   #copyright

Whale shark

2007 Schools Wikipedia Selection. Related subjects: Insects, Reptiles and
Fish

                   iWhale shark
   Whale shark in the Georgia Aquarium.
   Whale shark in the Georgia Aquarium.

                             Conservation status

   Vulnerable (VU)
            Scientific classification

   Kingdom:  Animalia
   Phylum:   Chordata
   Class:    Chondrichthyes
   Subclass: Elasmobranchii
   Order:    Orectolobiformes
   Family:   Rhincodontidae
   Genus:    Rhincodon
             Smith, 1829
   Species:  R. typus

                                Binomial name

   Rhincodon typus
   ( Smith, 1828)
   Range of whale shark
   Range of whale shark

   The whale shark, Rhincodon typus, is a gentle and slow filter feeding
   shark that is the largest living fish species. This
   distinctively-marked shark is the only member of its genus Rhincodon
   and its family, Rhincodontidae (called Rhinodontes before 1984), which
   is grouped into the subclass Elasmobranchii in the class
   Chondrichthyes. The shark is found in tropical and warm oceans and
   lives in the open sea. The species is believed to have originated about
   60 million years ago.

Naming

   The species was first identified in April 1828 following the harpooning
   of a 4.6 m (15 ft) specimen in Table Bay, South Africa. It was
   described the following year by Andrew Smith, a military doctor
   associated with British troops stationed in Cape Town. He proceeded to
   publish a more detailed description of the species in 1849. The name
   "whale shark" comes from the fish's large size and eating habits; that
   is, a shark as large as a whale that shares a similar filter feeder
   eating mode.

Distribution and habitat

   The whale shark inhabits the world's tropical and warm-temperate
   oceans. While thought to be primarily pelagic, seasonal feeding
   aggregations of the sharks occur at several coastal sites such as
   Ningaloo Reef in Western Australia; Útila in Honduras; Donsol in the
   Philippines; and Pemba and Zanzibar off the coast of Tanzania. Its
   range is restricted to about ±30 ° latitude. It is found to a depth of
   700 m. The whale shark is solitary and rarely seen in groups unless
   feeding at locations with an abundance of food. Males range over longer
   distances than females (which appear to favour specific locations).

Anatomy and appearance

   A size comparison of a whale shark and a human.
   Enlarge
   A size comparison of a whale shark and a human.

   As a filter feeder it has a capacious mouth which can be up to 1.5 m
   (5 ft) wide and can contain up to 300 rows of tiny teeth. It has five
   large pairs of gills. Two small eyes are located towards the front of
   the shark's wide, flat head. The body is mostly grey with a white
   belly; three prominent ridges run along each side of the animal and the
   skin is marked with a 'checkerboard' of pale yellow spots and stripes.
   These spots are unique to each whale shark and because of this they can
   be used to identify each animal and hence make an accurate population
   count. Its skin can be up to 10 cm (about 4 in.) thick. The shark has
   two pairs each of dorsal fins and pectoral fins. A juvenile whale
   shark's tail has a larger upper fin than lower fin while the adult tail
   becomes semi-lunate (or crescent-shaped). The shark's spiracles are
   just behind the eyes.
   Whale shark in main tank at Osaka Aquarium.
   Enlarge
   Whale shark in main tank at Osaka Aquarium.

   The whale shark is not an efficient swimmer since the entire body is
   used for swimming, which is unusual for sharks and contributes to an
   average speed of only around 5 km/h. The largest specimen regarded as
   accurately recorded was caught on November 11, 1947, near the island of
   Baba, not far from Karachi, Pakistan. It was 12.65 m (41.5 ft) long,
   weighed more than 21.5 tons (47,300 lb), and had a girth of 7 m
   (23 ft). Stories exist of vastly larger specimens - Quoted lengths of
   18 m (59 ft) are not uncommon in the popular shark literature - but no
   scientific records exist to support their existence. In 1868 the Irish
   natural scientist E. Perceval Wright spent time in the Seychelles,
   during which he managed to obtain several small whale shark specimens,
   but claimed to have observed specimens in excess of 15 m (49 ft), and
   tells of reports of specimens surpassing 21 m (69 ft).

