Freshwater fishes of the Northeastern Mata Atlântica ecoregion, Brazil: an updated checklist with distributional patterns of a highly endemic ichthyofauna.

We present an annotated and updated checklist of freshwater fish species occurring in the Northeastern Mata Atlântica ecoregion (NMAF), Eastern Brazil. A total of 305 native freshwater fish species are documented for this ecoregion, of which 210 are endemic. Distribution maps of 298 species are provided. There is a general pattern of increased sampling intensity in coastal zones, gradually diminishing towards the west as elevation increases. A bioregionalization algorithm identified four biogeographic units in the NMAF ecoregion: Northern Bioregion, Central Bioregion, Coastal Tablelands Bioregion and Southern Bioregion. The heterogeneous nature of the ichthyofauna in this area, along with the significant faunal overlap observed between NMAF and adjacent ecoregions, suggests that the approach of ecoregion delimitation may not be fully congruent with the current faunal compositions. This underscores the need for novel regionalization approaches that reinforce outcomes consistent with the diversity patterns evident within the ecoregion.