Using DNA to identify the sharks in squalene products
Madeline is trading tips, and drawing on insights from research into olive oil traceability to develop methods for determining which species are being used in shark liver oil products (squalene). The threatened gulper shark is the most common source, but Madeline wants to develop a protocol for extracting DNA from liver oil products to identify which shark species have been used for them. She will determine the best methods for extracting DNA from shark liver oil products and provide a tool for enhanced traceability and management in shark liver oil fisheries.
Madeline Green
I am highly motivated to help conserve, protect and manage species and natural systems. I’ve been obsessed with sharks for as long as I can remember and the fact that I am a shark scientist is still a shock to me today. Personally, I want to use my skills as a molecular ecologist to solve conservation challenges. I’m motivated by the challenge global fisheries pose to socio-ecological systems and threatened species, and for the past five years that’s where I have focused my research attention. I strongly believe that molecular tools will be key to monitoring fisheries in...
Molecular Monitoring of the Shark Liver-oil Trade
The aim of my work is to identify shark species from liver oil using molecular approaches.
The international trade in liver oil is a major driver of targeted fisheries for deep-water sharks and the retention of bycatch. Sharks are targeted for the squalene content of their liver oil. The preferred species from which the liver oil is obtained are the gulper sharks, one of the most threatened shark groups. By developing a protocol for extracting DNA from liver oil products we will be able to identify the shark species they come from. This project will determine the best methods for extracting DNA from shark liver oil products and provide a tool to improve traceability and management in shark liver oil fisheries.
Knowledge of the trade in shark liver oil encompasses a complex interplay of poorly understood ecological, economic and conservation dynamics. Driven primarily by the demand for squalene, a valuable compound used in cosmetics and human health products, this trade exerts significant pressure on populations of deep-water sharks. The unique properties of shark liver oil make it a sought-after commodity, contributing to targeted fisheries and incentivising fishers to retain bycatch. However, the trade’s sustainability is questionable due to a lack of management and the precarious conservation status of many shark species.
Understanding the shark liver oil trade has been overshadowed by the more conspicuous markets for shark and ray products, notably their meat and fins, which has led to limited attention and regulatory oversight. This relative obscurity has resulted in a lack of comprehensive data on trade volumes, species composition and ecological impact. It is alarming that most gulper shark species, the key contributors to the trade, are assessed as threatened on the IUCN Red List, and many face a high risk of extinction due to overfishing.
The complex nature of the liver oil trade is compounded by insufficient research and a lack of traceability tools. Recent research has involved the application of carbon isotopes to ascertain the origin of shark liver oil products. While this approach can identify products from Australia and New Zealand, other locations and species-specific information cannot be determined. This project’s objective to develop a protocol for DNA extraction from liver oil products is crucial. The approach aims to fill critical knowledge gaps of the liver oil trade by improving the accuracy of species identification and making it possible to assess species composition. Outcomes from this project offer a unique opportunity to improve effective conservation management, sustainable fisheries practices and targeted interventions, such as implementing trade regulations, to protect threatened sharks.
This project will use protocols previously developed for tracing olive oil on shark liver oil products to see if species can be delineated. Specifically, our project will
- Extract DNA from liver oil capsules using novel and widely applied commercial extraction methods.
- Extract DNA directly from single-source or multi-source liver samples.
- Identify shark DNA present in samples using an array of targeted qPCR, rtPCR and universal meta-barcoding primers.
- Raise awareness of shark species commonly used in shark liver oil products.
- Produce an open-access protocol for extracting DNA from shark liver oil products that will be available for researchers to use globally.
Summary of Results:
This research assessed whether DNA-based methods could be used to identify shark species from highly processed shark liver oil products, such as encapsulated supplements. Multiple DNA extraction approaches and molecular assays were tested on commercially available liver oil products to evaluate whether reliable genetic material could be recovered at the end of the supply chain.
The study found that refined shark liver oil products do not consistently retain usable DNA. Where genetic material was detected, results were highly variable and could not be confidently distinguished from contamination. These findings indicate that DNA-based species identification is unlikely to be reliable for refined liver oil products once they reach the consumer market.
This outcome provides important guidance for shark conservation and trade monitoring. It demonstrates that molecular traceability efforts should focus on earlier points in the supply chain, such as raw or minimally processed materials, and that alternative approaches may be required to support the monitoring of shark liver oil under emerging international conservation regulations.