Oceanic whitetip shark: Difference between revisions
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[[image:Carcharhinus longimanus 1.jpg|thumb|Oceanic whitetip photographed at the [[Elphinstone reef]], [[Red Sea]], [[Egypt]].]] |
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The oceanic whitetip is usually solitary and slow-moving, and tends to cruise near the top of the water column, covering vast stretches of empty water scanning for possible food sources. Sharks were known to mariners as 'sea dogs' until the 16th century, and ''C. longimanus'', the common ship-following shark, can indeed exhibit rather doglike behavior when its interest is piqued: when attracted to something that seems like food, its movements become more avid, and it will approach cautiously but stubbornly, retreating and maintaining the minimum safe distance if driven off, but ready for a rush of boldness if the opportunity presents. Whitetips are not fast sharks, but like many slow-movers, they are capable of surprising bursts of quickness — and while it is difficult to make claims of an animal's intelligence, the oceanic whitetip has an apparent cleverness that seems, like some of their behaviors, almost canine. |
The oceanic whitetip is usually solitary and slow-moving, and tends to cruise near the top of the water column, covering vast stretches of empty water scanning for possible food sources. Sharks were known to mariners as 'sea dogs' until the 16th century, and ''C. longimanus'', the common ship-following shark, can indeed exhibit rather doglike behavior when its interest is piqued: when attracted to something that seems like food, its movements become more avid, and it will approach cautiously but stubbornly, retreating and maintaining the minimum safe distance if driven off, but ready for a rush of boldness if the opportunity presents. Whitetips are not fast sharks, but like many slow-movers, they are capable of surprising bursts of quickness — and while it is difficult to make claims of an animal's intelligence, the oceanic whitetip has an apparent cleverness that seems, like some of their behaviors, almost canine. |
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Revision as of 11:36, 25 June 2006
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| Species: | C. longimanus
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The oceanic whitetip shark (Carcharhinus longimanus) is a large pelagic shark of tropical and warm temperate seas. It is named after both its oceanic habitat (living in deep waters), and the white tips on its fins. It is a stocky shark; its most notable features include its rounded fins and the fins' extreme length.
It is an aggressive fish which dominates feeding frenzies, and is said to have attacked more humans than all other shark species combined — as such it is a notable danger to survivors of oceanic ship and plane wrecks. Given its abundance and threat to humans it was a serious concern in the World Wars — for example, the Nova Scotia, a steamship carrying 1000 was sunk near South Africa by a German submarine and only 192 survived, with many deaths attributed to the oceanic whitetip shark.
Some cultures fish for the oceanic whitetip shark as a delicacy or for its fin.
Naming
The oceanic whitetip shark was first described by Rene Primevere Lesson in his 1831 account of his observations as naturalist on Louis Duperry's 1822–1825 circumnavigation of the world on the corvette Coquille. Lesson described two specimens found in the Tuamotu Archipelago in French Polynesia, and named the shark Squalus maou after a Polynesian word for "shark". However, Lesson's description and name were forgotten.
It was next described by Cuban Felipe Poey in 1861 as Squalus longimanus. The name Pterolamiops longimanus also occupied part of its history. The species epithet longimanus translates from Latin as "long hands" due to the shape of its pectoral fins. Its other, lesser-used, names include Carcharhinus obtusus (Garman 1881), Carcharhinus insularum (Snyder 1904), Pterolamiops magnipinnis (Smith 1958), and Pterolamiops budkeri (Fourmanoir 1961). As well as this variety of scientific names,the Oceanic Whitetip shark also has many common names in the English language: Brown Milbert's sand bar shark, brown shark, nigano shark, whitetip whaler, and whitetip shark.
The rules of the International Commission on Zoological Nomenclature (ICZN) are that the first published description has priority; so the valid scientific name for the Oceanic Whitetip Shark would seem to be Carcharhinus maou. However, Lesson's name remained forgotten for so long that Carcharhinus longimanus is currently the most widely used scientific name.
Its non-English common names include apoapo (Samoan), cazón (Spanish), galano (Spanish), galha branca (Portuguese), Hochsee-Weißspitzenhai (German), ikan yu (Malay), köpek baligi (Turkish), marracho (Portuguese), marracho oceánico (Portuguese), marracho-de-pontas-brancas (Portuguese), oceanische witpunthaai (Dutch), opesee-wittiphaai (Afrikaans), parata (Tahitian), patíng (Tagalog), rameur (French), requin à aileron blanc (French), requin blanc (French), requin canal (French), squala alalunga (Italian), tiburon oceanico (Spanish), valkopilkkahai (Finnish), weißspitzenhai (German), yeshalifes (Carolinian), yogore (Japanese), and zarlacz bialopletwy (Polish).
