Dinaric Alps or Dinaric Karst water systems inhabit 25% of the total of 546 fish species in Europe. Watercourses of this area inhabits a large number of endemic species of fish. The river Neretva and its tributaries represent the main drainage system in the east Adriatic watershed and the foremost ichthyofaunal habitat of the region. According to Smith & Darwall (2006) the Neretva river, together with four other areas in the Mediterranean, has the largest number of threatened freshwater fish species.
Degree of endemism in the karst eko-region is greater than 10% of the total number of fish species. Numerous species of fish that inhabited this area live in very narrow and limited areal and are vulnerable, so they are included on the Red List of endangered fish and the IUCN-2006. The Adriatic basin has 88 species of fish, of which 44 are Mediterranean endemic species, and 41 are Adriatic endemic species. More than half of the Adriatic river basins species of fish inhabit the Neretva, the Trebišnjica section known as Ombla, the Trebišnjica, the Morača rivers and their tributaries, and more than 30 are indigenous species.