Which sharks are the most endangered?Science Communicator, PhD Conservation Science
Sharks and their relatives (the skates, rays and chimaeras) have roamed the oceans for millennia. The evolutionary history of sharks stretches back for a staggering 440 million years, pre-dating the dinosaurs by about 200 million years and our own species by a great deal longer. Sharks have even survived five mass extinctions, including the ‘Great Dying’, an event that killed 90–96% of all species on earth. And yet in the present day we are seeing an unprecedented decline in shark populations. In just the past 50 years – a miniscule fraction of their immense existence – the global abundance of oceanic sharks and rays has plummeted by 71.1%. The number of sharks classified as endangered on the IUCN Red List of Threatened Species is climbing every year as new data shed light on their future. And the fact is, sharks are heading towards extinction. Fast.
How many sharks are endangered?
The most recent global assessment of the Class Chondrichthyes – otherwise known as the cartilaginous fishes, the group of animals to which sharks belong – showed that more than one-third of sharks, rays and chimaeras are threatened with extinction. Of the 1,199 species assessed, 121 are classed as Endangered, 90 as Critically Endangered and 180 as Vulnerable, according to criteria established by the International Union for the Conservation of Nature (IUCN). Looking at sharks specifically, 31.2% of all species assessed are threatened with extinction. And given the rate at which some species are declining, scientists expect that figure to grow in the coming years.
Why are sharks endangered?
So, why is it that so many sharks are now threatened with extinction, after being so successful for so long? The simple answer is, us. Sharks have been around long before humans entered the scene – in fact, they have almost 439,700,000 years on us – but our impact on them has been colossal, even in such a short time.
The biggest threat to sharks is overfishing. Overfishing occurs when fish are taken at a rate faster than they can reproduce, which means that their populations begin to fall. Sharks are particularly vulnerable to overfishing as they typically reproduce more slowly than other types of fish. Although there is huge variation between species, sharks are generally slow to reach sexual maturity, reproduce less often and tend to have relatively small numbers of young. This means that their populations can be driven down relatively easily if fisheries are not managed and operate unsustainably, which unfortunately happens in many instances.
Shark fisheries exist around the globe. Many species are caught for their meat, liver oil, fins and skin. As technology has advanced, fisheries have become bigger and more efficient, allowing for more sharks to be caught with less effort. For decades, many shark species have been fished at unsustainable levels and overfishing is now considered the primary cause of global shark declines. The international fin trade has helped drive overfishing; fins are one of the most valuable shark products on the market, providing an incentive to catch unsustainable numbers of sharks and even engage in illegal activity. Very recent science has shown that nine out of the 10 most common sharks found in the dried fin trade in Hong Kong are listed as threatened species.
An additional problem is bycatch; even when sharks are not directly targeted by fisheries, they may be accidentally captured by methods designed for other species. For example, longlining is a method where a great length of fishing line has baited hooks attached to it at intervals. An industrial longline, used to catch species like tuna, swordfish, halibut and cod, can be miles long and have up to 2,500 hooks. Sharks may still be attracted to the bait, even if they are not the intended target of the fishery.
Aside from fishing pressure, sharks are threatened by habitat degradation, persecution (as a result of fear and negative interactions with humans), harmful marine pollutants (including microplastics, agricultural run-off, fishing debris and man-made chemicals) and the effects of climate .
What does being endangered mean?
According to the Cambridge Dictionary, the term ‘endangered’ means in danger of being harmed or lost. When we use this word in relation to a wild species, we mean that the species may soon no longer exist because there are so few of its members alive – in other words, it is in danger of being lost from the planet forever. When we talk about endangered species of shark, we are referring to those which are at risk of going extinct.
What is the IUCN Red List?
The IUCN Red List of Threatened Species is the most thorough and complete information source on the conservation status of plants, fungi and animals in the world. Species are assessed by experts using the IUCN Red List Categories and Criteria to determine if they are at risk of extinction, and if so to what extent they are at risk. The Red List does not designate conservation actions, but the information can be used to inform and help prioritise conservation measures.
What are the IUCN Red List categories?
There are nine Red List categories in total and each one relates to the conservation status of a species – put simply, how close to extinction it is. If exhaustive surveys have failed to find a single individual of a species in the wild, then it is categorised as either Extinct (EX), or Extinct in the Wild (EW) if some individuals are alive in captivity. If individuals still exist in the wild, then the species is assessed against the five Red List criteria, which relate to the size of the population, whether the population is increasing or decreasing (and by how much) and its geographical range. A species has to meet certain thresholds within the criteria to be placed in one of the three threatened categories. For example, to be categorised as Critically Endangered (CR), the highest level of risk before becoming extinct, the population has to have declined by 80–90% in a specific timeframe, have a very restricted geographic range and/or have less than 250 mature individuals left in the wild.
The three threatened categories are (in order of highest to lowest risk):
- Critically Endangered (CR)
- Endangered (EN)
- Vulnerable (VU)
If a species does not qualify for any of these categories, it falls into two others. If it is close to qualifying in the near future, then it is placed in Near Threatened (NT). Or if it is considered to be at low risk of going extinct, it is classified as Least Concern (LC). Finally, if there isn’t enough data to make a complete assessment, then the species is said to be Data Deficient (DD). Or if it simply hasn’t been assessed yet, it is regarded as Not Evaluated (NE).
