From classical lab-barcoding to naked-eye DNA based assays to uncovering high-value seafood fraud “on site” in northern Spain

Seafood in northern Spain is a relevant component of the region’s cultural heritage. Fraud in the marketing of these species undermines product identity, violates consumer rights, and distorts fisheries data hindering sustainable fisheries management. In this study, 41 products from 32 commercial establishments along 18 sampling locations in Asturias, northern Spain, were monitored to assess seafood fraud in the commercialization of the native lobster Homarus gammarus and the native razor clams of the genus Ensis . Labels analysis revealed deficiencies in compliance with European Union regulations. Besides this, a classic barcoding strategy using the mitochondrial COI gene revealed that 4 (18%) out of 22 lobster products analyzed were substituted with the non-native species Homarus americanus , whereas 5 (26%) out of 19 razor clam products were mislabeled or substituted with the American species Ensis leei . These results suggest the existence of a probable widespread scenario of seafood fraud problems in the commercialization of these species. Naked-eye LAMP assays were also successfully developed for the visual identification of H. gammarus and E. leei species. Moreover, an onsite naked-eye DNA-based pilot test in a restaurant also detected seafood fraud. The proof of concept suggests that onsite tests could be useful for controlling seafood fraud.