In an increasingly conscious market, sustainability and traceability have become more important than ever—and seafood is no exception. According to a study conducted by Foodmix Marketing Communications last December, 62 percent of those surveyed check the sustainability of their seafood before purchasing at least occasionally, with 34 percent doing so always or almost always.

But little do these concerned customers know, they—and the brands who serve them—are often getting the bait-and-switch treatment, purchasing seafood products that claim to be one thing and turn out to be another. This practice, known as fish fraud, can include selling farm-raised fish as wild-caught, claiming the product comes from a certain location when it was actually sourced elsewhere, or trying to pass off one seafood species as a different one altogether.

“Generally, there aren’t a ton of regulations that prevent it, compared to beef or other meat,” says Joey Nguyen, owner of Poke Lab in Monterey, California. Although President Barack Obama’s Seafood Import Monitoring Program took effect this year, fish fraud is continuing to become more rampant in all sectors of the market.

Chris Cheeseman, owner of San Francisco–based fast casual TACKO, says fish fraud is more likely to occur within the quick-service segment due to the pressure to maintain lower price points. “I’ve seen people that buy a lot of inexpensive or frozen fish, and that’s where it starts to get muddy,” he says. “A lot of times these fish are coming from foreign waters, and you don’t really know what they are.”

While developing TACKO’s seafood program, which includes items like fish tacos, burritos, and lobster rolls, Cheeseman originally purchased frozen hamachi that seemed questionable, leading him to switch to fresh, local fish like yellowtail amberjack, mahi mahi, and rockfish.

Fortunately, not all seafood species are as apt as others to be mislabeled. Red snapper and shrimp are two of the biggest offenders, says marine ecologist John Bruno. He teaches a class on seafood forensics at the University of North Carolina at Chapel Hill and is writing a book on fish fraud. With the help of his students, Bruno works with local chefs to determine whether their seafood is actually what it claims to be.

“With shrimp, about one-third of what we buy that’s sold as fresh, local, wild North Carolina shrimp is actually imported,” Bruno says, noting that mislabeling of red snapper is even more widespread. “We go to local sushi restaurants, and it’s almost 100 percent mislabeled.”

Research conducted last year by UCLA and Loyola Marymount University came to similar conclusions. DNA tests of fish from 26 Los Angeles–area sushi restaurants revealed that 47 percent of sushi was mislabeled.

Like most deceptions, the motivation behind fish fraud is largely monetary. For example, Bruno says, wild North Carolina shrimp sells around $14–$18 per pound, while frozen shrimp imported from Ecuador may only cost $4–$5 online. Suppliers may also feel pressured to deliver the same fish—often in large quantities—on a consistent basis, even if it’s unavailable.

“If you’re supplying 1,000 pounds of fish every month and you only have 500 pounds of that fish, there’s a motivating factor to not lose the client to another company or vendor, so you’re going to want to fill that order,” Cheeseman says. “It’s financial, but I think it’s more about keeping the vendor relationship intact.”

As more species like red snapper feel the effects of overfishing and ecosystem destruction, the more likely fish fraud is to occur, as well. Furthermore, because “red snapper” is widely available in restaurants and grocery stores, consumers may be oblivious to how overfished the species is, instead assuming it is abundant.

But beyond the obvious environmental implications, why should restaurants and their guests care? For many, the answer starts with their wallets. “It’s like going to the Mercedes dealership and paying $60,000, then driving home with a used Hyundai,” Bruno says. “You’re getting really ripped off.”

Fortunately, there are ways to spot fish fraud or try to avoid it altogether. For distinctive species like salmon, tuna, and lobster, it’s hard to pull the wool over unsuspecting eyes, so taking a closer look at the fish should be the first step. However, generic white fish can be harder to identify without the use of forensic analysis.

That’s where people like Bruno and his seafood-curious students come in. Teams like his work with local chefs and restaurants to test fish by extracting DNA from the tissue, sequencing it, then comparing it to a database. It’s a straightforward process, costing about $20–$30 per sample, which Bruno concedes may still be price-prohibitive for operators. Still, it could serve as a means to test vendors and find trustworthy ones.

Close relationships with vendors—preferably local ones—help operators like Cheeseman avoid fish fraud. “The prevalence of fish fraud in my personal business is nonexistent, because I have these controls. I know what type of fish I’m getting, and it’s local; it’s either from Southern California or here in the Bay Area,” Cheeseman says.

Working with suppliers who proactively take measures of accountability is also useful, Nguyen says. “All of the fish we source has some sort of packaging to ensure quality and its sources,” he adds. “Salmon will have a tag pinned to it, for instance, that has the origin and a QR code to track it. We also check weights carefully.”

Nguyen says an abundance of information is the strongest indicator that a restaurant has found a reliable fish supplier, adding that the method of catch, location, and species of the fish should be readily available upon request. “If there’s resistance to getting those details, I generally pass on a supplier,” he says. “Ultimately if someone is trying to commit fraud, there are only so many steps you can take to mitigate that, be it farmed or wild. But building relationships with purveyors is very important.”

While seafood operators like Nguyen and Cheeseman don’t have an issue with fish fraud at their own restaurants, they are concerned about it becoming more widespread in the future.

“I’ve seen all the popular fish basically go off the market, and we’re left fighting over limited resources. So it’s a grave concern to me that fish fraud is going to increase year after year, just due to the scarcity,” Cheeseman says. “It may not be on everyone’s radar now, but it should be in the next five or 10 years.”