Forensic Fisheries: Using DNA to Investigate the Trade in Shark Liver Oil
SHOW NOTES
Madi has always had a strong connection with the marine environment, and remembers her first scuba diving lessons on the iconic Great Barrier Reef as one of her most treasured memories [6.37]. The vibrancy and abundance of marine life was unlike anything she’d seen previously, and the experience was made even more memorable by a visit from a humpback whale and her calf. “It was just this magical moment of me being like: I love the ocean. I love this place.” Years later, Madi is working to conserve that very same place by applying skills and techniques from genetics and molecular ecology to help us tackle one of the ocean’s greatest challenges: fisheries [9.20]. “I definitely have a mind where I want to work on applied research projects – so that’s where I’m directly trying to solve a problem,” explains Madi. “And fisheries definitely feels like the largest – some of the largest – challenges we have. It’s multi-sector, global, we have different people relying on fisheries in all different kinds of ways. The management is complicated, and that means the data collection is complicated as well, and that affects how we understand what we’re fishing, what we’re catching.” Madi is a population geneticist by trade, and was using DNA to figure out how animals were related across ocean basins. She began to wonder if the same skills and techniques could be applied to the monitoring and management of fisheries. Now, she runs the Forensic Fisheries Lab within the University of Tasmania, which has a whole team dedicated to the development and implementation of genetic and forensic tools to assist in the monitoring of international trade [11.13].
There are many facets to Madi’s research, but one particular aspect her lab has been concentrating on recently – and the focus of her Save Our Seas Foundation funded project, ‘Using DNA to identify the sharks in squalene products’ – is the trade in shark liver oil. But why is there a demand for the oil in the first place, and what is it used for [17.02]? Liver oil has many uses, particularly in the cosmetics and pharmaceutical industry. The main component of shark liver oil is squalene, which is thought to have a number of beneficial properties. “It has sometimes, in some studies, been shown to have possible anti-inflammatory and anti-cancer properties,” says Madi. “But that’s not well documented. It’s very unclear in the literature whether there is a direct benefit to be derived from this squalene compound. But, there is still this demand for it.” Shark liver oil is sold in capsules, to be taken as a supplement. But, it is also known for its moisturising properties, and because of this, has found its way into every corner of the cosmetics industry: sunscreen, foundation, moisturiser, lipstick, self-tanner…the list goes on.
“Something to note though is that you can get squalene can also be plant derived, so you can get squalene that is derived from oil from olives,” adds Madi [18.54]. There’s also squalane, which is human manufactured. But a problem is that it’s very difficult to ascertain where the squalene came from once it’s in the final product. And, the source isn’t always stated on the packaging, making it equally difficult for consumers to know what they’re buying. In fact, we know very little when it comes to the shark liver oil trade as a whole [20.18]. “We know that the fishery is primarily a by-catch fishery,” Madi explains. “Inshore sharks are harvested for other reasons – for fins, for meat – and they just happen to have spare livers. So [the fishermen] take those spare livers, and combine them as an additional product to get more money from.” Although less common, there are targeted fisheries for shark liver oil, which focus mainly on deep-water sharks. These species tend to have larger livers, with a higher concentration of squalene, meaning a targeted fishery is more viable. However, these deep-water species are slower to grow and reproduce, meaning that they often can’t cope with fishing pressure.
Outside of this, the trade in shark liver oil remains in the shadows [25.40]. “The difficulty is really around the product. Like, once it becomes oil, it’s very hard to identify what it is,” says Madi. Fins can reliably be identified to genus level, and even some information can be obtained from the colour or style of meat. But very little can be determined just from the appearance of oil. Another issue is the difficulty of extracting DNA samples from oil, because of how it is sometimes processed. Oil can be pressurised, heat-treated, or repeatedly filtered, which leaves little DNA behind. “You need super sensitive kits to even try and get DNA – if it’s even possible.”
But, Madi believes there is a way to extract DNA from shark liver oil – and it comes from a slightly unexpected place: the olive oil industry [27.24]. “There’s a little bit of evidence from the olive oil, food safety space, looking at how to trace olive oil back to different countries of origin. And they’re the kind of tools that we can try and apply to the shark liver oil trade.” For the last year, Madi and her team have been testing different methods to extract DNA from shark liver oil capsules. The capsules come from various companies – some clearly state the origin of the liver oil, whereas others are more ambiguous: “they would say things like, ‘sourced from clean, deep sea, Southern Ocean sharks…I mean, I don’t know what makes a clean shark, versus a dirty shark!”.
