Angel Shark

See text.
The angel sharks are an unusual genus of sharks with flattened bodies and broad pectoral fins that give them a strong resemblance to skates and rays. The 16-odd known species are in the genus Squatina, the only genus in its family, Squatinidae, and order Squatiniformes. They occur worldwide in temperate and tropical seas.

Appearance
While the forward part of the angel shark's body is broad and flattened, the rear part retains a muscular appearance more typical of other sharks. The eyes and spiracles are on top, and the five gill slits are on bottom. Both the pectorals and the pelvic fins are large and held horizontally. There are two dorsal fins, no anal fin, and unusually for sharks, the lower lobe of the caudal fin is longer than the upper lobe. Most types grow to a length of 1.5 m (5 ft), with the Japanese angelshark, Squatina japonica, known to reach 2 m.

Habitat
Angel sharks bury themselves in sand or mud, then jump up to snap up prey, which includes fish, crustaceans, and various types of mollusks.

Behavior
Although they are not normally aggressive, they do bite when stepped on or handled.

Reproduction
Angel sharks are ovoviviparous, with litters known up to 13 pups.

Commercial value
The sharks were long considered of no commercial interest, but in 1978, Michael Wagner, a fish processor in Santa Barbara, California, began to promote angel sharks, and 310 metric tons were taken off California in 1984. The fishery devastated the population and is now regulated.

Protection
Angel sharks have historically been heavily fished but education has played a role in reducing overfishing of these slow-reproducing chondrichthyes.

Species
Sawback angelshark, Squatina aculeata Cuvier, 1829
African angelshark, Squatina africana Regan, 1908
Argentine angelshark, Squatina argentina (Marini, 1930)
Chilean angelshark, Squatina armata (Philippi, 1887)
Australian angelshark, Squatina australis Regan, 1906
Pacific angelshark, Squatina californica Ayres, 1859
Sand devil, Squatina dumeril Lesueur, 1818
Taiwan angelshark, Squatina formosa Shen & Ting, 1972
Angular angel shark, Squatina guggenheim Marini, 1936
Japanese angelshark, Squatina japonica Bleeker, 1858
Clouded angelshark, Squatina nebulosa Regan, 1906
Smoothback angelshark, Squatina oculata Bonaparte, 1840
Squatina punctata Marini, 1936
Squatina squatina (Linnaeus, 1758)
Ornate angelshark, Squatina tergocellata McCulloch, 1914
Ocellated angelshark, Squatina tergocellatoides Chen, 1963
Eastern Australian angelshark, Squatina sp. A (provisional scientic name)
Western Australian angelshark, Squatina sp. B (provisional scientic name)
Cortez angelshark, Squatina sp. (provisional scientic name)

Basking Shark

The basking shark, Cetorhinus maximus, is the second largest fish, after the whale shark. It is a cosmopolitan species - it is found in all the world's temperate oceans. It is a slow moving and generally harmless filter feeder.
Like other large sharks, basking sharks are at risk of extinction due to a combination of low resilience and overfishing to supply the worldwide market for the shark's fins, flesh and organs.

Taxonomy
This shark is called the basking shark because it is most often observed when feeding at the surface and appears to be basking. It is also called bone shark, elephant shark, sun-fish and sailfish. It is the only member of the family Cetorhinidae. It was first described and named Cetorhinus maximus by Gunnerus in 1765 from a specimen found in Norway. The genus name Cetorhinus comes from the Greek, ketos which means marine monster or whale and rhinos meaning nose, the species name maximus is from Latin and means "greatest". It was later described as Squalus isodus by Macri in 1819, Squalus elephas by Lesueur in 1822, Squalus rashleighanus by Couch in 1838, Squalus cetaceus by Gronow in 1854, Cetorhinus blainvillei by Capello in 1869, Selachus pennantii by Cornish in 1885, Cetorhinus maximus infanuncula by Deinse & Adriani 1953, and finally as Cetorhinus maximus normani by Siccardi 1961.

Distribution and habitat
The basking shark is a coastal-pelagic shark found worldwide in boreal to warm-temperate waters around the continental shelves. It prefers waters between 8 and 14 degree C (46 and 57 degree F). It is often seen close to land and will enter enclosed bays. The shark will follow concentrations of plankton in the water column and is therefore often visible on the surface. They are a highly migratory species leading to seasonal appearances in certain areas of the range.

