Ecology of the lasca Protochondrostoma genei (Bonaparte 1939) in the Chiaro di Cialla Creek (Northeast Italy): new insights from a biodiversity hotspot affected by human impacts and alien species

Freshwater hydrological networks can host precious biodiversity hotspots but are also among the most threatened environments and inhabiting native fish fauna can be critically endangered by human activities presence of alien species. Therefore, proper knowledge is of pivotal importance to protect/restore these species, manage their habitats and keep biodiversity hotspots safe. In this study we investigate the ecology of the lasca Protochondrostoma genei, listed in the Annex II of the European Habitat Directive 92/43/EEC and among the endangered species in the Red List of Italian Vertebrates. Our study area was the Chiarò di Cialla Creek, partially included in a Site of Community importance (pSIC - IT3320041) and hosting other species listed in the Annexes of the Habitat Directive. Electrofishing sampling activities were carried out in 2024 throughout the whole creek, to analyze lasca population structure and fish community composition. Within the watercourse stretch included in the pSIC, main mesohabitats and substrate types were recorded, while values of main chemico-physical parameters were measured. The presence of anthropogenic impacts was checked. Distribution of alien species along the whole watercourse was checked, as the invasive common nase Chondrostoma nasus (negatively affecting the lasca population) was detected, and the brown trout Salmo trutta inhabits the upper watercourse stretch as consequence of introduction for fisheries. Our results highlighted a well-structured lasca population inhabiting mainly pools and glides, while in riffles the occurrence was lower than in other habitats. Unfortunately, the lasca shares its habitats with common nase, which increased its density in the last years. The present work provides new information about P. genei, that can be helpful to arrange management actions in the area and in other watercourses. Genetical investigations are now required to check potential hybridization between the lasca and common nase.