Data from long-term biodiversity monitoring of two hydroelectric dam projects in northeast Portugal is now available, covering the period from 2006 to 2023. The impact of dams on freshwater biodiversity is a topic of ongoing study, with research also being conducted in other regions, including the Mekong and China. The effects of dam construction on riverine ecosystems, including fish populations, are being examined in various parts of the world, with some areas showing signs of recovery.