Whitetip deep sea shark
| Whitetip deep sea shark | ||||||||||||
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Whitetip deep-sea shark ( Carcharhinus longimanus ) accompanied by pilot fish ( Naucrates ductor ) |
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| Carcharhinus longimanus | ||||||||||||
| ( Poey , 1861) |
The white tip deep sea shark ( Carcharhinus longimanus ), also called deep sea white fin shark , is a member of the family of requiem or gray sharks . As a deep sea shark, it is native to tropical, subtropical and warm-temperate regions worldwide and is one of the largest sharks in the world. It is classified as dangerous to humans and a number of attacks have been documented. Due to the high losses caused by deep-sea fishing, the formerly very common species is endangered; it is now seen as critically endangered, with an estimated 98% worldwide population decline.
features
With a body length of up to 390 cm, the whitetip deep-sea shark is one of the large shark species, but it rarely reaches more than 300 cm in length. The average lengths are between 180 and 190 cm, with the females usually becoming somewhat larger than the males. It has a maximum weight of almost 170 kilograms, the heaviest animal known to date weighed 167.5 kg. The species has the typical build of requiem sharks, often with a slight hump.
It is characterized by its very long, rounded fins compared to almost all other shark species. This applies particularly to the first dorsal fin, which, like the wing-like pectoral fins, is very large. The beginning of the first dorsal fin is immediately behind the end of the free inner edge of the pectoral fins. An interdorsal ridge may be present, but then it is not very well developed. The second dorsal fin is significantly smaller than the first. The anal fin is also larger than the second dorsal fin and drawn out in a long point, making its rear edge strongly concave . The caudal fin has a comparatively small lower and a very large upper lobe ( lobe ).
Its back color is gray-brown to bronze or bluish, although the color may vary regionally. The belly is white and may have a yellowish tone; the transition to the flanks is sharply delimited. The undersides of the pectoral fins are also white and can take on the color of the back, especially at the edges and towards the free rear end. The caudal fin and the first dorsal fin, the pectoral fins and the pelvic fins have conspicuous, white tips that can occupy large parts of the fins, while the second dorsal fin and the anal fin are drawn with an irregular black pattern of the tips. The white tips are particularly pronounced in young animals, but they can also be absent in adult sharks. In addition to the tips, the large fins often also have white speckles, which can also be black in young animals. A saddle-like, white spot can also be present between the first and second dorsal fin. The snout is long and flattened wide, and when viewed from above, it is strongly rounded. Seen from below, the mouth is wide and parabolic with short labial folds . The shark has 14 to 15 triangular, large teeth with strongly serrated edges in the upper jaw on each side of the jaw. In the lower jaw, there are 13 to 15 teeth on each side, which are significantly smaller and also triangular. The lower jaw teeth have a narrow, serrated tip and are slightly curved. Behind these teeth are five to seven other, flat-lying rows of teeth that move up into the main row if necessary. The eyes are relatively small and round and have a nictitating membrane , they are arranged in the middle of the head. The nasal pits are small and there is no injection hole . In total, like all species of the genus, the shark has five gill slits, the last two being arranged above the base of the pectoral fin.
distribution and habitat
The whitetip deep sea shark is native to tropical, subtropical and warm-temperate offshore regions around the world. The water temperature in the distribution area is 18 ° C to 28 ° C. This applies to the western Atlantic from Maine (USA) to Argentina , including the Caribbean and the Gulf of Mexico . This shark can also be found in the Red Sea and the entire Indian Ocean . In the western Pacific , its distribution area lies between China and northern Australia as far as the Philippines ; in the central Pacific he was sighted near Hawaii , Tahiti , the Tuamotu Archipelago , in the eastern Pacific off the Galápagos Islands , southern California to Peru . In the Mediterranean , the whitetip deep-sea shark is an occasional visitor and is rarely seen. The animals immigrate via the Strait of Gibraltar or the Suez Canal . In 1978 a 2.5 meter long animal was caught in one of the canals in Venice , and in 1998 a 3 meter long shark was sighted by a diver off Martigues , France. There is no reproduction in the Mediterranean.
