ABSTRACT Brazil harbors one of the highest number of fish species in the world; however, the occurrence of fish in high-altitude aquatic ecosystems remains largely underexplored. This study aimed (1) to investigate the occurrence of fish species in the Itatiaia Plateau (Itatiaia National Park), at altitudes ranging from 2,140 to 2,543 m; and (2) to analyze gaps in the altitudinal distribution of fish above 2,000 meters in Brazil. This was accomplished by compiling approximately one million occurrence records from digital biodiversity repositories and digital elevation models. The results indicate that there are no records of fish in high-altitude aquatic ecosystems (> 2,000 m) in Brazil. The highest altitudinal record (~ 1,944 m) is for Psalidodon cf. scabripinnis. There are many possible reasons for this: challenging climatic conditions, physical barriers to dispersal, isolation, historical absence, sampling gaps, and repository biases. This study highlights the gaps in knowledge regarding fish distribution and emphasizes the potential for future research to discover previously unknown species or species adapted to high altitudes in Brazil
