National Shark Research Consortium
Florida Program for Shark Research - Florida Museum of Natural History
Shark Basics
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How many species of sharks are there?
Currently there are approximately 375 described species of sharks, however new species are being described all the time. In addition, there are around 400 species of rays, a close relative of sharks. For detailed information on individual species, check out our bioprofiles!
Shark diversity!
© Photographers at FLMNH
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How long have sharks existed?
Fossil records indicate that ancestors of modern sharks swam the seas over 400 million years ago, making them older than dinosaurs! They are considered to be the first vertebrate with a complete jaw. Throughout time sharks have changed very little.
What is an "elasmobranch"?
Elasmobranchs are a closely related group of fishes, differing from bony fishes by having cartilaginous skeletons and five or more gill slits on each side of the head. In contrast, bony fishes have bony skeletons and a single gill cover. Elasmobranchs include sharks, rays, and skates.
Do sharks have bones?
No, sharks and all other fishes belonging to the class Chondrichthyes lack true bone, but rather have cartilaginous skeletons.
How long do sharks live?
While longevity data are not available for many sharks, maximum ages do vary by species. Some sharks like the smooth dogfish (Mustelus canis) may only live 16 years, while others such as the porbeagle shark, (Lamna nasus) may live as long as 46 years. Whale sharks (Rhincodon typus) the largest fish in the world may live over 100 years.
What does a shark's skin feel like?
Shark skin feels exactly like sandpaper because it is made up of tiny teeth-like structures called placoid scales, also known as dermal denticles. These scales point towards the tail and helps to reduce friction from surrounding water when the shark swims. Because of this, if someone rubbed the skin from the head towards the tail, it would feel very smooth. In the opposite direction it feels very rough like sandpaper. As the shark grows, the placoid scales do not increase in size, but rather the shark grows more scales. The silky shark (Carcharhinus falciformis) has small scales giving it a "silky" feel to the touch.
Do sharks sleep?
It was once believed that all sharks had to swim constantly in order to breathe and could not sleep for more than a few minutes at a time. Oxygen-rich water flows through the gills during movement allowing the shark to breathe. While some species of sharks do need to swim constantly, this is not true for all sharks. Some sharks such as the nurse shark have spiracles that force water across their gills allowing for stationary rest. Sharks do not sleep like humans do, but instead have active and restful periods.
Can sharks hear?
Sharks have an excellent sense of hearing with ears located inside their heads on both sides rather than external ears like humans. Sharks can hear best at frequencies below 1,000 Hertz which is the range of most natural aquatic sounds. This sense of hearing helps shark locate potential prey swimming and splashing in the water. Sharks also use their lateral line system to pick up vibrations and sounds.
Why do sharks have so many teeth?
Finetooth shark
© George Burgess
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Sharks have lots of teeth arranged in layers so if any break off, new sharp teeth can immediately take their place. Sharks can shed thousands of teeth during their life, this is why sharks teeth can be found washed onto beaches. Shark teeth also fossilize easily while the rest of the shark decomposes.
Is shark meat found in supermarkets safe for human consumption?
Although shark flesh contains high levels of urea and methylamine, any residual toxins that are not washed away when the carcass is cleaned will quickly dissipate when cooked. However, sharks may contain high concentrations of heavy metals, primarily in larger, older individuals. Shark meat is low fat and provides a good source of protein for people living in many parts of the world.
What is the fastest shark?
The shortfin mako is the fastest shark
©Jeremy Stafford-Deitsch
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The fastest shark is the shortfin mako (Isurus oxyrinchus). It has been recorded to reach swimming speeds of up to 20 mph (32 km/h). It can chase down some of the fastest fishes such as tuna and swordfish.
What is the largest shark? What is the smallest shark?
Whale shark: largest fish in the ocean
©Jeremy Stafford-Deitsch
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The largest shark, and also the largest fish in the ocean is the whale shark (Rhincodon typus). This massive plankton-feeder reaches lengths of over 20m (60 feet).
Etmopterus perryi
©Wendy Zomlefer
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The smallest shark is a deepwater dogfish shark known as Etmopterus perryi. This species which is found in the Caribbean Sea is mature at under 20cm (~8 inches).
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