Since 1996, mass mortalities of cultured Japanese pearl oyster Pinctada fucata martensii have been occurring in western Japan. Mortalities are accompanied with reddish-brown discoloration of the soft body, especially the adductor muscle of oysters. This disease was named “akoya oyster disease (AOD)”. However, the cause of the disease is still unidentified. As a control strategy of this disease, selective breeding of pearl oysters resistant to AOD has been conducted in several public institutes and private groups. The recent decline in outbreaks of AOD can be attributed, in part, to the introduction of selectively bred oysters that are resistant to this disease.
