Basking Shark

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Basking Shark

Basking sharks are found in the coastal waters in the northern and southern areas of the Atlantic and Pacific Oceans. Their diet mainly consists of plankton, which they capture with bristle structures known as gill rakers. The average lifespan of this species is not known.


Content List

1. Scientific & Common Names

2. Characteristics

a. Breeding

b. Behavior

3. History

4. Present Status

5. References


Scientific & Common Names

Kingdom - Animalia

Phylum - Chordata

Class - Chondrichtyes

Subclass - Elasmobranchii

Superorder - Selachimorphia

Order - Lamniformes

Family - Cetorhinidae

Genus - Cetorhinus

Species - C. maximus

Common Names - Basking Shark, Bone Shark, Elephant Shark, Sunfish (not to be confused with the Ocean Sunfish)


Characteristics

Basking sharks have grayish-brown backs and sides and pale undersides. They have large distinctive gill slits that go almost all the way around their heads, as well as cone-shaped snouts. Their mouths contain several gill rakers that help them filter food. This species is the second largest fish species in the world. Adults measure between 22 and 29 feet long and weigh an average of 4 tons. It is thought that some examples may reach up to 36 feet long or more.


Breeding

The breeding season for basking sharks is not known. Females undergo a gestation period that lasts for three or more years before giving birth to live offspring that hatch from eggs that develop in the womb. The offspring range from 4 to 6.5 feet in length and have a longer snout at birth. The snout gradually changes length throughout the young sharks’ first year.


Behavior

Basking sharks are named for their tendency to bask near the surface of the water with their dorsal fin sticking up in the air. They stay close to the surface with their mouth open in order to catch plankton and will sometimes leave the ocean’s open waters and swim in bays. Basking sharks typically migrate to warmer waters during winter and travel in large groups or in pairs. They also lose their gill rakers from time to time, which has led to theories that they either feed on bottom-dwelling creatures or hibernate during winter until they grow new ones.


History

Basking sharks still occur throughout their historical range, but some populations have undergone steep declines due to fishing. Between the 1950s and 1993, the total number of basking sharks decreased by 80 percent. Basking sharks were hunted for their oil, which was used to light lamps until the advent of petroleum. It was also hunted for its meat and its hide which was used in leather. Currently, it is sought for its fins which are used to make shark fin soup, and other parts which are used in traditional medicine in some cultures. Many countries have protected the basking shark and banned sale of products made from the animal in an effort to aid in increasing its population.


Basking sharks were originally placed in the family Lamnidate (mackerel sharks) with the great white and mako, and some scientists still favor this grouping. Most, however, recognize the separate family of Cetorhinidae.


Present Status

The basking shark is listed as vulnerable, although local populations in the northeastern Atlantic and northern Pacific Oceans are considered endangered. Their numbers have declined due to a combination of overfishing and a slow population recovery rate. The species is protected by legislation in several countries, including the United Kingdom, the United States and New Zealand.


References

   http://animaldiversity.ummz.umich.edu/accounts/Cetorhinus_maximus/
   http://www.flmnh.ufl.edu/natsci/ichthyology/gallery/Descript/baskingshark/baskingshark.html
   http://www.iucnredlist.org/details/full/4292/0
   The Sharks of North America, 2011, Jose I. Castro