Gentle Giant: Whale Shark (Rhincodon typus)

⇐ Monastery of Maulbronn in a Water DropOceanic Whitetip Shark (Carcharhinus longimanus) ⇒

ISO: 250

Shutter: 1/160

Aperture: f/8.0

Size: 2160x1440

Date: 06/08/2012

By: J├╝rgen Donauer

Camera: Canon EOS 7D

License: CC BY-SA, Shutterstock

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The whale shark (Rhincodon typus) is the biggest living fish on this planet. The gentle giants can become bigger then 10 metres in length. Here you see a baby that was about 4,5 to 5 metres long.

Source: Wikipedia

The whale shark (Rhincodon typus) is a slow-moving filter feeding shark and the largest known extant fish species. The largest confirmed individual had a length of 12.65 metres (41.50 ft) and a weight of more than 21.5 metric tons (47,000 lb), and there are unconfirmed reports of considerably larger whale sharks. Claims of individuals over 14 metres (46 ft) long and weighing at least 30 metric tons (66,000 lb) are not uncommon. The whale shark holds many records for sheer size in the animal kingdom, most notably being by far the largest living non-mammalian vertebrate, rivalling many of the largest dinosaurs in weight. It is the sole member of the genus Rhincodon and the family, Rhincodontidae (called Rhiniodon and Rhinodontidae before 1984), which belongs to the subclassElasmobranchii in the class Chondrichthyes. The species originated approximately 60 million years ago.

The whale shark is found in tropical and warm oceans and lives in the open sea with a lifespan of about 70 years. Although whale sharks have very large mouths, as filter feeders they feed mainly, though not exclusively, on plankton, which are microscopic plants and animals. However, the BBC program Planet Earth filmed a whale shark feeding on a school of small fish. The same documentary showed footage of a whale shark timing its arrival to coincide with the mass spawning of fish shoals and feeding on the resultant clouds of eggs and sperm.

The species was distinguished in April 1828 after the harpooning of a 4.6 metres (15.1 ft) specimen in Table Bay, South Africa. Andrew Smith, a military doctor associated with British troops stationed inCape Town, described it the following year. The name "whale shark" comes from the fish's physiology, being as large as some species of whales and also a filter feeder like baleen whales.

Description

As a filter feeder it has a capacious mouth which can be up to 1.5 metres (4.9 ft) wide and contains 10 filter pads and between 300 and 350 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 individual and are useful for counting populations. Its skin can be up to 10 centimetres (3.9 in) thick. The shark has a pair each of dorsal fins and pectoral fins. Juveniles' tails have a larger upper than lower fin while the adult tail becomes semi-lunate (crescent-shaped). Spiracles are just behind the eyes.

Whale shark in main tank at Osaka Aquarium
The whale shark is the largest non-cetacean animal in the world. The average size of adult whale sharks is estimated at 9.7 metres (31.82 ft) and 9 tonnes (20,000 lb). The largest verified specimen was caught on 11 November 1947, near Baba Island, in Karachi, Pakistan. It was 12.65 metres (41.50 ft) long, weighed more than 21.5 tonnes (47,000 lb), and had a girth of 7 metres (23.0 ft). Stories exist of vastly larger specimens – quoted lengths of 18 metres (59 ft) and 45.5 tonnes (100,000 lb) are not uncommon in the popular shark literature – but no scientific records support their existence. In 1868 the Irish natural scientist Edward Perceval Wright obtained several small whale shark specimens in the Seychelles, but claimed to have observed specimens in excess of 15 metres (49.2 ft), and tells of reports of specimens surpassing 21 metres (68.9 ft).

In a 1925 publication, Hugh M. Smith described a huge animal 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 metres (56 ft) long, and weighed approximately 37 tonnes (82,000 lb). These measurements have been exaggerated to 43 tonnes (95,000 lb) and a more precise 17.98 metres (58.99 ft) in recent years. A shark caught in 1994 off Tainan County, southern Taiwan reportedly weighed 35.8 tonnes (79,000 lb). There have even been claims of whale sharks of up to 23 metres (75 ft) and 100 tonnes (220,000 lb). 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 metres (15.1 ft) on one side and 12.2 metres (40.0 ft) on the other. No reliable documentation exists for these claims and they remain "fish stories".

Diet

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 macro-algae, plankton, krill, Christmas Island red crab larvae and small nektonic life such as small squid or vertebrates. It also feeds on small fish and the clouds of eggs and sperm during mass spawning of fish shoals. The many rows of vestigial teeth play no role in feeding. Feeding occurs either by ram filtration, in which the animal opens its mouth and swims forward, pushing water and food into the mouth, or by active suction feeding, in which the animal opens and closes its mouth, sucking in volumes of water that are then expelled through the gills. In both cases, the filter pads serve to separate food from water. These unique, black sieve-like structures are presumed to be modified gill rakers. Food separation in whale sharks is by cross-flow filtration, in which the water travels nearly parallel to the filter pad surface, not perpendicularly through it, before passing to the outside, while denser food particles continue to the back of the throat. This is an extremely efficient filtration method that minimises fouling of the filter pad surface. Whale sharks have been observed "coughing" and it is presumed that this is a method of clearing a build-up of particles from the filter pads. Whale sharks migrate to feed and possibly to breed.

The whale shark is an active feeder, targeting concentrations of plankton or fish. It is able to ram filter feed or can gulp in a stationary position. This is in contrast to the passive feeding basking shark, which does not pump water. Instead, it swims to force water across its gills.

Behaviour toward divers

A whale shark at Ningaloo Reef
Despite its size, the whale shark does not pose significant danger to humans. Although massive, whale sharks are docile fish and sometimes allow swimmers to catch a ride. although this practice is discouraged by shark scientists and conservationists. Younger whale sharks are actually quite gentle and can play with divers. In July 2011, several sources reported, with photographs, an incident of a diver who, allegedly, was nearly sucked into the mouth of a whale shark (but escaped unharmed) off the coast of Isla Mujeres, Mexico.

The shark is seen by divers in many places, including the Bay Islands in Honduras, Thailand, the Philippines, the Maldives, the Red Sea, Western Australia (Ningaloo Reef, Christmas Island), Taiwan, Panama (Coiba Island), Belize, Tofo Beach in Mozambique, Sodwana Bay (Greater St. Lucia Wetland Park) in South Africa, the Galapagos Islands, Isla Mujeres and Bahía de los Ángeles in Mexico, the Seychelles, West Malaysia, islands off eastern peninsular Malaysia, Sri Lanka, Oman, Fujairah, and Puerto Rico.

Tags: nature, ocean, fish, whale shark, shark, marine life, wildlife

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