A new method that uses gene sequencing to accurately distinguish between tuna species has the potential to support fisheries management and possible trade restrictions for endangered tuna species.
The new method, revealed in a paper published in PLoS ONE, the online open-access scientific journal, can make an identification from any kind of processed tuna tissue.
The true tunas – from the genus Thunnus – are among the most economically valuable fish in the world and are also among the most endangered of all commercially exploited fish. They are not to be confused with the tuna most commonly tinned, which comes from related families such as mackerel.
The paper, ‘A Validated Methodology for Genetic Identification of Tuna Species (Genus Thunnus)’, co-authored by Dr Jordi Viñas, a fish genetics specialist at Girona University in Spain and Dr Sergi Tudela, Head of Fisheries of WWF Mediterranean, proposes for the first time ever a genetic method for the precise identification of all eight recognised species of tuna.
Northern, southern and Pacific bluefin tuna are among the most stressed fish populations in the world, with the Principality of Monaco having lodged an application before the Convention on International Trade in Endangered Species (CITES) for a trade ban on the Atlantic (Northern) bluefin tuna where several fisheries have collapsed and failed to recover and the Mediterranean bluefin fishery is exhibiting advanced signals of impending collapse in the face of overfishing and decades of poor management.
The other tuna species are yellowfin, blackfin, longtail, bigeye and albacore tuna. Identification of traded forms of the fish is a highly complex process, which has hampered conservation efforts and was a potential limitation to the imposition of trade controls.
The analysis of the DNA sequence variability of two unlinked genetic markers, one a hypervariable segment of the mitochondrial genome and the other a nuclear gene, enables full discrimination between all the tuna species.
“This methodology will allow the identification of tuna species of any kind of tissue or type or presentation – including sushi and sashimi,” said Dr Jordi Viñas of Girona University. “The differentiation between different tunas, even those with highly similar genes, is now possible.”
