Are Sharks Fish Or Mammals

Sharks 101

Sharks can rouse fear and awe similar no other animal in the sea. Find out about the globe'due south biggest and fastest sharks, how sharks reproduce, and how some species are at take chances of extinction.

Mutual Proper name :: Sharks
Blazon :: Fish
Size :: 7 inches to 32.8 feet
Weight :: <1 ounce to 20.6 tons

Sharks star in blockbuster movies as claret-seeking villains, but in reality they're far more fascinating and complicated than they're often depicted in pop culture.

Based on fossilized teeth and scales, scientists believe that sharks take been effectually for more than 400 meg years—long before the dinosaurs. The ocean's peak predators have evolved into roughly 500 species that come in all different sizes and colors and take varying diets and behavior.

Anatomy

Like rays and skates, sharks autumn into a subclass of fish called elasmobranchii. Species in this subclass have skeletons made from cartilage, not bone, and have five to 7 gill slits on each side of their heads (well-nigh other fish accept only one gill slit on each side), which they use to filter oxygen from the h2o.

Whale sharks, the largest fish species on Earth, can grow to more than 55 feet, while dwarf lantern sharks accomplish a mere eight inches.

Formidable predators, sharks take mouths lined with multiple rows of individual teeth that fall out and abound dorsum on a routine basis. Their teeth come up in all sizes and shapes, from serrated like a razor to triangular like a spear.

Behavior

Sharks are found in deep and shallow waters throughout the world's oceans, with some migrating vast distances to breed and feed. Some species are solitary, while others hang out in groups to varying degrees. Lemon sharks, for example, accept been found to besiege in groups to socialize.

Scientists are still trying to figure out how long sharks live and have only studied the ages of a fraction of shark species. Most notable is the Greenland shark, Earth's longest-lived vertebrate at 272 years.

Most sharks consume smaller fish and invertebrates, only some of the larger species prey on seals, sea lions, and other marine mammals.

Attacks

People aren't on a shark'south card. Even though shark attacks have increased at a steady rate since 1900—a result of improve recording of attacks and a rising human population—they are still exceedingly rare: A beachgoer has only a ane in 11.five one thousand thousand chance of being bitten.

Sharks bite people out of curiosity, to defend themselves from a perceived threat, or because they misfile a homo with casualty.

Threats

Sharks may not be a significant threat to united states of america, but nosotros are to them. Humans are responsible for drastic declines in shark populations.

Overfishing is the biggest threat. An estimated 100 meg sharks are killed each year, mostly to supply demand for an expensive Chinese dish called shark fin soup. Some fisheries allow the grab of whole sharks, like whatever other fish, while others accept outright banned shark line-fishing. Sometimes fishermen cutting the fins off live sharks and dump the animals, finless, back into the sea, where they'll drown or drain out. This do is called shark finning, and it'due south done to salve infinite on the boat (the fins are the most valuable office of a shark) and to avoid surpassing line-fishing quotas.

Rising h2o temperatures and coastal development are also contributing to shrinking populations by destroying the mangroves and coral reefs that sharks use for convenance, hunting, and protecting immature shark pups.

A drop in numbers is bad news for sharks but as well for ocean health in general: Equally top predators of the body of water, sharks are critical for ensuring a balanced food web.

Spotter more than shark videos from National Geographic here.