The Kumamoto oyster () was first identified in Ariake Bay, Kumamoto Prefecture, Japan, by Amemiya (1928) as a variety of the Japanese or Pacific oyster, ("shikame" means "wrinkled" in Japanese). Ahmed (1975) elevated it to species status () after careful morphological analyses. Banks et al. (1993, 1994) provided genetic support for (Amemiya 1928) as a species distinct from the closely related Pacific oyster C. gigas (Thunberg 1793). Wang and Guo (2008) developed a simple, fast, and reliable method using multiplex PCR to identify and C. gigas. The Kumamoto oyster is now known to be widely distributed across East Asia, including Japan (Ariake Sea and Seto Inland Sea), Korea (Suncheon Bay), and China (southern China). In Japan, Kumamoto oysters only command a small share of trade in the oyster culture industry, chiefly due to its small size. Therefore, little attention has been paid to securing aquaculture broodstocks except for a recent endeavor to produce hatchery seedlings. However, in southern China, recent sharp declines in wild resources due to environmental pollution and marine reclamation has led to the development of artificial to meet demands for increased oyster yield. Kumamoto oysters were introduced from the American Taylor Shellfish Farms as exotic germplasm. A core-based group was built following two methods, and the performance traits and introduction feasibility of the oysters were evaluated in comparison with Chinese stock as the control. The American stock has faster growth, lower viability, and higher commodity rate than the Chinese stock. After 1 year, shell heights and fresh weight of the American stock increased by 11.48% and 48.12%, respectively, compared with the Chinese stock. Stock source was the main factor affecting performance, and there was no significant effect of mating strategy on phenotypic traits. This study found that the American oyster in China has strong growth potential and provides valuable experimental material for improving the Kumamoto oyster, while supplying excellent variety for the oyster industry in southern China.