Study Finds Significant Sushi Mislabeling, Part 2

Hiroshige woodblock print - Hirame and Mebaru Fish with Cherry Blossoms, from the series Uozukushi DP123589
Hiroshige woodblock print – Hirame (halibut) and Mebaru (black rockfish) with Cherry Blossoms

This is part 2 of my posts on sushi mislabeling (see part 1 on sushi mislabeling).

“Buyer beware” should be watchwords for anyone who eats fish in a restaurant. For various reasons — including fraud, ignorance, and sloppy supply chains — there’s a good chance that some of the fish served don’t match what the menu says.

In a recently released study, a team of researchers — with help from undergraduate students — collected and DNA-analyzed 364 fish samples from 26 sushi restaurants in Los Angeles that had good ratings on two on-line rating services. The team focused on nine popular fish: albacore tuna, yellowfin tuna, bigeye tuna, bluefin tuna, red snapper, yellowtail, halibut, mackerel, and salmon. In addition, when the menu listed “tuna,” they sometimes ordered it.   (The full reference and a list with Latin names for each fish is below.)

Forty-seven percent of the items were mislabeled, with some of the fish mislabeled 100% of the time.

A Focus on Three Fish

Let’s look at three of the fish in more detail: one which was mislabeled 100% of the time, and two which appear to have good labeling results (but a complex backstory).

Red Snapper

None of the orders for “red snapper” were were actually red snapper (Lutjanus campechanus). This isn’t surprising, as red snapper on a menu is a red flag for fish fraud watchers, as these examples indicate:

  • As part of their Seafood Fraud Campaign, Oceana sampled seafood from around the U.S., and found rampant mislabeling of snapper across the country (summarized in their PDF map of seafood testing results).
  • Consumer Reports: “None of the 22 ‘red snappers’ we bought at 18 markets could be positively identified as such.”
  • The Boston Globe: “The Globe-sponsored DNA testing found 24 of the 26 red snapper samples were in fact other, less prized species.”
  • On the Seafood Watch page for snapper, they advise: “Heads up: A lot of seafood is sold as “snapper” that isn’t actually snapper.”
  • Red snapper is one of the three top fraudulent foods in a piece by Larry Olmsted at Eater, who notes that one of New York’s top sushi restaurant doesn’t trust their suppliers enough to even consider serving the fish.

Red snapper has two main problems:  the fish’s biology and a messy name situation on the West Coast.  True red snapper has a relative (L. purpureus) that appears so similar that even some fish experts can be confused  (“overlapping, phenotypically similar species”). In California fisheries, you won’t find true red snapper, but there are unrelated fish that have been historically called ‘Pacific red snapper’ (rockfish that are Sebastes spp.). California law was recently modified to prevent ‘Pacific red snapper’ from being an acceptable market names for the Sebastes spp., but it will take a while for the market to adjust (and enforcement is weak).

Hiroshige woodblock print - Katsuo Fish with Cherry Buds, from the series Uozukushi DP123578
Hiroshige woodblock print – Katsuo (Skipjack Tuna) with Cherry Buds


The testing found low mislabeling rates for albacore tuna and generic ‘tuna’ (under 10%). Bigeye was mislabeled just over 25% of the time, but yellowfin was often mislabeled (78%). When albacore, yellowfin and bigeye were mislabeled, the replacement fish was another type of tuna 80% of the time. Among the mislabeled generic ‘tuna’ samples, only one was not a tuna species. Bluefin tuna (which should be avoided because we are fishing it to extinction) was never mislabeled. These results are consistent with an earlier DNA analysis of tuna from sushi restaurants (which I reviewed at the Ethicurean, and which was not cited in the article — how did the authors and reviewers miss it?).

An accurate menu is an essential part of choosing the fish with the least environmental impact, lowest mercury content, or to avoid digestive distress. Each of the tuna species has its own sustainability rating — bluefin tuna are highly threatened, while some tuna fisheries are well managed. To complicate things, the catch method and catch location are also important.  Seafood Watch uses these three criteria — what, how and where — for their tuna recommendations. Consequently, the recommendations are extensive and complicated, comprising 8 “best choice,” 32 “good alternative,” and 58 “avoid.” Unfortunately, the vast majority of restaurants aren’t aware of the catch method and region, so it’s tough to make an informed choice, but there are places that try hard to know the what, how and where about the fish they serve.

