Résumé
Since bioregionalization is considered as a primary step in conservation biogeography, we delineated the biogeographical regions of an understudied European biodiversity hotspot, the Balkan Peninsula, based on a database of native fish species distributions. In addition, the percentages of endemics and species assigned to Red List categories (IUCN) for each defined biogeographical region were quantified. This bioregionalization consists of seven groups of drainage basins that correspond to distinct regions of the Balkan Peninsula. The greatest percentages of endemic and threatened species were observed for the 'Prespa Lakes' and the 'Ionian Sea' regions. From a conservation perspective, the proposed bioregionalization based on freshwater fish distributions represents a benchmark for future studies aiming at implementing a network of freshwater protected areas across the Balkan Peninsula.