As someone who doesn't really eat a huge amount of fish, it never occurred to me that you can fairly easily pass one fish off as another, but apparently the practice is pretty widespread. The New York Times says it's an astounding 20-25%. However, it sounds like the technology is available to make a big dent:
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.Seems like it's going to take a while to ramp up though. Not like it wasn't hard enough to eat sustainably fished seafood in the first place, eh? Now you can't even be sure it's labeled correctly.
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.
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.