Researchers only tested seafood dinners sold in six District restaurants and said in most cases the species were closely related or considered acceptable alternatives for menu listing.
Of the 12 samples the research team found four menu items, one “Chilean Sea Bass” two “Tuna” and one “Rock Shrimp” had been mislabeled.
Legislation in Washington D.C. authorizes citizens to test if products are properly represented and, if not, to bring a lawsuit for the benefit of the general public.
Species swap
Keith Crandall, director of the Computational Biology Institute at the university, and his team used DNA barcoding to test 12 seafood samples purchased in six restaurants.
“Diners that ordered tuna got tuna - although maybe a slightly different type of tuna. We didn’t see the kind of outright seafood fraud that has been reported in other cities.”
He added that swapping out seafood does a disservice to customers trying to avoid species that are endangered or are paying a higher price for what they think is a delicacy.
The issue has been raised by Oceana who took 1,200 samples of seafood between 2010 and 2012 from US restaurants and stores and found that 33% of samples were mislabelled.
A study from UCLA and Loyola Marymount University found almost half of sushi was mislabeled.
They checked the DNA of fish ordered at 26 Los Angeles sushi restaurants from 2012 through 2015, and found that 47% percent of sushi was involved.
Use of DNA barcoding
Crandall recruited GW graduate student David Stern and his wife to visit six DC eateries and order seafood dinners.
Stern and his wife ordered 12 seafood items on the menu and snipped off a small sample, stored it in a test tube and brought it back to the lab.
Stern used DNA barcoding to identify a region of the Cytochrome Oxidase I mitochondrial gene. The technique compares the seafood sample with a database of DNA barcodes from known species.
The GW team found only one sample with a conservation concern.
The DNA barcoding analysis of the “Everything Tuna” sample identified it as Thunnus obesus, a tuna species listed as “Vulnerable” by the International Union for Conservation of Nature’s Redlist.
Researchers found one DC restaurant had listed Rock Shrimp on the menu but DNA barcoding showed it was serving Whiteleg shrimp.
Whiteleg shrimp are typically found in aquaculture farms and are not as flavorful as deep-water Rock Shrimp.
Crandall said that buyers for restaurants can inadvertently purchase mislabeled seafood as substitution of a cheaper fish for a more expensive species can happen anywhere along the chain from the fishing boat to the fishmonger or the restaurant.
The work was supported by Whitfield Bryson & Mason LLP. Jason Rathod, then of the firm, participated in discussions of study design, results and interpretation.
Source: PeerJ 5 e3234
“DNA Barcoding analysis of seafood accuracy in Washington, D.C. restaurants”
Authors: David B. Stern, Eduardo Castro Nallar, Jason Rathod, Keith A. Crandall