Involvement of Viral Nervous Necrosis in Larval Mortality of Hatchery-reared Pacific Bluefin Tuna Thunnus olientalis

Abstract

Amami Station of Fisheries Research Agency, Japan has experienced mass mortalities of Pacific bluefin tuna Thunnus olientalis in the process of seed production since around 2000. The mortalities mostly occurred at larval stages. In some cases of the mortalities, but not all cases, the diseased fish was characterized by vacuolation in the central nervous systems and retina, and a betanodavirus (RGNNV genotype) was detected in the affected fish by PCR and FAT methods and culture isolation. The present results suggest that VNN can be a cause of larval mortality of Pacific bluefin tuna.