Long-term responses of fish diversity to river regulation: a multi-metric approach

Abstract

Large dams disrupt river ecosystems, causing negative effects on fish assemblages. Few studies, however, have investigated how Neotropical fish diversity responds to river regulation in longer temporal scales. In this study, we used a multi-metric approach to investigated temporal changes in taxonomic and functional fish diversity over 15 years-period following the construction of a large dam in the Upper Tocantins River, Amazon. We analyzed biological and environmental data collected in the impounded area before (2000–2002) and after (2003–2014) river regulation. Diversity metrics responded differently to the impoundment. Some metrics were not affected, as they showed little variation over years, such as fish abundance, species, and trait richness. Other metrics changed significantly between periods, such as taxonomic composition, temporal beta diversity, and trait abundance. Species with traits that are sensitive to hydrological alterations declined in the impoundment, while sedentary species were favored. Assemblage trajectories were variable, but community structure developed into a different state in the impoundment. Landscape variables explained changes in fish dissimilarity over time. In general, our study supports the notion that fish diversity in Amazonian rivers is vulnerable to river damming, but also indicates that different metrics show particular responses to this disturbance.