Researchers at the University of Natural Resources and Life Sciences (Boku) Vienna have tagged thousands of Danube fish with transmitters to observe their migration. As they report, after warm days in March, endangered fish species such as barbel and nose found their way to their spawning grounds. The restoration of natural habitats on tributaries such as the Traisen and Große Tulln (both in Lower Austria) has a positive effect.
The Danube has been radically changed by river regulations, the expansion of hydropower and other interventions. Scientists at the Christian Doppler (CD) Laboratory for Dynamics of Meta-Ecosystems in Regulated River Landscapes (MERI), which opened last year at the Boku’s Institute of Hydrobiology and Water Management, are investigating the impact of these human activities on biodiversity and river ecosystem services. Building on this, they want to develop sustainable ecological measures and thus contribute to the stability of the Danube ecosystem.
The researchers are investigating, among other things, where fish species such as nose and barbel, which are considered characteristic species of the Danube, can still reproduce. To do this, they equipped thousands of fish with small transmitters and placed antennas on the Danube and the lower reaches of the Traisen and Großer Tulln. Together with existing antennas, they can thus record fish migrations to feeders and through different storage areas.
Antenna recorded hundreds of animals
After the water temperature of the Danube and its tributaries rose from five to ten degrees Celsius in March, the antenna on the Traisen had already recorded more than 300 tagged fish in March, which had migrated from the Danube to breed in the feeder, the researcher report. It is only a small part of several thousand Danube noses that currently inhabit the Lower Treisen to reproduce. The nose, with its pronounced spawn rash, which males develop on their skin during spawning season, is the first species to arrive, followed by the barbel, the researchers report.
“In order to find suitable spawning grounds, the fish increasingly migrate from the Danube to tributaries such as the Traisen or the Große Tulln,” explains Boku hydrobiologist Günther Unfer. As part of rehabilitation projects, the lower reaches of these two rivers have been made accessible and the quality of the habitat has been restored. They provide the formerly abundant nasal, now considered endangered due to massive habitat loss, the gravelly areas that are rapidly submerged and necessary for successful reproduction.
Source: Krone
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