The role of protected areas in the Balkan freshwater biodiversity conservation: The case of Blidinje Nature Park (Southwestern Bosnia-Herzegovina)

Freshwaters of the Balkan Peninsula show high levels of endemism and relict species, which are still little studied and are threatened by numerous anthropogenic stressors. Protected areas could give special opportunities to improve knowledge of their biodiversity and develop proper conservation measures for the most at-extinction risk species. The aims of this research were to: i) fill the knowledge gap regarding fish and crustaceans occurring in the main water bodies of the Blidinje Nature Park (Southwestern Bosnia-Herzegovina); ii) assess the population abundance and growth, for the species of conservational interest; iii) identify fish biodiversity hotspots in Bosnia-Herzegovina; iv) identify anthropogenic pressures and suggest proper conservation measures. Fish and crayfish data were collected in four sampling sites located on the main water bodies, using electrofishing and gillnets, in three sampling phases over the period July 2022-August 2023. The presence of three species at high extinction risk has been detected: Squalius tenellus , Aulopyge huegelii and Astacus astacus . Their populations were abundant, with balanced age structure and good growth performance. A spatial analysis allowed to quantify the fractions of the endemic species range covered by the Blidinje Nature Park, which were 6.1% and 2.3% for S. tenellus and A. huegelii , respectively. The presence of invasive Atlantic trout and overharvesting of crayfish seem to represent the main anthropogenic pressures on freshwater biota. The obtained information allowed to expand the knowledge on the distribution and population status of threatened species and to highlight diversity hotspots as valuable tools for their conservation and management.