Basking shark

569px-Cetorhinus_maximus_by_greg_skomal

Profile

Basking sharks are large sharks living mostly in temperate waters around the world. It is easy to recognize this shark in most pictures taken, as it usually has its mouth open wide as shown above. When their mouth is closed, though, they have the normal shape a shark would have. As with many sharks, basking sharks are a grayish-brown color on most of their body, but their underside is sometimes a lighter shade. There have been two recorded sightings of albino basking sharks, both in the North Atlantic. These sharks are very peaceful, being filter feeders and not hunters. Still, they have extremely rough skin, and when moving fast, this can hurt humans. These sharks are also called elephant sharks and bone sharks. The last one is probably due to the bone-like structures visible inside the shark’s mouth when it is open.

Size

Basking sharks are some of the largest fish in the world, second only to the whale shark. There is much controversy over how large these creatures can actually get. Some say they can reach 33 feet (10 m) long, but their average is thought to be 23 to 30 feet (7-9 m). There are even unconfirmed reports of these animals reaching 45 feet (13.7 m) in length. These may be bad estimates, people mistaking another animal for the basking shark, or there may actually be basking sharks this big. Basking sharks also have big mouths. No, they do not talk a lot. When fully open, these sharks’ mouths can be up to 3.3 feet ( 1 m) across!

Obviously an animal this large must also weigh a lot. The heaviest one recorded weighed 8,600 pounds (3,900 kg.). This is more than twice as much as a minivan weighs! About one quarter of their weight is their liver, which helps keep the shark buoyant while swimming.

Diet

These sharks are similar to whale sharks in another way besides their size. Both of these animals are filter feeders, eating plankton. They spend much of their time with their mouth open, filtering ocean water through their gill rakers. The white stripes inside the basking shark’s mouth are the gill rakers. When this happens, the plankton are kept as the sea water passes through. Because they have such a large mouth, basking sharks are able to filter a lot of water. They can filter about 53,000 cubic feet (1,500 cu. m) every hour. This is about the volume of nine tractor trailers!

Habitat and range

Basking sharks live in cool and temperate waters all around the world. Their range touches every continent except Antarctica. As you can see in the range map below, these sharks do not live in tropical areas near the equator, but they do live in warm areas further from the equator. They do inhabit waters in areas sometimes considered tropical, such as Australia, the Philippines, and Florida, but these are not on the equator. You can also see that basking sharks live in waters as far north as Scandinavia and as far south as the southern tip of South America. It does get cold in these places, but not nearly as cold as in others.

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During the spring and summer, these sharks spend their time closer to shore, but in the winter they migrate into deeper areas. There is evidence to support the idea that basking sharks actually hibernate in deep waters in the winter. They are not seen as much, if at all, in the winter, and they also lose their gill rakers in the winter.

Status and threats

The IUCN Red list has classified the basking shark as Vulnerable. These sharks used to be hunted for their liver oil, which was used for traditional Japanese medicine, oil for lamps, and for the manufacturing of cosmetics. While habitat loss is not a large threat to these sharks, overfishing is. The biggest threat to their existence right now is overfishing for use in shark fin soup. Although it is very hard to count how many basking sharks there are, they have undergone a population decrease of an estimated 80% in the last 60 years.

Reproduction

Basking sharks are extremely slow to reproduce. After mating, it can take up to three years for the female to give birth to her live young. Usually 4-5 baby sharks, called pups, are born at a time. At birth, these pups are at least 5.5 feet (1.7 m) long.

Not only do these sharks have a long gestation period, they also take a long time to mature. Males are not ready to mate until they are at least 12 years old, but this can be up to 16 years. Females wait until they are 18 years old to mate. These sharks are rather long lived. They have been known to live up to 100 years, though the majority of them do not live this long.

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Sources:

Photo credits:

  • Basking shark – Public Domain
  • Basking shark range – Maplab
  • Mystery animal  – Steven G. Johnson
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