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.
1. “Specious Species: Fight against Seafood Fraud Enlists DNA Testing”. Scientific American. November 10, 2011. <http://www.scientificamerican.com/article.cfm?id=dna-testing-for-seafood-fraud>
2. “Fake Fish: Experts Say Mislabeling of Seafood is Risky Business”. ABC News. May 27, 2011. <http://abcnews.go.com/US/fake-fish-experts-mislabeling-seafood-real-problem/story?id=13706266#.TsIE2XPb_fE>
3. “Mystery fish: The label said red snapper, the lab said baloney”. Consumer Reports Magazine. December 2011. <http://www.consumerreports.org/cro/magazine-archive/2011/december/food/fake-fish/overview/index.htm>
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.