The distribution of threatened freshwater fishes in Europe shows divergent patterns from the picture of the overall species diversity.

The highest concentrations of threatened freshwater fish species are found; (1) along the northern Mediterranean coast, (2) on the tip of the Crimean Peninsula, and (3) in coastal streams of Bulgaria and European Turkey. All three regions have many locally endemic species, with natural ranges limited to one or few streams, springs or rivers. In certain areas within these regions, almost every river has its own unique freshwater fish fauna composed of local endemics.