Abstract

Crassostrea gigas is a sessile bivalve commonly found in intertidal and subtidal zones. Due to its high environmental adaptability and rapid growth, it has become a commercially important aquaculture species worldwide, particularly in Asia. In South Korea, oyster farming is a major sector of marine aquaculture, with a production volume of approximately 267,000 tons in 2021. However, concerns over potential inbreeding depression caused by long-term monoculture practices highlight the need to maintain genetic diversity in cultured populations. This study aimed to assess the genetic diversity and population structure of C. gigas in South Korea by using 16 microsatellite markers. A total of 288 individuals were sampled from six locations: Ganwoldo (Taean), Iwon-myeon (Taean), Jindo, Shinan, Gunsan, and Tongyeong. The number of alleles per locus ranged from 4 to 27, with an average of 10. The observed and expected heterozygosity values were 0.541 and 0.592, respectively, indicating a relatively high level of genetic diversity in the populations analyzed. Analyses of genetic distance, pairwise FST values, UPGMA clustering, and principal component analysis (PCA) revealed little genetic differentiation among the Ganwoldo (Taean), Iwon-myeon (Taean), Jindo, Shinan, and Gunsan populations. However, the Tongyeong population exhibited a low but statistically significant genetic divergence (p < 0.05). These findings provide a valuable genetic baseline for the conservation, evaluation, and sustainable management of C. gigas resources in South Korea.