August 22, 1998 DNA Fingerprinting to Track Caviar
By J. Brainard
Economic turmoil in the former Soviet Union and rising U.S. demand for caviar have conspired to create tough times for the sturgeon, the homely, ancient creature from which the tasty fish eggs are harvested. Overfishing in the Caspian Sea, where most of the world's caviar originates, has driven many of the sturgeon's 25 species close to extinction. Several nations, however, are working to devise quotas that will protect the fish.
In anticipation of new rules, scientists are turning to the fish equivalent of DNA fingerprinting to determine which species produced any given sample of caviar. Researchers from the American Museum of Natural History in New York describe the approach in the August Conservation Biology.
"I think if Caspian sturgeon can be saved, it's through the establishment and adherence of species-level quotas," says Stephen R. Fain, genetics supervisor at the U.S. Fish and Wildlife Service's forensics laboratory in Ashland, Ore. Genetic tests will help investigators track harvested eggs from individual species and detect poaching, he says.
To trace caviar's origin, scientists cannot rely on sight alone. Traders market the salty delicacy in only three major categoriesbeluga, sevruga, and osetra (or Russian)distinguished by egg size. Certain species tend to produce eggs of a given size and are traditionally included in a category. Taste is not a reliable indicator of species, says Vadim J. Birstein, a coauthor of the Conservation Biology report.
Birstein told Science News that he and his colleagues offered their test to the Fish and Wildlife Service, which will monitor U.S. imports for compliance with the new international rules. However, they asked the agency to pay royalties for the use of the technique's patented parts, which identify DNA sequences unique to certain sturgeon species.
The agency instead developed its own test, which is based on sequencing one section of DNA common to all sturgeon species, says Kenneth W. Goddard, director of the forensics lab. This approach, yet to be published, uses characteristic variations in the genetic code to identify individual species. The agency wanted a tool it could share with enforcement agencies in other nations without bothering with fees, Goddard says.
Birstein and his colleagues raise a bone of contention by arguing that high demand has prompted unscrupulous suppliers to mix eggs of inferior species with those of finer caviar. Overall, U.S. caviar imports have doubled since 1991.
The scientists say they sampled 95 lots, mostly purchased in New York City stores. They found that about 25 percent contained species of sturgeon different from those that buyers would expect. These included three lots of beluga, which can fetch prices of $90 an ounce. Unless they use genetic testing, importers can be tricked by their suppliers, Birstein says.
However, after examining 105 samples purchased on the East and West Coasts, Fain suggests that only about 3 percent of lots are mislabeled.
According to Fain and Frank Chapman, a sturgeon researcher at the University of Florida at Gainesville, categories of caviar can legitimately contain more than one species, so Birstein and his colleagues may have overstated the degree of mislabeling. Birstein retorts that each of the major categories should contain eggs of only one species.
From Science News, Vol. 154, No. 8, August 22, 1998, p. 116.
Copyright © 1998 by Science Service.
Birstein, V.J. . . . R. DeSalle. 1998. Population aggregation analysis of three caviar-producing species of sturgeons and implications for the species identification of black caviar. Conservation Biology 12(August):766.
Chen, I.-C, et al. 1996. Preliminary studies on SDS-PAGE and isoelectric focusing identification of sturgeon sources of caviar. Journal of Food Science 61:533.
______. 1995. Differentiation of cultured and wild sturgeon (Acipenser oxyrinchus desotoi) based on fatty acid composition. Journal of Food Science 60:631.
DeSalle, R., and V. Birstein. 1996. PCR identification of black caviar. Nature 381(May 16):197.
Information on the IUCN World Conservation Unions Sturgeon Specialist Group is available at http://www.sturgeons.com.
Information about the National Fish and Wildlife Forensics Laboratory is available at http://www.lab.fws.gov.
Vadim J. Birstein
The Sturgeon Society
331 W. 57th Street, Suite 159
New York, NY 10019
Frank A. Chapman
University of Florida
Department of Fisheries and Aquatic Sciences
P.O. Box 110600
Gainesville, FL 32611-0600
Stephen R. Fain
U.S. Fish and Wildlife Service
National Fish and Wildlife Forensics Laboratory
1490 E. Main Street
Ashland, OR 97520
copyright 1998 ScienceService