The crab comes to Lake Vänern with cargo ships that have been to China, and when the ships' ballast water is emptied into the lake, small crabs and fry follow.
And the situation is starting to get so serious that it may be a question of future fishing to reduce the amount of wool hand crabs in Lake Vänern.
In the clip you see what the crab looks like, and the biologist Andrea Kilströmer tells what it can cause problems.