The role of coastal karst environments for the conservation of Anguilla anguilla (Linnaeus, 1758) in the Mediterranean area

Two observations (02/2022; 12/2023) of Anguilla anguilla (Linnaeus, 1758) in the non-touristic sector of the Valdemino cave (Grotta di Borgio Verezzi, LI160, Liguria, north-western Italy) raise interesting questions regarding the phenology of the species and its possible troglophilic behaviors in karst environments, especially close to the coastline. This preliminary work confirms the presence of eels in the drainage basins of the karst complex in which Valdemino cave develops, an area characterized by limestone and dolomitic rocks. In addition, a quantitative sampling was carried out in the Bottassano stream, one of the rare surface watercourses in the area, upstream of the cave and the dry stretch of the water body. The intermediate and terminal sectors of the stream, where the cave is located, are characterized by temporary surface flows in addition to possible sub-fluvial flows, while at the confluence with the Rio Carlando (about 3.5 km from the mouth), the water supply and the impermeability of the riverbed allow a residual surface flow useful for the passage and development of the species. These samplings led to the capture of five specimens in different life stages. Future research will include in-depth studies aimed at understanding whether the caves can represent a passage site, from the sea going up, or from adjacent watercourses going down through karst connections, or even represent an area of trophic interest and growth.