Fishy Diets – What Are You Really Eating?

In 2007, several people in the US sat down to what they thought was a harmless dinner of monkfish. Little did they know that this particular Chinese import was actually a toxic puffer fish that had entered the country under the cover of a more innocuous name (1). This scare began to draw more attention to the regulation of the fish market and labs began to investigate whether this incident was an aberration or a frequent occurrence. In the United States, most consumers are completely trustworthy of food labels and believe that a misrepresentation of a food product is extremely rare or nonexistent. This year, multiple labs investigated this assumption and did not like what they saw. Some of these labs included associates of Oceana (an environmental group), Consumer Reports Magazine, private lab companies like ACGT, Inc, and the Food and Drug Administration (FDA). Their results showed a massive problem in our country’s seafood regulation.

Seafood is a staple food in cultures around the world. It is commonly considered a healthy alternative to many other food groups and there are multiple delicacies found in oceans, rivers, and ponds. The FDA recognizes 45 species-specific market names for fish (4) and retail companies must legally identify their fish with these market names. Unfortunately, it is believed that 20-25% of seafood samples throughout the world are actually mislabeled, oftentimes as a more expensive species (3). In fact, the FDA port inspections speculate that a third of seafood sold in the U.S. is mislabeled. One reason for this may be that 86% of seafood eaten in the U.S. is imported and only about 2% of these imports are inspected (2). This deception costs consumers millions of dollars each year when they are under the belief that they are actually buying a more expensive fish (1). It also may cause health problems similar to the toxic puffer fish or allow endangered fish to be sold illegally, thus enabling the decimation of certain species.

During the occurrence of the puffer fish incident in 2007, fish samples were verified through protein analysis, or isoelectric focusing (1). Each fish species contains slightly different proteins in its body and this test identified the proteins by their electric charge differences. This older test was limited by its inability to determine the accuracy of the sample’s identity if it had been processed or cooked because these processes affected protein structures. This rendered the test useless in many different circumstances. The next step in seafood regulation was to determine a more efficient and reliable way to regulate seafood.

So what is the new technique that was developed to identify these species? The answer is simple; scientists are now able to use a DNA barcode to identify different fish species. Every living organism has a DNA sequence that is unique and contains the individual’s genetic information. A single species will have individuals with varying DNA sequences, but there will exist certain genes in common that are only usually found in that particular species. A gene is a stretch of DNA that codes for a protein, so this basically analyzes the same information as the old test, but at an earlier stage. DNA is not as easily affected as proteins by any processing done to the fish. Comparing DNA barcodes is easy to do and relatively inexpensive. It compares the sample’s DNA to a known database and matches the sample to its correct species (1). There is currently a global effort to finish a Consortium for the Barcode of Life (CBOL), which is a sequence reference library for every species of fish on earth for the specific gene, cox1 (4). It currently contains the gene sequencings for cox1 in most seafood species. If a lab needs to identify a species, they are able to do so by comparing their sample’s DNA to this library. This analysis requires only a gram of the sample and is able to identify the sample whether it is raw, frozen, steamed, or deep-fried (1). In fact, DNA barcodes could be extremely helpful for the FDA in many cases of food-related illness or economic fraud investigations. In order to begin testing on a regular basis, the FDA recently installed DNA-sequencing equipment in nine of its laboratories across the country in order to decrease seafood substitutions. This technology will allow the United States to take the next step in food safety and help ensure that regulations are upheld in order to decrease economic fraud, harmful substitutions, and a great threat to endangered species.

This shows a comparison of genes (or stretches of DNA) in different tuna species. The rows indicate the genes being analyzed from the different species and the columns indicate the specific nucleotide being looked at. Nucleotides make up DNA similar to how atoms make up different molecules. Highlighted boxes show specific nucleotides that cause a gene to be unique for a single species.

