The Editor says: According to statistics, one in five fish sold globally comes from illegal fishing, and the most common form of fraud is mislabelling lower-value catches as higher-value species. In response, the Aquaculture Stewardship Council (ASC) uses the concentration of these elements to create individual fingerprints for all seafood — a method known as Trace Elemental Fingerprinting (TEF) — to combat seafood fraud worldwide. Join us as we explore this remarkable technology! <Full article reprinted from China Dialogue Ocean: Chemical Fingerprints Make Seafood More "Transparent" >
Whether farmed or wild-caught, tracing seafood completely from source to table is an enormously challenging problem. Seafood supply chains are highly complex, often involving multiple countries and dozens of companies, resulting in a severe lack of transparency and rampant fraudulent practices. Seafood is also one of the most heavily traded commodities in the world. According to FAO data, total global fisheries and aquaculture production of aquatic animals reached 178 million tonnes in 2020, and that figure is expected to rise to 202 million tonnes by 2030. Seafood is the primary source of protein for approximately 3 billion people worldwide.
photo credit：mali maeder
Yet one in five fish sold globally comes from illegal fishing — with an annual value of US$23.5 billion at 2009 currency levels (approximately US$42 billion adjusted for inflation). The most common form of seafood fraud is mislabelling: passing off lower-value species as higher-value ones, such as labelling yellowfin tuna as bluefin tuna.
A March 2021 analysis by The Guardian found that nearly 40% of 9,000 seafood samples collected from restaurants, fishmongers, and supermarkets were mislabelled. The analysis reviewed 44 seafood studies, including a 2018 study that found the highest mislabelling rates in the UK and Canada (55%), followed by the United States (38%).
Full Supply-Chain Traceability for Seafood
The seafood industry is facing mounting pressure to achieve full supply-chain traceability. Wendy Banta, Head of Supply Chain Assurance at the Aquaculture Stewardship Council (ASC), states that "greater transparency equates to stronger accountability and assurance: being able to trace where seafood comes from means that a company's sustainability claims can actually be verified."
The ASC is a non-profit organisation responsible for setting protocols for sustainable farmed seafood. To improve traceability, the seafood industry is increasingly turning to technology to verify the origins of seafood and detect whether it was caught sustainably and legally. For example, scientists and regulators can trace the origin of samples by analysing natural chemical markers found in the shells, bones, and soft tissues of seafood.
photo credit：Shukhrat Umarov
China Dialogue Ocean spoke with Catherine Longo, Chief Scientist at the Marine Stewardship Council (MSC), about these technological developments. She said: "The greatest advantage of improving forensic methods in seafood supply chains is the ability to identify fraud risks — including species substitution and falsified origins — precisely, rapidly, and effectively." The MSC is a non-profit organisation that sets standards for sustainable fisheries worldwide.
Trace Elemental Fingerprinting of Seafood
"Trace elements" such as selenium, potassium, and zinc are ubiquitous in water, soil, and air, and are also present in minute quantities in the soft tissues of every living organism. The concentration of these elements can be used to create a unique fingerprint for any seafood product — a method known as Trace Elemental Fingerprinting (TEF). One study found that TEF achieved 100% accuracy in identifying the capture location of blue mussels and their soft tissues. TEF can therefore be used to verify seafood origin claims. Seafood producers and non-profit organisations such as the ASC have already begun using TEF combined with machine learning to combat fraudsters and improve supply-chain transparency. Banta explains: "The ASC's approach combines elemental analysis with advanced mathematical modelling, which allows for better differentiation between samples from different geographic regions and with greater certainty."
photo credit：Francesco Ungaro
TEF has been used as a forensic tool for the past 10 years to authenticate a wide range of food products including fruit, honey, and meat. Recent research suggests that TEF holds enormous potential for verifying the provenance of seafood — particularly farmed shrimp. In 2021, the ASC tested the technology in a pilot programme in Vietnam (one of the world's largest shrimp-producing nations) and found that TEF could correctly match unlabelled samples to their place of origin, with the organisation reporting an accuracy rate of 95%.
Chemical Fingerprinting
Another tool that can be used alongside TEF to combat global seafood fraud and illegal fishing is "chemical fingerprinting." This technique exploits isotopes — variants of elements with slightly different masses. These differing masses give each isotope its own physical properties, causing distinct reactions within the water cycle.
