Cancer is widespread in nature


Potash cancer has reached North Rhine-Westphalia

Crayfish used to be widespread. The streams, rivers and stagnant bodies of water in North Rhine-Westphalia were also often populated by them in high densities. Unfortunately, the native crayfish can only be found in a few bodies of water today and are threatened with extinction.

Stone crab - Photo: St. Kaminsky

In 2012 the distribution maps were revised again. The increase in reports that can be observed for almost all species is also due to the increased work of the volunteer mappers. So there is only one confirmed one in North Rhine-Westphalia Incidence of stone crabs. This illustrates the great endangerment of this species for NRW. At first glance, a number of 135 messages appears for the home Noble cancer high. A large number can be traced back to resettlement measures, without which the situation of the noble crayfish would be significantly worse. Isolated quarry ponds in particular are now a reasonably secure habitat for native crayfish.

The American one Camber cancer has populated almost all major rivers such as the Rhine, Ruhr and Lippe as well as the West German canal network. Unfortunately, the species was released into many quarry ponds by humans. The rather small type of cancer is very happy to hike and survives even in polluted and poorly structured waters. This, as well as the high rate of reproduction and the transport of the species by humans, has led to its almost widespread distribution in North Rhine-Westphalia.

The stocks of the also susceptible to the cancer plague Galician crayfish are less of a concern from the point of view of species protection, as this Eastern European species shows little tendency to spread.

Calico cancer - Photo: CH. Lukhaup

The first notice was received in 2017 that the Calico cancer Has reached NRW across the Rhine. This was confirmed beyond any doubt when several living specimens were detected for the first time in the Düssel in the city of Düsseldorf in August 2018. In addition to the risk of cancer plague transmission by this North American species, calico cancer also represents an extreme threat to floodplain waters, in which it can destroy almost the entire community.

The continuing strong tendency of the to spread is cause for concern Signal cancer. Numerous reports of the signal crab show how widespread the species is in NRW. Because of the difficult differentiation from the noble crayfish, this species is still released into new waters, ignorant of the consequences. Since it grows faster, reproduces more strongly and is much more aggressive, it is biologically superior to the noble cancer and displaces it even without the transmission of cancer plague.

The Red American crayfish lives in his home country in floodplains that are occasionally dry and so is best able to colonize new bodies of water over land. By releasing and escaping animals, a number of free-living areas have been created in NRW, especially in ponds and quarry ponds.

Further information at:

First distribution maps of the crayfish fauna in NRW

Non-native crayfish on the rise

Edelkrebs - Photo: Ch. Lukhaup

December 09, 2005 - Just in time for the conclusion of the first project phase, the Edelkrebs NRW pilot project was able to present the first distribution maps of the crayfish species occurring in NRW for the Cologne administrative district. Some of the more than 600 data sets used came from existing recording systems, such as the state fish species register of the LÖBF (today LANUV). Other bodies of water with crayfish incidence were identified through interviews with authorities, fishing licensees and divers, among others. In addition, around 100 trained, volunteer crayfish mappers had provided data by then. People interested in nature could also be reached through the public relations work of the project, who provided useful information on crayfish populations.

By the end of 2005, 92 stocks of the native noble crayfish (Astacus astacus) had been reported, although many reports had not yet been checked. Despite this uncertainty, a slight increase in the noble crayfish population could be assumed, but this is almost exclusively due to resettlement. The simultaneous disappearance of documented noble crayfish populations illustrates the ongoing endangerment of this species in North Rhine-Westphalia.

Australian crayfish - Photo: Peter Mülhens

In contrast, there was a very clear increase in many non-native species. Although the spread of the crayfish (Orconectes limosus), which has been found in our country for over 100 years, seems to be largely complete, other non-native species are still on the advance. On the basis of only three find reports in the state fish species register of North Rhine-Westphalia, the occurrence of the Galician marsh crayfish (Astacus leptodactylus), signal crayfish (Pacifastacus leniusculus) and red American marsh crayfish (Procambarus clarkii) has so far been assessed as low. The 53 reports of these species in the administrative district of Cologne recorded by the pilot project by the end of 2005, however, already showed a significantly greater distribution in our federal state. The pilot project aims to counteract the careless spread of these species by humans, among other things through education.

A new type of crayfish for North Rhine-Westphalia could also be detected through the work of the Edelkrebs project. The Australian crayfish species (Cherax quadricarinatus), which has apparently been released by aquarists, is a "warm water species", but it is unlikely that it will survive longer. In addition, unlike their American cousins, Australian crabs do not transmit "cancer plague". This fungal disease, which is fatal for local crayfish, continues to pose the greatest threat to local crayfish.

For questions:
Pilot project Edelkrebs NRW, Dr. Harald Groß, Neustraße 7, 53902 Bad Münstereifel, Tel .: 0 22 53/96 08 59, E-Mail: [email protected],