In the summer of 2004, a male whitetip shark, 230 cm long, was caught in the brackish water of a fjord on the west coast of Sweden. It is not known whether the animal came so far outside of its normal range through natural migration or whether it was possibly brought there by humans.
The animals prefer open open water ( pelagic ) over deep sea areas with water depths of at least 180 meters as a habitat . They are also found in the area of continental and island pedestals with water depths of at least 35 meters and over continental slopes . The species prefers to stay in the warm water layers near the surface and rarely goes deeper than about 150 meters. The information on the maximum depth ranges from 230 to 1082 meters. In the Red Sea, the shark often accompanies safari boats.
Way of life
behavior
The whitetip deep sea shark is a very active deep sea shark that usually swims at a slow to moderate speed. He spreads the large pectoral fins wide. It is diurnal and nocturnal, whereby it swims near the water surface especially during the day. As a rule, the shark is a solitary animal, but it can also come together in smaller or larger groups to hunt. Group formations according to size and gender were observed.
The shark is described as very curious and comes very close to divers. At the same time, it is very persistent and can also become very aggressive, especially in direct competition for food with silk sharks . The French marine researcher Cousteau describes Carcharhinus longimanus as the most dangerous species of shark for humans.
nutrition
The whitetip deep-sea shark feeds primarily on medium-sized to large deep-sea fish , including jackfish , golden mackerel , tuna , swordfish and barracudas . But also sea turtles , dolphins , octopus , sea birds, crabs and snails are part of its food spectrum. It also eats waste from ships and carcasses , such as whales; like other large sharks, it also regularly swallows indigestible objects.
The shark hunts, for example, by swimming in schools of fish, biting. It has also been observed to traverse schools of tuna with its mouth open until the fish swim straight into it. The hunt for deep sea fish makes it necessary to overcome long distances. Just like other pelagic predatory fish such as the silky shark ( C. falciformis ), the blue shark ( Prionace glauca ), the tiger shark ( Galeocerdo cuvier ) or the great white shark ( Carcharodon carcharias ), it is not picky about the choice of prey and attacks on the hunt all possible prey animals of suitable size (opportunistic predator). The wide range of food available allows these species to cope with almost any marine habitat. Correspondingly, however, it is also potentially dangerous for swimmers and divers, since it can also regard them as prey.
Although this shark does not form schools, it sometimes hunts in groups, especially the younger sharks form such groups. With larger prey and carcasses, they can also appear together with other deep sea sharks, especially blue sharks and hammerhead sharks . There are also known associations with pilot whale schools where the sharks benefit from the schools of fish they hunted.
Reproduction
The oceanic whitetip as other species of the genus Carcharhinus viviparous ( viviparous ) and forms a yolk sac - placenta . The 1 to 15 young sharks are born after a gestation period of around 12 months, with the older females having more young. The females give birth to their young in shallow coastal areas with cloudy water. It was with the animals in the western North Atlantic Ocean and in the southwest Indian Ocean a seasonality of breeding season observed in early summer, while in the central Pacific can be caught on pregnant females all year and here birth and mating are obviously not restricted to specific seasons.
The young animals have a size of about 60 to 65 centimeters, up to a size of 120 cm they still have black fin tips. The animals reach sexual maturity with 175 to 200 cm. This, together with the slow growth of the young, is probably one of the reasons why the reproduction rate of this shark is not particularly high despite the multiple births.
Taxonomic description
The white tip ocean shark was first described by René-Primevère Lesson in his notes during Louis Duperrey's circumnavigation of the world in 1822-1825 with the La Coquille . Lesson described two individuals he discovered in the Tuamotu Archipelago in French Polynesia and named the shark as Squalus maou after the Polynesian word for "shark". However, this first description was lost and forgotten.
In 1861 the Cuban Felipe Poey described the species again under the name Squalus longimanus . The epithet longimanus (from Latin for "long hand") refers to the size of the shark's pectoral fins, which are enlarged like wings compared to other species. After various taxonomic revisions, the shark was later classified as Pterolamiops longimanus and finally under the name Carcharhinus longimanus , which is valid today .
