Background: Despite limited access and rather deficient sampling in many lowland areas of eastern Ecuador, scientists have been able to demonstrate that this specific region of Amazonia houses extraordinarily high concentrations of species within several taxa - terrestrial and aquatic, plant and animal, vertebrate and invertebrate.

New information: In this work, we developed an updated list of the ichthyofauna of the Yasuní National Park (YNP), based on an extensive literature review and databases of the most representative ichthyological collections from Ecuador. Our results yielded 458 species of freshwater fishes distributed in 47 families and 13 orders. This number exceeded previous fish lists from YNP and accounts for a considerable proportion of species inhabiting the Napo River Basin as well as the entire Amazon River Basin.The higher-than-previously-reported species diversity within this protected area, the services these species provide to humans and the absence of invasive species underscore the need for greater efforts and investment in protecting and managing western Amazonian lands and waters.

Keywords: aquatic ecosystems; megadiversity; protected areas; teleosts; western Amazon.

Daniel Escobar-Camacho, Jonathan Valdiviezo-Rivera, Carolina Carrillo-Moreno, Pablo Argüello, Kelly Swing.