sterlets recorded in the project area is now increasing. In addition, 104 sterlets were equipped with hydro-acoustic transmitters, which provided valuable data to help find the most suitable habitats for the sterlets in the Danube.The project was very pro-active regarding public engagement, and this for example resulted in many press articles describing the project’s outcomes.
The project team also developed a management plan for protecting identified key habitats, for restoring new habitats, managing fish populations, and for future fish release strategies. The project complements other LIFE projects carried out on the Danube.