Diversity of fishes collected with light traps in the oldest marine protected area in Vietnam revealed by DNA barcoding

Knowledge of marine fish diversity remains largely incomplete in the Con Dao Archipelago, the oldest marine-protected area in Vietnam. Previous investigations of diversity established a species checklist for Con Dao but did not specifically target pre-settlement stages of reef fishes and short-life pelagic species even though they provide information on local biodiversity and on the ecological functions of their habitat. Species identification of small fishes is usually challenging, but in the present study, DNA barcode-based identification was used to update the species checklist for Con Dao marine coastal habitats. Fishes were sampled monthly over a 1-year period using light traps in coral reef, seagrass, and harbour habitats. Among a total of 11,509 individuals captured, 1248 specimens were selected for DNA barcoding analyses based on morphological differences, 1012 were successfully sequenced, and their COI sequences uploaded to the BOLD database. Among the 163 corresponding BINs, 120 were recorded for the first time in Vietnam while 40 (25%) were new to BOLD. It was impossible to assign a complete species name to 59 BINs (36%), because of gaps in the taxonomical coverage or mislabelled DNA barcodes (probably due to species misidentification). Among species observed in this study and belonging to 18 orders and 35 families, 85 and 59 were new records for Con Dao and Vietnam, respectively. The high proportion of new species records are probably related to the sampling gear used that is particularly appropriate for sampling crypto-benthic species of the families Gobiidae, Tripterygiidae, and Blenniidae. From a methodological standpoint, this study demonstrates that accuracy of the DNA barcode-based species identification can be greatly improved by careful revision of BINs, phylogenetic relationships with sibling BINs, and by using the taxonomical literature which can provide sequences of reference species.

Automated summary

Knowledge of marine fish diversity in the Con Dao Archipelago, Vietnam's oldest marine-protected area, is still incomplete. This study used DNA barcode-based identification to update the species checklist for Con Dao's marine coastal habitats. It found that a significant number of species were new records for both Con Dao and Vietnam, and that certain species could not be fully named due to taxonomical gaps or mislabelled DNA barcodes.