Il gambero di fiume nel versante adriatico del Parco Nazionale delle Foreste Casentinesi Monte Falterona e Campigna (Emilia Romagna-Toscana). Distribuzione, status ed esigenze ecologiche

n 2012, the National Park Authority sponsored a two-year investigation on the distribution, ecology and status of White-clawed crayfish populations (Austropotamobius pallipes complex) in the Adriatic side of its territory. Field surveys were carried out between April 2012 and October 2013 in 163 rivers of the Adriatic slopes of the protected area. In every watercourse where White-clawed crayfish was found we identified transects of 100 m in length. In each transect we collected the main morphological and environmental parameters and the quantitative estimate of the specimens. The White-clawed crayfish was found in 38 streams. The average length of the streams where the White-clawed crayfish is present is 10.49 km, the average width is 2.5 m, the average depth is 21.89 cm, the average slope is 6.88% and the average flow rate during the summer is 11.5 l / s. In watercourses longer than 15 km the White-clawed crayfish is only present in the upper reaches, while in watercourses shorter than 15 km the White-clawed crayfish is present throughout the course. As for the grain size of the river’s bottom, the species prefers to stay in streams where pebbles and boulders prevail and less frequently in those where prevail rock and pebbles or boulders and pebbles. In most cases the riverbed of the occupied waterways is almost entirely shaded. The dominant type of habitat is represented by wood and to a minor extent by semi-natural grasslands. A total of 3591 specimens were captured. The average density of the population expressed as CPUE is 1.90 and fluctuates from a minimum of 0.16 in Bidente Pietrapazza to a maximum of 3.18 in the Fosso of Forconali. The average sex ratio for all streams is 0.85. Larger males specimens are 106 mm in length and females 95 mm, while the smallest specimen is 12 mm long. Currently the biggest threat for the White-clawed crayfish is the restocking of brown trout (Salmo trutta) followed by water abstraction for agriculture, zootechnical, drinking and illegal fishing. To preserve the Park’s Whiteclawed crayfish populations it is reccomended: 1) to eradicate brown trout from streams where it is not native; 2) to develop a plan to identify the more suitable streams for fishery and trout restocking; 3) to control the water withdrawal in relation to the minimum flow of the waterways; 4) to increase surveillance to prevent acts of poaching; 5) to encourage public environmental education events to raise awareness to the problem of preservation of White-clawed crayfish.