Molecular and morphological evidence for the identity of the blackspot shark, Carcharhinus sealei, and the Indonesian whaler shark, C. tjutjot, with notes on their population structures

The requiem sharks of the genus Carcharhinus are captured as bycatch in the Indo-Pacific region. The lack of morphometric data due to the common practice of head and fin removal of sharks, hinders the implementation of shark management measures. Carcharhinus specimens found in the waters of Brunei Darussalam were identified using morphological analysis, and their identification was further validated by mitochondrial cytochrome c oxidase subunit I (COI) gene sequence analysis. This study successfully identified twenty-seven specimens as either the blackspot shark, Carcharhinus sealei, or the Indonesian whaler shark, Carcharhinus tjutjot, by molecular genetic analysis, although the difficulty of accurately identifying these sharks solely on morphology was encountered. Mitochondrial COI gene sequence analysis also suggested that C. tjutjot has two genetically distinct populations/groups, while C. sealei had a single panmictic population in the Indio-Pacific region. The findings suggest that C. sealei could be a more highly migratory species than C. tjutjot in the region.