   In a 1925 publication, Hugh M. Smith describes a huge whale shark
   caught in a bamboo fish trap in Thailand in 1919. The shark was too
   heavy to pull ashore, but Smith estimated that the shark was at least
   17 m (55.7 ft) and weighed approximately 37 tonnes (81,500 lb), which
   have been exaggerated to an accurate measurement of 17.98 m and weight
   43 tonnes in recent years. There have even been claims of whale sharks
   of up to 23 m (75 ft). In 1934 a ship named the "Maurguani" came across
   a whale shark in the Southern Pacific ocean, rammed it, and the shark
   consequently became stuck on the prow of the ship, supposedly with
   4.6 m (15 ft) on one side and 12.2 m (40 ft) on the other. No reliable
   documentation exists of those claims and they remain little more than
   "fish-stories".

Diet

   A whale shark in the Maldives.
   Enlarge
   A whale shark in the Maldives.

   The whale shark is a filter feeder - one of only three known filter
   feeding shark species (along with the basking shark and the megamouth
   shark). It feeds on phytoplankton, macro- algae, plankton, krill and
   small nektonic life, such as small squid or vertebrates. The many rows
   of teeth play no role in feeding - instead the shark sucks in a
   mouthful of water, closes its mouth and expels the water through its
   gills. During the slight delay between closing the mouth and opening
   the gill flaps, plankton is trapped against the dermal denticles which
   line its gill plates and pharynx. This fine sieve-like apparatus, which
   is a unique modification of the gill rakers, prevents the passage of
   anything but fluid out through the gills (anything above 2 to 3 mm in
   diameter is trapped). Any material caught in the filter between the
   gill bars is swallowed. Whale sharks have been observed "coughing" and
   it is presumed that this is a method of clearing a build up of food
   particles in the gill rakers. The shark can circulate water at a rate
   up to 1.7 L/s (3.5 US pint/s). The whale shark is an active feeder and
   targets concentrations of plankton or fish by olfactory cues rather
   than simply 'vacuuming' constantly. Whale sharks congregate at reefs
   off the Belizean Caribbean coast, supplementing their ordinary diet by
   feeding on the roe of giant cubera snappers, which spawn in these
   waters between the full and quarter moons of May, June and July, .

   The whale shark does not need to swim forward when feeding; it is often
   observed in a vertical position, 'bobbing' up and down swallowing water
   and actively filtering it for food.

Behaviour towards divers

   This species, despite its enormous size, does not pose any significant
   danger to humans. Divers and snorkelers can swim with this giant fish
   without any risk apart from unintentionally being hit by the shark's
   large tail fin.

   The shark is often seen by divers in Thailand, the Maldives, the Red
   Sea, Western Australia ( Ningaloo Reef), Gladden Spit Marine Reserve in
   Belize, Sodwana Bay ( Greater St. Lucia Wetland Park) in South-Africa
   and at the Galapagos islands. They are regularly seen from December to
   May in the Philippines ( at Donsol). Lucky divers have also come across
   whale sharks in the Seychelles and in Puerto Rico. Between December and
   September, they are well known to swim along the bay of La Paz in the
   Mexican Baja California. Sometimes, they are accompanied by smaller
   fish.

Reproduction

   The reproductive habits of the whale shark are obscure. Based on the
   study of a single egg recovered off the coast of Mexico in 1956, it was
   believed to be oviparous, but the capture of a female in July 1996
   which was pregnant with 300 pups indicates that they are viviparous
   with ovoviviparous development. The eggs remain in the body and the
   females give birth to live young which are 40 to 60 cm long. It is
   believed that they reach sexual maturity at around 30 years and the
   life span has been estimated to be between 60 and 150 years.

Conservation status

   Two whale sharks in the Okinawa Churaumi Aquarium.
   Enlarge
   Two whale sharks in the Okinawa Churaumi Aquarium.

   The whale shark is targeted by artisanal and commercial fisheries in
   several areas where they seasonally aggregate. The population is
   unknown and the species is considered vulnerable by the IUCN. Whale
   sharks are known to frequent the waters off Donsol in the Sorsogon
   province of the Philippines.

Whale sharks in captivity

   A whale shark is featured as the main attraction of Osaka Aquarium
   Kaiyukan and as of 2005, three whale sharks are being studied in
   captivity at the Okinawa Churaumi Aquarium in Japan. Four whale sharks,
   two males, Ralph and Norton, and two females, Alice and Trixie, are
   held in the Georgia Aquarium, in Atlanta. The two females were added on
   June 3, 2006 in hopes that reproduction in whale sharks could be
   studied in captivity. All four whale sharks were imported from Taiwan.

   Retrieved from " http://en.wikipedia.org/wiki/Whale_shark"
   This reference article is mainly selected from the English Wikipedia
   with only minor checks and changes (see www.wikipedia.org for details
   of authors and sources) and is available under the GNU Free
   Documentation License. See also our Disclaimer.
