PROJECT DESCRIPTION
BACKGROUND
Both the Danube and Inn rivers in Austria comprise stretches with different characteristics. On the one hand there are wide valleys with large river-floodplain systems, on the other hand some river sections are restrained to narrow valleys with steep slopes lacking floodplain habitats. The project addresses conservation issues in the Natura 2000 sites along both rivers. The main habitats depend on large floodplain-rivers. Herea large number of rare and protected (semi-)aquatic species, especially fish, live, including small and fragmented populations of the sterlet (Acipenser ruthenus) and thick shelled river mussel (Unio crassus) in tributaries and backwaters. However, these rivers contain heavily-modified sections. Thus, key habitats are largely missing and hydroelectric power plants pose a barrier for the movement and migration of fish and other aquatic organisms.
OBJECTIVES
LIFE Blue Belt Danube-Inn aims to provide high-quality fluvial habitats for (semi-)aquatic species, with a special focus on fish, and to support ecological connectivity by linking several Natura 2000 sites along the Danube-Inn Corridor. The project forms part of a systemic, large-scale approach to secure the ecological value of the sites in the long term, and has been designed within a comprehensive management strategy for the River Danube and the River Inn. The main objective is to improve habitat conditions and habitat connectivity and thereby foster the conservation status for the endangered fish species, including potamodromous medium-distance migrants sterlet (Acipenser ruthenus), asp (Aspius aspius), Danube salmon (Hucho hucho), and chub (Rutilus meidingeri) at local to regional scale. The large-scale approach will also foster metapopulation dynamics of fragmented populations of other fish species and thick shelled river mussel (Unio crassus).
Specifically, the project aims to:
- Create natural bypass rivers and side branches;
- Provide large-scale connectivity to foster metapopulation dynamics;
- Create high-quality habitats, such as shallow banks, gravel bars, and oxbows along the River Inn and the River Danube;
- Create natural, unfortified river banks in the River Inn and the River Danube;
- Implement fish passes to allow fish access to upstream section, tributaries, and large floodplain areas.
The project will contribute to meeting the requirements of the EU Water Framework Directive, and its measures will also help achieve good ecological status as specified in the River Management Plans. It also contributes to the implementation of the EU Habitats Directive and the Birds Directive.
RESULTS
Expected results:
Interlinking three large rivers, their floodplains, and tributaries:
- Migration of over 50 fish species through the bypass rivers and fishways including around 15 EU Habitats Directive Annex II species;
- Unhindered migration within the Danube from the iron Gate to the German/Austrian border (ca. 1 290 km);
- Unhindered migration from the Danube to the River Inn and the Salzach river;
- Unhindered migration within the River Inn (186 km between its mouth to the Danube at Passau to Rosenheim hydroelectric power plant);
- In total, more than 1 500 km of large rivers will be passable for fish, allowing unhindered access to remnants of floodplains, andseveral free flowing river sections, and numerous tributaries.
Providing 7 ha of high-quality fluvial habitat within the newly built bypass rivers:
- Increase of functional gravel bars (spawning, breeding, nurseries) by 3 ha;
- Spawning of several lithophilous fish species, including Danube salmon (Hucho hucho) and streber (Zingel streber);
- Breeding grounds for the common sandpiper (Actitis hypoleucos) and little ringed plover (Charadrius dubius);
- Creation of several hectares the Habitat Directive habitat types 3220, 3240, 3270, and 91E0* at the river banks;
- High productivity with respect to fish densities and biomass: total fish densities >1 000 individuals/ha, total fish biomass >100 kg/ha; high juvenile densities > 100 larval individuals/m² at shallow banks;
- Preservation and support of the rheophilous guild including several fish species listed in the standard data forms of the Natura 2000 sites.
Removal of embankments and creation of gravel bars (ca. 11 ha):
- Supporting all rheophilic fish species listed in the standard data forms, including asp and Danube salmon;
- Creation of a potential area for the habitat types 3220, 3240, and 91E0*;
- Actions benefit all fish species and other aquatic biota;
- Gravel bars benefit gravel-breeding birds, as well as migratory and wintering bird species.
De-sedimentation measures to create new and improved existing waters (ca. 14 ha):
- Creation of winter habitat for the fish fauna, as a retreat during flood events and as a habitat for stagnophile species;
- Creation of feeding habitat for diving water birds;
- Creation of habitat for larvae of young fish, and for the reproduction of phytophilous fish.
