Abstract
The white-clawed crayfish Austropotamobius pallipes complex populations are decreasing in the Foreste Casentinesi, Monte Falterona and Campigna National Park (Central Italy), due to several factors, including illegal poaching, predatory fishes, drought, and invasive alien species. Recently, the Northern raccoon Procyon lotor has been reported to be present in the area of the National Park and has started to predate on the white-clawed crayfish. The aim of the study was to update the distribution and population status of A. pallipes in the reserves, other sites of the National Park, and surrounding areas to assess the potential effects of the raccoon. Crayfish were sampled by hand or by traps in 14 sites; sampled individuals were sexed and measured. Signs of raccoon presence (e.g., footprints and predated crayfish) were also recorded. Our study confirms the impact of raccoon on native crayfish: indeed, where the invasive mammal is present (six sites), crayfish disappeared, or their populations have been dramatically reduced in number, with a size distribution skewed towards juveniles. In two sites, close to urban settlements, fresh footprints of P. lotor and predated specimens of A. pallipes were also observed. Populations of crayfish are still abundant or even increasing as compared with samplings conducted in the past where raccoon is absent (five sites). Urgent actions (e.g., control of raccoons, and monitoring and restocking of A. pallipes populations if feasible and where possible) should be taken into account to guarantee the survival of this protected species.
Highlights
Freshwater environments are among the ecosystems most threatened by human activities, and several impacts on them lead to a crisis in freshwater biodiversity (Abell, 2002)
The raccoon has been found to actively predate on A. pallipes (Boncompagni et al, 2021), and our study confirms the impact of this invasive mammal on native crayfish: where the species is present, FIGURE 4 | Fresh footprints of raccoons and predated Austropotamobius pallipes complex specimens in the study area
Crayfish disappeared or their populations have been dramatically reduced in number, affecting their size distribution
Summary
Freshwater environments are among the ecosystems most threatened by human activities, and several impacts on them lead to a crisis in freshwater biodiversity (Abell, 2002). Mating takes place only once per year in autumn and is followed by a long breeding period, until the spring/summer of the subsequent year, during which females hide in a shelter to take care first of the eggs and of the juveniles (Aquiloni et al, 2010) All these listed features make this crayfish vulnerable and, despite being listed in Annex II of the EU Directive on the Conservation of Habitats, Flora, and Fauna (92/43/EEC), in Appendix II of the Bern Convention, and being considered “endangered” on the Red List of the IUCN, its decline is still ongoing, caused by the joint action of multiple factors, such as habitat alteration, pollution, climate change, invasive alien crayfish, and disease spread (e.g., Alonso et al, 2000; Mazza et al, 2011, 2017)
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