If you’re a foodie, you probably recall all the exotic seafood menus you’ve sampled along the way – from white tuna and mackerel to that strange cucumber-looking sea urchin. However, you might be in for a surprise when you learn about your seafood’s true origins.

In 2015, the United States alone consumed roughly 5 billion pounds of seafood, placing it as the second largest seafood consumer after China. But what makes matters quite startling is that nearly half the time, the seafood we eat are not purported as what they are…

Wait, what??

Seafood fraud – the act of misrepresenting seafood products – occurs 25% to 70% of the time amongst common fish species such as wild salmon, Atlantic cod, and tuna. Thankfully, this issue is being addressed by several scientific testing methods, one of which is quite familiar to us: PCR.

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But first, let’s delve into the where, what, and how’s of this fishy business.

Where is the evidence for fish fraud?

Between 2010 and 2012, a non-profit conservation group called Oceana investigated more than 1,200 seafood samples across 21 states in the US. Their purpose was to confirm accurate food labeling. The study concluded that 33% of all collected samples were mislabeled – with tuna and snapper fish ranking highest for false advertising. In fact, 59% of fish labeled “tuna” and 87% of fish labeled “snapper” were imposters. Halibut, grouper, cod, and Chilean seabass were amongst other inaccurately labeled fish at 19% to 38% of the time.

In Oceana’s latest 2016 global report, one in five of over 25,000 seafood samples tested globally are mislabeled at each sector of the “seafood supply chain: retail, wholesale, distribution, import/export, packaging, processing and landing.”

The 2016 report investigated seafood fraud in 55 countries. What the study found was that 58% of the collected samples were substitute fish species that may cause illness. One such species is escolar, a commonly mislabeled fish that is found to be a substitution for white tuna in sushi restaurants across the US. Because escolar contains the indigestible wax ester gempylotoxin, escolar intake can lead to a condition known as keriorrhea. Keriorrhea produces leaky discharges per the rectum as a brownish or orange-colored oil. Other symptoms associated with keriorrhea include nausea, vomiting, and abdominal cramps.

How did this happen?

The global seafood supply chain is a very complex process. The fish we eat passes through so many different hands before getting to our dinner table. While over 90% of the seafood Americans consume is exported from different countries around the world, it’s interesting to note that a large chunk of this imported seafood is caught by American fishermen. This is then exported overseas for processing before importing back into the states. With so many moving variables, mislabeling can occur intentionally or unintentionally by fisheries, wholesalers, or even restaurant chefs.

So, what does this all mean?

Inaccurately labeled food is not only commercial deception money-wise, but also a sustainability and health issue.

• Adulterated fish are oftentimes cheap fish being sold as a high-end fish: a $6/pound tilapia disguised as a $17/pound red snapper

About one-fifth of halibut in the U.S. is mislabeled. The overfished Atlantic halibut is often substituted for the Pacific Halibut so we may be unknowingly consuming halibut that is endangered

• Fish that pose species-specific health risks to consumers are being sold under false advertisement: higher mercury level tilefish sold as the low mercury halibut

How is the US government addressing this problem?

Most recently in December 2016, the Obama administration announced a final rule to address illegal fishing and seafood fraud in the United States. This final rule requires the National Oceanic and Atmospheric Administration (NOAA) to install a Seafood Import Monitoring Program, which will allow for a greater level of traceability and transparency in the seafood supply chain.

How is the FDA detecting fish fraud?

DNA barcoding for fish species identification is a project being administered by scientists at the United States Food Drug Administration (FDA). Once a fish’s identity is confirmed through DNA testing, a new barcode is created for that species and subsequently inputted into a database. This database serves as a reference for profiling fish and fish-related products.

What DNA-based testing method is implemented into this FDA process?

The whole fish is first collected before a sample piece is removed for DNA testing. Once the DNA is exacted and purified, it undergoes the polymerase chain reaction (PCR) in a real-time PCR instrument (for quantitative output). PCR amplifies the target DNA sequence in a series of heating and cooling cycles so that in the end, an abundant amount of the target sequence can be detected.

So you may ask, why do we need to replicate so many copies of the target DNA sequence? The reason is that without amplification, detecting the target sequence would be akin to trying to find a needle in a haystack. In other words, it would be nearly impossible. Since PCR is a highly sensitive and specific test, this technique is utilized widely and can be completed within 30 minutes on average.

How can I protect myself from adulterated fish?

• Be skeptical of very low prices as the cheapest prices may reflect adulteration

• Purchase from reputable brands and sources

• Buy the whole fish as opposed to fillets

• Build a relationship with your local fishermen and ask questions about the type of fish and where and when it was caught