Estimating habitat availability for fish is important to quantitatively assess the impacts of environmental stressors on natural systems and it’s essential for an effective legislation, protection and restoration of ecosystems. This study aimed to establish a biunivocal relationship between trout spawning habitat and flow rate in three rivers of the Aosta Valley, using trout as a bioindicator. Building on the literature analysis conducted by PhD Giovanni Negro, it was possible to define approximate baseline conditions for a model capable of predicting suitable areas for trout spawning, based on the characteristics of the riverbed. In October 2023, field surveys were conducted to characterize hydromorphological monitoring units (HMUs) using the MesoHABSIM method.