Grey nurse shark

Grey nurse shark

Overview
The sand tiger shark or grey nurse shark (Carcharias taurus) is a species of shark that inhabits coastal waters worldwide. It lives very close to the shorelines and beaches of North America, hence the name, sand tiger shark. Despite a fearsome appearance and strong swimming abilities, it is a relatively placid and slow moving animal. The sand tiger hunts close to shore in the surf zone
Surf zone
As ocean surface waves come closer to shore they break, forming the foamy, bubbly surface we call surf. The region of breaking waves defines the surf zone. After breaking in the surf zone, the waves continue to move in, and they run up onto the sloping front of the beach, forming an uprush of...

. This has caused many instances of accidental attacks upon humans.
Discussion
Ask a question about 'Grey nurse shark'
Start a new discussion about 'Grey nurse shark'
Answer questions from other users
Full Discussion Forum
 
Unanswered Questions
Encyclopedia
The sand tiger shark or grey nurse shark (Carcharias taurus) is a species of shark that inhabits coastal waters worldwide. It lives very close to the shorelines and beaches of North America, hence the name, sand tiger shark. Despite a fearsome appearance and strong swimming abilities, it is a relatively placid and slow moving animal. The sand tiger hunts close to shore in the surf zone
Surf zone
As ocean surface waves come closer to shore they break, forming the foamy, bubbly surface we call surf. The region of breaking waves defines the surf zone. After breaking in the surf zone, the waves continue to move in, and they run up onto the sloping front of the beach, forming an uprush of...

. This has caused many instances of accidental attacks upon humans. 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.

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
Sicily
Sicily is a region of Italy, and is the largest island in the Mediterranean Sea. Along with the surrounding minor islands, it constitutes an autonomous region of Italy, the Regione Autonoma Siciliana Sicily has a rich and unique culture, especially with regard to the arts, music, literature,...

. 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 species' scientific name from C. taurus to C. triglochis. 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 won by default. However, experts realized that taurus belongs after Odontaspis. Therefore, the name was changed to Odontaspis taurus. In 1977, a South African shark expert, Leonard J.V. Compagno, challenged the Odontaspis taurus name and substituted eugomphodus, a somewhat unknown classification, for taurus. However, many taxonomists and experts question his change saying that there is not a significant difference between Odontaspis and Carcharias. Also, experts argue that taurus should be used in place of eugomphodus because taurus is more commonly used and researched.

The name was then reverted to back to its original determination by Rafinesque because of disagreements and fear of confusion. The final naming is still up for debate among shark experts.

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. Their mouth extends beyond their eyes, and they usually swim with their mouth open. Their snout is flattened with a conical shape, and their body is stout and bulky with two large, grey dorsal fin
Dorsal fin
A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...

s that are almost equal in size. The tail is elongated and has a long upper lobe, and the dorsal fins are set back almost beyond the pectoral fins and are broad-based. The pectoral fins are triangular, and the tail is almost one-third as long as the head of the shark. The sand tiger shark's head is rather pointy, not round and the teeth are smooth edged and sharp-pointed. 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. Adult sharks tend to have reddish-brown spots mostly on their backs, but also scattered around their entire body. In addition, juvenile sand tiger sharks have yellow-brown spots on their bodies. The sand tiger shark usually has a grey back and white underside. The males also have a grey reproductive organ with a white tip. 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). In August 2007, an albino specimen was photographed off South West Rocks, Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

.

Diet


The diet of the sand tiger shark consists of fish, young sharks, rays
Batoidea
Batoidea is a superorder of cartilaginous fish commonly known as rays and skates, containing more than 500 described species in thirteen families...

, and crustaceans. Sand tigers have been spotted around large schools of bluefin, and many of the sharks have been know 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. However, the sand tiger prefers bony fish such as eels, mullets, and sea basses. They also hunt a variety of mollusk and crustaceans, including rock lobster, crabs, squid, and octopus. Humans do not serve the sand tiger as a diet resource.

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. 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. What allows the sharks to float in the water is their ability to store air inside their bellies. The sharks go up to the surface of the water, gulp a large amount of air, and float for long periods of time. This species is the only known shark to do such an activity.

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. Spearfishing may lead to aggressive behavior; however, humans are rarely attacked when fishing this way. 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. Of the twenty-nine unprovoked attacks, many have been reported to be mistaken. Only two human fatalities have resulted from unprovoked sand tiger attacks.

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. There have been only three total reportings 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.

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.

Reproduction


The sand tiger shark must reach a status of sexual maturity before mating, this goes for males and females. Male tend to reach their maturity at about six to seven years old, approximately six feet long. Females reach it when approximately seven feet long, about nine to ten years old. Mating often occurs around the months of March and April. 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. Female sharks have two uteri
Uterus
The uterus or womb is a major female hormone-responsive reproductive sex organ of most mammals including humans. One end, the cervix, opens into the vagina, while the other is connected to one or both fallopian tubes, depending on the species...

. 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. Hydroids grow on the mother's teeth during pregnancy because she stops eating. When the young are around three feet long, the mother gives birth to them in a lengthy labour. The gestation
Gestation
Gestation is the carrying of an embryo or fetus inside a female viviparous animal. Mammals during pregnancy can have one or more gestations at the same time ....

 period is approximately eight to nine months.

Conservation status


This species is listed as vulnerable on the International Union for Conservation of Nature Red List, and as endangered under Queensland's Nature Conservation Act 1992
Nature Conservation Act 1992
The Nature Conservation Act 1992 is an act of the Parliament of Queensland that provides for the legislative protection of Queensland's threatened biota. As originally published, it provided for biota to be declared presumed extinct, endangered, vulnerable, rare or common...

. 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
National Marine Fisheries Service
The National Marine Fisheries Service is a United States federal agency. A division of the National Oceanic and Atmospheric Administration and the Department of Commerce, NMFS is responsible for the stewardship and management of the nation's living marine resources and their habitat within the...

 (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
Endangered Species Act
The Endangered Species Act of 1973 is one of the dozens of United States environmental laws passed in the 1970s. Signed into law by President Richard Nixon on December 28, 1973, it was designed to protect critically imperiled species from extinction as a "consequence of economic growth and...

. 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 prohibitive species. 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
World Conservation Union
The International Union for Conservation of Nature and Natural Resources is an international organization dedicated to finding "pragmatic solutions to our most pressing environment and development challenges." The organization publishes the IUCN Red List, compiling information from a network of...

. 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. 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. 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.

External links