Species composition and distribution of common Crassostrea and Saccostrea oysters along the coast of Hainan Island

Oyster cultivation is a pivotal economic industry in Hainan Island, South China, where a high oyster species diversity is shown. However, the specific distribution and biodiversity of oyster resources in the island have remained unclear. To elucidate the diversity of oyster species and their distribution there, 307 oyster samples were collected from 29 sites in the intertidal zone around the island, and were identified using both morphological and molecular approaches. A minimum of 12 oyster species were identified in taxonomy, including Crassostrea species (C. gigas angulata, C. sikamea, C. iredalei, C. dianbaiensis, C. talonata, C. ariakensis, and C. hongkongensis), and Saccostrea species (S. malabonensis, S. mordax, S. echinata, S. circumsuta, and S. mordoides). The results revealed a remarkable diversity of oyster species along the coast of the island. Particularly noteworthy are that S. malabonensis and S. mordax constituted 36