Author(s): Julien Di Pane; Jerome Prunier; Vincent Dubut; Olivier Lepais; Veronique Gouraud; Laurence Tissot; Jeremy Piffady; Pierre Bompard

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Keywords: Hydropower; Ecological assessment; Fish; Effective population size; Genetic connectivity

Abstract: To better understand the effects of hydropower management on aquatic populations, it is essential to first assess their ecological status. However, estimating fish abundance in large river systems remains challenging using conventional methods such as electrofishing, which are often limited by depth, flow conditions, or restricted accessibility. Genetic approaches for population assessment, particularly the concept of "effective population size" (Ne), offer a promising alternative. Effective population size represents the average number of individuals contributing genes to the next generation. Neutral genetic markers, such as microsatellites, are commonly used to estimate Ne based on genetic diversity. The Lower Ain River and its tributaries represent an area of major importance for both hydropower production and fisheries resources. Within a cascade of six dams currently operating along the river, a pumped- storage facility is in the planning phase and is expected to mitigate the impacts of hydropeaking and improve temperature conditions of the downstream river, beneficial for aquatic life. This work is being carried out as part of the European Horizon ReHydro project, which aims to develop methods and tools for assessing the environmental benefits of refurbishment projects. To assess the ecological status of brown trout (Salmo trutta fario), a genetic study was initiated in

DOI: https://doi.org/10.64697/iahr.proc.ise2026.abs.198

Year: 2026