The regional council of Freiburg (RP) had a cancer protection plate installed in the Merzhausen Mühlbach (Breisgau-Hochschwarzwald) in the past few days. This slippery obstacle, which the company Sulzberger from Freiamt installed with the active help of nature conservation experts at the RP, is intended to protect native crabs in the upper reaches of the stream from crayfish plague.
The rare species noble crab and stone crab are to be protected. In the Mühlbach and its tributaries in the Hexental there is still a very large and nationally important stone crab population. “There was imminent danger. The invasive, alien signal crabs are already very widespread in the lower reaches ”, explains the biologist Gabriel Rösch from the RP.
With the crab protection plate, at least the crayfish and stone crabs in the upper reaches should be protected. A sign was also placed on the bank informing passers-by about the purpose of the measure. The signal crab – you can recognize it by the red underside of its claws and by the white spots on the top – is only a carrier of cancer plague. The immigrant from America does not get sick himself. For native cancers, however, the disease is always fatal. “That is why it is particularly important that the cancer protection plate and the water are not entered and that no crabs are removed or moved,” Rösch asks the population for help.
Regardless of whether the signal cancer is infected with the cancer plague, it will displace the stone cancer from the entire river system due to its competitive strength and its high rate of spread. For this reason, the crab protection plate was now installed on a fall in the water.
The principle of the crab protection plate is simple: the crabs, and this affects all species, cannot find a hold on the slippery plate and can therefore no longer get into the upper reaches of the water. We are actually in favor of patency and against closures and falls in rivers, but the protection of endangered species is the higher priority here, explains Rösch. The jumping brown trout may be able to overcome the obstacle. The cancer populations in the Mühlbach have been mapped and monitored by an expert commissioned by the nature conservation authority for several years. This will continue to monitor and monitor the effectiveness of the cancer protection sheet in the future.
The stone crayfish is listed as a priority species of the Habitats Directive and is on the Red List of Germany as a severely endangered species. In Germany, stone crayfish occurs only in Baden-Württemberg and Bavaria. In the administrative region of Freiburg, the focus is on the Black Forest and various tributaries from the Dreisam and Glotter. The nature conservation administration in the region has already had positive experiences with cancer protection plates in the Wehratal and on the Kander. The cancer protection sheet, which cost 10,000 euros including installation, was financed with natural preservatives as part of the special program to strengthen biological diversity in the state of Baden-Württemberg.
Further contributions from the Freiburg Regional Council
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