This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: The Danube gudgeon had been considered extinct in the Inn River for more than 100 years. Only a few years ago, the highly endangered species was rediscovered there.
Now, researchers at the Technical University of Munich (TUM) have documented the fish in another section of the Inn. The finding emerged from a joint research project with hydropower operator VERBUND examining the effects of nature-like fishways on fish populations and river ecology. Christoffer Nagel, a researcher at the Chair of Aquatic Systems Biology at TUM, the finding came as a surprise.
He rediscovered the Danube gudgeon during field surveys in the Inn River: "Over the course of my research, I have seen hundreds of thousands of fish. Rediscovering such a rare species that was believed lost from the river is a truly special experience and something I never expected." The Danube gudgeon (Romanogobio uranoscopus) is considered highly endangered and is particularly sensitive to declining water quality and changes to its natural habitat. Its presence is therefore considered an indicator of good ecological conditions in a river.
Only a few years ago, the species was recorded in the Inn for the first time in more than a century downstream of the Ering-Frauenstein dam, located about 13 kilometers (8 miles) farther downstream. Together with the latest finding near Simbach, researchers see this as an indication that the species may have expanded its range within a larger section of the Inn. The detection of the Danube gudgeon in the Inn adds to a series of positive findings from a long-term research project conducted at the Chair of Aquatic Systems Biology and led by professor Jürgen Geist.
Systematic fish surveys in 12 largely nature-like fishways along the Inn River recorded approximately 38,000 individuals representing 36 fish species. In addition to isolated records of particularly rare species such as the Danube gudgeon, researchers have regularly recorded protected species including bullhead, barbel, common nase, huchen and grayling. Fishways enable fish to move through river systems where migration routes would otherwise be interrupted by numerous hydropower facilities.
Fish depend on these migrations throughout their life cycle, from early development and feeding to reproduction. Along the Inn, side channels have been created to provide alternative routes around barriers. These bypass channels allow fish to circumvent hydropower facilities.
Extract — continue reading at the source.
