We've covered this story in the past, but it's nice to see the press still working it over. Sushi fraud works because very few people actually recognize the subtle taste differences between various seafoods. So, restaurants can save some big bucks by, for example, serving you pacific rockfish yet claiming it's red snapper (to be fair, it's sometimes the distributors that are deceiving the restaurants, but any seafood establishment worth its salt should know the difference).
In a recent Wired Magazine report on "mislabeled" tuna, researchers ordered tuna from "31 sushi restaurants and then used genetic tests to determine the species of fishes in those dishes. More than half of those eateries misrepresented, or couldn’t clarify, the type of fish they were mongering."
We first covered this type of story wayyyy back in 2001 when the Houston Press reported on red snapper and lobster being faked using pacific rockfish and langoustine as substitutes. Last year, we also reported on the two kids who fingered rogue Manhattan sushi bars by analyzing fish DNA.
In the not-so-distant future, we will all have DNA hand scanners that we can point at our toro sashimi, but until then, caveat emptor....