Fisheries and biotic homogenization of freshwater fish in the Brazilian semiarid region

The construction of dams in Brazilian semiarid regions has been a common governmental practice since the early 1900s, initially with the aim of providing water to meet the needs of humans and animals, and, later, to improve fisheries. Along with dams, several nonnative fish species were introduced with the intention of supplying new fisheries. We used a dataset compiled since the 1950s for the following: (i) evaluate fisheries for native and nonnative species across space–time scales and (ii) quantify the spatial and temporal changes in taxonomic and functional similarity of freshwater fish assemblages in semiarid reservoirs. Overall, fisheries for native species decreased over time, while fisheries for nonnative species increased during the early periods, which then, for the most part, decreased after 2000. At the Inter-region scale, we recorded a transition from homogenization to differentiation over time, both in taxonomic and functional terms. At the Intra-region scale, we also found a transition phase from taxonomic homogenization to differentiation over time, while functional differentiation was recorded for most of the regions. This study highlights the variation in fisheries for native and nonnative species over a period of ~ 70 years, and the homogenization dynamics of Brazil’s semiarid freshwater fish resulting from the construction of dams, stocking programs, and aquaculture using nonnative species.