Re-visiting the occurrence of mislabeling in frozen "pescada-branca" (Cynoscion leiarchus and Plagioscion squamosissimus - Sciaenidae) sold in Brazil using DNA barcoding and octaplex PCR assay.

In Brazil, Cynoscion leiarchus and Plagioscion squamosissimus are the species allowed to be labeled as "pescada-branca". These species have high economic value, especially when sold in the form of fillets. Therefore, when morphological traits are removed, fish are highly prone to be substituted, which has been reported for species of the family Sciaenidae sold in Brazil, including "pescada-branca". We have sequenced 618 bp of the COI of 143 samples to re-evaluate the occurrence of substitutions in frozen "pescada-branca" marketed in Brazil. We observed more than 73% of mislabeling, with only 26.57% being P. squamosissimus, and none, C. leiarchus. In general, the substitutes were closely related Sciaenidae, but cheaper species, which indicates commercial fraud. Based on these results we used 1.2 kb of COI to develop an octaplex PCR assay that unequivocally identified the target species and six substitute species through the banding pattern. Specific reverse primers combined with a universal forward primer were used in the protocol and identified the species C. leiarchus (290 bp), N. microps (340 bp), M. ancylodon (470 bp), C. acoupa (540 bp), C. microlepidotus (850 bp), P. auratus (950 bp), C. virescens (1050 bp), and P. squamosissimus (1140 bp). The DNA barcoding and the multiplex PCR were accurate and specific to authenticate processed products labeled as "pescada-branca". The multiplex assay constitutes a cost-effective alternative for the authentication of these products and other sciaenids. Additionally, we suggest that the multiplex assay can be adopted by both companies and regulatory agencies to prevent commercial fraud in the marketing of processed fishery products in Brazil and other countries where these products are commercialized.