It’s a lot of hard work and time spent in the lab, but recently, the Forensic Fisheries team had an exciting breakthrough [31.00]. “In the last month, we have been able to successfully and reliably get DNA from these capsules – so it’s a really exciting time!” enthuses Madi. This research is so new it isn’t published yet. But the hard part is over: “Now, we’ve got shark primers, and we’ve selected the DNA that is connected to sharks. And then we’ll sequence that DNA to see if we can identify the sharks that are in there, across all these different oils.” Another important step is to identify the conditions and protocols needed to ensure that this tool can be reliably used across a variety of settings, including at fish markets. This would mean that, potentially, oil could be traced back through the supply chain. “The further you go down the line of processing into a capsule, the less DNA you’re going to have,” explains Madi. “But we have a question around, well, now it works for tiny fragments of DNA, very degraded, from the capsule end. But what are the actual other points across the seafood supply chain that we can do this, and get much better DNA, because it’ll be much less processed?” Those longer pieces would allow scientists to be able to identify not only the species, but also where it came from. “Where I hope to be in five years is provenance. So, can we say, what ocean basin, at minimum, this shark came from.”
It’s an innovative and exciting project that could go a long way to improving the traceability and sustainability of the trade in shark liver oil. But in the meantime, there are ways that we, as consumers, can help [37.06]. Some companies that use squalene will specify where it was sourced – plant-derived, human-manufactured, or from shark liver oil. If the source is from shark liver oil, a ‘good’ company will state which fishery it comes from and have information on that fishery’s practices. But, if this information isn’t freely available (and in many cases, it isn’t), then Madi’s advice is to avoid that product. “It just takes a little Google,” she says. “For me, skincare has been a good one. I always look at the ingredients list, research the company, and try to use squalane [the synthetic option], not squalene, where possible.” She also recommends trying to buy local, to reduce your carbon footprint.
“So yeah, buying local, looking at the ingredients, opting for plant squalene or human-manufactured squalane,” Madi summarises. We won’t always get it right – but being conscious, and trying our best, matters: “It’s not about a few doing it perfectly – it’s about everyone trying imperfectly when it comes to sustainability and consumer choice.”
ABOUT OUR GUEST
Dr Madeline Green
Dr. Madeline Green is an interdisciplinary researcher with expertise spanning marine science, fisheries, conservation, and entrepreneurship. Madeline has a rich background in marine ecology and molecular research, with a focus on commercial fisheries and elasmobranch movement ecology. Madeline earned her PhD from the University of Tasmania in 2019. For over a decade, she has been dedicated to the study of marine species, with a particular focus on sharks and rays across the Indo-Pacific Ocean.
As a post-doctoral research fellow (2020-2023), Madeline began developing forensic tools for estimating fisheries landings and monitoring illegal, unreported, and unregulated (IUU) fishing activities. Madeline is currently a Research Fellow at the Institute for Marine and Antarctic Science (IMAS) and the PI for the forensic fisheries group. Her role is to develop cutting-edge genetic technologies to reconstruct catch data for commercial fishing vessels, enhance monitoring of data-poor fisheries and track seafood supply chains for frequently unmonitored seafood products (e.g., shark liver oil).
Madeline’s work also extends to understanding the genetic relationships between marine species, their movement patterns, and population dynamics, with the purpose of improving fisheries management for highly threatened species.
Follow Madi on Instagram
Madeline‘s Save Our Seas Foundation funded projects:
PAPERS MENTIONED
Boube, T., Azam, C.S., Guilbert, A., Huveneers, C., Papastamatiou, Y.P., Mourier, J., Trujillo, J.E., Femmami, N., Kunovsky, A., Bersani, F. and Laurent, E., 2023. First insights into the population characteristics and seasonal occurrence of the great hammerhead shark, Sphyrna mokarran (Rüppell, 1837) in the Western Tuamotu archipelago, French Polynesia. Frontiers in Marine Science, 10, p.1234059.
Finucci, B., Pacoureau, N., Rigby, C.L., Matsushiba, J.H., Faure-Beaulieu, N., Sherman, C.S., VanderWright, W.J., Jabado, R.W., Charvet, P., Mejía-Falla, P.A. and Navia, A.F., 2024. Fishing for oil and meat drives irreversible defaunation of deepwater sharks and rays. Science, 383(6687), pp.1135-1141.
Green, M.E., Hardesty, B.D., Deagle, B.E. and Wilcox, C., 2024. Environmental DNA as a tool to reconstruct catch composition for longline fisheries vessels. Scientific Reports, 14(1), p.10188.
Majluf, P., Matthews, K., Pauly, D., Skerritt, D.J. and Palomares, M.L.D., 2024. A review of the global use of fishmeal and fish oil and the Fish In: Fish Out metric. Science Advances, 10(42), p.eadn5650.