According to the rules of the International Commission for Zoological Nomenclature (ICZN), the first published description is used as a priority for naming. Accordingly, the scientific name Carcharhinus maou should be preferred for this species. Since the first description of Lessons was lost and unknown for so long, the name Carcharhinus longimanus was retained as a generally accepted scientific name.
Systematics
The whitetip deep-sea shark is now classified as a species of the genus Carcharhinus and can be clearly distinguished from the other representatives of the genus by a number of morphological features. The genus currently includes around 30 species. This type forms within this genus probably a monophyletic group with dusky ( C. obscurus ), the Galapagos Shark ( C. galapagensis ), the Silky ( C. falciformis ), the sandbar shark ( C. plumbeus ), the bignose shark ( C. Altimus ) and the Caribbean reef shark ( C. perezi ), characterized by molecular biological features and morphological features such as the interdorsal ridge on the back and the large triangular teeth in the upper jaw.
Subspecies of the whitetip shark are not described.
Humans and whitetip deep sea sharks
The whitetip deep sea shark can be dangerous to humans. Due to its way of life far from the coast, encounters are rare, however there are a number of documented cases of attacks on swimmers, divers and boats by this species as well as others in which the white tip deep-sea shark is suspected as the attacker. A number of divers reported that whitetip deep-sea sharks circled them persistently and approached them at regular intervals.
Most of the accidents after plane crashes and ship sinkings in the high seas of the Pacific during World War II are attributed to them. In these cases, the victims were mostly wounded, who were easy prey for the sharks. Hennemann reports on a report by the South African Oceanographic Research Institute (ORI), according to which it is suspected that whitetip deep-sea sharks caused the deaths of many people when the ship Nova Scotia was sunk by a German submarine off the coast of Natal . Most of the shark attacks on the survivors of the USS Indianapolis in July 1945 are said to have been caused by the whitetip deep-sea shark. This story was portrayed at length in the movie Jaws in a monologue by the character Quint, played by Robert Shaw .
In the documentary Le Monde du silence by Jacques-Yves Cousteau , whitetip deep-sea sharks were filmed together with a large blue shark as they "attacked" the carcass of a sperm whale calf that had previously been killed by Cousteau after an accident . The diving team involved reported that individual sharks regularly approached them and had to be chased away by blows on the snout.
Endangerment and population development
The IUCN put Carcharhinus longimanus on the Red List of Endangered Species in May 2008 and classified it as vulnerable ( endangered ). The high pressure caused by fishing in a large part of its distribution area is given as the cause of danger . It is mainly caught as bycatch in deep-sea fishing with longlines and trawls. Its very large fins are also very popular as the basis of the well-known shark fin soup , the carcass is disposed of after the fins have been removed. Due to the very imprecise data on deep-sea fishing, there are no specific catch figures or information on population size and change.
Individual populations in northwestern and western Atlantic are currently considered already as threatened with extinction ( critically endangered ). In these, the population numbers fell by over 70% between 1992 and 2000. In the Gulf of Mexico, the decline from the 1950s to the 1990s was even 99.3%.
While the whitetip deep-sea shark, together with the blue shark and the silky shark, was the most common type of large shark a few years ago and its occurrence was very common in areas with sea depths over 180 meters, it is only encountered occasionally today.
In March 2013, at the CITES Species Conservation Conference in Bangkok , it was decided to regulate the trade in whitetip deep-sea sharks; the regulation came into force on September 14, 2014.
literature
- Leonard JV Compagno : FAO Species Catalog. Volume 4: Sharks of the world. An annotated and illustrated catalog of shark species known to date. Part 2: Carcharhiniformes. (= FAO fisheries synopsis. Volume 4, No. 125, Part 2). Food and Agriculture Organization of the United Nations, Rome 1984, ISBN 92-5-101383-7 , pp. 484–86, 555–61, 588 ( full PDF , species portrait ).
- Leonard JV Compagno, Marc Dando, Sarah Fowler: Sharks of the World. Princeton Field Guides, Princeton University Press, Princeton / Oxford 2005, ISBN 0-691-12072-2 , p. 330.
- Alessandro De Maddalena, Harald Bänsch: Sharks in the Mediterranean. Franckh-Kosmos Verlag, Stuttgart 2005, ISBN 3-440-10458-3 , pp. 192-195.
