Seasonal variations in gonadal development of third-generation golden shell colored strain were investigated in relation to environmental factors from November 2013 to October 2014, and the general nutrient components of the mantle, gill, gonadal-visceral mass, and adductor muscle were examined. In addition, the nutritive content of the golden shell colored strain was compared with that of commercially cultured oysters. The histological analysis showed that the female to male sex ratio was approximately 1:1, and the gonads of both sexes developed synchronously. Gametogenesis began in February and spawning started in June and appeared to continue until August when water temperature was high and food was abundant. Mean oocyte diameters increased gradually from the beginning of gametogenesis and reached their maximum (36.99 μm) before spawning. The biochemical analyses showed that total gonadal fat content was relatively low compared with that of total protein and glycogen, but fat accumulated as the gonads developed, indicating that lipid is a major component of bivalve oocytes. Glycogen content decreased significantly during sexual maturation, whereas total protein content increased as the gametes matured. Golden shell colored oysters had significantly higher protein content, but significantly lower glycogen and fat contents in the mantle than those of commonly cultured oysters (<0.05). General nutritional composition was not different among the other three organs. These results indicate that nutritive content was similar in the common and golden shell colored oysters and provide data for breeding the golden shell colored strain in the future.