You may think you are buying mahi-mahi, but chances are it's really yellowtail. The red snapper you order in a restaurant could be talapia. 
 
 Seafood consumers are being exploited by mislabeled fish products, according to the environmental group Oceana, which has released a report entitled Bait and Switch: How Seafood Fraud Hurts Our Oceans, Wallets and Our Health. 
 
 “We can track organic bananas back to packing stations on farms in Central and Latin America, yet consumers are given little to no information about one of the most popular foods in the United States – seafood,” said Dr. Michael Hirshfield, senior vice president for North America and chief scientist for Oceana. “With imports representing the vast majority of the seafood eaten in the United States, it’s more important than ever to know what we are eating and where, when and how it was caught.” 
 
 Minimal inspection 
 
 The report says that while 84 percent of the seafood eaten in the United States is imported, only two percent is currently inspected, with almost no thought given to potential fraud. In fact, the report says recent studies have found that seafood may be mislabeled as often as 25 to 70 percent of the time for fish like red snapper, wild salmon and Atlantic cod, disguising species that are less desirable, cheaper or more readily available. 
 
 “We’ve tested well over 1,000 fish fillet samples over the past four years, from more than 50 cities across the country,” said William Gergits, co-founder and managing member of Therion International, LLC, a worldwide leader in DNA testing of seafood. “Results from our DNA lab show that about half the time the fish you are eating is not the species listed on the menu.” 
 
 Consumers shortchanged 
 
 The report maintains that consumers are frequently shortchanged, served a cheaper fish than the one they've paid for. With about 1,700 different species of seafood from all over the world now available in the U.S., the report says it is unrealistic to expect consumers to be able to independently and accurately determine what fish is really being served. 
 
 “Seafood fraud puts consumers and restaurants trying to make honest, eco-friendly choices at a disadvantage,” said Ellen Kassoff Gray, general manager and co-owner of top-tier D.C. restaurants Watershed and Equinox. “We need the U.S. government to provide us with the tools to make good decisions for our oceans, our pocketbooks and our health. It’s just good business.” 
 
 Oceana says the technology now exists to accurately identify different species of fish and that these tools should be put into action to stop what it calls seafood fraud. It says the government should implement existing laws, increase inspections, and improve coordination and information sharing among federal agencies. 
 
 The group said it is also working to ensure that the seafood sold in the U.S. is safe, legal and honestly labeled, including requiring a traceability scheme where information such as when, where, and how a fish is caught follows it throughout the supply chain – from boat to plate – allowing consumers to make more informed decisions about the food they eat. ||||| “Customers buying fish have a right to know what the heck it is and where it’s from, but agencies like the F.D.A. are not taking this as seriously as they should,” said Michael Hirshfield, chief scientist of the nonprofit group Oceana, referring to the Food and Drug Administration . 
 
 On Wednesday, Oceana released a new report titled “Bait and Switch: How Seafood Fraud Hurts Our Oceans, Our Wallets and Our Health.” With rates of fraud in some species found to run as high as 70 percent, the report concluded, the United States needs to “increase the frequency and scope” of its inspections. 
 
 DNA bar coding, as it is called, looks at gene sequences in the fish’s flesh. “The genetics have been revolutionary,” said Stefano Mariani, a marine researcher at University College Dublin , who has published research on the topic. “The DNA bar coding technique is now routine, like processing blood or urine. And we should be doing frequent, random spot checks on seafood like we do on athletes.” 
 
 Policing the seafood industry has historically been challenging because even the most experienced fishmongers are hard pressed to distinguish certain steaks or fillets without the benefit of scales or fins. And many arrive in supermarkets frozen and topped with an obscuring sauce. 
 
 Older laboratory techniques to identify fish meat looked at the mix of proteins in flesh samples, but were unreliable, expensive and cumbersome. Investigators often relied instead on laborious legwork, tracking inconsistent fish names on paperwork as seafood moved across international borders. Eighty-four percent of seafood consumed in the United States is now imported, often passing through a multistep global supply chain. 
 
 With the new genetic techniques, the gene sequence found in a fish sample is compared with an electronic reference library like that maintained by the International Barcode of Life Project, which now covers 8,000 varieties of fish compiled by biologists over the last five years. The testing is now relatively cheap: commercial labs charge about $2,000 for analyzing 100 fish samples, for an average of $20 apiece, but the cost is under $1 per sample for labs that own the equipment. 
 
