It feeds mainly on bony fishes and cephalopods, and has been known to drive them into compacted schools before launching open-mouthed, slashing attacks. [7], The silky shark is one of the three most common pelagic sharks along with the blue and oceanic whitetip sharks, and counts among the most numerous large oceanic animals in the world with a population of at least tens of millions. [9] Mine Dosay-Abkulut's 2008 ribosomal DNA analysis, which included the silky, blue, and bignose sharks, confirmed the closeness of those three species. The species was also given greater protection through an Appendix II listing by the Convention on the International Trade in Endangered Species, which … The upper teeth are triangular and strongly serrated, with a notch in the posterior edge; they are erect at the center and become more oblique towards the sides. Regional assessments have found similar trends, estimating declines of some 90% in the central Pacific from the 1950s to the 1990s, 60% off Costa Rica from 1991 to 2000, 91% in the Gulf of Mexico from the 1950s to the 1990s, and 85% (for all large requiem sharks) in the northwestern Atlantic from 1986 to 2005. [13] In 1988, Leonard Compagno assigned it phenetically to an informal "transitional group" also containing the blacknose shark (C. acronotus), the blacktip reef shark (C. melanopterus), the nervous shark (C. cautus), the copper shark (C. brachyurus), and the night shark (C. [15], The silky shark has a cosmopolitan distribution in marine waters warmer than 23 °C (73 °F). [2] The silky shark's common name comes from the fine texture of its skin compared to other sharks, a product of its tiny, densely packed dermal denticles. The silky shark tends to be more aggressive if encountered on a reef than in open water. ... Sickle Shark, Sickle-shaped Shark, Sickle Silk Shark, Net-eater Shark. Experiments in which these sounds were played underwater attracted sharks from hundreds of meters away. [40], Silky sharks in most parts of the world are thought to reproduce year-round, whereas mating and birthing in the Gulf of Mexico take place in late spring or early summer (May to August). Regardless of which one dominates, the two predators do not engage in any overtly aggressive behavior against each other. The silky shark is listed on Annex I, Highly Migratory Species, of the United Nations Convention on the Law of the Sea, though this has yet to result in any management schemes. If a large number of sharks is present, they tend to remain inside the prey school, while the dolphins consign themselves to the periphery, possibly to avoid incidental injury from the sharks' slashing attacks. A two-thirds majority was needed to secure listing, but the silky shark and thresher shark proposals were adopted with support from 79% of Parties voting. The newborn sharks spend their first months in relatively sheltered reef nurseries on the outer continental shelf, growing substantially before moving into the open ocean. [23], The dorsal and pectoral fins are distinctive and help to distinguish the silky shark from similar species. Considering that the scalloped hammerhead shark is categorized as “critically endangered” by the IUCN Redlist of Threatened Species, these new … Garrick, J. (1982). A narrow dorsal ridge runs between the dorsal fins. Improving the conservation and management of the silky shark, the thresher sharks and mobula rays ALARMED that the IUCN Shark Specialist Group estimates that one-quarter of shark species (sharks, skates, rays, chimaeras) are threatened with extinction, primarily due to overfishing; Females give birth to litters of up to 16 pups annually or biennially. [8], Fossilized teeth belonging to the silky shark have been found in North Carolina: from the vicinity of two baleen whales, one in mud dating to the Pleistocene-Holocene (circa 12,000 years ago) and the other in Goose Creek Limestone dating to the Late Pliocene (circa 3.5 million years ago – Mya), as well as from the Pungo River, dating to the Miocene (23–5.3 Mya). Organized by the IUCN Shark Specialist Group (SSG), the study was conducted by 15 scientists from 13 different research institutes around the world, with additional contributions from scores of other SSG members. This species often trails schools of tuna, a favored prey. [24] One of the largest members of its genus, the silky shark commonly reaches a length of 2.5 m (8.2 ft), with a maximum recorded length and weight of 3.5 m (11 ft) and 346 kg (763 lb), respectively. One central Pacific study has found females growing much slower than males, but the results may have been skewed by missing data from large females. Since 2017, the silky shark has been classified as a vulnerable species by the International Union for Conservation of Nature (IUCN). [8] Females grow larger than males. In the Central and Eastern Tropical Pacific silky sharks are even more endangered and classified as ’vulnerable.’ The silky shark is viviparous, meaning that the developing embryos are sustained by a placental connection to their mother. It is one of the most abundant sharks in the pelagic zone, and can be found around the world in tropical waters. C. falciformis are migratory and found in oceanic and coastal habitats of tropical water. signatus). [45] Males and females reach sexual maturity at ages of 6–10 years and 7–12+ years, respectively. Because of their abundance, they form a major component of commercial and artisanal shark fisheries in many countries. [28], Studies conducted off the Florida coast and the Bahamas have shown that silky sharks are highly sensitive to sound, in particular low-frequency (10–20 Hz), irregular pulses. Silky sharks are mostly found in the coastal and oceanic wa­ters of trop­i­cal oceans, mainly at tem­per­a­tures above 23°C. [1] The litter size ranges from one to 16 and increases with female size, with six to 12 being typical. The large size and cutting teeth of the silky shark make it potentially dangerous, and it has behaved aggressively towards divers. C. falciformis is a top level predator (Frazelle, 2016), a piscivorous shark that feeds on a variety of fish (IUCN, 2016), and can often be found accompanying a school [45] The maximum lifespan is at least 22 years. Spinner sharks get their name from their interesting feeding strategy, which involves spinning through a school of fish, snapping them up, and often leaping into the air. A scientific description of the silky shark was first published by the German biologists Johannes Müller and Jakob Henle under the name Carcharias (Prionodon) falciformis, in their 1839 Systematische Beschreibung der Plagiostomen. Since 2017, the silky shark has been classified as a vulnerable species by the International Union for Conservation of Nature (IUCN). [4][7] The coloration quickly fades to a dull gray after death. It has a rounded apex, an "S"-shaped rear margin, and a free rear tip about half as long as the fin is tall. [1] Organizations such as the International Commission for the Conservation of Atlantic Tunas and the Inter-American Tropical Tuna Commission have also taken steps to improve fishery monitoring, with the ultimate goal of reducing shark bycatch. IUCN Status: Near Threatened . The fins (except for the first dorsal) darken at the tips; this is more obvious in young sharks. The silky shark has a slender, streamlined body and typically grows to a length of 2.5 m (8 ft 2 in). Status in the IUCN Red List: No Entry found in Red List. In the Pacific Ocean, the northern extent of its range runs from southern China and Japan to southern Baja California and the Gulf of California, while the southern extent runs from Sydney, Australia, to northern New Zealand to northern Chile. Eastern Atlantic and Indian Ocean sharks seem to match or exceed the size of northwestern Atlantic sharks, but the figures are based on relatively few individuals and more data are needed. They can be found in the northwestern Atlantic, in the western, central, and eastern Pacific, and in the Indian Ocean. [37][47] As of May 2009, the International Shark Attack File lists six attacks attributable to the silky shark, three of them unprovoked and none fatal. Furthermore, their association with tuna results in many sharks being taken as bycatch in tuna fisheries. Conversely, if a large enough group of dolphins gathers, they become able to chase the sharks away from the prey school. [4] Tracking studies in the tropical eastern Pacific and northern Gulf of Mexico have found that cruising silky sharks spend 99% of their time within 50 m (160 ft) of the surface, and 80–85% of their time in water with a temperature of 26–30 °C (79–86 °F); the pattern was constant regardless of day or night. [19] Larger sharks generally move longer distances than smaller ones. In 1989 alone, some 900,000 individuals were taken as bycatch in the southern and central Pacific tuna longline fishery, seemingly without effect on the total population. Silky sharks are classified as ‘near threatened’ by the International Union for Conservation of Nature (IUCN). [10][11] Fossil teeth have also been found in Pliocene strata at the Cava Serredi quarry in Tuscany, Italy. [2] When attacking tightly packed fish, silky sharks charge through the ball and slash open-mouthed, catching the prey fish at the corners of their jaws. [25] Fishery data on this shark are often confounded by under-reporting, lack of species-level separation, and problematic identification. & Simpfendorfer, C. Report Card Remarks In Australia, there is no take of Silky Sharks in the tuna fisheries. "The force of bites by the Silky Shark (, CS1 maint: multiple names: authors list (, International Union for Conservation of Nature, United Nations Convention on the Law of the Sea, International Commission for the Conservation of Atlantic Tunas, https://dx.doi.org/10.2305/IUCN.UK.2017-3.RLTS.T39370A117721799.en, "The phylogenetic relationships among requiem and hammerhead sharks: inferring phylogeny when thousands of equally most parsimonious trees result", "NMFS Cooperative Shark Tagging Program 1962–63: An atlas of shark tag and recapture data", "Distribution, abundance, and habits of pelagic sharks in the central Pacific Ocean", "A review of shark agonistic displays: comparison of display features and implications for shark-human interactions", "Interactions between marine predators: dolphin food intake is related to number of sharks", ISAF Statistics on Attacking Species of Shark, 10.1577/1548-8446(2005)30[19:ITCOSP]2.0.CO;2, "Robust estimates of decline for pelagic shark populations in the northwest Atlantic