The fight against crayfish plague continues: Since January 1st, large areas of the Brugga and its tributaries in the Dreisamtal between Kirchzarten and Oberried (Breisgau-Hochschwarzwald district) have been released for use again. The entry ban issued due to the crayfish plague only applies to a few areas of the water system. As reported by the regional council of Freiburg (RP), no all-clear can be given for the lower reaches of the Brugga. The crayfish plague is still active here. The Breisgau-Hochschwarzwald district office has therefore initially extended its general decree, which first came into force on July 26, 2019, until December 31, 2022.
To contain the crayfish plague in the Brugga and its tributaries, the RP built a second crayfish barrier in the creek in Neuhäuser, a district of Kappler, last September. Therefore, the ban on entering the Brugga only applies to the area from the Engenwald playground to the confluence with the Dreisam and in the Krebsgraben in the Neuhäuser district, where the crayfish plague broke out in 2019. The aim is to prevent the spread of the still active animal disease in the lower reaches of the stream to essential sections and tributaries located upstream. The ban on entering this area also applies to dogs that are not allowed to bathe in the Brugga or in its tributaries. Leisure activities and fishing in the water should also be avoided as long as the animal disease is rampant (the closed area is marked in blue on the overview map in the appendix).
The ban on entering the Zastlerbach and Krummbach and their small tributaries was lifted in June 2021. The upper reaches of the Brugga above the Engenwald playground have been accessible again since January 1st.
The crayfish plague pathogens, which are harmless to humans, endanger the protected and very rare jackdaw crayfish. As reported by the RP, the monitoring continued this year shows a conspicuous absence of living jackdaw shrimps in the lower reaches of the Brugga, where isolated dead jackdaw shrimps were still found. “This indicates a latent crayfish plague reservoir in this area, from which there is a very high risk of the disease spreading to essential upstream parts of the Brugga and its tributaries,” explains Regina Biss from the nature conservation department of the RP. However, by draining the connecting waters and building the second crayfish barrier, it has so far been possible to prevent the spread of crayfish plague to other waters.
The first cancer barrier in Brugga at the Engenwald playground and the second cancer barrier in the Neuhäuser district follow the recommended double barrier principle: should invasive crabs or crayfish plague overcome the first barrier, the second barrier serves as a further safeguard. The area between the closures is regularly examined as part of cancer monitoring in order to detect a possible immigration of invasive crayfish or a spread of crayfish plague at an early stage and, if necessary, to be able to take countermeasures. The jackdaw population above the barriers will also continue to be examined to check the success of the measures to contain the disease.
Background information:
The crayfish plague pathogen that got into the Brugga comes from the invasive camber cancer, which has not yet been identified in the Brugga’s water system. The crayfish plague broke out in the Krebsgraben in March 2019 and was introduced into the Brugga. It had spread rapidly in the lower reaches of the water body. The RP had initiated immediate measures to preserve the endangered cancer population. The lower water authority at the Breisgau-Hochschwarzwald district office has issued a ban on entering the Brugga and its tributaries.
Crayfish plague is a fatal, highly contagious disease in native crayfish caused by a fungus-like pathogen, Aphanomyces astaci. The stages of transmission of crayfish plague, known as spores, can be introduced into a body of water through any damp object that has come into contact with contaminated water, such as rubber boots, nets and pots, as well as the damp fur of dogs or the feathers of waterfowl. There is no effective treatment or vaccine against crayfish plague. The measures taken on the Brugga aim to curb the spread of the disease. The duration of the epidemic is not foreseeable, since only a few spores in the water are sufficient to cause the crayfish plague to flare up again.
(Press release: Freiburg Regional Council, 06/30/2022)
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