Abstract: To understand the species of oysters in the coastal area of Tianjin, a total of 127 wild oysters were collected from three sampling sites, including the Duliujianhe river estuary, Beijiang Power Plant Breakwater and Dongjiang Port. First, morphological indexes were measured, and then cytochrome oxidase I（COI）gene sequence was analyzed. The oyster species were further identified. The results showed that 9 haplotypes were obtained from 16 COI gene sequences. The Haplotype diversity（h）and Nucleotide diversity（π）were 0.767 and 0.001 73 respectively. Cluster analysis results showed that the oyster sequences obtained in this study first clustered into a branch with Crassostrea gigas, and then clustered into a branch with Crassostrea angulata. Based on the results of morphological observation and molecular identification, the oyster samples collected from the three locations along the coast of Tianjin were all Crassostrea gigas, indicating that the composition of oyster species in Tianjin sea area was relatively simple. The Talonostrea talonata and Crassostrea ariakensis as previously reported were not found in this study, and further sampling sites are needed to obtain more comprehensive conclusions. The results of this study are of great significance for understanding the status of existing oyster resources and protecting species diversity in Tianjin.

Key words: Tianjin coast, oyster species, morphology index, cytochrome oxidase I, molecular identification