A new paper published October 27 in PLoS ONE, the online, open-access scientific journal, unveils for the first time a method to accurately distinguish between all eight tuna species from any kind of processed tissue using genetic sequencing.
Tunas are among the most economically valuable and yet the most endangered commercially exploited fish in the world.
Identification of these species in traded forms, which are typically dressed, gilled and gutted, or loin and belly meat, and either fresh or frozen, is a highly complex process - which may hamper conservation efforts on trade comtrols.
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 recognized species of tuna.
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 eight 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."
"Our findings are particularly relevant for the highly overfished, overtraded - and hence endangered Atlantic bluefin tuna, for which there is a growing campaign to impose a temporary ban on international trade," added co-author Dr Sergi Tudela of WWF. "There will now be no trace of doubt when seeking to identify chilled or frozen tuna flesh at port or point of sale."
The paper will remain available to download for free from the website of PLoS ONE and will be submitted to the relevant tuna fishing and trade management and control authorities.
Funding: This work was done thanks to funding from OAK Foundation and Prince Albert II of Monaco Foundation. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing interests: The authors have declared that no competing interests exist.
Dr Jordi Viñas, Laboratory for Genetic Ichthyology, Biology Department, University of Girona, Spain
Tel: +34 97 241 8168
Dr Sergi Tudela, WWF Mediterranean, Spain
Tel: +34 93 305 6252
Communications Officer, WWF Mediterranean, Italy
Tel: +39 06 844 97 224
Citation: Viñas J, Tudela S (2009) A Validated Methodology for Genetic Identification of Tuna Species (Genus Thunnus). PLoS ONE 4(10): e7606. doi:10.1371/journal.pone.0007606
PLEASE LINK TO THE SCIENTIFIC ARTICLE IN ONLINE VERSIONS OF YOUR REPORT (link goes live after embargo ends): http://dx.plos.org/10.1371/journal.pone.0007606
FOR A PRESS-ONLY PREVIEW OF THE FULL ARTICLE, VISIT THE FOLLOWING URL: http://www.plos.org/press/pone-04-10-vinas.pdf
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