The occurrence and spread of non-native crayfish species is one of the many threats to biodiversity and the aquatic ecosystem as a whole. Threats take many forms, including severe impacts on native species and the structure and function of ecosystems due to habitat alteration, predation, competition, disease transmission, and the displacement of native species over large areas. To prevent this threat, a combination of several measures must be proposed to at least control invasive crayfish and prevent their spread to new sites, with priority given to sites where specially protected animals are found. From the point of view of the spread of invasive crayfish species, the stone crayfish and noble crayfish are the most threatened, both by predation by non-native crayfish and by crayfish plague (caused by Aphanomyces astaci). However, other fauna and flora are also threatened by predation (invasive crayfish are responsible, for example, for the loss of freshwater pearl mussel in Germany).
Under normal circumstances, invasive crayfish species are significantly more successful in competition with our species. This success is due to a wider ecological adaptability, higher reproductive potential, greater migration ability, and aggressiveness. In comparison to those native to Europe, invasive crayfish belong to the so-called r-strategists (short-lived animals, with the exception of signal crayfish, which reproduce quickly and have a large number of offspring), which are more resistant to pollution and disturbance of their habitat. Because it entered the Czech Republic via the river Labe, the spinycheek crayfish is primarily found in in large watercourses and their tributaries; the signal crayfish was primarily introduced in stagnant waters. However, thanks to their wide ecological adaptability, both species have spread to medium and small streams, including relatively polluted locations.
Currently, in the wild, we can demonstrably encounter a total of three species of non-native crayfish from the families Astacidae (signal crayfish) and Cambaridae (spinycheek crayfish, marbled crayfish). The red swamp crayfish (along with the marbled crayfish) is a very popular species in aquarium breeding and it also runs the risk of being irresponsibly released into the wild. It cannot be ruled out that, especially in the vicinity of large cities, there are already established populations that have not yet been discovered. All four listed species are potential carriers of the most serious disease of our native crayfish, crayfish plague.
In the Czech Republic, there is currently a lack of systematic practice to deal with the elimination of invasive crayfish. The spread of non-native crayfish, such as the signal or marbled crayfish, is increasingly threatening native crayfish, as well as other critically endangered fauna and flora. In recent years, the incidence of invasive crayfish infected with crayfish plague has also increased, and, as resistant vectors, they can infect native crayfish populations. Most of the measures to regulate invasive crayfish take place within research projects that are not aimed directly at the eradication or regulation of crayfish, but at the implementation of other types of outputs. In the course of the project, we will verify the effectiveness of measures that are not commonly used in the Czech Republic in practice using the methodology and the web application. For the practical verification of the recommended procedures, various sites were selected where it is possible to apply a complete range of measures.
The results of applied research will be implemented as part of the project; this will subsequently lead to the reduction or elimination of invasive crayfish or prevent the further spread of these crayfish to sites with specially protected animals. The measures will be carried out in accordance with the "Methodology for the regulation and eradication of invasive species of crayfish: selection of appropriate methods depending on the nature of the water body" (the methodology describes different procedures for regulation of non-native crayfish that can be used in selected sites) using the application "Crayfish in the Czech Republic – application to support decision-making in the conservation of our native crayfish and fish" (the application implements the procedures defined in the methodology to recommend appropriate measures). The mobile application "Crayfish in the Czech Republic" (see above) will also be used to improve public awareness of the issue of protection against the non-native crayfish species invasion. General education is the first (basic) measure to prevent the spread of non-native species of crayfish due to ignorance;, only then does it make sense to take further measures aimed at regulating or even eradicating established populations.
Education of both the professional and lay public is the cheapest and most effective way to prevent the spread of invasive crayfish . For this reason, lectures will be held on possible damage caused by the introduction and spread of invasive crayfish, and proposed measures will also be presented, both at seminars for state administration and lectures for the public. Results from previous projects will also be presented, such as the mobile application "Crayfish in the Czech Republic", through which anyone can report new crayfish occurrence and also, for example, identify the crayfish species. Using the application, the user can also learn basic information about native crayfish and their protection, as well as about non-native (invasive) crayfish. Educational activities will be carried out on both local (in selected sites) and general level, always using the most appropriate methods of communication:
Invasive crayfish are the most successful and widespread invasive species that have colonized most of the European continent over the past 100 years. Among the main priorities is their elimination in the early stage of spread. Complete eradication of invasive crayfish species in sites where populations have already been established is considered virtually impossible. In such cases, efforts should be directed towards population control and population isolation. The methods used in the elimination of invasive crayfish can be divided into several groups:
The main contribution of the project is the practical verification of new applied research results, which are focused on the regulation and eradication of non-native species of crayfish.
The project result will be the reduction of the population density or even the eradication of crayfish non-native species at six selected sites. Given that this is probably the first attempt at comprehensive measures against non-native crayfish in the Czech Republic, the project will have a significant demonstration effect. The partial results are as follows:
