September 12, 2010 Leave a comment
Grad students learn PCR, uncover fish fraud
It’s a great thing if you get your name published in the journal Nature, the pinnacle of publishing achievement for a biologist, while you’re still in school. Such was the fate of six graduate students participating in a course designed to teach them DNA extraction, amplification, and sequencing. They identified a real question to answer in the course of applying their techniques, and their results got them brief communication in Nature and national recognition. Not bad; I hope everyone also earned an “A.”
The group, led by professors Peter Marko and Amy Moran at the University of North Carolina-Chapel Hill, suspected that fish being sold as red snapper in markets in the U.S. were actually mislabeled, in violation of federal law. This kind of fraud is nothing new; marketers have in the past created “scallops” by cutting scalloped-shaped chunks from the wings of skates (part of the cartilaginous fish group), and have labeled the Patagonian toothfish as Chilean sea bass.
Protections can drive fraud
Such mislabeling has far-reaching implications, well beyond concerns about defrauding consumers of the fish they want. If fisheries and fish dealers are reporting their catches as red snapper or scallops or sea bass when they are, in fact, other marine species, then data on the abundance and distribution of all of these species will be misleading. Red snapper, Lutjanus campechanus, was placed under strict management in 1996, a move that gave incentive to the fishing industry and retailers to mislabel fish. Some experts suspect that many fish under heavy restriction end up with their names on a different species for market.
Who is responsible for the mislabeling? Fishermen pull in their catches and identify them on the boat or at the dock. The catch goes to a fish dealer, who is also responsible for reporting what species and how many of each species were caught. This report becomes the official number for the species. The dealer then sends the fish on to the retail market, where it is sold in stores and restaurants. Misidentification on the boat or dock is one reasonable possibility because some of the species identified in the North Carolina study frequent the same types of habitat, primarily offshore waters around coral reefs. These species, which include vermillion snapper and silk snapper, do look very much like red snapper, although there are some identifiable morphological differences.
One filet is just like the other?
So misidentification could be an honest mistake or purposeful change at the boat or dock, or it could be a willful relabeling at the restaurant or market. By the time a fish is processed, it consists essentially of a filet that is indistinguishable from that of other, similar fish. Hapless consumers end up paying twice as much for silk snapper, thinking they’re getting the pricier red snapper, instead.
But the DNA sequencing the North Carolina group performed not only turned up species closely related and very similar to red snapper, but also uncovered some sequences that have no identity with those of known species in gene databanks. In other words, fish of unknown identity are being caught, sold, and eaten as red snapper before we even have a chance to document what they are, their habitats, or their numbers.
Mislabeling is rampant
The grad students and professors also found that some of the fish being marketed as Atlantic red snapper were, in a few cases, from the other side of the planet, including the crimson snapper, which occurs in the Indo-West Pacific. All told, they found that 77% of the fish samples from stores in the eastern and midwestern U.S. were mislabeled as red snapper.
One way to prevent such mislabeling is to require identification of the country of origin of fish sold at market. The USDA has instituted such a program, although confusion will likely persist about fish caught in international waters. And the mislabeling isn’t only a U.S. phenomenon.
In the meantime, how do you know you’re getting red snapper? Some fish ecologists recommend avoiding it entirely because it still suffers from overfishing; however, one way to know your fish is to ask for it with the skin on, or completely intact. If you’ve got a smart phone, you can just look up the image and compare. Alternatively, you could just order the salad.