- Ralf Michael Hennemann: Sharks & rays worldwide . 1st edition. Year Top Special, Hamburg 2001, ISBN 3-86132-584-5 , p. 141-143 .
Individual evidence
- ↑ a b c d e Carcharhinus longimanus in the IUCN Red List of Threatened Species 2019. Accessed July 12, 2020.
- ↑ a b Whitetip Ocean Shark on Fishbase.org (English)
- ^ Leonard JV Compagno: FAO Species Catalog. (= FAO fisheries synopsis. Volume 4 , No. 125, Part 2). tape 4 : Sharks of the world. An annotated and illustrated catalog of shark species known to date. Part 2: Carcharhiniformes . Food and Agriculture Organization of the United Nations, Rome 1984, ISBN 92-5101383-7 , p. 484-86, 555-61, 588 ( PDF ).
- ↑ a b c Alessandro De Maddalena, Harald Bänsch: Sharks in the Mediterranean. Franckh-Kosmos Verlag, Stuttgart 2005, ISBN 3-440-10458-3 , p. 192 ff.
- ^ Marine Life News. British Marine Life Study Society, accessed July 16, 2020 .
- ↑ E. Lieske, R. Myers: Coral reef guide Red Sea. Franckh-Kosmos Verlag, Stuttgart 2004, ISBN 3-440-09356-5 , p. 15.
- ^ Jacques-Yves Cousteau, Philippe Cousteau: The Shark: Splendid Savage of the Sea. Doubleday & Company, New York 1970, ISBN 0-385-06892-1 .
- ^ Excursus on opportunistic robbers. in the species portrait tiger shark. De Maddalena, Bänsch, 2005, p. 207.
- ^ Ralf Michael Hennemann: Haie & Rochen worldwide . 1st edition. Year Top Special, Hamburg 2001, ISBN 3-86132-584-5 , p. 141-143 .
- ^ A b Integrated Taxonomic Information System: Carcharhinus longimanus. Accessed October 15, 2008.
- ↑ a b c Compagno, 1984.
- ↑ according to ITIS there are 31 species, but the species status of individual species has not yet been conclusively clarified.
- ↑ GJP Naylor: The phylogenetic relationships among Requiem and hammerhead sharks: inferring phylogeny When Thousands of Equally most parsimonious trees result. In: Cladistic. Volume 8, No. 4, 1992, pp. 295-318, doi: 10.1111 / j.1096-0031.1992.tb00073.x .
- ^ Mine Dosay-Akbulut: The phylogenetic relationship within the genus Carcharhinus. In: Comptes Rendus Biologies. Volume 331, No. 7, 2008, p. 500, doi: 10.1016 / j.crvi.2008.04.001 .
- ↑ Whitetip deep-sea shark in the hai.ch database
- ^ AJ Bass, JD D'Aubrey, N. Kistnasamy: Sharks of the east coast of southern Africa. Volume 1: The genus Carcharhinus (Carcharhinidae). (= Investigation Reports of the Oceanographic Research Institute. Volume 33). Oceanographic Research Institute, Durban 1973, ISBN 0-86989-008-5 (cited in Compagno, 1984).
- ↑ R. Aidan Martin: Elasmo Research . Accessed October 16, 2008.
- ↑ IUCN : You can swim but you can't hide - more oceanic sharks on the IUCN Red List. , Notification dated May 22, 2008
- ^ Cites resolution: Endangered shark and manta ray species should be protected. In: Spiegel Online . March 11, 2013, accessed December 12, 2017 .
- ↑ Protection of species: Humans now have to protect these sharks better. In: The time . September 12, 2014, accessed December 12, 2017 .
Web links
- Whitetip deep sea shark on Fishbase.org (English)
- Whitetip deep sea shark in the hai.ch database
- Whitetip deep sea shark in nature-in-pictures
- Cathleen Bester: Oceanic Whitetip Shark. Florida Museum of Natural History. Accessed October 15, 2008
- Ben S. Roesch: Biology and Behavior of the Oceanic Whitetip ( Memento of October 10, 2006 in the Internet Archive )
