How Many Species of Shark Are There? Shark Diversity

How many shark species are known?

The number of shark species keeps rising. A detailed checklist published in 2016 by German ichthyologist Simon Weigmann listed 509 species of living sharks, in 105 genera, 34 families and nine orders. When researchers assessed every cartilaginous fish for the IUCN Red List in a study published in 2021, they included 536 sharks.

Most of the increase comes from new discoveries in the deep sea and from genetic studies showing that what looked like one species is really two or more. In 2015, for example, scientists described the ninja lanternshark from deep water off the Pacific coast of Central America, a small, dark shark whose scientific name, Etmopterus benchleyi, honors Jaws author Peter Benchley. Because many deep-water areas remain barely explored, the total will almost certainly grow.

Sharks are only part of a larger group. Together with about 610 species of rays and skates and about 50 chimaeras, they make up the cartilaginous fish, about 1,200 species in all. Rays are close relatives of sharks with flattened bodies and gill slits on their underside, as explained in Are stingrays related to sharks?

The main groups of sharks

Scientists sort sharks into eight or nine orders. The bramble and prickly sharks are sometimes placed in an order of their own, which makes nine.

The ground sharks are by far the largest order and include most of the sharks people see along warm coasts, such as the bull shark, tiger shark and the hammerheads, including the great hammerhead. The mackerel sharks are a small order but contain many of the best-known giants, among them the great white shark.

From tiny lanternsharks to whale sharks

Sharks vary enormously in size and lifestyle. The smallest known species, the dwarf lanternshark, lives at depths of about 280–440 m (920–1,440 ft) off Colombia and Venezuela and reaches only about 20 cm (8 in). Like other lanternsharks, it has light-producing organs that help it blend in with faint light from above.

At the other extreme, the whale shark is the largest fish in the world, commonly 8–12 m (26–39 ft) long, and feeds on plankton and small fish. The basking shark, another plankton feeder, regularly reaches 7–8.5 m (23–28 ft). Between them lies a huge range of forms: flat angel sharks that bury themselves in sand, wobbegongs disguised as weedy rocks, hammerheads with wide, flattened heads, threshers with tails as long as their bodies, and the slow Greenland shark of Arctic waters.

Many ways of life

Shark species differ just as much in how they feed. Only three, the whale shark, the basking shark and the deep-water megamouth shark, are filter feeders that strain plankton from the water. Angel sharks and wobbegongs lie hidden on the seabed and ambush passing fish, thresher sharks stun schooling fish with their long tails, and sawsharks slash at prey with their toothed snouts. The small cookiecutter shark bites neat round plugs of flesh out of much larger fish and dolphins. The bonnethead, a small relative of the hammerheads, eats large amounts of seagrass along with crabs and shrimp, making it the only shark known to be an omnivore.

Where do sharks live?

Sharks live in every ocean, from tropical coral reefs to polar seas. Many species, especially dogfish and lanternsharks, live on deep continental slopes, and sharks are common down to about 2,000 m (6,600 ft). The deepest confirmed shark record is a Portuguese dogfish at about 3,700 m (12,100 ft).

Only a few sharks enter fresh water. The bull shark can travel far up rivers, and a handful of rare river sharks of the genus Glyphis live in rivers and estuaries of southern Asia and northern Australia.

How many shark species are threatened?

Many shark species are in trouble. The 2021 global assessment found that about 36% of shark species are threatened with extinction, compared with about 41% of rays and 9% of chimaeras. Overfishing, both targeted and as accidental bycatch, is the main threat to every threatened species, and the problem is worst for large species in tropical coastal waters.

A separate 2021 study estimated that numbers of oceanic sharks and rays have fallen by about 71% since 1970. Sharks grow slowly, mature late and have few young, so populations recover slowly once they decline. The scale of fishing is covered in How many sharks are killed each year?