Umbrella terms conceal the sale of threatened shark species: A DNA barcoding approach

Food fraud in the seafood industry is a growing concern, including the authenticity and provenance of seafood products that are often unable to be confidently verified along complex, and at times obscure, supply chains. Among the diverse types of seafood fraud, mislabelling and species substitution are common, and have potential implications on human health, the economy, and species conservation. In particular, shark meat can be difficult to monitor, associated with the use of an array of convoluted nomenclature or ambiguous umbrella terms. In Australia, shark meat fillets are a popular seafood item sold under the umbrella term flake in takeaways, and fish and chip shops. We collected samples of flake as sold to consumers at 104 retailers in South Australia and used DNA barcoding to determine the shark species being traded. At least nine distinct species were identified, with only 27% of all samples identified as gummy shark (Mustelus antarcticus), a species that has sustainable fisheries, is locally caught, and is one of two species that is recommended to be labelled as flake in Australia. Four species were threatened taxa, including the CITES Appendix II listed short-fin mako (Isurus oxyrinchus) and smooth hammerhead (Sphyrna zygaena). Of all the samples and shops analysed, only 11% of retailers correctly identified the species they sold, another 20% were mislabelled and the remaining only had ambiguous labelling. Ultimately, the umbrella term flake allowed for species misrepresentation but DNA barcoding was an effective tool to test ambiguous labelling in processed and cooked shark meat products, and can guide policy, management, and compliance efforts to mitigate mislabelling, empowering consumers to make informed decisions and champion sustainable seafood.