and Gulf of Mexico", "Reply to 'Robust estimates of decline for pelagic shark populations in the Northwest Atlantic and Gulf of Mexico, Florida Museum of Natural History Ichthyology Department, Species Description of Carcharhinus falciformis, https://en.wikipedia.org/w/index.php?title=Silky_shark&oldid=986567070, Creative Commons Attribution-ShareAlike License, Confirmed (dark blue) and suspected (light blue) range of the silky shark, Phylogenetic relationships of the silky shark, based on allozyme sequences, This page was last edited on 1 November 2020, at 17:30. [32] Known parasites of this shark include the isopod Gnathia trimaculata,[33] the copepod Kroeyerina cortezensis,[34] and the tapeworms Dasyrhynchus variouncinatus and Phyllobothrium sp. [2] However, given the highly migratory nature of the silky shark and its association with tuna, no simple way is known to reduce bycatch without also affecting the economics of the fishery.[21]. Short, shallow furrows are present at the corners of the mouth. It is one of the most abundant sharks and can be found in tropical waters around the world. Their predators include killer whales (orcas), large sharks, and humans. [28] Some sport fishers catch silky sharks. [28][37], The silky shark is an opportunistic predator, feeding mainly on bony fishes from all levels of the water column, including tuna, mackerel, sardines, mullets, groupers, snappers, mackerel scads, sea chubs, sea catfish, eels, lanternfishes, filefishes, triggerfishes, and porcupinefishes. [11], Initial efforts to resolve the evolutionary relationships of the silky shark were inconclusive; based on morphology, Jack Garrick in 1982 suggested the blackspot shark (C. sealei) as its closest relative. "Sharks of the genus, Hoffmayer, E. R., Franks, J. S., Driggers, W. B. [4][22], The skin is densely covered by minute, overlapping dermal denticles. The silky shark has ranked high in terms of vulnerability to overfishing in Ecological Risk Assessments conducted by scientists affiliated with the International Commission for Conservation of Atlantic Tunas (ICCAT) and Indian Ocean Tuna Commission (IOTC). The pectoral fins are narrow and sickle-shaped, and particularly long in adults. [39], Like other members of its family, the silky shark is viviparous: once the developing embryo exhausts its supply of yolk, the depleted yolk sac is converted into a placental connection through which the mother delivers nourishment. [1][2] The meat (sold fresh or dried and salted), skin, and liver oil may also be used,[4] as well as the jaws: this species is the predominant source of dried shark jaw curios sold to tourists in the tropics. With prey often scarce in its oceanic environment, the silky shark is a swift, inquisitive, and persistent hunter. Silky shark species of fish ... IUCN taxon ID: 39370 NCBI taxonomy ID: 202609 ITIS TSN: 160310 Fossilworks taxon ID: 83188 Global Biodiversity Information Facility ID: 2418095 WoRMS-ID for taxa: 105789 FishBase species ID: 868 CITES Species+ ID: 67979 New Zealand Organisms Register ID: 302e9db1-37e0-40a9-9b72-33f4ce089827 Summary The Silky Shark is a large bodied oceanic Froese, Rainer and Pauly, Daniel, eds. Their underside… Highly mobile and migratory, this shark is most often found over the edge of the continental shelfdown t… The Silky shark is a type of shark of the genus Carcharhinus, family Carcharhinidae. [26] When confronted, the silky shark may perform a threat display, in which it arches its back, drops its tail and pectoral fins, and elevates its head. Established in 1964, the IUCN Red List of Threatened Species has evolved to become the world’s most comprehensive information source on the global conservation status of animal, fungi and plant species. [6][7] The back is metallic golden-brown to dark gray and the belly is snowy white, which extends onto the flank as a faint lighter stripe. [20][21] In the northern Atlantic, most sharks follow the Gulf Stream northward along the U.S. East Coast. ), along with 25 grey reef sharks (C. amblyrhynchos) and a lone silvertip shark (C. albimarginatus). Silky shark 濃い青は生息が確認された領域、薄い青は生息が予想される領域 [2] クロトガリザメ (黒尖鮫、 Carcharhinus falciformis ) は、 メジロザメ属 に属する サメ の一種。 Although slow-reproducing like most other sharks, the wide distribution and large population size of the silky shark was once thought to buffer the species against these fishing pressures. One account from the Red Sea describes 25 silky sharks following a large pod of bottlenose dolphins (Tursiops sp. Reproduction occurs year-round except in the Gulf of Mexico, where it follows a seasonal cycle. However, Japanese fisheries in the Pacific and Indian Oceans have recorded no change in catch rate between the 1970s and the 1990s,[1] and the validity of the methodologies used to assess declines in the Gulf of Mexico and the northwestern Atlantic have come under much debate. Over repeated exposures, silky sharks habituate to the sound change and stop withdrawing, though it takes them much longer to do so compared to the bolder oceanic whitetip shark. The first dorsal fin is relatively small, measuring less than a tenth as high as the shark is long, and originates behind the free rear tips of the pectoral fins. The shark then proceeds to swim in tight loops with a stiff, jerky motion, often