Mapping conservation priorities in the Mediterranean: the issue of non-native freshwater fish introductions

Contributions presented at the international NeoFishMed workshop on New Approaches for Assessing the Impacts of Non-native Freshwater Fishes in the Mediterranean Region are reviewed. Rivers in Mediterranean-climate regions are characterised by a dynamic hydrology, resulting in severe droughts during summer and flash flooding in winter. These types of systems, when disturbed by human actions, seem to be particularly suitable to the establishment of non-native freshwater fish species (i.e. where the natural, highly variable hydrological conditions have been replaced by regulated discharge regimes as a result of reservoir construction). The Mediterranean region is considered one of the six global invasion hotspots, with non-native freshwater fishes representing >25% of all fish species in riverine assemblages. From a conservation perspective, this region is characterised by increased competition for scarce water resources as well as high endemicity and biodiversity. Key points on introduction pathways, ecosystem vulnerability and human impacts, as well as future trends for the Mediterranean region, are presented. A case is made to develop, using innovative analyses, evidence-based assessments of impacts by non-native species on Mediterranean ecosystem vulnerability to underpin the development of future policy and appropriate management tools.