The main species directly targeted by the project is the cray fish Austropotamobius pallipes (Lereboullet, 1858) listed in Annexes II and V under the EU Habitats Directive. Native populations of A. pallipes have undergone a remarkable contraction and decline over the last 50 years on a widespread basis in Europe (Souty-Grosset et al. 2006, Atlas of Crayfish in Europe).
In Italy the decline has been about 74% over the last 10 years (Holdich et al. 2009, KMAE). This species is also listed as ‘endangered’ by the IUCN (Füreder, 2013). Residual populations of A. pallipes are now confined to small high gradient streams and headwater, where the crayfish IAS have not yet expanded and the habitat is less influenced by human activities (Ghia et al. 2013, Freshw Crayfish).
These populations are nowadays isolated reproductive units, often confined to single mountain streams or to separate basins. The conservation status for A. pallipes populations in the Italian continental biogeographic region (including north-Western Apennine) has been reported as “unfavourable-inadequate” and in “considerable decline”, thus with a negative trend in the short term (Genovesi et al. 2014, ISPRA).
However, northwestern Italy is a hotspot for A. pallipes where high nucleotide diversity was detected and different groups overlap (Trontelj et al. 2005, Mol Phylogenet Ev.). So, conservation strategy for A. pallipes in northern Italy, must take into account the complexity of the biogeographic pattern and the progressive isolation of local demes (Bernini et al. 2016, Conserv Genet).
In the project area, according to the 2014 Natura 2000 SDFs and Specific Measures of Conservation (MSC) the species is still present in 24 out of 28 sites. An estimation of 50 A. pallipes populations is plausible, but often they are relict, appear low-density and are confined to small streams.
Quantitative data are deficient within the overall project area. For the first time in Italy, 2 newly established populations of the invasive cold-water crayfish Pacifastacus leniusculus have been recently detected within project site “Lago del Brugneto” (IT1331019), placed at the headwater of Trebbia river basin (1.070 km2), and at the edge (about 3 km) of the site “Rocca dell’Adelasia” (IT1322304) (Capurro et al. 2007, Aquat Invas; Bo et al. 2016, Natural Hist Sci); both sites still host some residual A. pallipes.
P. leniusculus(American signal cryfish) populations are still restricted, this species is the most successful crayfish IAS (Invasice Alien Species) in Europe and its bioecological attributes leave no doubt that many more Italian lakes and streams (still populated by the native species) will become occupied by signal crayfish, causing strong negative impacts on freshwater biodiversity and ecosystem functioning. Moreover, the most widespread other two invasive America Italy, Procambarus clarkii (red swamp crawfish)and Orconectes limosus (spiny-cheek crayfish), are spread overall the Po river plain area and represent a potential threat overall the project area, especially in the hill area, i.e. within “Basso Trebbia” (IT4010016) A. pallipes has disappeared recently due to P. clarkii colonization of the area.
All 3 Inivasive Alien Species of Union concern represent strong competitors for the native crayfish and the carriers of the crayfish plague, which is responsible of the rapid extinction of A. pallipes populations and they represent one of the most dangerous threats to the native species as well as an excessive release of salmonids for repopulation with possible spread of pathogens.