Who decided if a shark is endangered?
For sharks, rays, skates and chimaeras, the IUCN Species Survival Commission (SSC) Shark Specialist Group (SSG) is responsible for all Red List assessments. All assessments are reviewed by the Red List Authorities (RLA) and checked by the Red List Unit (RLU) before they are published.
Which species of shark are endangered?
According to recent science, more than one-third of chondrichthyans – the sharks, rays, skates and chimaeras – are threatened with extinction. And some of the species that fall into that category may surprise you. Great white sharks are considered Vulnerable (VU), threatened by non-target fisheries and persecution. Everyone’s favourite gentle giant, the whale shark, is classified as Endangered (EN) despite the closure of some commercial fisheries in the 1990s and early 2000s. It is still commonly caught in some regions and in other areas is at risk from boat collisions, which can cause serious injury. Even species that aren’t yet in a threatened category are hurtling towards endangered status. For example, the blue shark is the most common species encountered in the international fin trade. Demand for its fins has placed it firmly in the Near Threatened (NT) category, which means that without conservation action, it is expected to be at risk of extinction in the near future.
In total, 167 species of shark and 220 species of ray are threatened with extinction – to write about them all here would make for an extremely long article! But you can find them all on the Red List website.
10 of the most endangered shark species
It’s difficult to say which species of shark are the most endangered, and there are certainly more endangered species than the 10 on this list. But all the species here are classified as Critically Endangered (CR) on the Red List – meaning they are considered most at risk of extinction – for various reasons. Some might be familiar to you, and some you may never have heard of because they are so incredibly rare.
- Pondicherry shark Carcharhinus hemiodon (CR, possibly extinct)
An extremely rare species of requiem shark, the pondicherry was last seen in India in 1979 and is now only known from about 20 museum specimens. It is thought to be fairly small, reaching a maximum length of 102 centimetres (3 feet 4 inches), and has a long, pointed snout. Identifying this species is pretty tricky, given its potentially wide range throughout the Indo-Pacific and close similarities to other species.
- Lost shark Carcharhinus obsoletus (CR, possibly extinct)
As the name suggests, the lost shark hasn’t been seen for some time – in fact, the last known record of this species was from 1934! Very little is known about this small, slender whaler shark, except that it was found in the South China Sea and most likely declined due to heavy fishing pressure.
- Ganges shark Glyphis gangeticus (CR)
The Ganges shark is quite an unusual species in that it relies on tropical river and estuarine habitats. Unfortunately, this has made it susceptible to fishing pressure and the modification and degradation of its habitat, and experts now believe it to be locally extinct in Pakistan, Myanmar and Borneo, with continued declines in other parts of its range in the Indo-West Pacific. Only two other known species of river shark exist and both are also endangered.
- Daggernose shark Isogomphodon oxyrhynchus (CR)
With its unmistakable flat, extremely long snout and spike-like teeth, the daggernose is pretty easy to spot. However, sightings in the wild are a now a rarity. It is declining steeply due to intense and unmanaged fishing throughout its West Atlantic range, in addition to its slow reproductive cycle. The last recent sighting was of a neonate in 2016.
- Sandtiger shark Carcharias taurus (CR)
The sandtiger is a large shark (maximum length 325 centimetres; 10 feet 8 inches) found in tropical and warm temperate seas. It has one of the lowest reproductive rates of all shark species: two pups are born every other year, and adults only reach sexual maturity at 6–7 years (males) and 9–10 years (females). This makes it extremely vulnerable to exploitation.
- Oceanic whitetip Carcharhinus longimanus (CR)
The oceanic whitetip’s inquisitive nature and preference for surface waters make it particularly susceptible to fishing pressure. The global population is estimated to have undergone a dramatic decline of 98% over the past 60 years.
- Scalloped hammerhead Sphyrna lewini (CR)
We all know and love hammerheads, but did you know that they are at an extremely high risk of extinction? The large coastal and semi-pelagic scalloped hammerhead is estimated to have experienced a steep decline of 77–97%. Targeted for its meat and fins, it is also caught as bycatch by non-target fisheries.
- Short-tail nurse-shark Pseudoginglymostoma brevicaudatum (CR)
As well as having a tongue-twister of a Latin name, this bottom-dweller has a penchant for the coral reefs of Kenya, Tanzania and Madagascar. But as coral reefs are threatened, so is the short-tail. Destruction and loss of its reef habitat, as well as the fact that it has little to no refuge from fishing, have contributed to a steep decline in this species.
- Great hammerhead Sphyrna mokarran (CR)
The second hammerhead species on our list, the great hammerhead, has experienced a decline of more than 80% throughout its range. It is caught by both target and non-target fisheries and is retained for its fins.