Works Cited

1. “Specious Species: Fight against Seafood Fraud Enlists DNA Testing”. Scientific American. November 10, 2011. <;

2. “Fake Fish: Experts Say Mislabeling of Seafood is Risky Business”. ABC News. May 27, 2011. <;

3. “Mystery fish: The label said red snapper, the lab said baloney”. Consumer Reports Magazine. December 2011. <;

4. Lowenstein, Jacob H., George Amato, and Sergio-Orestis Kolokotronis. (2009) The Real maccoyii: Identifying Tuna Sushi with DNA Barcodes – Contrasting Characteristic Attributes and Genetic Distances. PLoS ONE 4:4-14.

This entry was posted in Science of Everyday Things by kgagesch. Bookmark the permalink.

About kgagesch

My name is Kelsey and I am a senior at DePauw University. I am currently studying a major in Biology and a minor in Applied Music. I have spent a large amount of my free time conducting research, including kinesiology, molecular biology and ecology and evolution biology. I am in Science Research Fellows, an honors program at DePauw that promotes undergraduate research. I also play the flute and piccolo in the DePauw University Symphony Orchestra and Flute Choir. I am currently applying to medical school and look forward to enjoying the rest of my time at DePauw!

4 thoughts on “Fishy Diets – What Are You Really Eating?

  1. Although DNA barcoding the seafood provides a very accurate way to test the species of seafood, I wonder how this technique would apply to real world inspection for seafood imports. My major concerns are the cost and the duration of this test. The author provided little information in these regards. If the associated costs are high and the length of the test is long, such technique may not be able to be employed in industry. I am not sure if the nine labs with DNA sequencing devices would be enough. The author mentioned that only 2% of the imported seafood are inspected currently. Is this cause by the long test time of the old technique, or other reasons such as insufficient legal regulations. If it was the latter one, merely applying the new technique would not be really helpful. What we need are more effective administrative schemes.

  2. I really enjoyed this post! After reading what you found about DNA barcoding, I looked around online for a while to see other ways in which this technology may be used. I found an article in Scientific American about the use of DNA barcoding in plants.

    It appears that scientists hope to utilize the plant genome for a very similar purpose, to prevent the illegal trade of endangered species, prevent mis-identification of species, and to avoid accidentally mis-labeled potentially toxic additives.

    Unfortunately, working with a plant genome is a bit more complicated than with a fish genome. Plant genomes are much more similar between different species than fish genomes. This forces botanists to utilize more than one gene for identification, and even then testing is only 70% accurate. Despite this, it appears that 70% is sufficient to accomplish the identification goals that inspired the use of barcodes in the first place. The only time it seems to be a significant issue is when new plant species are discovered that may not fit well into this system.

    Different articles seem to cite the technology as being cost effective. If these systems really are inexpensive, I am eager to see how they influence the quality of imported goods within our lifetime. It is amazing to see the seemingly innumerable number of ways we can utilize genetic studies in order to improve our world!

  3. I found this really interesting as I would have thought that it would be easy to identify fish differences by sight to a trained investigator. After reading your post about all the fraud that was going on I was curious to know where most of the fraud happened in the process. I expected it to be mislabeled from the very beginning of the import process but was surprised to find that most of the problems came from independent restaurants and that supermarkets were less likely to have mislabeled seafood. It made sense though that it would be easier to pass off fish as something else when it is cooked than when its raw, but I was surprised to read that sometimes its the chef’s that are tricked as I assumed that they would be the best people to spot the differences just behind the trained fish inspectors that work at supermarket distribution centers.

  4. This article reminded me of the documentary “The Cove,” which follows a group of environmentalists/activists/marine biologists as they try to uncover and expose a massive dolphin slaughtering grounds in Japan. They also revealed that massive amounts of fish meat in Japanese markets were being falsely advertised and were in fact dolphins. The narrator explained that many Japanese people are unknowingly at risk of mercury poisoning. Dolphin meat contains very high levels of mercury, and it is often purposefully mislabeled as whale meat, which some people in Japan prefer to eat. Eating this meat has been associated with diseases like Parkinson’s, arteriosclerosis, hypertension, etc.

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