Distribution and habitat
The oceanic whitetip is found worldwide in deep, open water, preferring a temperature greater than 18°.[1] They are extremely common and widely-distributed, and a map of their habitat appears as a wide band around the world. It may typically be found in equatorial waters; or, specifically, between 20° north and 20° south latitude. In 2004 an Oceanic Whitetip was however found dead as far north as the west coast of Sweden. [2]
The shark typically dwells in the upper layer of the ocean — from the surface to a depth of 150 metres [1] — though it prefers off-shore deep-ocean areas. According to longline capture data increasing distance from land correlates to a greater population of sharks. It typically lives on its own, though some gatherings are notable where food is available. Unlike many animals it does not operate on a day-and-night basis, but rather swims during both — its swimming style is slow with the pectoral fins widely spread. Despite their decided isolation from others of the same species they may be observed with pilot fishes, dolphin fishes, and remoras. In 1988 Jeremy Stafford-Deitsch reported seeing the species accompanied by a shortfin pilot whale.
Anatomy and appearance
The most distinguishing characteristic of C. longimanus is its long, winglike pectoral fins (hence the specific name longimanus, which is Latin for "long-handed") and dorsal fin. These fins are noticeably larger than they seem like they should be, although not so large that it may be thought that C. longimanus is a Goblin shark; they are also conspicuously rounded. The shark's nose is rounded also, and its eyes are circular with nictitating membranes.
C. longimanus has a 'typical', although somewhat flattened shark body, often with a mildly humpbacked aspect. It is bronze, brown, bluish, or grey dorsally (the color varies by region), and white ventrally (though it may occasionally have a yellow tint). The teeth of the upper jaw are triangular and serrated, while those in the lower jaw are narrow and somewhat fang-like. Most of the fins on its body (dorsal, pectoral, pelvic, and caudal) have a white tips (very young specimens and the very occasional adult will lack these), from whence the name comes. As well as the white tips a mottling may be noticed on the fins — and even black marks on young specimens. Finally a saddle-like marking may be noted between first and second dorsal fins.
The shark has several kinds of teeth — those in the mandible have a serrated tip and are relatively small and triangular (with a thinner tip). There are between 13 and 15 teeth on either side of the symphysis. The upper jaw teeth are much larger and broader with entirely serrated edges — there are 14 or 15 along each side of the symphysis. The denticles lie flat — they typically have between 5 and 7 ridges.
The maximum size of the oceanic whitetip shark is 4 metres (13 feet), although usually not more than 3 m (10 feet). Its maximum weight is 170 kilograms (374 pounds). The female is larger than the males (though typically only by 10 centimetres) with males about 1.8 m, and females about 1.9 m.
Diet
C. longimanus feeds mainly on pelagic cephalopods and bony fish[1]. However, its diet is often far more varied and less selective than this — it is known to eat threadfins, stingrays, sea turtles, sea birds, gastropods, crustaceans, mammalian carrion and even rubbish dumped from ships. The bony fish it does feed on include lancetfish, oarfish, barracuda, jacks, dolphinfish, marlin, tuna, and mackerels. Its method of obtaining food often includes biting into a group of fish, or swimming through schools of tuna with an open mouth. When feeding with other species, it becomes aggressive. It has been observed (by Peter Benchley) swimming among pilot whales and eating the pilot whales' faeces.
Behavior
The oceanic whitetip is usually solitary and slow-moving, and tends to cruise near the top of the water column, covering vast stretches of empty water scanning for possible food sources. Sharks were known to mariners as 'sea dogs' until the 16th century, and C. longimanus, the common ship-following shark, can indeed exhibit rather doglike behavior when its interest is piqued: when attracted to something that seems like food, its movements become more avid, and it will approach cautiously but stubbornly, retreating and maintaining the minimum safe distance if driven off, but ready for a rush of boldness if the opportunity presents. Whitetips are not fast sharks, but like many slow-movers, they are capable of surprising bursts of quickness — and while it is difficult to make claims of an animal's intelligence, the oceanic whitetip has an apparent cleverness that seems, like some of their behaviors, almost canine.
Groups are often formed when several nearby individuals converge on a food source, whereupon the fabled "feeding frenzy" may occur (a behavior not seen in coastal or inshore species of sharks). The frenzy seems triggered not by blood in the water per se, or by bloodlust, but by the species being especially high-strung and goal-directed when not slowly plying the open ocean, conserving energy between infrequent food events. C. longimanus is a competitive, opportunistic predator with great incentive to exploit the resource at hand, rather than avoiding trouble in favor of a possibly easier meal in the future.
