Over the past few years, several consumer and news organizations have researched and tested seafood available in supermarkets and restaurants. The findings:

• Some 35 percent of seafood samples in the U.S. were found mislabeled; 
• Of the fish that were most commonly mislabeled, 
• Red Snapper topped the list (at 86 percent being mislabeled);  
• Nearly 16 percent of grouper was mislabeled; 
• In one out of five cases, Atlantic or farmed salmon was substituted for wild or King salmon; and
• “White tuna” was mislabeled 100 percent of the time. 

A more recent investigation into fish labeling fraud carried out in Europe revealed that 32 percent of seafood in Italy, 30 percent of all hake in Spain and 19 percent of cod in Ireland were mislabeled. Repeated studies have shown that these results are not one-off, but seafood fraud is consistent and not showing signs of any improvement.

E. Pearce Smith, Laboratory manager, GeneScan, at Eurofins talks about the challenges in testing seafood authenticity. There are a couple of issues with regards to seafood fraud, Smith says: “From an economic standpoint, you could be buying a cheaper fish (for instance a breaded tilapia fillet instead of a breaded grouper fillet) for more money. Also, from a quality point of view, you lose out.”

More importantly, Smith adds, from a food safety perspective, if you are unknowingly processing a wild grouper sandwich, you are not considering the right safety, microbiological and decomposition markers for the wild fish. Or if it is a farmed tilapia product, you are not looking at prohibited veterinary drugs in farmed fish.

The horsemeat scandal that rocked large regions of Europe in 2013 was the basis for this focus, Smith says. “With horsemeat being sold as beef, producers were not testing their beef products for bute or phenylbutazone, an anti-inflammatory used by vets mainly to treat pain and fever in horses.”

When testing is an art as well as a science

So far, seafood species authentication depended on tests that were developed many years ago. FDA published a protein method known as isoelectric focusing, in which you take a piece of a tissue, digest it into a slurry and run it out into a gel. By comparing the banding pattern to known references, you can conclude what kind of fish it is. The problem with this technique, Smith says, is that it is often inconclusive, or at least open to interpretation in many cases.

So, about three years ago, FDA decided to abandon this 1950s technology for a more modern technology – DNA barcoding.  So now, instead of using a protein pattern, the test involves isolating the DNA and amplifying a specific section of it for analysis. 

“In a relatively short sequence, of about 700 base pairs, it’s very easy to distinguish one species of fish from another,” Smith says, adding that now food companies want to drive the switch from the protein testing to the DNA method.  Testing for the protein requires a lot more hands-on time and testing one sample can take several hours, Smith explains. “With the DNA method, you can automate the testing to a much higher degree to handle hundreds of sample a day. And with the cost of sequencing dropping, such testing is no longer cost-prohibitive,” he adds.

Robust methodology

The new methodology is robust because DNA is a very stable molecule, according to Smith. “You can test raw or cooked fish with this method, while the protein test was not as good at spanning the pre- to post-processed product. You can also test a finished product such as a frozen fish dinner.”

What are the limitations? Smith lists a few examples: Testing a food product that could have multiple types of fish, such as a fish cake or Surimi, which are ground up into a paste, and could have multiple seafood products in them. Canned tuna is not suitable for testing, because the high pressure process involved is very destructive and you may not be able to get a nice clean read of the DNA. FDA has identified about 150 unique species as targets for substitution, or of high commercial value at risk of being substituted for monetary gains.

“The samples that we get from food producers usually turn out to be what we expect them to be, but sometimes, they don’t. When we get samples from consumer groups, about 30 percent are mislabeled. Also, variations in regional names for that particular fish also contribute to confusion and mislabeling,” Smith explains.

FDA is now publishing the reference sequences for the different species of fish to make identification quicker and easier. Earlier people had to rely on private databases and some of these, while good, weren’t easily accessible. 

Smith sees a lot of demand for testing species such as salmon (differentiating pink salmon Oncorhynchus gorbuscha, Chinook salmon Oncorhynchus tshawytscha, or Coho salmon Oncorhynchus kisutch); and red snapper (which faces high demand but is low in supply, and is commonly substituted with other fish of the same size or color). He says that the importance for this testing is growing increasingly as companies are importing seafood product, and it is critical that the species be correctly identified on the packaging. Imports are the source of as much as 90 percent of the fish consumed in the U.S., and only about 2 percent of those products are inspected, he adds.