Sand tiger shark: Difference between revisions
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The '''sand tiger shark''' or grey nurse shark |
The '''sand tiger shark'''(''Carcharias taurus'') or '''grey nurse shark''' is a species of shark that inhabits coastal waters worldwide. It lives close to the shorelines and beaches of North America, hence the name, sand tiger shark. It also dwells in the waters of Japan, Australia, South Africa, Great Britain, and Scandinavia. Despite a fearsome appearance and strong swimming abilities, it is a relatively placid and slow moving animal. This species has a sharp, pointy head, and a bulky body. The sand tiger's length can reach 10 to 11 feet (about 3.2m to 3.3m). They are grey with reddish-brown spots on their backs. The sand tiger hunts close to shore in the surf zone, and between the [[epipelagic]] and the [[mesopelagic]] regions of the [[water column]]. The sand tiger has been known to herd together when hunting larger schools of fish. Their diet consists of bony fish, crustaceans such as [[thunnus|bluefin]], squid, and skates. Two behaviors that set the sand tiger apart from other sharks is its reproductive activities, and its ability to gulp air from the surface in an effort to float effortless throughout the water. After mating, a unique embryonic development process takes place called [[aplacental viviparity]]. This is when one embryo feeds off of other embryos in the mother's uterus. The sand tiger is currently under the vulnerable status on the International Union for Conservation of Nature Red List. It is the most widely kept shark in public aquariums around the world due to its large size and higher adaptability to captivity than other large sharks. |
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==Taxonomy== |
==Taxonomy== |
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Revision as of 00:39, 6 December 2011
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| Species: | C. taurus
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| Carcharias taurus Rafinesque, 1810
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The sand tiger shark(Carcharias taurus) or grey nurse shark is a species of shark that inhabits coastal waters worldwide. It lives close to the shorelines and beaches of North America, hence the name, sand tiger shark. It also dwells in the waters of Japan, Australia, South Africa, Great Britain, and Scandinavia. Despite a fearsome appearance and strong swimming abilities, it is a relatively placid and slow moving animal. This species has a sharp, pointy head, and a bulky body. The sand tiger's length can reach 10 to 11 feet (about 3.2m to 3.3m). They are grey with reddish-brown spots on their backs. The sand tiger hunts close to shore in the surf zone, and between the epipelagic and the mesopelagic regions of the water column. The sand tiger has been known to herd together when hunting larger schools of fish. Their diet consists of bony fish, crustaceans such as bluefin, squid, and skates. Two behaviors that set the sand tiger apart from other sharks is its reproductive activities, and its ability to gulp air from the surface in an effort to float effortless throughout the water. After mating, a unique embryonic development process takes place called aplacental viviparity. This is when one embryo feeds off of other embryos in the mother's uterus. The sand tiger is currently under the vulnerable status on the International Union for Conservation of Nature Red List. It is the most widely kept shark in public aquariums around the world due to its large size and higher adaptability to captivity than other large sharks.
