The use of Shark Liver Oil

Photo by Zoya Tyabji Gulper Sharks captured off the Andaman Islands, India and later processed for their liver oil.

Written by Dr Brit Finucci

The use of sharks for their oil is not new. Globally, sharks have been targeted for their liver oil for centuries, and this product is an essential marine resource for many coastal communities. All shark livers contain a natural organic compound known as squalene. Squalene in the liver helps a shark maintain its buoyancy. This natural lipid or fat molecule is also used for many cosmetic, pharmaceutical, and technological applications, such as sunscreen products, anti-ageing supplements, and biofuels. Indeed, while the public is increasingly familiar with other shark traded products like fins or meat, most people are unaware that their everyday household products may contain squalene from a diversity of shark species. Although there are readily available plant-based and synthetic alternatives, shark-derived squalene is still in high demand as it is typically the most cost-effective source in terms of extraction. Yet, despite the presence of squalene in international trade for decades, virtually nothing is known of the shark liver oil trade. Furthermore, even though there is an ever-growing body of medical literature for its application in human health, its use has only recently been brought to light with the COVID-19 pandemic.

Historically, the shark liver oil trade has affected many shark species, especially deepwater ones that have the most concentrated and highest quality source of squalene in their livers. Deepwater sharks, species that spend most of their lifecycle at depths greater than 200 m, account for nearly half of the global shark diversity. They are also characterised by life histories (e.g. late maturity, low fecundity) that make these species unable to withstand exploitation. In fact, Gulper Sharks (genus Centrophorus) have been highly impacted due to localised population declines from targeted fisheries that have collapsed over short periods of time (less than 20 years). For example, at a fish landing site in Cochin, India, Gulper Shark landings declined by 60% over a three-year period, from 114 tonnes (t) in 2008 to 39 t in 2011. However, information on most fisheries where liver oil is extracted is often anecdotal and lacks quantitative data. Often, when a fishing area becomes depleted, fishers simply move onto new fishing grounds, offering little refuge or recovery for these species. When widespread collapse occurs, resulting actions, such as fisheries closures, can have detrimental effects on both the local fishing communities and the marine environment. Today, 75% of Gulper Sharks (nine species) are assessed at a very high or extremely high risk of extinction (Endangered or Critically Endangered) by the IUCN Red List of Threatened Species due to overfishing.

There is a lack of transparency on the source of shark liver oil and the species affected by the trade. Furthermore, while there have been reports that shark liver oil has been used to develop some of the COVID 19 vaccines, the scale of the squalene demand from the pharmaceutical industry to create COVID vaccines is unknown. Without this information, we cannot determine if shark liver oil is being obtained from a sustainable and legal source or address the effect the trade is likely having on sharks. The newly established IUCN SSC Shark Specialist Group Deepwater Chondrichthyans Working Group will be working towards establishing projects to collect information on national and international liver oil supply chains so we can better quantify the impacts of the shark liver oil trade and identify alternatives to reduce pressure on those species most at risk of extinction.

Take-home messages: • Shark liver oil contains a natural organic compound known as squalene. • Squalene is used in many cosmetic, pharmaceutical, and technological applications. • Sharks may be targeted specifically for their shark liver oil (and sometimes for their meat) or retained as bycatch species and used for their liver oil. • The shark liver oil trade has affected species highly susceptible to population decline, including the Basking Shark (Cetorhinus maximus), Greenland Shark (Somniosus microcephalus), Tope

Shark (Galeorhinus galeus), and gulper sharks (Centrophorus spp.).

As a result, targeted fisheries for these species have collapsed over short periods. • There is a lack of transparency on the source and trade route of shark liver oil, with much of it likely being sourced from unsustainable fisheries. • Alternatives to shark-derived squalene, including syntheticderived and plant-based squalene, are available and should be considered in the production of vaccines. • With the growing global demand for vaccines, renewable energies, and alternative medicines, a failure to assess the impact of the use of squalene on shark populations may have long-term consequences by increasing targeted fisheries for these species and placing additional pressure on already susceptible populations.

Oil extraction of shark livers captured in the deepwater shark fisheries off Sri Lanka.