A team of scientists at the University of South Australia, led by marine ecologist Zoe Doubleday, is developing chemical fingerprinting. Doubleday notes that TEF works well for distinguishing one shrimp population from another. However, other factors — such as an animal's metabolism and the time of day — can also alter trace element concentrations in fish and seafood. As a result, trace elemental fingerprinting is less stable and consistent than chemical fingerprinting when it comes to identifying the origin of a species.
Doubleday and her team are developing oxygen isotope chemical fingerprinting. These natural chemical markers, found in shells and bones, are similar across many different marine animals. Oxygen isotopes are determined by the composition and temperature of the ocean rather than by the biology of the animal, making them useful for establishing where an animal comes from.
"An octopus, a clam, and a fish living in the same bay will all have the same chemical values," Doubleday explains. "We've developed a technique that works across many different seafood species, as well as a more universal marker, in an attempt to pinpoint true geographic location."
As technology advances, the cost and difficulty of regulation are both falling — making it simply not worth the risk to commit seafood fraud. — Catherine Longo
The method scientists use involves extracting oxygen isotopes absorbed in the calcium carbonate of shells and bones from different seafood species, then analysing the isotopes' chemical and geographic origins using a spectrometer. At the same time, the team has mapped the chemistry of the world's oceans, allowing them to match isotope data to specific locations.
Doubleday notes that this approach is particularly well-suited to tracking animals living at different latitudes and temperatures. Using chemical fingerprinting, researchers can calculate whether fish, cephalopods (such as squid and octopus), and shellfish originate from tropical Southeast Asian waters or from the cooler waters of southern Australia. They have recorded a location accuracy rate of up to 90%.
photo credit：Kindel Media
Doubleday says: "Japan and where I live in southern Australia are at roughly the same latitude, so species from both areas will have similar values. We're working on a new marker influenced by geology that can help us refine these results — clearly, many animals live at similar latitudes."
Chemical fingerprinting uses oxygen isotopes and is therefore better suited for testing a wider variety of seafood: "Using oxygen isotopes means we're analysing the ratio of elements, not their quantity."
Scientists can determine the origin of a sample by analysing the ratio of light to heavy isotopes of a particular element within that sample. This ratio varies according to climate, location, and environmental conditions. "It is governed by many physical laws, whereas trace elemental fingerprinting can only measure the concentration of an element," Doubleday adds.
A Scalable Scientific Solution
Doubleday suggests that, for instance, government agencies could use chemical fingerprinting to screen seafood at the processing stage — where shells are typically discarded and can easily be archived for analysis.
An MSC spokesperson echoed this view to China Dialogue Ocean, describing chemical fingerprinting as an important tool that can extend detection capabilities beyond a limited range of species, enabling the technology to be used for market-wide monitoring.
In 2021, MSC's Longo co-authored a research report analysing the ability of chemical fingerprinting technology to detect fish capture locations. The MSC spokesperson said the report demonstrated enormous potential for the technology to be deployed more broadly. Currently, a lack of empirical research to confirm the technology's accuracy across a wider range of aquatic species and bodies of water is hampering its development.
The technology is still in its early stages, with a long road ahead before it sees practical, widespread application. The University of South Australia team's next step is to test samples of unknown origin, while scientists will continue mapping the chemistry of the global oceans.
Banta notes that it remains unclear whether tools such as chemical fingerprinting are susceptible to changes in ocean chemistry and temperature — there are several variables and unknowns, one of which is long-term climate change. The MSC also agrees on the need to continue monitoring changes in the chemical elements that determine product characteristics, in order to ensure detection accuracy.
Doubleday cautions that the technology is not a silver bullet against seafood fraud: "No single method can solve every problem — a multi-pronged approach is needed." Other tools include DNA tracking, blockchain technology (to improve supply-chain transparency), and electronic monitoring equipment onboard vessels. "If resources allow for combining multiple methods to infer provenance, the level of certainty is much higher," Doubleday concludes.
Longo says: "Increasing the digitalisation of supply-chain operations and product provenance can be a powerful deterrent to fraud. As technology advances, the cost and difficulty of regulation are both falling — making it simply not worth the risk to commit seafood fraud."
Full article reprinted from: China Dialogue Ocean — Chemical Fingerprints Make Seafood More "Transparent", Author: Isabelle Gerretsen, Published: 2023-11-07
Editor: Jenny Tsai
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