Taxonomy
Scientific naming process
The sand tiger shark's scientific name, Carcharias taurus, was originally determined by Rafinesque, a Turkish naturalist, after catching a specimen off the coast of Sicily. The scientific name has since undergone many disputes and changes. Twenty-seven years after Rafinesque's original naming, Müller and Henle, German biologists, changed the genus name from C. taurus to Triglochis taurus.[2] The following year, the Swiss-American naturalist, Jean Louis Rodolphe Agassiz, introduced the name idea of Odontaspis cuspidata based upon examples of fossilized teeth. Agassiz's name was used for 120 years, only to cease in 1961 when three paleontologists and ichthyologists, W. Tucker, E.I. White, and N.B. Marshall, requested to repeal the Odontaspis cuspidate name. The experts' request for a name change from Odontaspis to Carcharias was rejected and Odontaspis was approved by the ICZN. However, experts realized that taurus belongs after Odontaspis. Therefore, the name was changed to Odontaspis taurus.[2] In 1977, a South African shark expert, Leonard J.V. Compagno, challenged the Odontaspis taurus name and substituted Eugomphodus, a somewhat unknown classification, for Odontaspis. However, many taxonomists and experts question his change saying that there is not a significant difference between Odontaspis and Carcharias. However, after changing the name to "Eugomphodus taurus", Compagno played a key role in changing the name of the shark to "Carcharias taurus". He proposed the name because it fit best to the characteristics of the shark because "Carcharias taurus" means "a shallow-water shark with sharp jagged teeth". The ICZN approved this name, and today the name is used among shark experts.[2]
Common Names
Since the sand tiger is a cosmopolitan species, there are many common names. The grey nurse shark, the name commonly used in Australia and the United Kingdom, is the second most used name of the shark. Other names used include spotted ragged tooth in South Africa and blue-nurse sand tiger in India.[3]
Description
Sand tigers have many features that distinguish them from other shark species. The sand tiger's eyes tend to be smaller than other sharks and lack eyelids.[4] The sand tiger shark's head is rather pointy, not round and the teeth are smooth edged and sharp-pointed. Their mouth extends beyond their eyes, and they usually swim with their mouth open. The sand tiger is most widely feared and know because of its three rows of protruding, sharp teeth. These teeth are very unique to this species of shark. Their snout is flattened with a conical shape. Their body is stout and bulky. Adult sharks tend to have reddish-brown spots mostly on their backs, but also scattered around their entire body.[4] In addition, juvenile sand tiger sharks have yellow-brown spots on their bodies.[5] The sand tiger shark usually has a grey back and white underside. The males also have a grey reproductive organ on the underside with a white tip. The tail is elongated and has a long upper lobe. They have two large, grey dorsal fins that are almost equal in size. The dorsal fins are set back almost beyond the pectoral fins and are broad-based.[6] The pectoral fins are triangular, and the tail is almost one-third as long as the head of the shark. The sand tiger's length on average can reach up to 10 to 11 feet (about 3.2m to 3.3m) . They can weigh 350 pounds (about 159 kg).[7] In August 2007, an albino specimen was photographed off South West Rocks, Australia.[8]
Diet
The diet of the sand tiger shark consists of fish, young sharks, rays, and crustaceans.[9] Sand tigers have been spotted around large schools of bluefin, and many of the sharks have been known to attack tuna trapped in nets. The Sand tiger hunts a variety of fish along the Atlantic coast of North America. These fish include skates, mackerel, menhaden, butterfish, flounder, weakfish, bonito, alewives, and silver hake.[10] However, the sand tiger prefers bony fish such as eels, mullets, and sea basses.[11] They also hunt a variety of mollusk and crustaceans, including rock lobster, crabs, squid, and octopus.
Behavior
Sand tiger sharks will often shelter in caves during the day, when they are more sluggish, and they become active and feed at night. The sand tiger shark is the only known shark to gulp and store air in its stomach, which maintains the shark's neutral buoyancy while swimming and allows them to hunt motionlessly and quietly as not to alert their prey.[11][12] When preying upon large schools of fish, this species has been known to gather a hunting herd.[13] The sand tiger can appear to be rather lazy because they effortlessly float through the water, searching for prey. Many sand tigers group together. In these schools, the sharks hunt large prey or mate with other sharks.[14] As the shark matures, it tends to eat larger prey such as other sharks, dolphins, and swordfish. However, biologists observed that the sand tiger swallows their prey whole 93.7 percent of the time. Swallowing large prey whole can cause health problems such as esophagus, heart, and liver damage.[15] Since the sand tiger is docile, it is the most aquarium kept shark around the world.[12]
Aggressions with humans
