The animal poses no danger to humans but can carry a serious infection for native crayfish, which can also be found in Lake Balaton. The term "invasive species" carries a negative connotation, which is increasingly mentioned in relation to Hungary. These are alien animals or plants that can settle outside their natural range, reproduce in large numbers, and cause significant damage in their new habitat. They rapidly displace native species, primarily because they do not yet have natural enemies in the new environment. At the European level, action against invasive species began as early as the 1970s. Despite this, their numbers show no sign of decline, causing serious concern for experts in our country as well. Even in frequently visited places like Lake Balaton, they are particularly noticeable, and the problems they cause are also attracting attention from the general public. How long can a species be considered alien? The answer is not simple, because for example, the common ...