Study area: Lower Iguaçu river basin highlighting the existing hydroelectric dams (SA: Foz do Areia; SE: Segredo; SS Salto Santiago; SO: Salto Osório; SC: Salto Caxias; and BI: Baixo Iguaçu) and the Iguaçu National Park (left). Sampling sites are located in tributaries (black dots) and the main channel (red dots) of the Iguaçu River (right). Sampling sites in tributaries were indicated considering their upstream (a), intermediate (b), and downstream location (c).