Invasive alien species in Switzerland - Schweizer ...

An inventory of alien species and their threat to biodiversity and economy in Switzerland FOEN 2006 68
alien crayfish could be enough to wipe out a healthy population of their European
relatives. Migrating specimens of alien crayfish were observed even in low-density
situations, so a reduction might not prevent their spread. Thus, prevention of further
introductions of species into and within Switzerland should have highest priority to
safeguard native biodiversity and ecosystems. North American crayfish species are of
greatest concern. With respect to releases of problematic freshwater species (e.g. for
fishing and from aquarium dumping) an awareness-raising campaign would be crucial
to sensitize the public to the potential problems caused by alien species. Accidental
arrival of new species with ship traffic can only be minimized by effective treatment of
ballast water and ships’ hulls. Crayfish species other than those mentioned above must
be regulated too. An Australian species, Cherax destructor Clark for example, has been
found in Switzerland (Stucki and Jean-Richard, 2000) and is being kept as a pet in
aquariums and garden ponds owing to its beautiful appearance. The release of pets is
illegal, but the unfortunate fact is that it is used as a way of getting rid of unwanted
individuals, and they are also capable of escaping from ponds.