DNA barcoding reveals fraud in commercial common snook () products in Santa Marta, Colombia.

The common snook is one of the main commercial fish species in the Caribbean region, including Colombia, where its populations have drastically decreased due to overfishing and environmental degradation. Thus, there is a market imbalance between the availability of snook products and their demand by consumers, which creates an opening for fraudulent actions such as species substitutions. Legislation in Colombia (and most Caribbean countries) lacks effective tools for the easy and rapid detection of frauds. Furthermore, there are very few studies published in scientific journals addressing this issue, of which none include as the target species. Therefore, in order to investigate the existence of mislabeling in common snook products in Santa Marta, the present study analysed 44 frozen snook fillets from the five commercial brands available in the city. Moreover, 15 fresh snook fillets from six of the main fish markets were also analysed. To discover the frequency of possible frauds in labeling, samplings were carried out in July, September and November of 2019. Sample analyses involved the identification of each fillet at species level through molecular barcodes (16S-rRNA and COI), whose sequences were verified using BLAST and BOLD, and corroborated by a phylogenetic analysis. As a result, an astonishing 98% of the supermarkets fillets were found to be fraudulent, contrasting with a single case registered in the fish shop samples. The species used to substitute snook include the Pacific bearded brotula (38 samples), the Nile perch (4 samples) and the acoupa weakfish (1 sample). Based on these results, there is a high rate of fraudulent labeling in the marketing of common snook in the city of Santa Marta, which calls for urgent actions to be taken by the corresponding authorities.