River restoration and ecological flows: Habitat availability for fish species in the Ticino River (Italy)

Climate change is affecting the water availability and the temperature of rivers, leading to modifications in their biodiversity and posing new challenges for water management. This thesis focuses on investigating the habitat availability for temperature-sensitive fishes during a low-flow period, as part of the T°Cino project aimed at identifying mitigation strategies for the arising problems in the Ticino River (Italy). This study was performed in two sections of the river (Turbigo and Vigevano), located in northern Italy, which is an area significantly impacted by flow regulation and climate change. Through field surveys and the implementation of the MesoHABSIM methodology, the habitat suitability for five different species (bullhead, Italian spring goby, Italian vairone, Po brook lamprey, and marble trout) was assessed to contribute to the T°Cino project’s objectives. The results indicate that in both sections, the habitat is suitable for Italian vairone, while Po brook lamprey and Italian spring goby face unsuitable conditions due to the substrate composition. Observations of bullhead and marble trout indicated that, although they face some habitat limitations in terms of water depth, velocity, and substrate composition, other factors such as water temperature or the introduction of alien species may influence the species distribution and presence. The study suggests that factors beyond low flows and morphology, including water temperature and the presence of alien predatory species (e.g., Silurus glanis), contribute to the decline in species abundance. This thesis provides valuable insights for developing effective mitigation strategies for the river, however, further research is necessary to propose more effective environmental flows in the Ticino River.