Crayfi sh have played a signifi cant role in the social and cultural activities of Europe since the Middle Ages (Souty-Grosset et al. 2006). Larger crayfi sh species, especially noble crayfi sh, were spread by monasteries and royalty, and became important in the diet of both common people and aristocrats. Even today, people come together for crayfi sh parties in order to celebrate their harvest or a good summer activity, especially in Scandinavia. Crayfi sh and their body parts (particularly the gastroliths) were used in popular medicine for centuries. In scientifi c terms, freshwater crayfi sh are often considered keystone species in freshwater habitats (Momot 1995, Dorn and Wojdak 2004) or ecosystem engineers (Creed and Reed 2004, Edwards et al. 2009), due to their prominent impact on the physical structure of their environment as well as on biological interactions. Despite all of these interests and their ecological signifi cance, details of crayfi sh distributions in Europe were for a long time incomplete and fragmented. The European network CRAYNET (“European crayfi sh as keystone species-linking science, management and economics with sustainable environmental quality”) emphasized knowledge-based management strategies (Souty-Grosset et al. 2006). After decades of scattered information sources, one of the key results of the project, the ‘Atlas of Crayfi sh in Europe’ (Souty-Grosset et al. 2006) represented a major advance in providing summary information about the diversity, ecology, distribution and conservation of crayfi sh in Europe.