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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