August 24, 2008
Sushi Sellers Flunk DNA Test in High School Project
By John Schwartz
Many sushi restaurants and seafood markets are playing a game of bait and switch, say two high school students turned high-tech sleuths.
In a tale of teenagers, sushi and science, Kate Stoeckle and Louisa Strauss, who graduated this year from the private Trinity School in New York , took on a freelance science project in which they checked 60 samples of seafood, using a simplified genetic fingerprinting technique to see whether what the fish diners buy is what they think they are getting.
They found that 23 percent of the fish samples with identifiable DNA were mislabeled. A piece of sushi sold as the luxury treat white tuna turned out to be Mozambique tilapia, a much cheaper fish that is often raised by farming. Roe purported to be from flying fish was actually from smelt. Seven of nine samples that were called red snapper were mislabeled, and they turned out to be anything from Atlantic cod to Acadian redfish, an endangered species.
What may be most impressive about the experiment is the ease with which the students accomplished it. Although the testing technique is at the forefront of research, the fact that anyone can take advantage of it by sending samples off to a lab meant the kind of investigative tools once restricted to crime labs can move into the hands of curious diners and amateur scientists everywhere.
The project began, appropriately, over dinner about a year ago.
Kate Stoeckle's father, Mark, is a scientist and early proponent of the use of DNA bar coding, a technique that greatly simplifies the process of identifying species. Instead of sequencing the entire genome, bar coders - who have been developing their field only since 2003 - examine a single gene. Mark Stoeckle's specialty is birds, and he admits that he tends to talk shop at the dinner table.
One evening at a sushi restaurant, Kate Stoeckle recalled asking her father, "Could you bar code sushi?"
Mark Stoeckle replied, "Yeah, I think you could - and if you did that, I think you'd be the first ones."
Kate Stoeckle, who is now 19, was intrigued. She enlisted Strauss, who is now 18.
Their field technique was simple, Kate Stoeckle said. "We ate a lot of sushi."
Or, as Mark Stoeckle put it, "It involved shopping and eating, in which they were already fluent."
They sampled four restaurants and 10 grocery stores . Once their purchases were home, they cut away a small piece and preserved it in alcohol. They sent those off to the University of Guelph in Ontario, where the Barcode of Life Database project began. A graduate student there, Eugene Wong, works on the Fish Barcode of Life (dubbed, inevitably, Fish-BoL) and agreed to do the genetic analysis. He compared the teenagers' samples to the global library of 30,562 bar codes representing nearly 5,500 fish species. (Commercial labs also perform the analysis for a fee.)
Three hundred dollars' worth of meals later, the young researchers had their data back from Guelph: 2 of the 4 restaurants and 6 of the 10 grocery stores had sold mislabeled fish.
Mark Stoeckle said he was excited to see a technology used in a new way.
"The smaller and cheaper you make something," he said, "the more uses it has." He compared bar coding to another high-tech-wonder- turned-everyday-gadget, GPS.
Eventually, he predicted, the process will become more automatic, cheaper and smaller so that a handheld device could perform a quick analysis and connect to the database remotely. What his daughter did, he said, is like dropping film off at the supermarket for developing. The next generation could be more like a digital camera that displays the results on the spot.
The results of the teenagers' research are being published in Pacific Fishing magazine, a publication for commercial fishermen. The sample size is too small to serve as an indictment of all New York fishmongers and restaurateurs, but the results are unlikely to be a mere statistical fluke.
The experiment does serve as a general caveat emptor for fish lovers, particularly because the students, their parents and their academic mentor all declined to give the names of the vendors, citing fear of lawsuits. Besides, they noted, mislabeling could occur at any stage of the process.
Kate Stoeckle said the underlying message of the research was simple. "If you're paying for white tuna and you're eating tilapia, I think you'd want to know that."
Although the girls did not present the project for a grade at school, they made sure to mention it on their college applications. Both will enroll at Johns Hopkins University this autumn.
Neither, however, expects to major in the sciences. "I've always been into art history," Strauss said, "which is really different from this." Kate Stoeckle, who is the granddaughter of the late singer and actress Kitty Carlisle Hart, is thinking about studying writing or psychology. But that, they said, is the point.
"If we found it interesting - which we did - I think lots of people like us can do it, too," Stoeckle said.
Peter Marko, a professor at Clemson University in South Carolina, who used a more detailed genetic technique in a 2004 paper to show that red snapper was commonly mislabeled, called the girls' project "quite remarkable," though he added that genetic analysis has been simplified to the point that students can now perform the task without sending samples off to a place like Guelph.
Marko prefers to work with whole genomes - "more information is better," he explained - which can be sequenced now with lightning speed. He plans to perform a broad genetic comparison of fishes that were separated millions of years ago by the rise of the Isthmus of Panama.
"The technology is allowing us to ask questions that really would not have been possible in the past."
The girls worked under the tutelage of Jesse Ausubel of the Rockefeller University in New York, a champion of the DNA bar coding technique and a colleague of Mark Stoeckle. Ausubel said the girls "have contributed to global science" by adding to the database, which is built on a model similar to that of Wikipedia, in which people around world can contribute. In a way, Ausubel said, their experiment marks a return to an earlier era of scientific inquiry.
"Three hundred years ago, science was less professionalized," he said, and contributions were made by interested amateurs. "Perhaps the wheel is turning again where more people can participate."
Originally published by The New York Times Media Group.
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