Cryptic morphology within and among oyster species causes taxonomic confusion and may complicate aquaculture and management efforts . In Hawai'i, resurgence in traditional fishpond aquaculture and an associated interest to farm both native and non-native oysters has spurred recent interests to identify unknown species. Similarly, native oyster culture has been piloted recently to determine whether these species can assist with water quality improvement in polluted areas. These commercial and environmental efforts are complicated by the wide phenotypic variation among oysters. The Pacific Aquaculture and Coastal Resources Center (PACRC) at the University of Hawaii Hilo has been culturing Dendostrea sandvichensis since 2010. A collaboration with the Waiwai Ola Waterkeepers Hawaiian Islands led to an effort to increase production and required collection of broodstock from the wild. D. sandvichensis has not been observed to exceed 3 cm (DVM) in the wild although hatchery-produced specimens may grow to at least 6 cm (DVM). T he small size has led to further confusion in identifying specimens given that at least four extant native species have been documented and potentially as many as four non-native oyster species . It had been suspected for some time that additional species may exist in Hawai`i. Thus, some of the oysters that had phenotypic characteristics suggesting they might not be D. sandvichensis were utilized for DNA barcoding.
We sequenced two partial gene fragments, the mitochondrial cytochrome c oxidase subunit I (COI) gene and 16S ribosomal RNA (16S) gene, in 18 unidentified and 31 known oyster specimens. Molecular data identified 72% of unknown samples as Ostrea stentina (Payraudeau , 1826), a globally distributed species that has been previously recorded along North Atlantic, South American, Mediterranean, North African, Japan, and New Zealand coasts. The remaining unknown samples were the native Dendostrea sandvichensis (G. B. Sowerby II, 1871), and nonnative Crassostrea gigas (Thunberg, 1793). The latter is a commercial species that was introduced to Hawai'i from multiple sources during the 20thcentury. This study provides the first official record for O. stentina in the state. These findings have significant ramifications including the possibility of culturing O. stentina, regulatory complication and the paucity of additional information about the distribution of this species in Hawai`i.