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Ecosystem services of large European Rivers: implications for management Schletterer, M. 1,2 1 TIWAG – Tiroler Wasserkraft AG, Eduard-Wallnöfer-Platz 2, 6020 Innsbruck, Austria 2 University of Innsbruck, Institute of Ecology, River Ecology and Conservation, Technikerstraße 25, 6020 Innsbruck, Austria Ecosystem services (ES) – i.e. “benefits that societies obtain from nature” – are rapidly gaining traction in studies on ecosystem management and have become a key concept for linking ecosystem functionality with human welfare. Fish species and their specific habitat requirements as well as fish biodiversity and its development in general are highly valuable indicators to assess riverine ES. Due to their migratory behavior, fish are an excellent indicator of the status of the riverine connectivity (hydromorphological conditions). Fish migration is not only taking place during spawning, but also for dispersion, to reach feeding habitats, to access shelter habitats (e.g. summer / winter habitats or shelters during flood events) as well as in case of displacement (upstream movement after drift due to flood events). Thus, re-establishment of the river continuum to rehabilitate riverine fish populations is considered a basic step towards the aims of the European Water Framework Directive (WFD ). Comparison of fish communities and fisheries between the two largest river systems in Europe - the Volga (3531 km) and the Danube (2850 km) - stressed that additive effects of multiple stressors cause impacts on fish communities of large rivers. Integrated management taking into account these stressors is needed in order to enhance riverine fish diversity and fisheries. The implementation of the WFD necessitates the application of effective measures towards the establishment of an ecological continuum. Therefore examples from the river Inn, the third largest of the Danube's tributaries by discharge, with different the options to overcome fragmentation (“from vertical slot to fish lift”) as well as monitoring strategies along those fishways are presented. When evaluating aquatic systems, it is important to consider reference conditions (“baseline”) in the analyses; this is exemplified for alpine rivers as well as for the lowlands. Both, zoobenthos or fish are important indicator groups in freshwater systems. Therefore precise fieldwork and taxonomic resolution is needed to assess all components of the community. This can be supported by a novel technique – analyses of environmental DNA (eDNA), i.e. to detect the presence of macroorganisms from water samples which include trace amounts of their DNA. Thus a pilot study was carried out in Austrian rivers to evaluate the efficacy of the eDNA methodology for fish surveys, i.e. water samples from 29 sites in Eastern Tyrol were screened in 2015 using the metabarcode approach and next-generation illumina sequencing, providing the first Austrian data set in which eDNA and electrofishing methods have been directly compared. Analyses of biodiversity – combining classical and novel methodologies – and the application of the flagship species concept is an important basis for monitoring and management strategies of river systems in order to preserve and restore their ES. Best wishes Martin