Thousands of tourists pass along the macadam road from the Municipality of Fojnica towards Mount Vranica. Their final destination is Prokoško Lake, located in the center of the livestock farming village at over 1,600 meters above sea level. Once a peaceful place, today, it is teeming with nature lovers from all over the world, as well as with new settlers who are building holiday cottages on the banks of the glacial lake.

However, behind the inspiring natural beauty lies a not-so-beautiful story about the extinction of the Bosnian alpine newt (Triturus Alpestris Reiseri), a stenoendemic amphibian for which Prokoško Lake was once the largest and only habitat.

Massive expansion of construction, problems with sewage and water supply, organic waste and uncontrolled stocking of the lake with the various species of fish have all disturbed the natural balance in this area. Instead of rare, orange-bellied amphibians, only large shoals of fish can be seen in Prokoško Lake today.

Herpetologist Adnan Zimić, who has been researching amphibians for many years, says that the biodiversity of the lake has been largely disrupted due to the peak of pressure from the fish. Initial research conducted as part of the Sustainability of Protected Areas (SPA) project, implemented by UNDP BiH and financed by the Global Environment Facility (GEF), showed that no species of invertebrates are present in Prokoško Lake, not even common toad tadpoles, which normally tolerate the presence of fish.

“Preliminary field research indicates very alarming and devastating data, on the basis of which we can now definitively claim that the once largest and most numerous subpopulation of the Bosnian alpine newt has gone extinct from Prokoško Lake. The coastal zone where the newt once lived is now occupied by the common minnows and gudgeons, the fish communities with an extremely large number of individuals in the population”, Zimić explained.

According to experts, only destocking of the lake can have a long-term impact on the return of newts to Prokoško Lake. Therefore, as part of the SPA project, their intention is to improve the stability and state of the newt population in this area, which will also mean harvesting fish from the lake.

“It is through this project that interest has been shown for the first time in both Prokoško Lake and the critically endangered newt. This is also the first time we have a preliminary insight into the relative sizes of subpopulations, their habitats and levels of threat, which is the initial step in protecting the species”, said Zimić.

On the other hand, ichthyologist Adem Hamzić explains that the true state of biodiversity in the lake will be determined through ichthyological field research, planned for the spring, summer and fall of 2024. This research will reveal the species of fish that live in Prokoško Lake.

“It is assumed that all these fish are carnivores, which is the reason why they cause great damage to newts by eating newt eggs, larvae, and adults. During the research, food chains will be established based on the contents of the fish’s gastrointestinal tract, and then all species will be harvested with an electric generator. All surviving fish will be transferred to other localities in the area of Fojnica”, said Hamzić.