Francais | English | Espanõl

From Wikipedia, the free encyclopedia

Not to be confused with whitetip reef shark.

iOceanic whitetip shark
Conservation status
Image:Status iucn3.1 VU.svg Vulnerable (VU) </div>
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Chondrichthyes Subclass: Elasmobranchii Order: Carcharhiniformes Family: Carcharhinidae Genus: Carcharhinus Species: C. longimanus
Binomial name
Carcharhinus longimanus (Poey, 1861)
Range of oceanic whitetip shark

</div>

The oceanic whitetip shark, Carcharhinus longimanus, is a large pelagic shark of tropical and warm temperate seas. It is a stocky shark, most notable for its long, white tipped rounded fins.

This aggressive but slow-moving fish dominates feeding frenzies, and has attacked more humans than all other shark species combined — it is a notable danger to survivors of oceanic ship wrecks and downed aircraft.<ref name="RQ">Martin, R. Aidan.. Elasmo Research. ReefQuest. Retrieved on 6 February, 2006.</ref> <ref name="nova">Bass, A.J., J.D. D'Aubrey & N. Kistnasamy. 1973. "Sharks of the east coast of southern Africa. 1. The genus Carcharhinus (Carcharhinidae)." Invest. Rep. Oceanogr. Res. Inst., Durban, no. 33, 168 pp.</ref> Recent studies<ref name="baum">Baum, J.K. and Myers, R.A. 2004. Shifting baselines and the decline of pelagic sharks in the Gulf of Mexico. Ecology Letters. 7(3): 135–45.</ref><ref name="IUCN">IUCN. IUCN Red List of Threatened Species: Carcharhinus longimanus. Retrieved on 18 July, 2006.</ref> have shown that its numbers are in steep decline — its large fins are highly valued as the chief ingredient of shark-fin soup and, as with other shark species, the oceanic whitetip faces mounting pressure from fishing throughout its range.

Contents 1 Taxonomy 2 Distribution and habitat 3 Anatomy and appearance 4 Diet 5 Behavior 6 Reproduction 7 Relationship to humans 8 Conservation status 9 See also 10 References 11 External links

[edit] Taxonomy

The oceanic whitetip shark was first described by naturalist Rene Primevere Lesson in his account of observations made during 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.<ref name="ITIS">ITIS. Integrated Taxonomic Information System: Carcharhinus longimanus. Retrieved on 31 July, 2006.</ref>

It was next described by Cuban Felipe Poey in 1861 as Squalus longimanus.<ref name="ITIS"/> The name Pterolamiops longimanus has been used during its history. The species epithet, longimanus, refers to the size of its pectoral fins (longimanus translates from Latin as "long hands").<ref name="flmnh">Cathleen Bester. OCEANIC WHITETIP SHARK. Florida Museum of Natural history. Retrieved on 22 July, 2006.</ref> Its other, less frequently used, synonyms include Carcharhinus obtusus (Garman 1881), Carcharhinus insularum (Snyder 1904), Pterolamiops magnipinnis (Smith 1958), and Pterolamiops budkeri (Fourmanoir 1961). The oceanic whitetip shark has many common names in English: Brown Milbert's sand bar shark, brown shark, nigano shark, whitetip whaler, and whitetip shark.<ref name="flmnh" />

The rules of the International Commission on Zoological Nomenclature are that in general the first-published description has priority; therefore the valid scientific name for the oceanic whitetip shark should be Carcharhinus maou. However, Lesson's name remained forgotten for so long that Carcharhinus longimanus is the widely accepted scientific name.<ref name="FAO">Leonard J. V. Compagno (1984). Sharks of the World: An annotated and illustrated catalogue of shark species known to date. Food and Agriculture Organization of the United Nations, 484–86, 555–61, 588.</ref>

[edit] Distribution and habitat

The oceanic whitetip is found globally in deep, open water, with a temperature greater than 18° C (64.4° F).<ref name="fishbase">Ed. Ranier Froese and Daniel Pauly. Carcharhinus longimanus. FishBase. Retrieved on 6 February, 2006.</ref> It prefers waters between 20 and 28° C (68 and 82.4° F) and tends to withdraw from areas when temperatures fall below this.<ref name="FAO" /> They were once extremely common and widely distributed, and still inhabit a wide band around the globe; however, recent studies suggest that their numbers have drastically declined.<ref name="baum" /> An analysis of the US pelagic longline logbook data between 1992–2000 (covering the Northwest and Western Central Atlantic) estimated a decline of 70% over that period.<ref name="IUCN" />

They are found worldwide between 45° north and 43° south latitude.<ref name="fishbase" /><ref name="ITIS" /> In 2004, an oceanic whitetip was discovered dead on the west coast of Sweden—far beyond what was once considered the northern boundary of its range.<ref>Eli. Fishwatcher. Fishwatcher. Retrieved on 6 February, 2006.</ref>

