Some DNA testing of fish from various sources in America, including sushi restaurants, has found that consumers may not be getting the fish they’re paying for:

The results showed that 25 percent of the girls’ samples were mislabeled: half of the restaurant samples and six out of 10 grocery store samples.

In every case, less desirable or cheaper fish was substituted for its more expensive counterpart, Stoeckle said. She and her father would not divulge the names of vendors, citing a fear of lawsuits.

“It’s not the fishermen, and it might not even be the restaurants,” she said. “Most likely, the mislabeling is occurring somewhere at the distribution level.”

For example, fish sold as white tuna turned out to be cheaper Mozambique tilapia, flying roe fish was replaced with smelt, and red snapper was mislabeled as Atlantic cod and Acadian redfish, an endangered species.

I’ve seen a few investigative reports on Japanese TV about restaurants deliberately mislabeling fish, but I don’t recall the use of DNA testing in those investigations. It would be interesting to see more DNA testing similar to the study done in America, only on a larger scale.