Molecular authentication by DNA barcoding and multiplex PCR assay reveals mislabeling and commercial fraud of the Acoupa weakfish (Cynoscion acoupa), an economically important sciaenid marketed in Brazil

The Cynoscion acoupa is an important fishery resource in Brazil and the only species allowed to be labeled under the commercial designation pescada-amarela (Acoupa weakfish). Therefore, we used the DNA barcoding to evaluate the authenticity of fillets labeled as pescada-amarela and, from the results, we developed a multiplex PCR assay to identify the target species and its substitutes. A 597-bp cytochrome C oxidase subunit I (COI) sequence was obtained from 141 fillets and compared with the sequences of whole Sciaenidae fish that were identified based on the morphology and the sequences from the BOLD and GenBank public databases. The results revealed high substitution rates (45.4%), with 39.72% of the fillets being identified as Cynoscion virescens, 3.55% as Cynoscion microlepidotus, 1.42% as Macrodon ancylodon, and 0.71% as Plagioscion auratus. The species used as substitutes were of lower commercial value, which indicates commercial fraud aimed at increased profits. Additionally, we used 1.2 kb of COI to design species-specific reverse primers, which were combined with a universal forward primer in the multiplex assay to distinguish pescada-amarela from the substitute species. The assay distinguished the species by amplifying similar to 470, similar to 540, similar to 850, similar to 950 and similar to 1050 bp DNA fragments from M. ancylodon, C. acoupa, C. microlepidotus, P. auratus and, C. virescens, respectively. The protocols are sensitive and specific for the authentication of Sciaenidae and the multiplex assay is a fast and cost-effective alternative that can be adopted by companies or governmental agencies to authenticate pescada-amarela and other processed Sciaenidae marketed in Brazil (M. ancylodon e C. virescens), preventing fraud and ensuring safe consumption.