The shark spends most of its time in the upper layer of the ocean—to a depth of 150 metres (500 ft)<ref name="fishbase" />—and prefers off-shore, deep-ocean areas. According to longline capture data, increasing distance from land correlates to a greater population of sharks.<ref name="flmnh" /> Occasionally it is found close to land, in waters as shallow as 37 m (120 ft), mainly around mid-ocean islands such as Hawaii, or in areas where the continental shelf is narrow and there is access to deep water nearby. It is typically solitary, though gatherings have been observed where food is available.<ref name="FAO" /> Unlike many animals, it does not have a diurnal cycle, but is active during both day and night.<ref name="flmnh" /> Its swimming style is slow, with the pectoral fins widely spread. Despite their habitual isolation from members of their own species, they may be observed with pilot fishes, dolphin fishes, and remoras.<ref name="flmnh" /> In 1988, Jeremy Stafford-Deitsch reported seeing an individual accompanied by a shortfin pilot whale.<ref>Stafford-Deitsch, Jeremy (1988). Shark: A Photographer's Story. Sierra Club Books.</ref>

[edit] Anatomy and appearance

The most distinguishing characteristic of C. longimanus is its long, winglike pectoral and dorsal fins. The fins are significantly larger than in most other shark species, and are conspicuously rounded. The shark's nose is rounded and its eyes are circular, with nictitating membranes.<ref name="flmnh" />

C. longimanus has a 'typical', although somewhat flattened requiem shark body, often with a mildly humpbacked aspect. It is bronze, brown, bluish or grey dorsally (the color varies by region), and white ventrally (although it may occasionally have a yellow tint). The maximum size of the oceanic whitetip shark is 4 metres (13 ft), although usually it does not exceed 3 m (10 ft). Its maximum weight is 170 kilograms (370 pounds). The female is larger than the male (although typically only by 10 centimeters (4 in)) with males about 1.8 m (71 in), and females about 1.9 m (75 in).<ref name="flmnh" /><ref name="FAO" />

Most of the fins on its body (dorsal, pectoral, pelvic, and caudal) have a white tips (juvenile specimens and occasional adults may lack these). As well as the white tips, the fins may be mottled—and in young specimens can even have black marks. A saddle-like marking may be apparent between first and second dorsal fins.<ref name="flmnh"/> The shark has several kinds of teeth—those in the mandible (lower jaw) have a thin serrated tip and are relatively small and triangular (somewhat fang-like). There are between 13 and 15 teeth on either side of the symphysis. The teeth in the upper jaw are triangular, but much larger and broader with entirely serrated edges—there are 14 or 15 along each side of the symphysis.<ref name="flmnh"/> The denticles lie flat and typically have between five and seven ridges.<ref name="flmnh"/>

[edit] Diet

C. longimanus feeds mainly on pelagic cephalopods and bony fish.<ref name="fishbase" /> However, its diet can be far more varied and less selective—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 feeds on include lancetfish, oarfish, barracuda, jacks, dolphinfish, marlin, tuna, and mackerel. Its methods of predation include biting into groups of fish and swimming through schools of tuna with an open mouth. When feeding with other species, it becomes aggressive.<ref name="FAO" /> Peter Benchley, author of Jaws, observed this shark swimming among pilot whales and eating their faeces.<ref>Benchley, Peter (2002). Shark Trouble. Random House.</ref>

[edit] 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.<ref name="flmnh"/> Until the 16th century,<ref>Online Etymology Dictionary. Retrieved on 2006-08-08.</ref> sharks were known to mariners as 'sea dogs'<ref>RF Marx (1990). The History of Underwater Exploration. Courier Dover Publications, 3.</ref> and the oceanic whitetip, the most common ship-following shark,<ref name="FAO" /> exhibits dog-like behavior when its interest is piqued: when attracted to something that appears to be 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 itself. Oceanic whitetips are not fast sharks, but they are capable of surprising bursts of speed. It is commonly found competing for food with silky sharks, making up for its comparatively leisurely swimming style with an aggressive attitude.<ref name="FAO" />

Groups are often formed when nearby individuals converge on a food source, whereupon the fabled "feeding frenzy" may occur. This seems to be triggered not by blood in the water per se, or by bloodlust, but by the species' highly strung and goal-directed nature (conserving energy between infrequent feeding opportunities when it is not slowly plying the open ocean). The oceanic whitetip 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.<ref name="FAO" />

There does not seem to be a segregation by sex and size as with some other species. Whitetips will follow schools of tuna or squid, and will trail groups of cetaceans such as dolphins and pilot whales as scavengers of their prey. Their instinct to follow is so strongly imprinted, as the result of countless millennia of baitfish migrations, that they will accompany ocean-going ships. When whaling took place in warm waters, oceanic whitetips were often responsible for much of the damage to floating carcasses.<ref name="FAO" />

