The freshwater crayfish (Austropotamobius pallipes Italicus) in the Adamello Park
The crayfish was reported, until a few years ago, in many streams in the park as well as in the River Oglio. Today its presence is sporadic and limited to certain valleys of the protected area (areas of Sonico, Malonno, Berzo Demo, Niardo, Breno).
The main causes of the depletion of Austropotamobius italicus pallipes in the Park include the hydroelectric exploitation of many streams, with drastic reductions in flow in the stream beds and a consequent impoverishment of ecosystem functionality in the streams subject to catchment, the uncontrolled introduction of ichthyofauna in watercourses and, of course, poaching.
On the valley floor the autochthonous crayfish, once widespread along the course of the River Oglio, is now reported in only a few places.
Brief bio-ethology of the species
The freshwater crayfish is a Crustacean belonging to the Astacidae Family. The only autochthonous species in Italy is Austropotamobius pallipes, with the subspecies A. p. italicus Faxon. The subspecies A. p. pallipes Ler. is instead present in Corsica, Switzerland and France. Piedmont and Liguria mark the geographical border between the two subspecies. The crayfish has a greenish-brown colour, can reach 12 centimetres in length and has a maximum weight of 90 grams.
Mating takes place in autumn, the eggs hatch in spring. The larvae, which grow by direct development, in the first year of life undergo 5-6 moults, during which the chitinous exoskeleton is abandoned for a few days to allow the body of the crustacean to grow. In the adult ecdysis usually takes place once a year. The crayfish has mainly nocturnal habits and is omnivorous, feeding on insects, amphibian and fish larvae, annelids, molluscs, aquatic plants and organic debris. The main predators of the species are voles and fish (salmonids).
Its ideal habitat consists in mountain watercourses which are fresh and with good environmental characteristics, not too turbulent, well-oxygenated and with maximum water temperatures of 20-22°C. The ideal pH ranges from neutral (pH 7) to pH 8; the presence of a certain amount of calcium salts is very important for creating the exoskeleton.
The crayfish was inserted in the IUCN “Red Book” of Invertebrates, because of its rarity. The crustacean has in fact suffered a drastic decline in stocks in recent decades due to two main factors: water pollution and the spread of a disease caused by the fungus Aphanomyces astaci, which originated in the United States.
Unlike those of American origin, European crayfish were helpless when attacked by the disease which literally decimated them. In addition, allocthonous species were, thanks to their increased resistance and high fertility rate and primarily for economic reasons, thoughtlessly introduced to many Italian watercourses, further aggravating the already precarious situation of the autochthonous crayfish.
Aims of the “Crayfish Project”
The project’s aim is to re-establish, in the Adamello Park, small autonomous populations of Austropotamobius pallipes in some watercourses presenting the ideal ecological and chemical-physical characteristics for the species and subject to an examination of the causes of the crustacean’s disappearance in the areas where re-establishment of the species is planned.
Intervention to re-establish populations of freshwater crayfish in the Adamello took place as follows:
Step 1 – Survey of the presence and distribution of the crayfish in the Adamello Park in recent years through bibliographical search and selective field trips;
Step 2 – Census of stocks of species both within the park and in adjacent areas;
Step 3 – Collecting of specimens of Austropotamobius pallipes in some parts of Vallecamonica where stocks permit, for verification of the genetic compatibility with those that will be introduced;
Step 4 – Stabulation, if necessary, and subsequent release of small populations of crayfish in some suitable watercourses in the Park;
Step 5 – Monitoring of the re-established populations;
Step 6 – Diffusion of information, with educational purposes, about the project of biological re-establishment of the species.
In September 2000, thanks to the help of the owner of “Troticoltura Viola ” of Malonno, more than 250 crayfish (born in 2000, in 1999, sub-adult and adult), were caught and then released during the night in suitable watercourses in the Park. As well as staff of the protected area and experts in this sector, provincial gamekeepers and Corps of Forest Rangers based in Edolo also took part in key phases.