Incorrect fry-stocking, fishing economy

In numerous water bodies not directly connected with the rivers, which were key sites for the noble crayfish, an excessive fishing activity caused crayfish withdrawal. Stocking lakes (especially small ones) and ponds with the eel poses a great threat for the noble crayfish. Even though the eel is a native and vulnerable species, it should be remembered that it has never been a part of the ichthyofauna of the closed water bodies, as it has never had natural water passage to get there.