DNA barcoding of fisheries catch to reveal composition and distribution of cutlassfishes along the Taiwan coast

Multiple cutlassfishes share similar morphological characteristics and habitats and together contribute to substantial fisheries catch in the northwestern Pacific coast. Because information on the composition and distribution for these cutlassfishes is currently lacking, they are being managed as one species. To fill this knowledge gap, we initiated a survey of species composition and distribution for cutlassfishes at several primary landing sites along Taiwan coast (longitudes: 120-122°E, latitudes: 22.5-25°N) during 2013-2014. We conducted sampling on multiple fisheries (total N = 1305): pair trawlers (at the NE and SW coasts), stick-held dip nets (northern coast), fyke nets (NW coast), and set nets (E coast). Using the DNA barcoding methods (with mitochondrial DNA genes 16S rDNA and Cytochorome C oxidase I (COI)), we confirmed presence of four cutlassfish species in the fisheries catch: Trichiurus japonicus, T. nanhaiensis, T. lepturus, and Tentoriceps cristatus. The T. japonicus is a dominant species that constitutes 40-100% of catch abundance of cutlassfish throughout Taiwan coasts, while the other three species are generally in lower abundance than T. japonicus and display relatively confined distributions. Our findings provided advanced knowledge on composition for cutlassfishes and highlighted a need to account for differences in abundance, distribution and life histories among various cutlassfish species for management of the multispecies fisheries in the NW Pacific.