Long-lost fish species rediscovered in another section of the Inn River

After more than a century of being considered extinct in the Inn River, researchers at the Technical University of Munich (TUM) have rediscovered the Danube gudgeon in a new section of the waterway. This highly endangered species, sensitive to declining water quality and habitat changes, was found during field surveys conducted in collaboration with hydropower operator VERBUND.

Dr. Christoffer Nagel, a researcher at TUM, expressed surprise at rediscovering such a rare species that was believed lost from the river. The Danube gudgeon's presence signals good ecological conditions in a river, and its discovery in the Inn indicates it may have expanded its range within the larger section of the river. The finding is part of a long-term research project led by professor Jürgen Geist, which has documented approximately 38,000 individuals from 36 fish species across 12 nature-like fishways along the Inn.

Nature-like fishways provide suitable habitats for a wider range of species, benefiting the Danube gudgeon due to its preference for gravel-bottomed, fast-flowing, and well-oxygenated sections of rivers. VERBUND project manager Johannes Wesemann sees the discovery as confirmation of their renaturation approach, which revitalizes the entire river ecosystem.

The researchers attribute the success to years of collaboration among researchers, hydropower operators, water management authorities, fisheries, conservationists, and local stakeholders.