Carassius gibelio in Greece: the dominant naturalised invader of freshwaters

Abstract

Ichthyofauna in the Hellenic freshwaters is quite diverse consisted of 161 species (including 28 non-natives), out of the 546 native species in Pan- European level. However, the status of many aquatic ecosystems is currently degraded as a result of a variety of anthropogenic impacts. This has direct reflection on the conservation status of the indigenous and native fish species whose populations are in many cases declining in favor of the invasive ones. Prussian carp (Carassius gibelio) is probably the most dom- inant invasive species and currently is considered as naturalized in about 26 lake and river basins. Its successful adaptation and proliferation is mainly attributed to its dual reproductive mode (allogynoge- netic and gonochoristic), the opportunistic-omnivo- rous feeding habits and the ability to withstand and flourish in adverse ecological conditions. Accord- ingly, it exerts competitive, as well as destructive effects upon the indigenous fish species (sperm parasitism, antagonism for food, spawning grounds and spawning substrates) and therefore, efforts are needed to sustain a relative balance of the popula- tions. This review aims to critically discuss the status of C. gibelio in Greece, the intrinsic causes of establishment and the observed impacts on ecosys- tems. Finally, reasonable actions are proposed related to exploitation of C. gibelio stocks and a path model for the protection of native fish species and their ecosystems.