Promotion of the natural environment and occurrence of freshwater pearl mussels (Margaritifera margaritifera) in the Malše catchment area

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Project objectives: Population enhancement of the endangered river pearl mussel in the border-region river Malše through the introduction of young individuals, description of the exact reasons why the species at this site have not been increasing in the long term and elaboration of the basics for the improvement of the water quality and the reduction of erosion in the entire cross-border catchment area. The most important outputs are: Introduction of cultured river pearl mussels from several breeding cycles into the border river; description of the habitat deficiencies of this species that are currently preventing the mussel from multiplying; creation of cross-border conceptual documents to improve the entire catchment area. Last but not least, cooperation between local authorities, forestry administrations, fishermen and nature conservation groups in the Czech Republic and Austria will be promoted, which are linked by their common interest in the endangered species as an indicator of clean rivers. At the same time, the river pearl mussel is highlighted as an ideal patron species (as defined by the IUCN) of a number of other rare organisms of the clear mountain streams and as a symbolic indicator of a clean river, which is well managed on both sides of the border. Results are achieved with three work packages and through publicity. The planned measures include: 1) Direct protection of the river pearl mussel and their host (brown trout), adjustment of the host's habitat. 2) Refining information on the habitat, measures to reduce further damage to the habitat, identification of threats by monitoring the habitat. 3) More effective protection of the species by targeted clarification of the key actors in the catchment area. The project is based on best practices and itself has an innovative character. For the first time in Europe, a three-stage selection is used for determining the introduction locations. 1) First, the stability and permeability of the soil is evaluated. 2) Annual monitoring of the oxygen content and the water purity under the river floor is carried out using automatic probes. 3) The survival of the mussels at the best selected sites is monitored using the bioindicators (using small mussels in cages). Cultivated individuals are introduced in the best possible locations. Another innovative approach is the detailed work with stakeholders (landowners, local residents and fishermen, foresters, farmers and municipal counsels on both sides of the border). It is only through this level of involvement by the local actors that it is possible to achieve the water quality close to drinking water level necessary for the species’ reproduction. Sensitisation increases the protection of this species from negative human activities (e.g. direct killing of individuals due to pearl hunting).

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