Red sea bream iridovirus (RSIV) causes an acute and highly contagious disease, tentatively designated red
sea bream iridoviral disease (RSIVD). Since 1990, outbreaks of RSIVD have resulted in high mortalities in
cultured red sea bream Pagrus major in southwestJapan, primarily in the summertime. The disease has
caused mass mortalities among cultured marine fish,which include 18 Perciformes, 1 Pleuronectiformes and
1 Tetradontiformes (Matsuoka et al. 1996). A recentsurvey showed that 25 species of fish are susceptible to this virus (authors' unpubl, data).