Beyond Bycatch: The Species Diversity of Tonguesole (Pleuronectiformes: Cynoglossidae) in Coastal Fisheries of the Tanintharyi Region, Southern Myanmar

Flatfishes in the family Cynoglossidae are an important coastal fishery in Myanmar. Due to the overlapping morphologies of multiple tonguesole species, caught both as bycatch from trawl fisheries and targeted specifically by small scale fishers, they are all marketed under a single local name, “khwayshar”. This presents a management challenge given the potential differences in the species-specific life-histories, population dynamics, fishing vulnerability and harvest rates. This study investigated the species diversity of tonguesole landings from coastal communities of the Tanintharyi Region of southern Myanmar. DNA barcoding was used to distinguish potentially 10 different species, of which five were identified to species level and five at the genus level. Unconfirmed genetic identifications were based on external morphology. The poor efficacy of DNA barcoding for tonguesole species identification resulted from the limited DNA barcode reference sequences available for the family Cynoglossidae in public databases. An asymmetric occurrence and relative abundance of the identified species in landing sites where samples were collected suggested that the most common species was Cynoglossus oligolepis (Bleeker, 1855), a new species record for Myanmar, followed by Cynoglossus lingua Hamilton, 1822. The results of the present study provide new information to characterise the tonguesole fishery as a first step in the development of management plans for the coastal fishery in Myanmar.