People associate the sand tigers with a vicious demeanor because their teeth protrude from their mouths when their jaws are closed; however, they are generally not a threat to humans. The sand tiger has not been known to attack humans without being provoked. This shark is very docile, only attacking when harassed.[16] Spearfishing may lead to aggressive behavior; however, humans are rarely attacked when fishing this way.[11] When the sharks get aggressive, they tend to steal the fish or bait. Sand tigers, in search of fish, roam the surf of the Atlantic coast, often in close proximity to humans. There have been twenty-nine unprovoked attacks. Only two human fatalities have resulted from unprovoked sand tiger attacks.[11]
Habitat and range
Sand tiger sharks usually live in sandy coastal waters, estuaries, shallow bays, and rocky or tropical reefs, at depths of up to 190 meters, although sand tiger sharks inhabiting even deeper depths have been recorded. As far as the sand tiger's location in the water column, it roams between the epipelagic and the mesopelagic regions.[11] There have been only three reports of sand tiger sharks in Canadian waters: in the Minas Basin of Nova Scotia; near St. Andrews, New Brunswick; and off Point Lepreau, New Brunswick. The sand tiger shark can be found in the Atlantic, Pacific and Indian Oceans, and also in the Mediterranean and Adriatic Seas.[11]
In the Western Atlantic, the sand tiger shark is found in the coastal waters around the United States (from the Gulf of Maine to Florida), in the northern Gulf of Mexico around the Bahamas and Bermuda, and from southern Brazil to northern Argentina. The sand tiger shark is also found in the eastern Atlantic from the Mediterranean Sea to the Canary Islands, at the Cape Verde Islands, along the coasts of Senegal and Ghana, and from southern Nigeria to Cameroon. In the western Indian Ocean, the shark's habitat ranges from South Africa to southern Mozambique, but it does not live around Madagascar. The sand tiger shark has also been sighted in the Red Sea and may be found as far east as India. In the western Pacific, it has been sighted in the waters around the coasts of Japan and Australia, but not New Zealand.[1]
The sand tiger tends to dwell in warmer waters, and migrates according to their hemisphere's seasonal changes (south for the winter; north for the summer). However, when migrating, the species tends to not travel great distances.[17]
Reproduction
Males tend to reach their sexual maturity at about six to seven years old, approximately six feet long. Females reach maturity when approximately seven feet long, about nine to ten years old.[4] Mating often occurs around the months of March and April in the Northern Hemisphere.[4] During mating, the male sand tiger grasps the females fins with his teeth. This can often leave deep cuts in the female's head that heal normally within a week. The male shark uses "claspers", which are the male's two reproductive organs between his pelvic fins, to inseminate the female.[18] The sand tiger shark has one of the lowest reproduction rates of all species of sharks, therefore, they are easily affected by any population pressure.[12] Female sharks have two uteri. The reproductive process of the sand tiger, aplacental viviparity, is a process in which developing embryos in the mother's uterus are killed and devoured by one to two surviving pups. There are even reports of biologists probing the bellies of landed females and having their fingers nipped by the cannibalistic young with their fully developed teeth.[19] Hydroids grow on the mother's teeth during pregnancy because she stops eating.[20] When the young are around three feet long, the mother gives birth to them in a lengthy labour. The gestation period is approximately eight to nine months.[4]
Conservation status
This species is listed as vulnerable on the International Union for Conservation of Nature Red List,[1] and as endangered under Queensland's Nature Conservation Act 1992. It is a U.S. National Marine Fisheries Service Species of Concern. Species of Concern are those species about which the U.S. Government’s National Oceanic and Atmospheric Administration, National Marine Fisheries Service (NMFS), has some concerns regarding status and threats, but for which insufficient information is available to indicate a need to list the species under the U.S. Endangered Species Act. According to the National Marine Fisheries Service, any shark caught must be released soon after it is caught with minimal harm, and is considered a prohibited species.[4] The population of the sand tiger has been reduced over twenty percent in the past ten years, which means the shark is considered vulnerable by the World Conservation Union. The reason for the decline in the population of the sand tiger consists of many factors. In Japan, the sand tiger shark is a very popular food. The shark can be smoked, consumed fresh, salted, roasted, or stewed. Sand tigers can sometimes be caught by fishing trawls, but they are more commonly caught with a fishing line. Sang tigers' fins are also a very popular trade item in Japan.[1] Thus, overfishing is a major contributor to the population decline. Shark liver oil is a very popular product in beauty products such as lipstick. As a result, sand tigers are used for these products.[4] In northern Australia, nets are put in place to protect swimmers from sand tigers. Many sharks are caught in the nets, most of which are strangled or taken by fishermen.[1] Estuaries along the United States of America's eastern Atlantic coast houses many of the young sand tiger sharks. These estuaries are very susceptible to point-source pollution that can be extremely harmful to the pups.[4]
References
- ^ a b c d e "Carcharias taurus". The IUCN Red List of Threatened Species. 2011. Retrieved 2011-11-29.
