By Morgan Heim
Next time you head out to your favorite sushi restaurant, you might want to think twice about ordering the tuna. There's a good chance the fish on your plate could be an endangered species.
A new study by the American Museum of Natural History conducted DNA investigations on tuna at restaurants in New York City and Denver and found that nearly 30 percent of the tuna tested was actually endangered bluefin, and less than half of that was labeled as such.
A single bluefin tuna can sell for tens of thousands of dollars at market, a popular draw for the fishing industry. But that popularity comes with a price. Western stocks of northern bluefin tuna now hover around 10 percent of their "pre-exploitation" numbers. And last October, the country of Monaco nominated northern bluefin tuna for a listing under a complete international trade ban by the Convention on International Trade in Endangered Species (CITES), according to a press release.
The serving up of a critically endangered fish is not necessarily on the shoulders of the restaurants. They might not know they're doing it, just as consumers might not know they're eating it. This is because the eight species of tuna are so genetically similar - closer than humans are to chimpanzees - that even with DNA testing, it's hard to distinguish the difference, and once tuna arrives to the U.S. market, the U.S. Food and Drug Administration-approved marketing label is simply "tuna." A new and improved method of genetic detective work just might help change all that.
"When you eat sushi, you can unknowingly get a critically endangered species on your plate," says Jacob Lowenstein, a graduate student affiliated with the Museum and Columbia University in the press release. "But with an increasingly popular technique, DNA barcoding, it is a simple process for researchers to see just what species are eaten at a sushi bar."
DNA barcoding can be used to identify what animal became which product, even down to the origin of a leather handbag, according to the press release. In the case of the bluefin tuna, DNA barcoding defines a genetic key of 14 nucleotides exclusive enough to identify whether the tuna being served is bluefin. A similar method has been used to identify endangered whales on the Asian market and wildlife being sold in the African bushmeat trade.
With any luck, researchers will develop a handheld barcoding machine that can be used to identify fish on-site.
This study can be found in the current issue of PLoS ONE.