Genetic tuna tracking opens new options in race to save fish and fisheries



Posted on 27 October 2009  | 
An Italian purse seine vessel fishing Mediterranean bluefin tuna
An Italian purse seine vessel fishing Mediterranean bluefin tuna - Italian fishers were 40 per cent over quota on the imperilled fishery for 2007
© ATRTEnlarge
Madrid, Spain – 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 today 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 recognized 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, which can be dressed, gilled and gutted, or loin and belly meat, and either fresh or frozen – 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.

"..findings are particularly relevant"

“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 commercial 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.

(PLoS ONE is the first journal of primary research from all areas of science to employ a combination of peer review and post-publication rating and commenting, to maximize the impact of every report it publishes. PLoS ONE is published by the Public Library of Science (PLoS), the open-access publisher whose goal is to make the world’s scientific and medical literature a public resource.)

An Italian purse seine vessel fishing Mediterranean bluefin tuna
An Italian purse seine vessel fishing Mediterranean bluefin tuna - Italian fishers were 40 per cent over quota on the imperilled fishery for 2007
© ATRT Enlarge

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