The whitetip reef shark (Triaenodon obesus) is a species of requiem shark, in the family Carcharhinidae, and the only member of its genus. A relatively small species, few whitetip reef sharks are longer than 1.6 m, this species is easily recognizable by its slender body and short but broad head, as well as tubular skin flaps beside the nostrils, oval eyes with vertical pupils, with characteristic white markings on the tips of several of its fins. These markings gave it its common name. It is an agile swimmer well suited for its mostly reef habitat existence.
The whitetip reef shark is widely distributed across the entire Indo-Pacific region. In the Indian Ocean, it is found from northern KwaZulu-Natal, South Africa to the Red Sea and the Indian subcontinent, including Madagascar, Mauritius, Comoros, the Aldabra Group, Seychelles, Sri Lanka, and the Chagos Archipelago. In the western and central Pacific, it occurs from off southern China, Taiwan, and the Ryukyu Islands, to the Philippines, Southeast Asia, and Indonesia, to northern Australia, and is also found around numerous islands in Melanesia, Micronesia, and Polynesia, as far as Hawaii to the north, and the Pitcairn Islands to the southeast. In the eastern Pacific, it occurs from Costa Rica to Panama, and off the Galápagos Islands.
Associated almost exclusively with coral reef habitats, whitetip reef sharks are most often encountered around coral heads and ledges with high vertical relief, and additionally over sandy flats, in lagoons, and near drop-offs to deeper water. They prefer very clear water and rarely swim far from the bottom. This species is most common at a depth of 8-40 m. On occasion, they may enter water less than 1 m deep. Individuals may stay within a particular area of the reef for months or years, frequently returning to the same shelter. A whitetip reef shark can survive for six weeks without food. These sharks are not territorial and share their home ranges with others of their species, they do not perform threat displays.
During the day, whitetip reef sharks spend much of their time resting inside caves. Unlike other requiem sharks, which rely on ram ventilation and must constantly swim to breathe, this shark can pump water over its gills and lie still on the bottom. This species feeds mainly on bony fishes, including eels, squirrelfishes, snappers, damselfishes, parrotfishes, surgeonfishes, triggerfishes, and goatfishes, as well as octopuses, spiny lobsters, and crabs. Whitetip reef sharks hunt primarily at night when many fishes are asleep and easily taken. After dusk, groups of sharks methodically scour the reef, often breaking off pieces of coral in their vigorous pursuit of prey. Multiple sharks may target the same prey item, covering every exit route from a particular coral head. Each shark hunts for itself and is in competition with the others in its group. Like all sharks, whitetip reef sharks rely on electroreceptors in their snouts to detect the electrical charges of nearby prey. Although they are formidable predators, whitetip reef sharks are preyed upon by larger fish, such as tiger sharks and giant grouper.
Unlike its Oceanic cousin, the white tip reef shark is more harmless and is seldom aggressive unless provoked. They are also fearless and curious, as the whitetip reef sharks may approach swimmers closely to investigate. However, these sharks readily attempt, and quite boldly, to steal catches from spear fishers, which has resulted in several people being bitten in the process. Whitetip reef sharks are well-suited to ecotourism diving, and with conditioning, they can be hand-fed by divers.
The International Union for Conservation of Nature (IUCN) has assessed this species as Vulnerable, as its numbers have dropped in recent decades due to increasing, and thus far unregulated, fishing pressure in the tropics. Its restricted habitat, low dispersal, and slow reproduction are factors that limit this shark's capacity for recovering from overfishing.
#Nature #Fish #NightHunting
4 окт 2024