[edit] Reproduction

Mating season is in early summer in the northwest Atlantic Ocean and southwest Indian Ocean, although females captured in the Pacific have been found with embryos year round, suggesting a longer mating season in this region.<ref name="FAO" />. The shark is viviparous - the embryos develop and are fed (by a placental sac) in utero. It has a gestation period of one year. Litter sizes vary from one to 15 with the young born at a length of about 0.6 m (24 in).<ref name="IUCN" /> Sexual maturity is reached at close to 1.75 m (70 in) for males and 2 m (80 in) for females.<ref name="IUCN" />

[edit] Relationship to humans

It is a commercially important species to the extent that its fins are prized for soup and its meat and oil frequently utilized. It is used fresh, smoked, dried and salted for human consumption and its hide utilised for leather.<ref name="FAO" /> It is subject to fishing pressure throughout virtually its whole range<ref name="IUCN" /> - although it is more often taken as bycatch than by design, since it takes bait from longlines intended for other species.<ref name="FAO" />

The oceanic whitetip poses a minimal threat to bathers or inshore sportsman, but a high risk for humans caught in the open ocean in conditions in which they might be seen as prey.

Famed oceanographic researcher Jacques Cousteau described the oceanic whitetip as "the most dangerous of all sharks".<ref>Cousteau, Jacques-Yves & Cousteau, Philippe (1970). The Shark: Splendid Savage of the Sea. Doubleday & Company, Inc.</ref> Despite the greater notoriety of the great white shark and other sharks habitually found nearer the shore, the oceanic whitetip is considered responsible for more fatal attacks on humans than all other species combined, as a result of predation on those shipwrecked or from aircraft downed in the open ocean.<ref name="FAO" /> 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.<ref name="RQ"/> Also during World War II, the Nova Scotia, a steamship carrying approximately 1000 people near South Africa was torpedoed and sunk by a German submarine. There were only 192 survivors, and many deaths were attributed to the oceanic whitetip shark.<ref name="nova" />

Even though the oceanic whitetip is highly opportunistic and aggressive; and has been known to attack humans for food,<ref name="RQ" /> divers have swum with this shark repeatedly without being harmed (it is a popular draw for dive tourism because of its size and the perceived danger). However, divers are advised to approach the shark only with extreme caution, not spear fish near this shark and if the shark comes too close or gets too inquisitive to get out of the water as soon as possible. It is generally suggested that if a shark starts to push the diver, then to hit it on the snout, gills or eyes, but anecdotal evidence suggests that this may be less effective in deterring whitetips than with other species of sharks.<ref name="FAO" />

[edit] Conservation status

In 1969, Lineaweaver and Backus wrote of the oceanic whitetip: "[it is] extraordinarily abundant, perhaps the most abundant large animal, large being over 100 pounds [45  kg], on the face of the earth".<ref>Thomas H. Lineaweaver III and Richard H. Backus (1969). The Natural History of Sharks. Lippincourt.</ref> There was little further population study until 2003 when the numbers were estimated to have dropped by as much as 70% in the Northwest and Western Central Atlantic between 1992–2000.<ref name="IUCN" /> Another study focusing on the Gulf of Mexico, using a mix of data from US pelagic longline surveys from the mid-1950s and observations from the late-1990s, estimated a decline in numbers in this location of 99.3% over this period.<ref>Baum, J.K. and Myers, R.A. 2004. Shifting baselines and the decline of pelagic sharks in the Gulf of Mexico. Ecology Letters. 7(3): 135–145.</ref> However, neither changes in fishing practices nor differences in the data collection methods were fully considered. Because of this there is debate as to validity of the estimations.<ref>Baum, J.K., Kehler, D. and Myers, R.A. 2005. Robust estimates of decline for pelagic shark populations in the northwest Atlantic and Gulf of Mexico. Fisheries 30: 27–30.</ref> As a result of these findings its status on the IUCN Red List was moved to "Vunerable" globally (from "Lower Risk/Near Threatened") and "Critically Endangered" in the Northwest and Western Central Atlantic areas.<ref name="IUCN" /> Under the 1995 UN Agreement on the Conservation and Management of Straddling Fish Stocks and Highly Migratory Fish Stocks (UNFSA), coastal and fishing states are specifically required to adopt measures to ensure the conservation of listed species, but little progress has been made in this area with regard to the oceanic whitetip.<ref name="IUCN" />

[edit] See also

• List of sharks
• Shark attack

[edit] References

General references

[edit] External links

• ARKive - images and movies of the oceanic whitetip shark (Carcharhinus longimanus)
• Oceanic Whitetip shark, Carcharhinus longimanus MarineBio"
• Whitetip Oceanic Shark profile, Florida Museum of Natural History.
• Biology and Behaviour of the Oceanic Whitetip.

cs:Žralok dlouhoploutvý

de:Weißspitzen-Hochseehai fi:Valkopilkkahai fr:Requin longimane ja:ヨゴレ (魚類) nl:Witpunthaai