DNA barcoding of commercial fish products using dual mitochondrial markers exposes evidence for mislabelling and trade of endangered species

Fish fraud has been extensively reported in world fish trade. The fraud includes IUCN Red List and CITES-listed species. Hence, there is a growing need to identify the trade of endangered and threatened species that has been misused to satisfy consumer needs. Here, we apply DNA barcoding by using dual mitochondrial marker; cytochrome b ( Cytb ) polymorphic fragment and cytochrome c oxidase subunit I ( COI ) to authenticate 50 commercial fish products collected from the Malaysian market. The dual marker system improves species detection in tested fish products even in highly processed food and exposes the trade of one critically endangered (also CITES-listed) and three endangered or near threatened species under the IUCN red-list status. Our result also indicates that 36% of fish products in the Malaysian market is mislabelled and might cause concern for food safety. The newly developed Cytb primer pair also shows a higher success rate by identifying 92% of the tested samples compared to 40% for COI primer. This work suggests the dual-marker DNA barcoding approach is more effective in detecting food mislabelling and is indeed a promising tool to help regulatory bodies obtain a clearer standpoint for monitoring endangered fish trade to prevent further biodiversity loss.