The really scary facts about sharks: one third face extinction

Last December, a vast report compiling global research on the state of chondrichthyans (the group name for sharks, rays, and chimaeras) was finally completed. Its findings are sobering. In what it terms "catastrophic declines", one third of chondrichthyans are threatened with extinction, with recognisable species like whale sharks, manta rays, and hammerheads on the list, as well as hundreds of lesser-known ones. 

Sharks and their kin have been largely understudied until relatively recently. The report, which itself was commissioned in 2005, finds that over a quarter of the known species have only been discovered in the last twenty years.

As research has increased in the last decade or so due to leaps in technology, so too has scientists’ concern. The report, as well as a flurry of other papers published over the last few years, reflect what conservation scientist Dr. Lauren de Vos terms a sudden “wide vision”; where scientists have become suddenly aware of the scale of threats and loss of diversity, “before we even knew we had it”.

The last couple of decades have been particularly unkind to biodiversity of all types; as development, pollution and climate change have each emerged as serious forces to contend with. These have all been found by the report to be existential threats to sharks, rays, and chimaeras by themselves, but none compare to overfishing. Its findings indicate that of the third of chondrichthyans threatened with extinction, two thirds are threatened by overfishing alone.

Sharks’ biggest threat: overfishing

Such a wasteful practice begs solutions, and there have been instances of successful efforts to drastically reduce bycatch in some fisheries. Since the late 2000's, albatross bycatch has seen reductions of up to 99% by vessels that have made simple changes to their fishing gear and practices. But these changes take concerted and cooperative effort and often require the buy-in from many players, from government to fishing lobbies.

Another reason for such high levels of bycatch is that fishers are often motivated to not avoid it. Dr de Vos expands on this: “In many cases there's now an incentive not to mitigate bycatch...if you've seen a sawfish* in your bycatch and you can sell those fins, you're going to keep catching sawfish”. This blurred line between ‘wilful’ bycatch and genuinely incidental bycatch, combined with the collapse of many traditionally-fished fish populations means that sharks are now retained for their meat more frequently. Shark conservation began formally in the 1990’s, prompted by scientists’ increasing worry around the negative consequences of shark finning (the practice of removing shark and rays’ fins for use and discarding their often still-alive bodies).

In 2005, when the report was first commissioned, shark finning had been proven to be contributing to huge declines in sharks, and was scientists’ main concern. But by the time the report was published last year, scientists were surprised to learn that the shark meat trade had grown to overtake the fin trade in both commercial value and volume – by almost double.

^{_{*All 5 species of sawfish are critically endangered}}

"Not all greed and organised crime"

In the popular imagination, fishing has often been cast as the enemy of conservation. Obviously, fishing is a problem, but the reality is far more nuanced – here is where the distinction between 'fishing' and 'overfishing' needs to be made. Marine biologist and CEO of the Save Our Seas Foundation, Dr James Lea, frames this conundrum simply: “It's not all greed and high-level organized crime trade and sports cars...a lot of the reason sharks are in such a dire state is [because] people need to live and eat.”

Fishing, and the communities involved in fishing activities, may pose the biggest threats to chondrichthyans; they also have the potential to offer the greatest solutions. Dr Lea sums up this idea – “you're not trying to stop people from fishing, but make sure that their grandchildren, if they want, can still be fishermen like them...everyone is part of the same problem and solution.”

Further threats

Habitat loss and degradation is also identified as a major threat, as many chondrichthyans rely on coastal ecosystems like mangroves, and underwater ecosystems like seagrass beds and coral reefs, at different life stages. As the report makes very clear, we often don’t know enough about species’ lives to be able to know what habitats to protect until they’ve already gone. A 2013 paper found that the growth and survival rates of lemon sharks, who are protected as adults but whose reliance on mangroves as ‘nurseries’ when young has been overlooked, were severely negatively affected when mangroves were removed to make way for coastal development.

Deep sea mining is another example of this. We know very little about deep sea life, including sharks, yet exploration is underway, with projects scheduled for the near future. What we do know, as is detailed in a 2024 paper, is that deep sea shark species are incredibly vulnerable due to their slow reproduction and long life cycles, and without truly having all the facts, disturbing their habitats would likely push species toward extinction. Bottom trawling (a fishing practice of dragging huge heavy nets along the sea bed), is another culprit; it disturbs habitat structures, and repetitive trawling can destroy them completely. A 2009 study analysing thousands of pictures taken of the seafloor found that once delicate habitats such as coral reefs had been destroyed by chronic trawling, they did not recover.

