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Reconnecting Europe’s rivers the smart way

Barriers on Europe’s rivers can improve fishing, be a source of energy and reduce the passage of invasive species, but they can also be a flood risk, interfere with migration patterns and fragment habitats. So what’s the best approach to reconnecting our rivers? One EU-funded project is providing some answers.
Reconnecting Europe’s rivers the smart way
Rivers rank amongst the most threatened ecosystems in the world. We depend on them for hydropower, food production and for drinking water. But in 2015 only half of Europe’s surface water met the target of ‘good ecological status’ as defined by the EU’s Water framework Directive. The EU-funded AMBER project has presented the results of its case study on the management of the dams on the Nalon-Narcea basin, in Asturias, Spain, and their findings offer interesting insights into both the natural and social science elements that go into sustainable river management.

A two-pronged approach

AMBER researchers, based at the University of Oviedo, worked with local stakeholders and city councils to involve them in the study: public engagement and a familiarity with local priorities on the part of researchers, allied with the resident’s understanding of the research aims, is key to successful resource management. In order to achieve those objectives, the project formulated and validated a questionnaire, which they are now disseminating. This will shine a light on the opinions of residents of the Upper Nalon regarding the reserves.

To analyse the biodiversity of the ecosystem in a non-invasive manner, researchers applied molecular tools they developed to create a thorough inventory that avoided the need to disturb biota with electrofishing. eDNA (environmental DNA) from the water samples was extracted, giving a clear picture of local biodiversity and macroinvertebrates, fish and birds should be detectable from these samples. The team hopes also to see traces of mammals visiting the streams.

The project recently published a paper on the identification of salmonids in eDNA from water samples taken from the river Nora, along with other target sites in Asturias. They write, ‘Our tool allows for a rapid overview of the Salmonidae community without the use of real-time PCR systems, and in the particular case of Spain it allowed the detection exotic and native salmonids at the same time. As it is, the method is ready to be used in Spanish waters, but it could be easily adapted for application in other regions by checking for any cross-amplification with the local aquatic fauna.’

Dams - challenged ecosystems

The area under study includes the Tanes and Rioseco reservoirs, which are involved in the production of energy. Water is pumped from Rioseco to Tanes during the night and its direction is reversed during the day to produce energy. The uppermost zone is located within the UNESCO Biosphere Reserve and Natural Park of Redes. The ecosystem is dominated by forest and the two reservoirs are rich in amphibians. The basis for the trophic chain of the ecosystem are its diverse group of aquatic invertebrates, at its top are otters. Second in the chain are two native salmonoid fish: brown trout (Salmo trutta) and Atlantic salmon (Salmo salar). However, the Atlantic salmon cannot reach upstream areas due to the impassable dams, meaning that only natural populations of brown trout occur in the case study zone.

Dams, by their nature are artificial ecosystems and are rarely the subject of environmental protection and as such they can have exotics released into them. In the case of these reservoirs, the team found rainbow trout (Oncorhynchus mykiss) and European minnow (Phoxinus phoxinus) that were introduced for different purposes: the first were released into the reservoirs for recreational fishing, and the second as fishing bait.

This case study feeds into the AMBER (Adaptive Management of Barriers in European Rivers) project’s central objective, to address the complex challenge of river fragmentation. The tools the project has developed can be used, on one hand, to assess public opinion regarding water reserves, dams and resource management and, on the other, to identify species non-invasively wherever the need arises. The eDNA procedure could be a useful way to detect salmonids in places where these species are exotic and represent a danger to the local fauna. It could also serve to detect escapes from aquaculture, a big problem for local wild populations.

For more information, please see:
project website

Source: Based on project information and media reports

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