COI-based DNA barcoding could be an efficient tool for species
identification of deep-sea fishes and could lead to the discovery of
cryptic species diversity. However, the availability of reference
sequences of deep-sea fishes for DNA barcoding is limited, especially
for fishes in the northwestern Pacific Ocean. In this study, we
performed DNA barcoding of mesopelagic and demersal fish species on the
continental shelf and upper slope, collected from deepwater fisheries
around Japan and southern Taiwan, to accumulate the reference sequences
of deep-sea fishes in the northwestern Pacific Ocean. Overall, we
obtained the COI sequences of 123 species from 50 families. Genetic
diversity within each species for which COI sequences were obtained from
multiple specimens was examined, and we found that Chimaera
phantasma (Chimaeridae), Harpadon microchir (Synodontidae), and
Pyramodon ventralis (Carapidae) showed high intraspecific genetic
differentiation of more than 2% Kimura two-parameter distance.
Moreover, for 19 widespread deep-sea fishes, a comparison between our
data and previously acquired COI sequence data suggested a high level
(more than 2% Kimura two-parameter distance) of genetic differentiation
between the northwestern Pacific Ocean and other oceans in each
widespread species. These results suggest that many cryptic species or
regional populations have not yet been discovered in deep-sea fishes.
Alternatively, genetic differentiation was not found worldwide for six
species. These results indicate that many taxonomic and biogeographical
issues remain for deep-sea fishes, and our DNA barcoding data would
provide better understanding of these issues.