Saving freshwater crayfishes: extinction drivers identification and ecosystem services assessment

In northern Italy, the native crayfish Austropotamoboius pallipes, once largely widespread, is currently at the edge of extinction in numerous hydrographic basins. Since the early two thousands the spreading of allochthonous crayfishes, carrier of a dreadful pathology, added its detrimental effect to habitat pollution and alteration in threatening the survival of native populations. Our study aims to perform a large scale research of the relationships between freshwater pollution and alien crayfish spreading in determining extinctions of native crayfish populations in Alpine and Apennine countries. Moreover we want to assess the differences in ecosystem services provision among sites with and without populations of A. pallipes and identify management strategies to prevent further spreading of alien crayfish species. During 2016 we sampled 194 sites, 140 lotic, 54 lentic. We chose 101 sites in which the native species A. pallipes occurred till 2006 before American crayfishes (spp?) spreading and in which there were available data on the water quality. We sampled each of the 194 sites at least twice during this period in order to assess the crayfish detection probability and we repeated environmental analyses. A. pallipes still occurs in 63 sites, while in 38 sites is extinct. No significant environmental changes occurred in the extinction sites, but we found at least one site occupied by a species of alien crayfish in the same catchment basin. Alien crayfishes are mostly linked to lentic habitats that provide ecosystem services for fishing and recreational activities. In streams, barriers like polluted stretches or dams played a role in allowing the persistence of native populations, although strongly isolating them, by preventing contacts with the pathology carried by allochthonous crayfishes. Conservation actions of native species that take into account the provision of wetlands ecosystem services are urgently needed to prevent further alien crayfish spreading.