turning broadside towards the perceived threat. The IUCN Red List of Threatened Species 2017: e.T39370A117721799. [38] A well-established association exists between this species and tuna: off Ghana, almost every tuna school has silky sharks trailing behind, and in the eastern Pacific, these sharks inflict such damage to tuna fishing gear and catches that fishery workers have given them the moniker "net-eating sharks". This pelagic shark, formerly abundant in all tropical oceans, has declined by an estimated 85% in the last 20 years, and is now listed as vulnerable and declining by the International Union for the Conservation of Nature (Rice & Harley, 2013; IUCN, 2017). [12] Carcharhinus elongatus, an earlier representative of its lineage with smooth-edged teeth, is known from Oligocene (34–23 Mya) deposits in the Old Church formation of Virginia, and the Ashley formation of South Carolina. [2] Females give birth after a gestation period of 12 months, either every year or every other year. However, data now suggest that silky shark numbers are declining around the world, which prompted the IUCN to reassess its conservation status to Vulnerable in 2017. The caudal fin is fairly high with a well-developed lower lobe. The pectoral fins are long and slim, and have dusky coloured tips.Silky sharks are normally dark grey with a shade of bronze, but are sometimes a golden-brown colour. Although multiple individuals may feed at once, each launches its attack independently. The Silky shark is large, slim, and grows up to a maximum length of 3.3 metres. Subsequent authors have assigned this species to the genus Carcharhinus. Nevertheless, mounting evidence indicates the silky shark has, in fact, declined substantially worldwide, a consequence of its modest reproductive rate which is unable to sustain such high levels of exploitation. [14], More recently, Gavin Naylor's 1992 phylogenetic analysis, based on allozyme sequence data, found that the silky shark is part of a group containing large sharks with a ridge between the dorsal fins. The five pairs of gill slits are moderate in length. [6], The specific epithet falciformis is Latin for "sickle-shaped", which refers to the outline of the dorsal and pectoral fins. It may also take squid, paper nautilus, and swimming crabs, and fossil evidence indicates it scavenged on whale carcasses. The silky shark is an active, inquisitive, and aggressive predator, though it will defer to the slower but more powerful oceanic whitetip shark in competitive situations. They are often caught as by-catch in tuna fisheries. The silky shark ( Carcharhinus falciformis) is listed on the IUCN Red List of Threatened Species as Near Threatened globally but Vulnerable in some regions due to continued declines in their populations around the world. Cases of individual sharks persistently harassing divers and even forcing them out of the water have been reported. Current IUCN Conservation Status of Silky Sharks|Conservation Evidence|NOAAUNEP World Conservation Monitoring Centre: Silky Sharks|Check the Seafood Watch List for this speciesSilky sharks, Carcharhinus falciformis, are considered dangerous to humans because of their aggressive nature and size. It is the most common shark caught as bycatch in the eastern Pacific and Gulf of Mexico tuna fisheries, and the second-most common shark caught as bycatch (next to the blue shark) overall. [26] This shark is often found around floating objects such as logs or tethered naval buoys. A .F. The second dorsal fin is tiny, smaller than the anal fin, with a drawn-out free rear tip up to three times as long as the fin is tall. It occurs throughout the Indian Ocean, as far south as Mozambique in the west and Western Australia in the east, including the Red Sea and the Persian Gulf. [2][28][30], The life history characteristics of the silky shark differ across its range (see table). On occasion, it may venture into coastal waters as shallow as 18 m (59 ft). The silky shark is an opportunistic predator feeding mainly on bony fishes from all levels of thewater column, including tuna, mackerel, sardines, mullets, groupers, snappers, mackerel scads,sea chubs, sea catfish, eels, lanternfishes, filefishes, triggerfishes, and porcupinefishes. A large, slim shark, the Silky shark has a fairly stretched , rounded snout, a relatively slanting first dorsal fin with a blunt top that is located behind the edges of the pectoral fins, a small second dorsal fin with an extremely long free rear tip (more than two times the height), and a low inter-dorsal ridge (ridge between the dorsal fins). [2] Sharks from more temperate waters may grow slower and mature later than those in warmer regions. The anal fin originates slightly ahead of the second dorsal fin and has a deep notch in the posterior margin. The Silky Shark get its name for its smooth skin. [2][4][10] Good feeding opportunities can draw silky sharks in large numbers; one such feeding aggregation in the Pacific has been documented "herding" a school of small fishes into a compact mass (a bait ball) and trapping it against the surface, whereupon the sharks consumed the entire school. Downloaded on 09 June 2015. Silky shark French: Requin soyeux Spanish: Tiburón jaqueton Appearance: Large, slim shark with moderately large eyes.