Action C4 Inteventions for the autochthonous water fauna

The interventions in favor of the autochthonous water fauna aim at restoring the biodiversity and the fish species of community interest in the Natura 2000 areas the project is dedicated to: Salmo trutta marmoratus, Austropotamobius pallipes, Cottus gobio and Lampetra zanandreai, Barbus plebejus included in the Annex II of the Directive 92/43/EEC, and Thymallus thymallus, an important species of conservation interest listed in the Decrees of the Preseident of the Italian Republic 357/97 and 120/003.

A first intervention will regard the renaturalization of a 150-meters-long stretch of the Taglio di Sile, in the locality of Fossa Storta di Vedelago (TV). Along this stretch - where the interventions aimed at recreating a habitat which could be suitable for the project's target species, and at safeguarding those species - a series of works will be carried out through the installation of stream baffles, built with completely natural materials fulfilling the following functions for these species: directing the stream towards key-habitats, such as the shelters under the riverbanks; facilitating, thanks to their position, the formation of meanders and the total morphological variability; cleaning from the muddy sediments the pebbly areas for the egg laying of the fishes and the critical areas for the reproduction of the macro-invertebrates; reducing the erosion; creating areas with a slow current, downstream of the baffles, to cause the formation of bars; facilitating the growth of the riparian vegetation; maintaining a low water temperature; furthermore, they also function to shade, as a shelter, as a reproduction and food area, to build micro-habitats and increase the diversity and the environmental variety necessary for the development of the biodiversity.

The choice of using baffles as a tool for the functional ecological revitalization is particularly useful in this stretch of the Sile river, characterized by low water and a light gradient, with no holes and shelters for fishes. They are cheap and easy to build or modify, to adapt them to the place's condition. They will be built as rock baffles with poles and stream bank fascines. Along with the baffles, also shelters for fishes with a high environmental value will be built under the riverbank. The artificial shelter will be built in the baffle's body, leaving some holes within the devices placed on the riverbed.

Also gravel beds for the marble trout and for the grayling will be built, just downstream of the baffles on the opposite riverbank, in those areas where the stream flows faster, in order to prevent the cracks from being obstructed and to allow a good oxygenation of the pebbly mattress. The interventions regarding the protection of the target species will be carried out through specific regulations dealing with the fishing activities interfering with both the species and the habitats. Such interventions are at the Province's expanses. Restocking actions will be also implemented through the introduction of young fishes, 4 to 6 cm long young marble trouts and 9 to 12 cm long graylings.

As far as the Cottus gobio (European bullhead) is concerned, on the basis of the experience deriving from the LIFE "SCI d'acqua" project, it is provided to foster both the reproduction and the relaying, intervening as already described for A. pallipes, with the control of the allochthonous predators and the fixing of the riverbed. For the European bullhead it is provided the use of artificial underlayers (such as pierced bricks) to achieve the morphological-functional improvement of the river bottom. The interventions will start from the natural populations of the Sile river, and they will focus on the capture and reintroduction of the fish species in the chosen areas, fostering their distribution all over the selected areas. The areas involved will be those situated near the springs and near the Taglio del Sile.