German conservation strategies for native crayfish species with regard to alien species

In Germany three native and five alien crayfish occur regularly in the wild. Astacus astacus, Austropotamobius torrentium, and Austropotamobius pallipes are the native species. The stocks of A. astacus were heavily affected by the crayfish plague that spread quickly in the last century beginning in the seventies in southern Germany. Isolated populations of A. astacus can still to be found in several lakes and rivers. A. torrentium is naturally distributed in the southern part of Germany and it occurs in many small rivers and brooks. A. pallipes is only known from the south-west of Germany where a few populations exist. The most widespread alien species is Orconectes limosus, which was introduced in the last century from North America. Astacus leptodactylus has been imported since the turn of the century from countries of eastern Europe and Asia Minor for the table market. Crayfish farmers first introduced Pacifastacus leniusculus in the 1960s and a few populations occur in the wild. Procambarus clarkii can be found in a few ponds and recently a population of Orconectes immunis was found in a stream. The aquarium trade probably imported both species. The precise production, catch and import levels in Germany are unknown. A total of around 110 metric tons is imported, mostly A. leptodactylus, but also Cherax destructor from Australia. German crayfish farmers grow increasing amounts of A. astacus for stocking purposes and consumption, about 10 tons is produced for the table market. Fisheries and conservation laws protect native species in various ways. The catch of A. astacus and A. torrentium with minimal sizes is allowed, only A. pallipes is protected. The release of alien crayfish is illegal, but these rules seem to be ineffective. People are often not aware about the dangers of releasing alien crayfish in the wild. Information and education is therefore important. Seminars for anglers are provided and pamphlets and brochures are produced and distributed to the public.