Pathological obstacles of newly-introduced fish species in Mediterranean mariculture: a review

Species diversification has been extensively employed in Mediterranean mariculture industry as a tool to relief the crisis resulting from market saturation and overproduction of the two main representatives, sea bass (Dicentrarchus labrax) and gilthead sea bream (Sparus aurata). Numerous new promising candidates belonging to several fish families such as Sparidae, Polyprionidae, Serranidae, Sciaenidae, Soleidae, Carangidae and Scombridae have been introduced to provide alternative culture choices in Mediterranean. The farming potential of these species in production scale has received some or little success partly due to the fact that their entrance has not been accompanied without the presence of considerable pathological problems. Bacterial outbreaks causing serious problems have been mainly induced by Photobacterium damsella subsp. piscicida, Vibrio alginolyticus, V. harveyi, Tenacibaculum maritimum and Flavobacterium sp. Detrimental parasitic pathogens included the myxosporean Enteromyxum leei, the ciliates Cryptocaryon irritans and Uronema spp., the flagellate Amyloodinium occelatum, the monogenean Zeuxapta seriolae and the digeneans Paradeontacylix-like spp. Viral encephalopathy and retinopathy infections and the chlamydia-like bacteria causing Epitheliocystis disease are also of significance importance. Numerous other agents of lesser pathogenic significance as well as other occasionally recorded pathogens are also mentioned in this review. Additional research effort has to be devoted to the pathogenesis of important pathogens and the interactions with their hosts to assist the viability of new fish species farming in Mediterranean region.