Fish fauna in a Protected Greek lake: biodiversity, introduced fish species over a 80-year period and their impacts on the ecosystem

Abstract –  Lake Pamvotis is a tertiary natural shallow lake located in the NW of Greece. For biogeographical reasons, it historically contained only four fish species: two endemics ( Phoxinellus epiroticus , Squalius pamvoticus ), one native to the West Greece ( Barbus albanicus ) and the ubiquitous Anguilla anguilla . These species were almost exclusively present in the lake before 1920, forming remarkable commercially exploited populations. From the 1930s through the 1990s, 20 species were introduced into the lake for purposes of eutrophication control or to enhance the fishery. These introductions, some of them accidental have led to the apparent decline, even loss, of the native species. During the last three decades the fish fauna of the lake has shifted from the native, clear-water species to a predominance of introduced species, mainly those adapted for turbid eutrophic water ( Rutilus panosi , Cyprinus carpio and Carassius gibelio , and several Asian cyprinids). The current fish assemblage in the lake is dominated by introduced species particularly the Mosquitofish ( Gambusia affinis ) and the Lourogobios ( Economidichthys pygmaeus ) in the littoral zone, the benthopelagic allogynogenetic Prussian carp ( C. gibelio) , and the opportunistic Trichonis roach ( R. panosi ), in the pelagic zone.