Project Concept – Saving threatened Telestes fishes in Croatia

The Balkan region is the hotspot of European biodiversity. As well as wolves, bears and lynx, its freshwater habitats are the most important sites for threatened freshwater biodiversity both in the European continent and across the wider Mediterranean basin.

While for many years this “blue heart” of Europe has remained untouched by the developments which have driven the loss of freshwater species in central and western Europe, it is now coming under increasing pressure. Experts warn that planned developments in the Balkan region could result in the loss of one in ten European fish species (Weiss pers. comm in Nelsen 2018). Shoal has identified the Balkans as a critical global hotspot for threatened freshwater fish, and will work with local partners across the region.

Our initial project is focused on the conservation of five Critically Endangered and Endangered species of the genus Telestes – a remarkable group of fishes which have evolved in the crystal clear waters of Croatia’s karstic landscapes, often in complete isolation from other species. They are now threatened by habitat loss and the introduction of invasive species. Our initial project partners with the Croatian Institute for Biodiversity to save these species from extinction.

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Balkan Biodiversity

The Balkan region stretches from Slovenia to Northern Greece and is regarded as the great hotspot of European biodiversity (Griffiths et al., 2004). As a hotspot of European flora and fauna, the Balkan region is home to some of the continent’s largest and most charismatic species. Brown bear, Eurasian lynx and grey wolves are all found across the region – two thirds of Europe’s remaining large carnivores are in the Balkan states (WWF 2017). The peninsula is also considered one of Europe’s two most important places for birds (Savic 2008). Some of the region’s most fascinating and biologically integral groups of species are also its smallest. The peninsula is recognised as a global centre for subterranean biodiversity (Pipan et al., 2018) and the site of an “evolutionary explosion” of invertebrates. Finally, the Balkans are also classified as one of 156 global centres of plant diversity, with only five others located in Europe (Milanović and Djordjević-Miloševic 2016). By almost any metric then the Balkans are Europe’s stand-out centre of species diversity and endemism – these states have been referred to as “the green heart of Europe” (WWF 2017). Yet while this description is undoubtedly accurate, it overlooks one of its most outstanding and diverse groups of wildlife.

Freshwater life

The freshwater biodiversity of the Balkans is perhaps its best-hidden ecological secret. Recent reviews have identified the Balkans as the most important area for threatened freshwater biodiversity both within Europe and the wider Mediterranean Basin, harbouring the continent’s highest concentration of endemic freshwater fish species (Freyhof 2012). In many places in Europe wild free-flowing river systems are a distant memory, while in the Balkan region they remain a breathtaking reality (Chamberlain 2018). In total, the Balkan peninsula hosts 193 native species of freshwater fish (37% of the European total) with 56% of species endemic to the region (Oikonomou et al., 2014). Among its fish fauna are also some of the largest, most charismatic and most economically valuable species in Europe. For example, 65% of the global population of the Danube Salmon, one of the largest species of freshwater fish in Europe, is found in the rivers of the Balkan region (Freyhof et al., 2015). At the other extreme, the region also has a particular abundance of smaller species which have adapted to regions extensive karstic habitats, with numerous distinct endemic species and genera (Telestes, Phoxinellus, Delminicthys). These fishes have in many cases evolved in complete isolation from any other fish species in low nutrient, crystal clear waters. Fishes are also not the only freshwater wonders of the Balkans. This region is also one of the most important areas in Europe for freshwater molluscs with the ancient lakes of Lake Ohrid and Lake Prespa hosting a wealth of species. Many of the species now found in Lake Prespa and Lake Ohrid are relict species and their relatives can be found only in the fossil record. For this reason, Lake Ohrid is sometimes referred to as “the museum of living fossils”.

native species of freshwater fish in the balkan region, 37% of the European total.
of threatened species of freshwater mollusc in Europe occur in the Balkans.
of Balkan rivers in “pristine” or “good” hydrological condition in 2012.

Species status and conservation

Karst Spring © Michel Roggo

The aquatic environments of the Balkan region remain relatively intact – as Chamberlain (2018) identifies, it is one of the few places in Europe where true wilderness remains, with pristine river systems winding through towering mountains and sweeping across undeveloped floodplains. As they were for continental species during the last ice age, these ecosystems are a refuge and safe haven for aquatic and terrestrial species alike. However, this time it is not an ice sheet which is causing the retreat and decline of species populations, but the rising tide of human development.  The region is currently the backdrop for one of the most ambitious hydropower expansion plans in the world, with up to 2,800 projects planned (Schwarz 2017). In a comprehensive review of the threats to European freshwater species, Freyhof (2012) finds that at least 44% of freshwater molluscs (373 species) and 37% of Europe’s freshwater fishes (194 species) are threatened with extinction – making these two taxonomic groups the most threatened within Europe. Furthermore, from all European threatened species, 151 molluscs (52%) and 52 freshwater fishes (28%) occur in the Balkans. This makes the Balkans a critical site for the conservation of aquatic fauna within Europe, and therefore a critical focus for Shoal. Experts fear planned developments in the Balkan region could result in the loss of one in 10 European fish species (Weiss pers. comm in Nelsen 2018).


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Griffiths H.I, Krystufek B, Reed J.M, 2004, Balkan Biodiversity: Pattern and Process in and European Hotspot, Kluwer Academic Publishers, Dordrecht, Boston, London

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