The major toxicity concern for tuna relates to mercury, as sensitive populations (like pregnant women) have been advised to limit mercury exposure. Mercury content varies among the species of tuna, so if you’re trying to avoid mercury intake, you want to eat the right species.  There is also a second significant concern that is about a strange labeling practice:  some sushi restaurants use the term “white tuna” for the fish called escolar (Lepidocybium flavorunneum), which can cause serious digestive discomfort (because of gempylotoxin, an indigestible wax. For details, see page 237 of the FDA Bad Bug Book.). To be sure, some people probably love escolar’s flavor and aren’t affected by the gempylotoxin, but for the sake of transparency, a non-tuna fish should not be called tuna — just call it escolar and let diners make an informed choice.


The researchers reported that menu labels for salmon were highly accurate (87% accuracy).  However, for salmon the questions go beyond “does the served item match the menu description?” because salmon is available from the wild and from fish farms. And therefore, the question “is this farmed or wild?” is important — and often inaccurately answered by restaurants.  The sushi study under review here didn’t venture into the farmed vs. wild question — their focus was strictly on species labeling.

The farmed vs. wild question was investigated in detail by the research and advocacy group Oceana a few years ago as part of the Oceana seafood fraud campaign.  In the Oceana study of salmon labeling they found significant mislabeling: 47% of salmon samples were mislabeled, with the most common mislabeling being farmed Atlantic salmon labeled as “wild salmon”. Restaurants had much higher mislabeling rates than grocery stores (67% vs. 20%), with much higher mislabeling in the off-season (16% mislabeled in season vs. 63% out of season).

What to Do?

After presenting their dismaying results, the authors propose some policy upgrades that could help reduce mislabeling:

  1. Improve international and federal policies related to traceability (better labeling of country of origin, wild vs. farmed, and catch method)
  2. Increase enforcement. This one is not easy because of the limited resources available to regulators.  In Los Angeles County, for example, the relevant agency is limited to visual inspections and paperwork checks. At the federal level, inspection agencies are woefully underfunded.
  3. Improve inspectors’ capabilities with additional training and emerging technology (the size of DNA analysis tools has shrunk dramatically in recent years, as a piece in Nature about a “pint-sized DNA sequencer” illustrates)
  4. Continue to use monitoring and DNA sampling to identify fish fraud. When it is found, use the results to help restaurants and grocers pressure their wholesalers.
  5. Citizen science and social media can play a role: DNA analysis to identify mislabeling and social media to educate consumers.

I have another initiative for the list:  the restaurant and seafood trade associations could pool their funds to build a DNA analysis team that could start checking for mislabeling. The results could be used to pressure bad actors and improve the accuracy for all involved.

Unfortunately, fish fraud is a major challenge for eaters. How many of us can differentiate between tuna species on a sushi platter? Or how many of us know the what a true red snapper fillet looks like?

But there are still simple steps you can take to find more sustainable seafood:

  • Follow the recommendations of  organizations like Monterey Bay Aquarium’s Seafood Watch
  • Ask questions at the seafood counter or restaurant: What is this fish? How do you know?  Where was it caught? How was it caught? Is it farmed or wild?
  • Start exploring the good choices like sardines, anchovies and farmed mussels, oysters and clams. You might find some new favorites.
  • Consult Fish2fork, a program that develops restaurant ratings using questionnaires filled out by restaurants and through independent examination of restaurants’ online menus.


The fish collected in the study:  albacore tuna (Thunnus alalunga), yellowfin tuna (T. albacares), bigeye tuna (T. obesus), bluefin tuna (T. thynnus, T. maccoyii, T. orientalis), red snapper (Lutjanus campechanus), yellowtail (Seriola lalandi), halibut (Hippoglossus hippoglossus, H. stenolepis), mackerel (Scomber spp., Scomberomorus spp.), and salmon (Salmo salar, Oncorhynchus spp.).


“Using DNA barcoding to track seafood mislabeling in Los Angeles restaurants,” Demian A. Willette, Sara E. Simmonds, Samantha H. Cheng, Sofia Esteves, Tonya L. Kane, Hayley Nuetzel, Nicholas Pilaud, Rita Rachmawati, Paul H. Barber, accepted for publication in Conservation Biology, doi: 10.1111/cobi.12888

“The Real maccoyii: Identifying Tuna Sushi with DNA Barcodes – Contrasting Characteristic Attributes and Genetic Distances,” Jacob H. Lowenstein , George Amato, Sergios-Orestis Kolokotronis, PLOS ONE, November 18, 2009, DOI: 10.1371/journal.pone.0007866

From my archives at the Slices of Blue Sky and The Ethicurean

Image credits
“Hirame and Mebaru Fish with Cherry Blossoms, from the series Uozukushi (Every Variety of Fish)” and “Katsuo Fish with Cherry Buds, from the series Uozukushi (Every Variety of Fish)”  by Utagawa Hiroshige (Japanese, Tokyo (Edo), 1797–1858), via The Metropolitan Museum of Art, licensed under CC0 1.0

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