I see those turks are offered as aquarium pets for a few euros.. But it already seemed to be introduced in western Europe since the 1950 to replace the Astacus astacus which was wiped out by a pest which was introduced with Amrican crayfish in Europe. According reports it is widely spread over whole Europe except, Spain, Portugal and Ireland yet not. So there seems no turning back, welcome or not. They reproduce with about 400 egs per cycle. In Belgium it was 10 years ago already reported in huge numbers in all kind of waters.. 🙂