Crayfish distribution updating in central Italy

Introductions of non-indigenous crayfish have received great attention from biologists and policy makers during the last decade. Purposes of this study are to update the knowledge about the crayfish distribution in Latium (central Italy), and to show how interactions between indigenous and non-indigenous species can affect their distribution. The main findings of this study were (1) the great decrease of the Austropotamobius pallipes populations and (2) the alarming spread of the four non-indigenous species red swamp crayfish Procambarus clarkii (the main widespread crayfish), spiny-cheek crayfish Orconectes limosus, narrow-clawed crayfish Astacus leptodactylus, and yabby Cherax destructor. We never observed indigenous and non-indigenous crayfish living in syntopy, although we noted that white-clawed crayfish had become extinct at sites where non-indigenous crayfish species exist now. Other type of problems (i.e. illegal harvesting and over-abstraction of water for human use) can also reduce the distribution and abundance of the indigenous crayfish stocks. The distribution of Italian crayfish populations has not been studied sufficiently and more studies are required nationwide to assess the conservation status of A. pallipes and the occurrence of non-indigenous species. A national database of crayfish records ought to be constructed and regularly updated.