Identification of tuna species used by the Portuguese canning industry through a DNA-based approach.

Despite the popularity of canned tuna in Portugal, limited research has explored how tuna species vary across brands and seasons. Accurate species identification is crucial to preserve both the economy and ecology of global tuna fisheries, as mislabelling and the use of certain species can have far-reaching implications. Our study analysed the diversity of tuna species used by the Portuguese tuna canning industry, focusing on brand-specific and seasonal variations, using molecular barcoding methods. In this industry, the occurrence of different species was observed only in products using water as a preservation medium. Skipjack tuna was predominant across all preservation media and brands analysed. Nonetheless, other species like Thunnus obesus and T. albacares, or Auxis spp. (not considered true tuna) were also detected. The use of different species was limited to cans produced during the second quarter of the year, which could reflect differences in seasonal availability of different tuna species or in sourcing strategies/market preferences of each company. Finally, more than one species was detected inside the same container in four brands, violating current European legislation. These results provide the first broad assessment of species used in the Portuguese tuna canning industry and showed the inclusion of vulnerable species is limited.