All set to splurge on a fillet of red snapper - at about $7.95 a pound - for a midsummer meal?
You might want to take a DNA kit to the fish counter, along with the Food and Drug Administration's definition of Lutjanus campechanus, in case the seller wants to argue.
It could well be a fake.
A study released Thursday by the University of North Carolina found that more than 75 percent of store-labeled red snapper it tested from nine unnamed retailers in eight states bore the genetic makeup of other fish.
Some were close relatives, says Peter Marko, the assistant professor of marine sciences whose students made the accidental discovery during a DNA-sequencing project.
But in terms of culinary quality and cost, the differences between red snapper and the most frequent market substitutes are hardly microscopic.
"The best snapper out there is genuine red snapper," says Bob Brodeur, chef at the Conch House Marina Resort in St. Augustine, Fla., and buyer of about $1 million a year in fish.
The alternatives - including similar fish commonly known as sheephead, porgies, and grunts - can have market values of less than half that of red snapper. Until he sets them straight, Mr. Brodeur says, wholesalers he encounters often try to pass off such fish as their pricier cousin.
Some industry observers call the UNC study the latest window on the deep and long-running problem of seafood mislabeling.
Experts differ on where in the supply chain the mislabeling most often occurs, and how often it may simply be the inadvertent result of clumsy shorthanding. But many say the economic incentive for fraud by big-volume sellers is clear.
"The profits in mislabeling fish can equal or exceed [those of] drug dealing," says Tim Duffy, a consumer advocate in Covina, Calif. Enforcement is lax, Mr. Duffy adds, even though labels can be blatantly false.
He points to the alleged marketing of pieces of the "wings" of skate - a fish that resembles a small manta ray - as scallops. And Duffy says he recently found a packet of Atlantic cod labeled "product of China."
"I wasn't great in geography," he says, "but I don't think the Atlantic Ocean goes to China."
On that front, new country-of-origin labels could help - a little. The Department of Agriculture has delayed until 2006 implementation of such labels for beef, pork, and lamb, says a USDA spokeswoman. But their seafood program will take effect at the end of September.
Fish caught in international waters will be linked to the country whose flag the ship flies, however, complicating the task of determining specific origin.
Monitoring for the accuracy of a given fish's identity might seem a simpler task. Fish are passed along the line by a standard set of handlers, says UNC's Marko.
"Fishers catch them, and they identify them, and then they sell their fish to a dealer in what's called a fish-house in most states," he explains. "And then that dealer sells them to retailers." Dealers typically submit the catch data to regulatory agencies, he says. "So that's when they get recorded as whatever particular species they are."
The job of making sure the subsequent labels don't lie falls to the Food and Drug Administration, says Linda Candler, spokeswoman for the National Fisheries Institute, the leading trade group for the fish and seafood industry. She acknowledges that the red-snapper study points to the need for consumers to be more aware - ask to have the skin left on, or buy whole, she advises.
But she also asserts, despite the UNC study, that species substitution is "fairly rare," and she points out that the FDA is less than aggressive about policing for it.
"They don't devote a lot of resources to individually going into retail markets and checking," Ms. Candler says. "And in some cases it has to be a DNA test to confirm it anyway. What they normally do is wait until they get word of something, usually from a competitor, so it's kind of a self-policing process."
In the government's view, that process generally works, says Rebecca Lent, deputy director of the National Marine Fisheries Service, part of the National Oceanic and Atmospheric Administration. She says experienced fishermen and dealers tend to keep one another in check at the docks.
"We suspect that in most cases this accidental or other kinds of mislabeling occurs further up the retail chain, closer to the consumer, whether it's in a restaurant or a fish shop," says Dr. Lent.
About all that seafood shoppers can do, she says, is press grocers for information, and look for one they can trust.
"When I go to the seafood market, I say 'Is this albacore, is this bluefin - or skipjack?' says Lent. "I want to know what kind of tuna it is, and I want to know where it's from."