- ^ a b c "The Tangled Taxonomy of the Sandtiger Shark". ReefQuest Centre for Shark Research. 2007. Retrieved 2011-10-18.
- ^ "Common names of Carcharias taurus". fish base.org. 2011. Retrieved 2011-12-04.
- ^ a b c d e f g h "Sand tiger shark" (PDF). NOAA National Marine Fisheries Servicel. 2011. Retrieved 2011-11-28.
- ^ "Sand shark Carcharias taurus Rafinesque 1810". UNITED STATES DEPARTMENT OF THE INTERIOR. 2009. Retrieved 2011-10-25.
- ^ "SAND TIGER SHARK". Florida Museum of Natural History. 2011. Retrieved 2011-11-21.
- ^ "Meet the Animals". The Maritime Aquarium of Long Island. 2011. Retrieved 2011-11-29.
- ^ "Rare albino shark rules deep". thetelegraph.com.au. 2007. Retrieved 2008-08.
{{cite web}}: Check date values in:|accessdate=(help) - ^ "Recovery plan for the Grey Nurse Shark (Carcharias taurus) in Australia". Australian Government: Department of Sustainability, Environment, Water, Population and Communities. 2002. Retrieved 2011-10-18.
- ^ "Sand Tiger Shark". The Discovery Channel. 2011. Retrieved 2011-11-28.
- ^ a b c d e f "Florida Museum of Natural History Ichthyology Department: Sand tiger Shark". Florida Museum of Natural History. 2009. Retrieved 2011-10-18.
- ^ a b c "Sand Tiger Shark". National Geographic Society. 2009. Retrieved 2011-10-26.
- ^ "The Sand Tiger Shark". University of Delaware College of Earth, Ocean, and Environment. 2008. Retrieved 2011-12-05.
- ^ "Fact Sheet: Sand Tiger Sharks". Dr. Erich K. Ritter. 2011. Retrieved 2011-11-29.
- ^ Lucifora, L.O.; Garcia, V.B.; Escalante, A.H. (January 27, 2009). "How can the feeding habits of the sand tiger shark influence the success of conservation programs?". Animal Conservation (2009). 12 (4): 291–301.
- ^ "Sand Tiger Shark". National Geographic. 2009. Retrieved 2011-10-20.
- ^ "Sand Tiger Sharks, Carcharias taurus". MarineBio.org, Inc. 2011. Retrieved 2011-12-05.
- ^ "SAND TIGER SHARKS: Characteristics". Nautilus Productions Inc. Retrieved 2011-12-04.
- ^ "Sand Tiger Shark". New England Aquarium. Retrieved 2011-10-26.
- ^ "Sand Tiger Shark". Elasmo Diving. Retrieved 2011-11-29.
Bibliography
- NOAA National Marine Fisheries Service (1999). "Sand tiger shark" (pdf). Retrieved 28 November 2011.
{{cite web}}: Check date values in:|accessdate=(help) - Gilmore, R. Grant; Dodrill, Jon W.; Linley, Patricia A. (September 1982). "Reproduction and Embryonic Development of The Sand Tiger Shark, Odontaspis Taurus" (PDF). FISHERY BULLETIN. 81 (2): 215–217.
- Lucifora, L.O.; Garcia, V.B.; Escalante, A.H. (January 27, 2009). "How can the feeding habits of the sand tiger shark influence the success of conservation programs?". Animal Conservation (2009). 12 (4): 291–301.
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