Bad news for Seafood Watch card-carrying sushi lovers. That toro (fatty tuna) you ordered — thinking the stuff’s okay since some toro’s on the “good choices” column on the Seafood Watch card (PDF) — may actually have been bluefin tuna — which means you just gobbled up a beleagured, almost-wiped-out species.

Went for the shiro maguro (white tuna) instead because it’s on the “Best Choices” column? Then you may have ingested escolar — a fish that’s actually banned in Japan and Italy because eating it can give you terrible tummy aches.

This bad news comes not from an ocean protecting eco-nonprofit, but from a group of scientists working on DNA barcoding — a new species-identification technique for which scientists “has been collecting fish, reading their genes and uploading the information to a database called FISH-BOL,” according to Wired.

To do this DNA work, scientists collected tuna sushi samples from New York City and Denver restaurants in 2008. What they found: Tuna’s often mislabeled or underlabeled — and restaurant employees asked about the tuna often are misinformed or underinformed about the tuna they’re selling.

For your own health, the mislabeling of escolar as white tuna / albacore is the most troubling. In the study, titled “The Real maccoyii: Identifying Tuna Sushi with DNA Barcodes – Contrasting Characteristic Attributes and Genetic Distances,” researchers write:

Our study documents five cases of escolar being sold under the name “white tuna”, “white tuna (albacore),” and “super white tuna.” Escolar is banned for sale in Japan and Italy because it contains high levels of wax esters that can cause considerable gastrointestinal distress. According to Shadbolt et al. “symptoms range from mild and rapid passage of oily yellow or orange droplets, to severe diarrhea with nausea and vomiting. The milder symptoms have been referred to as keriorrhea [i.e. flow of wax in Greek]”. While it is not illegal to sell escolar in the US, and this is not an unambiguous case of economic fraud, the potential consequences of this mislabeling are clearly troubling.
For the health of the environment, the fact that drastically overfished bluefin tuna’s sometimes just labeled as just tuna — leading eaters to assume the stuff’s not bluefin — is the most troubling. According to the researchers, 79% of menu listings they studied “gave no indication of what species was being served,” and 41% of descriptions from the chef or wait staff were wrong or uninformative. The scientists’ conclusion’s dire for would-be eco-ethical pescatarians: “The only way for consumers to positively avoid consuming bluefin is abstinence from tuna sushi if the verbal confirmations we found is representative.”

There is, however, one less drastic option for tuna-loving Sushi fans: Stick to sushi restaurants with an eco-ethical mission. The Sustainable Sushi blog points to three: Bamboo Sushi in Portland, Oregon; Mashiko in Seattle, Wash., and Tataki Sushi in San Francisco. In addition, Monterey Bay Aquarium keeps a list of Monterey Bay-area restaurants that serve only sustainable fish.

Know of other sushi restaurants with similar sustainable ethics in your town? Recommend them in the comments.

Also on MNN:

Sushi fraud: When "tuna" isn't tuna
All that's labeled tuna isn't actually tuna. Some of it's escolar, a fish that could give you serious tummy trouble.