A long-running study in the UK's waters does however provide some hope; when a previously overtrawled area was protected from fishing activities within a larger area ( a 'marine protected area', or MPA), ecosystems bounced back.

Underwater ecosystems are also affected from different angles by pollution. On a contaminant level, industrial, mining or agricultural runoffs can affect both the quality of the water by reducing oxygen and increasing nutrient density (eutrophication), and can cause bioaccumulation of heavy metals and and other chemicals inside marine life, particularly affecting sharks because of their longer lifespans and tendency to be higher on the food chain. A 2021 paper in Nature found that sharks in the Bahamas, although locally protected in a relatively pristine environment, contained toxic levels of heavy metals, which had accumulated up the food chain. Plastic is also an emerging threat, and its effects on sharks are just beginning to be studied. In a 2022 study, 80% of small-spotted catsharks in Sicily were found to have ingested plastic, but the resulting health effects were not obvious, and further study was recommended.

Climate change, which was identified in the report as a significant emerging threat to sharks, is also a direct threat to their habitats; an obvious example being the intensifying bleaching and dying of coral reefs. A 2024 Nature article found that global coral bleaching events are increasingly frequent and severe; the Great Barrier Reef has experienced 5 in the last 8 years.

Another ill effect of climate change is to push sharks into less-safe areas. As waters warm, sharks, who are particularly sensitive to temperature, are pushed into cooler and more oxygenated areas, increasing their potential for conflict with human activity. A 2024 paper modelling climate scenarios found that whale sharks are projected to experience far more lethal ship strikes as they move away from warming waters.

‘Cautious’ optimism

For some species, it may be "too late", as Dr Lea explains; numbers have dropped beyond the threshold to be able to repopulate, or crucial habitats have disappeared. Yet he describes himself as "cautiously optimistic". The report paints a grim picture for sharks, but it also offers solutions: The first is to encourage better fisheries management, with an emphasis on working at the grassroots level. The second is to mitigate bycatch through changes in fishing gear and practices. The third is to enforce the boundaries of existing marine protected areas, and adding to them. Finally, it is to make sure that the legal processes already in place are adhered to and expanded upon. These are all complex tasks and require layers of expertise, coordination, and cooperation. Yet in spite of the clearly difficult task ahead, "cautiously optimistic" seems to be the consensus amongst the scientists interviewed.

One reason for this is the relatively recent proliferation of technology and interest in the last few years. As Sarah Fowler(OBE), a veteran shark scientist describes, when she was commissioned in 1990 to contribute to the first global chondrichthyan status report in the 90’s, shark conservation “barely existed”. That first report had a few dozen contributors and covered tens of regions; in her words “sketchy” compared to 2024’s hefty tome, which covers 158 countries, and has over 350 contributors.

Over the course of the last twenty years, scientists have gone from only being able to track a shark manually to having access to a far more sophisticated array of global tracking and monitoring methods, as well as huge advances in genetic identification. There are also more scientists themselves, with far more diverse backgrounds than the territorial "old white men" Dr Lea describes as dominating the field until recently. A combination of these factors has led to a large volume of high quality research in a short amount of time.

This research has had real-life impacts. Fowler talks about the heartening developments in protections for sharks that have happened in recent years, highlighting the global trade regulations introduced in 2022 for over 130 shark species. Previously only 3 shark species had these types of protections. The increase of the introduction of marine protected areas (MPAs) in recent years is another reason to feel hopeful. 

Scientists also talk about gaining hope from a shift in approach. Traditionally, scientists have been thought of as detached observers who stick to their narrow field of study. The work of conservation requires good science, but is increasingly recognised by scientists in the field as unlikely to succeed without so-called ‘softer’ skills like collaboration and communication between different kinds of scientists and other affected parties.

Dr Isla Hodgson, a scientist who specialises in human-wildlife conflict, emphasises the importance of social dimensions in conservation and speaks about feeling hopeful after becoming aware of "the sheer volume" of people working on a problem “from the angle of the seas have to work for everybody”. In the same vein, Loyiso Dunga, who works specifically with coastal communities to implement grassroots solutions, explains that “every ecosystem is different, and [so are] the dynamics around it. Examples that actually do work in conservation are the ones that are relevant to the people living there…those are the people who have the most vested interest in protecting them.”

The cause of chondrichthyan survival has gathered much momentum; enough data has been gathered, policies put in place, and dedicated scientists involved to be cause for optimism. But in Dr de Vos’ words;  “we've got to hope that it all happens at once; everyone gets a good system and just keeps working together…I don't think we have another 20 years left”.

*note: this is a mock-up for a student project, all photographs belong to the stated sources . I have blurred the watermarks to be less distracting, the credited source owns the rights.