DNA barcoding reveals a high incidence of fish species misrepresentation and substitution on the South African market

Abstract

The mislabelling of fishery products has emerged as a serious problem on global markets, raising the need for the development of analytical tools for species authentication. DNA barcoding, based on the sequencing of a standardised region of the cytochrome c oxidase I (COI) gene, has received considerable attention as an accurate and broadly applicable tool for animal species identifications. The aim of this study was to investigate the utility of DNA barcoding for the identification of a variety of commercial fish in South Africa and, in so doing, to estimate the prevalence of species substitution and fraud prevailing on this market. A ca. 650 base pair (bp) region of the COI gene was sequenced from 248 fish samples collected from seafood wholesalers and retail outlets in South Africa, following which species identifications were made in the Barcode of Life Database (BOLD) and in GenBank. DNA barcoding was able to provide unambiguous species-level identifications for 235 of 248 (95%) samples analysed. Overall, 10 of 108 (9%) samples from wholesalers and 43 of 140 (31%) from retailers were identified as different species to the ones indicated at the point of sale. Although some cases of mislabelling were potentially unintentional due to misapplied market nomenclature, a far greater proportion represented serious and seemingly deliberate acts of fraud for the sake of increased profits. This study has highlighted that the existing legislation pertaining to seafood marketing in South Africa is inadequate or poorly enforced and requires urgent revision. In the light of the results presented here, DNA barcoding appears to hold great potential for fish authentication monitoring by both regulatory bodies and industry, the utilisation of which could enhance transparency and fair trade on the domestic fisheries market.