- Angelsharks: Family Squatinidae
The final place on our ‘most threatened’ list goes to not one, but 23 species of shark. Angelsharks are the third most threatened family of elasmobranchs in the world, with more than half considered threatened with extinction. Their flattened body makes them look more like rays, but they are classed as sharks due to the placement of their pectoral fins and gills. Angelsharks are extremely vulnerable to overfishing; they are very slow to reproduce and tend to not travel very far, making only localised movements. Some species were so intensively fished that they were once called ‘white tuna’.
Guitarfish and Wedgefish
In this article we’ve focused mainly on sharks, but it’s also worth mentioning their relatives, the rays. The most recent global assessment of Chondrichthyans found rays to be more threatened than previously estimated, with 36% of all species heading for extinction. Shark-like rays in particular are in the danger zone. These are rays that have a body that looks like a shark’s, but a flattened head and gills located on the underside of the body. They include the sawfish, which are large, shark-like rays with a distinctive toothed rostrum. They are considered highly valuable and have been extensively fished for their fins and sought-after rostra, which are sold as curios. All species of sawfish are now listed as Endangered or Critically Endangered on the IUCN Red List. Among the shark-like rays are also the giant guitarfish and the wedgefish (collectively known as the ‘rhino rays’), which have been declared the world’s most threatened marine fish by the IUCN Shark Specialist Group. All but one of the 16 species are listed as Critically Endangered, primarily due to overfishing for their meat and fins.
What is being done to help save endangered sharks?
Given that overfishing is the dominant issue impacting sharks globally, it makes sense to start there. But it’s not as easy as simply banning shark fisheries. Many people – including those in developing nations – rely on sharks as a source of food and income. Decisions to curb this problem will have to take place on an international scale and be translated into national, regional and local action, while taking into account the needs of communities. It’s a hugely complex and difficult matter to tackle. But some steps have been made in the right direction, including:
- The addition of more sharks and rays to CITES: The Convention on International Trade in Endangered Species of Wild Fauna and Flora, or CITES, is an agreement between governments that aims to ensure that trade in animals and plants does not threaten their survival. If a species is listed on CITES, trade in that species is subject to certain controls and regulations. The past two decades have seen increasing numbers of sharks and rays added to CITES, including Critically Endangered guitarfish and wedgefish and Endangered longfin and shortfin mako sharks, following news of their rapid decline due to intensive fishing pressure. In November 2022, a landmark vote for sharks and rays occurred at CITES COP19, the conference where member states review and decide on proposals to list new species on CITES. Four proposals were being reviewed: to add all 56 species of unlisted requiem sharks, five species of small hammerhead, six additional unlisted species of guitarfish and two species of freshwater stingray. An overwhelming majority voted to pass all four, a historic moment for shark conservation that will see more than 100 species of shark and ray now afforded protection in international trade. It will also bring approximately 90% of the fin trade under regulation. Although the enforcement and implementation of any measures is another story, it is a sign that the plight of sharks and rays is receiving global political recognition.
- More sharks and rays added to the CMS: Like CITES, the Convention on Migratory Species (CMS) is an international agreement. The CMS aims to coordinate conservation measures for species that cross national borders and has a Memorandum of Understanding (MOU) for sharks under which all participating governments have committed to the conservation of certain migratory shark and ray species. Thirty seven species of sharks and rays are included on Annex I of the MOU, which recognises species that need coordinated action to safeguard their populations. This includes the Critically Endangered oceanic whitetip, which was added in 2020.
- More research and scientific advances: We are finding out more about sharks every day: what areas are most important for them, where threats overlap these sites, their life histories… All this information is hugely important when designing marine policy or fisheries management strategies. Scientists around the globe are working tirelessly to help inform shark conservation, while advances in methodology and technology are enabling us to investigate them in more depth than ever .
- Consideration of sharks and rays in Marine Protected Area (MPA) designations: MPAs can be useful tools to help conserve sharks and rays, but first we need to establish sites that are critical for the survival and well-being of sharks. These include feeding and breeding grounds, nursery areas and last refuges for Critically Endangered species. Until recently, this information had been limited to academic circles, or at least had not been looked at on a global scale. The Important Shark and Ray Areas (ISRAs) initiative is developing a spatial tool that will assist decision-makers and managers by highlighting areas around the world that should be prioritised for shark conservation and advising what measures to take. This information could be used in future MPA designations to ensure sharks are not overlooked and it will also bring migratory species into the conversation (typically, migratory species are often neglected as they do not stay in one place and are therefore difficult to conserve on a broad scale). Another initiative is the Shark and Ray Recovery Initiative (SARRI), which focuses on securing ‘shark recovery zones’ to protect critical habitat for some of the most endangered species found in the developing world. It is currently working to recover eight focal species: zebra sharks, scalloped hammerhead sharks, pelagic thresher sharks, sawfish, wedgefish, giant guitarfish and eagle rays.
While these are very important steps, so much more needs to be done to bring species back from the brink and safeguard all shark populations. This includes tackling the fin trade, putting a stop to Illegal, Unreported and Unregulated (IUU) fishing practices, stronger enforcement of existing fisheries regulations and establishing catch limits for commercially fished shark species.