Zeuxapta seriolae (Meserve, 1938) Infections in Cultured Greater Amberjack, Seriola dumerili (Risso, 1810), from the Middle Eastern Adriatic Sea

Parasitic diseases pose significant challenges to the success of mariculture. The health management strategies used in sea-cage aquaculture are not completely effective at preventing parasites from entering through interactions with wild fish. This study monitored the health status of greater amberjack (Seriola dumerili, Risso 1810) over a two-month period following their introduction to the farm in the Middle Eastern Adriatic Sea in July 2019. Zeuxapta seriolae was detected on the gills after 722 degree days (DD), with a 28% prevalence, a mean abundance of 1.00 parasite per fish (four examined arches), and a mean intensity of 3.57 parasites per infected fish. From 985 DD, prevalence was 100%; the parasite burden continued to rise, and by the final sampling at 1535 DD, the mean abundance reached 212.68 parasites per fish (53.17 per gill arch). At that point, fish express a sudden loss of appetite; no external symptoms were observed, except for mortality. This is the first report of Z. seriolae in cultured greater amberjack in the Adriatic Sea, and the study emphasises the difficulties in applying effective biosecurity measures in floating net cages.