Are fish introductions a threat to endemic freshwater fishes in the northern Mediterranean region?

Abstract

Seventy species of exotic or transplanted fish species have been introduced into this region, 60% of them in the last 40 years. The effects of these introductions on endemic species have rarely been described. The few exceptions are: hybridization of Salmo marmoratus with Salmo trutta; the extinction of three endemic species of Phoxinellus in a Turkish lake owing to the introduction of Stizostedion lucioperca; and the spatial displacement of Aphanius in sites where Gambusia affinis occurs. A further phenomenon possibly attributable to the introduction of exotic fish is the increased turbidity in Lake Mikri Prespa following the introduction of Carassius auratus. Because of the paucity of information, the effects of introductions on endemic species remain controversial. It is therefore essential to initiate conservation action plans, for each catchment in wetland areas rich in endemic fish. An awareness campaign directed at land managers and decision-makers on the role and importance of fish in the functioning of aquatic ecosystems must also be undertaken very soon.