Addressing skate and ray mislabelling from the Cantabrian Sea (southern Bay of Biscay) through collaboration between scientists and market managers

Elasmobranchs face extinction crisis, with one third of species threatened by overfishing, habitat loss and climate change. Commercial mislabelling exacerbates this problem by masking illegal trade, undermining conservation efforts, and fueling Illegal, Unreported and Unregulated (IUU) fishing. This study assesses the extent of species mislabelling in skates and rays commercialized in primary fish markets of the Cantabrian Sea using DNA barcoding and evaluates whether science-based intervention involving species identification guides can reduce mislabelling. Between November 2024 and March 2025, tissue samples were collected at a fish market for barcoding genetic identification analysis. A total of 416 individuals from eight genetically identified species revealed a global mislabelling rate of 23.1%, based on discrepancies between the species label at sale and the species identified through genetic analyses. The most mislabelled species were Raja montagui and Raja brachyura , while Raja clavata was commonly used as a substitute label. Mislabelling also concealed the trade of protected or regulated species, including Leucoraja circularis and Raja undulata . In February 2025, an intervention was implemented through collaboration between scientists and fish market managers. Identification guides were distributed, informal training was provided to fishermen and market workers, and commercial labelling at auction was partially updated. Consequently, mislabelling decreased from 26.6% to 20.6%, indicating partial but significant effectiveness. These findings highlight the importance of combined efforts to improve traceability for long-term conservation strategies in Rajidae populations.