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 Douglas Karas, a spokesman for the F.D.A., said in an e-mail that the agency had been working with scientists to “validate” DNA testing for several years. It recently purchased gene sequencing equipment for five F.D.A. field laboratories and hoped to use it “on a routine basis” by the end of this year. 
 
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 This new type of scrutiny could allow hundreds of thousands of samples to be tested each year, rather than the hundreds that are now rigorously analyzed, said Dr. Paul Hebert, scientific director of the Barcode of Life project, based in Guelph, Ontario . In March, the F.D.A. issued an alert to inspectors about mislabeled fish. It had already used bar coding as irrefutable evidence to prosecute sellers or issue warnings involving seafood “misbranding,” Mr. Karas said, much as prosecutors use DNA evidence in sex crime cases. 
 
 But it will take time to clamp down on a lucrative and, apparently, widespread practice. Dale Sims, chief fishmonger for Cleanfish, a San Francisco-based supplier of high-end sustainable seafood, said he’d seen thresher shark labeled as shark, swordfish and mahi-mahi all in the same market, as well as many other obvious substitutions. 
 
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 “It infuriates me but it’s hard to correct,” he said. “I’m embarrassed to say that there’s been a lot of fragmentation in this industry. So if someone is unscrupulous, it’s been easy to get away with it.” 
 
 For consumers, the issue is about dollars and cents — wanting to get the quality and type of fish they paid for. “If you’re ordering steak, you would never be served horse meat,” said Dr. Hirshfield of Oceana. “But you can easily be ordering snapper and get tilapia or Vietnamese catfish.” 
 
 Environmentalists worry that duped diners may be unwittingly contributing to declining fish stocks , buying food they have been told to avoid. Dr. Hebert said that in testing samples from the United States and Canada , his lab had even detected meat from endangered sharks being sold to diners. “If it were labeled endangered species,” he said, “you couldn’t sell it and you wouldn’t buy it, right?” 
 
 Most of the research has been done not by regulators but by individual fish biologists and geneticists; to date no definitive national study has been carried out on the scope of the fraud. 
 
 Dana Miller, a doctoral student who worked with Dr. Mariani in Dublin studying the mislabeling of cod , the most popular fish in Ireland , said, “we expected with all the policies and legislation and inspections, the numbers would be pretty low.” But 25 percent of samples of fresh cod and haddock and over 80 percent of the smoked products, were in fact something else. Irish cod stocks are overfished. 
 
 “If you can’t even trust that the name is right, then how can you trust anything else on the package, including the date?” she said. In Europe, seafood labels include the fishery where it was caught. In the United States, it must list only a “country of origin” although that is often the processing country rather than where it is caught. 
 
 The group Cleanfish is experimenting with an electronic tagging system through which each fisherman or processor would enter his code onto a tag on each fish, making its journey from the sea to the plate fully transparent. Cleanfish buys only whole fish since its outward appearance helps to verify its identity. 
 
 And bar coding is becoming more accessible every year. Today, fish samples are sent to labs for testing, but scientists predict that there will be desktop DNA bar coding systems within five years and, in 10, inspectors will carry hand-held detectors. 
 
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 “Everyone should be using this technique — there should be spot checks and fines,” said Dr. Hebert of the DNA bar coding project. “If there were no speed traps and radar checks, there would be a lot more speeding.”
– The fish that shows up on American plates is often a different fish than advertised, and US seafood lovers are getting routinely ripped off as a result, the nonprofit Oceana group says in a new report. Yellowtail commonly subs for mahi-mahi, for instance, and tilapia for red snapper, notes Consumer Affairs. The New York Times goes further, calling tilapia the "Meryl Streep of seafood" because it so often plays the role of more expensive fish. Such allegations have been around for a while, but Oceana says the problem isn't getting any better. It cites studies showing that fish is mislabeled 25% to 70% of the time, depending on the species. What's more, the FDA inspects only a tiny fraction of US seafood, of which 84% is imported. The Times has details on how a process called "DNA bar coding" could someday make the problem go away, assuming the FDA embraces it.