Will the European sturgeon return to the Rhine?
Expert(s) |
Marc Weeber
|
Tom Buijse
The European sturgeon (Acipenser sturio), up to 5 metres long and 400 kg heavy, once swam everywhere in north-western Europe. Due to overfishing, dams and pollution, this primordial fish almost became extinct. In the 1990s, it was saved by a French breeding programme and it is now being investigated whether the sturgeon can return to the Rhine. Information on the main habitats and migration routes is very important for this. In new research led by Sportvisserij Nederland and Wageningen University, Deltares is using the D-Eco Impact tool, which will help put the puzzle together as to whether reintroduction is feasible.
Determine suitable spawning and nursery areas
This new study, financially supported by the EU MERLIN project, examined the availability of essential habitats for sturgeon to assess whether stocking of this endangered fish species could continue. The Rhine offers opportunities for the return of sturgeon as the river is still in open connection with the North Sea over a length of 850 km and has improved water quality. Unknown was whether there are sufficient spawning and rearing sites due to all human changes to the river. The study went through three stages. Debora van Dieren, TU Delft, collected and modelled the necessary river information for this purpose. First, the habitat requirements of the sturgeon were identified. Then, 1D models and additional data were used to determine flow velocity, depth and sediment size over the German and Dutch areas. These data were processed with the D-Eco Impact softwaretool into GIS maps (geographic information maps) showing the quality spawning and rearing areas of the sturgeon.
By looking through the eyes of the fish, you start observing the ecosystem and water management in a different way. Other fish species will also benefit from this research on the sturgeon.
Niels Brevé, Sportvisserij Nederland and Wageningen University
Positive result
D-Eco Impact compares river information with sturgeon requirements, helps with data processing and makes this study reproducible for other rivers. The calculation is easy to extend with new information. The study has a good result: it shows that suitable spawning grounds are mainly in the German state of North Rhine-Westphalia, while suitable juvenile grounds are mainly in the Netherlands. However, a critical note is in order: river suitability is only part of the puzzle as it is significantly reduced by infrastructure - such as dams and inland navigation.
With the D-Eco Impact tool, we can calculate the ecological impact in projects faster and find future-oriented solutions for it. In this study, we used D-Eco Impact to calculate suitable spawning and juvenile habitat for sturgeon.
Marc Weeber, Product Owner Water Quality and Ecology at Deltares
Role of D-Eco Impact in the Rhine
The comparison between data and requirements provides a clear, spatial picture of the Rhine's suitability for sturgeon reintroduction and identifies opportunities for habitat restoration and protection for different life stages. The results also provide an insight into the expected effects of climate change. The method is designed in such a way that, if sufficient data is available, it can also be applied to other rivers in north-western Europe. This enables comparisons between rivers for future reintroduction projects.
More details on this research and the potential for restoring the sturgeon's natural habitats can be found in this scientific publication: 'Assessing Potential Spawning and Nursery Habitat Availability in the River Rhine for the Critically Endangered European Sturgeon'.
