UNC finds there’s something fishy about seafood labels

It’s summer, which means shrimp season is ramping up on the North Carolina coast. But research from UNC-Chapel Hill shows that the seafood on diners’ plates may not be what they expect.

UNC students recently published two studies on mislabeled seafood. In a study of North Carolina grocery stores and seafood markets, they found that over a third of the shrimp marketed as “local” was actually a shrimp species only found in the Pacific Ocean.

Red snapper was even harder to find. All the restaurants and seafood markets they sampled were selling other fish labeled as “red snapper.” Among the grocery stores, only Whole Foods was truly selling red snapper.

“What was surprising to me was how unsurprising the results were,” said Erin Spencer, who analyzed the data about red snapper as a master’s student at UNC. This is because mislabeled seafood has been common for decades, but this was some of the first work focusing extensively on North Carolina.

Mislabeling seafood is not just misleading. People can also get sick from mislabeled food, by unknowingly eating something they’re allergic to or not being able to take proper precautions for certain kinds of seafood.

And when the origin of seafood is mislabeled, especially seafood falsely labeled local, it hurts local industry and can allow exploitative labor practices to thrive.

“You try to do the right thing as a consumer, and you buy what you think is local, but it’s hard when you don’t know what you’re buying,” said John Bruno, the UNC biology professor who supervised the research.

Louisiana recently banned the mislabeling of crayfish and shrimp, he noted, after research showed a significant amount of “local crayfish” was actually imported from Chinese farms, and may have been harvested by Uighur political prisoners.

How phony fish is identified

The team identified the phony fish through “DNA barcoding.” This involves extracting a small segment of DNA, making many copies of it, and comparing the sequence they find to known standards.

DNA barcoding is especially useful for catching mislabeled seafood because it’s almost impossible to tell apart similar species once they’re broken down into cuts like fillets. Thanks to advances in biotechnology, the process is cheap and fast — the team could get DNA sequences within 24 hours of sending samples to the lab.

In fact, the process is so simple, most of the work was done as part of a new kind of introductory course at UNC: course-based undergraduate research experiences, or CUREs. The students learned about DNA barcoding just a few weeks before analyzing their own samples.

Morgan Korzik was the lead author on the study about shrimp and was an undergrad in the Seafood Forensics CURE. He is going to graduate school in forensic science in the fall and said getting to learn practical techniques like DNA barcoding helped in applying to graduate programs and internships.

Korzik appreciated the professors letting students design their own research. He said the group chose to study shrimp mislabeling because most previous research on mislabeled seafood focused on endangered species.

Korzik said he was surprised by one trend that showed little difference between coastal and inland stores in the frequency of labeling imported shrimp as local. Bruno said local sellers in fishing areas were just as likely to mislabel shrimp as national chains.

For snapper, Spencer was surprised that while grocery stores did occasionally sell real red snapper, none of the special seafood markets they sampled that claimed to sell it actually did. Instead, it would usually be another, less expensive species of snapper.

She also pointed out the group did not test several markets because they didn’t stock red snapper out of season. Instead, they suggested other fish a buyer might consider.

May not be fish market’s fault

Because seafood supply chains are complicated, it’s not necessarily a market’s fault if something is mislabeled.

“A lot of seafood changes hands five to seven times before it ends up at a grocery store,” Bruno said. “Even for coastal restaurants, they often buy it from a distributor rather than a fisherman.”

Each point along the chain is an opportunity for mislabeling. And if multiple restaurants or stores share an unscrupulous distributor, they might all be duped.

“This made me more skeptical of the things I’m buying in general, not just seafood,” Korzik said.

Individually, there’s not much a person can do to verify their seafood at the store. Government agencies educate the public on different fish seasons, which can help inform buyers.

Ultimately, it will take structural changes. Seafood prices that sound too good to be true probably are.

“There’s no such thing as a $10 grouper sandwich,” Spencer said.

She encourages people to ask stores and restaurants where their seafood comes from. It might not guarantee the label is accurate now, but stores will invest in the effort if customers show they care. For instance, Whole Foods now emphasizes traceability of its seafood.

Bruno’s classes are now in the process of certifying seafood sellers in North Carolina for accurate labeling, and future work could help stores identify reliable vendors. They may also work to ban mislabeling in North Carolina, following Louisiana’s lead.

This story was originally published July 6, 2020 at 8:00 AM with the headline "UNC finds there’s something fishy about seafood labels."