Freshwater crayfish were previously absent in the territory stretching from the Caspian Sea basin to the Amur basin. That gap is now being filled, mainly due to the eastward invasion of the narrow-clawed crayfish Astacus leptodactylus, which has currently approached Lake Baikal. This invasion is the result of unauthorized releases. Further spread of the narrow-clawed crayfish or other crayfish species in Siberia may be expected.