Fish are such an important feature of Prespa because of the high level of endemism or uniqueness of the species that live in its lakes. Twenty three species of fish have been found in the Lesser and Great Prespa Lakes, out of which 9 species, or sub-species, are local or regional endemics, including the endangered Prespa trout, and for this reason they are protected by European and national legislation. These distinct fish species have come about as a result of the longevity of the lakes, which are amongst the oldest in Europe, being millions of years old. This long span of time, together with the separation of the lakes from other bodies of water, brought about the evolution of these unique species of fish, especially adapted to the particulars of the natural environment in Prespa.
These unique fish species have, furthermore, contributed to Prespa’s being counted as one of the ten most important wetlands in the Mediterranean, according to the “Red List of Freshwater Fish in the Mediterranean”, though all the endemic species, except for the Prespa chub, have been characterised as “Vulnerable” or “Endangered”, in accordance with the International Union for Conservation of Nature (IUCN) Red List. On the other hand, fish are the main prey of the exceptional waterbird community of the lakes, particularly the numerous piscivorous birds. In addition, the local fisheries, which can regulate the status of populations to an extent, are an important, though largely supplementary, economic activity that has existed for centuries.
The important fish fauna in the two lakes are confronted with a number of threats, which include changes to water quality, i.e. nutrient and other pollution originating from agricultural, urban and industrial waste, as well as factors negatively affecting their habitat, especially their spawning grounds. They suffer also from other anthropogenic threats such as the introduction of non-native invasive fish species.
In order to contribute to their conservation, since 1991 the Society for the Protection of Prespa (SPP) has systematically monitored the development of fish populations in the lakes and Prespa’s rivers by means of sampling research methods and, particularly for the endemic Prespa trout, in collaboration with the French Tour du Valat research institute which has worked on the species since the mid-1980s. The ongoing fish monitoring programme has provided valuable data on species needs, population trends and preferences. These results are unique for the area, and they continue to be used by different relevant stakeholders and the management body when taking management decisions.
In order to document the threats to the Prespa trout and propose conservation measures, the SPP has studied the species since 1998, with intensive research carried out in 2005-2008 in the rivers where it is found in Greece, as well as North Macedonia, in additional collaboration with the environmental organisation BIOECO. These investigations resulted in a Trout Action Plan that includes the scientific information on the species, as well as proposed measures for its conservation. Furthermore, a project focused on the biology and ecology of the endemic Prespa barbel, concluded with the production of a Species Action Plan, more than half of which has been successfully implemented.
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Catsadorakis, G., Papadopoulou, E., Petrakos, M., Koutseri, I. “Status of Fisheries at Megali Prespa Lake and Mikri Prespa Lake, Greece, Based on a Census of Fishermen’s Opinions”, Environment and Ecology Research 2018, 6(6): 583f-592.
Bounas, A., G. Catsadorakis, I. Koutseri, H. Nikolaou, D. Nicolas, M. Malakou & A.J. Crivelli. 2021. Temporal trends and determinants of fish biomass in two contrasting natural lake systems: insights from a spring long-term monitoring scheme. Knowledge & Management of Aquatic Ecosystems. 422, 28.