Abstract
Akoya pearl culture is important aquaculture industry in Japan. Since the 1990s, the Japanese pearl industry become down-scaling due to mass mortality of pearl oyster (Pinctada fucata) caused by Akoya oyster disease and harmful red tide. To cope with this situation, it has been necessary to develop an efficient selective breeding program focused on reducing mortality and improving pearl quality. We conducted several selective breeding programs for resistance to disease by using the nacre-deposition ability and/or shell-closing strength of the recipient oysters as indicators. Results from rearing trails have demonstrated that selectively bred oysters had significantly lower mortality compared to those from natural populations or the control non-selective oysters. Moreover, we clarified that nacre thickness of pearl produced from a lineage with increased nacre-deposition ability was thicker than that from oysters with lesser ability groups. This result suggested that nacre-deposition ability is the heritable trait, and could be used as selective indicator to improve both survival rate and pearl quality in recipient oysters. With regard to donor oysters, selective breeding research is performed to develop a lineage with white nacre in the shell, which produced precious white color pearl. From these results, we concluded that our selective breeding programs on disease resistance and pearl quality traits are efficient for improvement of productivity and sustainability of pearl culture industry in Japan.
