The research, published earlier this month in the journal Food Control, is the first of its kind to examine DNA in the fish and chips sold in the region.
They determined what type of fish were being sold as flake, a term used to describe shark meat fillets.
“Only 27 per cent of all samples were identified as gummy shark, a species that has a sustainable population, and is one of only two species that is recommended to be labelled as flake in Australia,” study co-author Ashleigh Sharrad said in a statement.
Researchers found four threatened species, including the short-fin mako shark and smooth hammerhead shark, being sold as flake at some takeaway outlets.
They identified nine different types of shark species in the study, including some not found in Australian waters.
While mislabelling and species substitution have been found to be common in the sea food industry, it is particularly difficult to monitor shark meat as the classification of these fishes involves an array of complex nomenclature.
“Food fraud in the seafood industry is a growing concern and mislabelling may occur. It can have potential implications on human health, the economy, and species conservation,” said Professor Bronwyn Gillanders from the University of Adelaide.
Only one in 10 retailers could correctly identify the type of fish being sold out of all the flake samples analysed.
About 20 per cent of the fillets were mislabelled and the remainder had “ambiguous labelling”.
While a broad variety of species were being sold as flake, smaller retailers can’t be accused of mislabelling as they are most likely “unaware” when they purchase bulk, processed or frozen fish fillets, explained researchers.
While the Australian Fish Names Standard recommends the term “flake” be used only to describe gummy sharks and New Zealand rigs, researchers found this guideline to not be mandatory.
The new findings underscore the need for clearer national guidelines or labelling laws for shark fillets, they said.
The new results can guide policy, management and compliance efforts that can help mitigate mislabelling and empower consumers to make informed decisions, according to the researchers.