Factors causing mass mortality of cultured young bluefin tuna <i>Thunnus orientalis</i> during the spring of 2017 in Asou bay, Nagasaki, Japan

Abstract

Mass mortality of cultured young blueˆn tuna Thunnus orientalis, with the loss of approximately 2,400 individuals, occurred in Asou bay, Tsushima, Nagasaki, Japan in April 2017. Blood ‰uke eggs were observed in the gills of deadˆsh, butˆsh without severe infection also died. At the time, a noxious red tide of Heterosigma akashiwo was also detected (13 90 cells mL -1 ). However, the density of blood ‰uke eggs in theˆsh gills, or con-