Digenea of Adriatic cage-reared northern bluefin tuna (Thunnus thynnus thynnus)

Cage rearing of northern bluefin tuna (Thunnus thynnus thynnus) in the Adriatic Sea is a relatively novel branch of aquaculture, with scarce literature on fish pathologies. In this study, viscera and gills of 52 specimens of 13 kg tuna showed an interesting composition of digenean parasitofauna. Most abundant and prevalent were the members of the Didymozoidae family Coeliodidymocystis abdominalis, Didymocystis wedli, Platocystis alalongae, Koellikerioides internogastricus, Koellikerioides intestinalis and Koellikerioides apicalis, isolated from various tissues. Ventricular, kidney and gill tissues showed disseminated granulomas, presumed to be the eggs of the blood trematode Cardicola forsteri, however no adult forms were found. This is the first report on tuna digenean parasitofauna in the Adriatic Sea.