There seems to be a segregation by sex and size, at least in some parts of the world. Whitetips will follow schools of tuna or squid, and will follow groups of cetaceans such as dolphins and pilot whales as scavengers of the cetaceans' prey. They follow boats as well, and indeed seem to have a vital following-impulse, developed over countless millennia of baitfish migrations and doglike hope that the followed might drop a piece of whatever he is eating.
Reproduction
Mating season is in early summer in the northwest Atlantic Ocean and southwest Indian Ocean. Viviparous (young hatch, live and are fed in utero by a placental sac), with litter size varying from one to 15 young. There is a gestation period of one year. Sexual maturity is reached near a length of 1.75 to 2 m for males and females, respectively, though they are born at a size of about 0.6 m.
Importance to humans
The oceanic whitetip is the most common shark in its range, and perhaps the most abundant large animal in the world. It is a commercially important species to the extent that its fins are prized for soup and its meat and oil frequently used — although it more often appears on boats by chance than on purpose. It steals fish from lines and snatches bait, and is considered more of a nuisance than a resource. The oceanic whitetip poses an extremely minimal threat to bathers or inshore sportsman, but a substantial one for humans caught in the open ocean in conditions in which they might be seen as likely prey.
Famed oceanographic researcher Jacques Cousteau has described the oceanic whitetip as "the most dangerous of all sharks". Despite the greater notoriety of the great white shark and other sharks who are often found nearer the shore, the oceanic whitetip is probably responsible for more fatal attacks on humans than all other species combined, by preying on those who are shipwrecked or downed from planes in the open ocean through disaster or war. These incidents are not included in common shark-attack indices for the 20th and 21st centuries, but would appear to total in the thousands worldwide, with one incident alone, the torpedoing of the USS Indianapolis on July 30, 1945, giving a minimal figure of 60–80 killed by sharks. [3] The oceanic whitetip, unlike the great white and others, is abundant, highly opportunistic and aggressive; and will attack humans for food.
Even though this is one of the most dangerous sharks, divers have swum with this shark again and again without being harmed. However, divers are advised to approach the shark only with extreme caution and to not spear fish near this shark; and hit it on the snout, gills or eyes if it starts to push the diver.
See also
Notes and References
- Template:IUCN2006 Database entry includes a lengthy justification of why this species is vulnerable
- ^ a b c Ed. Ranier Froese and Daniel Pauly. "Carcharhinus longimanus". FishBase. Retrieved 6 February.
{{cite web}}: Check date values in:|accessdate=(help); Unknown parameter|accessyear=ignored (|access-date=suggested) (help) - ^ Eli. "Fishwatcher". Fishwatcher. Retrieved 6 February.
{{cite web}}: Check date values in:|accessdate=(help); Unknown parameter|accessyear=ignored (|access-date=suggested) (help) - ^ Martin, R. Aidan. "Elasmo Research". ReefQuest. Retrieved 6 February.
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- Leonard J. V. Compagno, Sharks of the Order Carcharhiniformes, Princeton University Press, 1988, ISBN 0-691-08453-X
- Leonard J. V. Compagno, Sharks of the World: An annotated and illustrated catalogue of shark species known to date, Food and Agriculture Organization of the United Nations, 1984
- William N. Eschmeyer, Special Publication of the Center for Biodiversity Research and Information, no. 1, vol 1-3, California Academy of Sciences, 1998, ISBN 0-940228-47-5
- Richard H. Backus, Stewart Springer and Edgar L. Arnold, Jr. A contribution to the natural history of the white-tip shark, Pterolamiops longimanus (Poey), 1956, Deep-Sea Research vol. 3
- A. J. Bass, J. D. D'Aubrey and N. Kistnasamy, Sharks of the east coast of southern Africa. 1. The genus Carcharhinus (Carcharhinidae), 1973, Oceanographic Research Institute, Durban
- Leonard J. V. Compagno, FAO Species Catalogue, Vol. 4, Parts 1 and 2, Sharks of the World, 1984, Rome: FAO
- Richard Ellis, The Book of Sharks, 1976, New York: Grosset & Dunlap
- Thomas H. Lineaweaver III and Richard H. Backus, The Natural History of Sharks, 1969, Philadelphia: Lippincourt.
- Reader's Digest, Sharks: Silent Hunters of the Deep, 1989, Sydney: Reader's Digest
- Jeremy Stafford-Deitsch, Shark: A Photographer's Story, 1988, San Francisco: Sierra Club Books
- Jacques-Yves Cousteau, Requins-sauvages de la mer
- Froese, Rainer; Pauly, Daniel (eds.) (2005). "Carcharhinus longimanus" in FishBase. 09 2005 version.
- "Prionace glauca". Integrated Taxonomic Information System. 16 November.
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