Anatomy and appearance
The basking shark is one of the largest known sharks, second only to the whale shark. The largest specimen accurately measured was trapped in a herring net in the Bay of Fundy, Canada in 1851. Its total length was 12.27 m (40 ft 3 in), and weighed an estimated 19 tons. There are reports from Norway of three basking sharks over 12 m (the largest being 13.7 m), but those are considered dubious since few if any sharks anywhere near such size have been caught in the area since. Normally the basking shark reaches a length of between 6 metres (20 ft) and a little over 8 m (26 ft). Some specimens surpass 9 or even 10 m, but after years of hard fishing, specimens of this size have become exceedingly rare.
These sharks possess the typical lamniform body plan and have been mistaken for great white sharks. The two species can be easily distinguished, however, by the basking shark's cavernous jaw (up to 1 m in width, held wide open whilst feeding), longer and more obvious gill slits (which nearly encircle the head and are accompanied by well-developed gill rakers), smaller eyes, and smaller average girth. Great white sharks possess large, dagger-like teeth, whilst those of the basking shark are much smaller (5-6 mm) and hooked; only the first 3 or 4 rows of the upper jaw and 6 or 7 rows of the lower jaw are functional. There are also several behavioural differences between the two (see Behavior).
Other distinctive characteristics of the basking shark include a strongly keeled caudal peduncle, highly textured skin covered in placoid scales and a layer of mucus, a pointed snout (which is distinctly hooked in younger specimens), and a lunate caudal fin. In large individuals the dorsal fin may flop over when above the surface. Coloration is highly variable (and likely dependent on observation conditions and the condition of the animal itself): commonly, the colouring is dark brown to black or blue dorsally fading to a dull white ventrally. The sharks are often noticeably scarred, possibly through encounters with lampreys or cookiecutter sharks. The basking shark's liver, which may account for 25% of its body weight, runs the entire length of the abdominal cavity and is thought to play a role in buoyancy regulation and long-term energy storage.
In females, only the right ovary appears to be functional: if so, this is a unique characteristic among sharks.

Diet
The basking shark is a passive filter feeder, filtering zooplankton, small fish and invertebrates from up to 2,000 tons of water per hour. Unlike the megamouth shark and whale shark, the basking shark does not appear to actively seek its quarry, but it does possess large olfactory bulbs that may guide it in the right direction. Unlike the other large filter feeders, it relies only on the water that is pushed through the gills by swimming; the megamouth shark and whale shark can suck or pump water through their gills.

Behavior
Studies in 2003 have disproved the idea that basking sharks hibernate and have shown that they are active throughout the year. In winter, basking sharks move to deeper water (depths of up to 900 m) feeding on deep water plankton. Satellite tagging confirmed that basking sharks move thousands of kilometres during the winter months locating plankton blooms. It was also found that basking sharks shed and renew their gillrakers in an ongoing process, rather than over one short period.
They feed at or close to the surface with their mouths wide open and gill rakers erect. They are slow-moving sharks (feeding at about 2 knots) and do not attempt to evade approaching boats (unlike great white sharks). They are harmless to humans if left alone and will not be attracted to chum.
Basking sharks are social animals and form schools segregated by sex, usually in small numbers (3 or 4) but reportedly up to 100 individuals. Their social behaviour is thought to follow visual cues, as although the basking shark's eyes are small, they are fully developed and have been known to visually inspect boats, possibly mistaking them for conspecifics. Females are thought to seek out shallow water to give birth.
These sharks have few predators, but orcas and tiger sharks are known to feed on them, and the aforementioned lampreys are often seen attached to them, although it is unlikely that they are able to cut through the shark's thick skin.
Even though the basking shark is large and slow it can breach and has been reported jumping fully out of the water. This behaviour could be an attempt to dislodge parasites or comensals. There are doubts as to the accuracy of these observations - since the basking shark has a recorded top swimming speed of 4 mph and has not been observed to jump, even under the stress of harpooning.

Reproduction
Basking sharks are ovoviviparous: the developing embryos first rely on a yolk sac, and as there is no placental connection, they later feed on unfertilized ova produced by the mother (a behaviour known as oophagy). Gestation is thought to span over a year (but perhaps 2 or 3 years), with a small though unknown number of young born fully developed at 1.5-2 m (5-6.5 ft). Only one pregnant female is known to have been caught; she was carrying 6 unborn young. Mating is thought to occur in early summer and birthing in late summer, following the female's movement into shallow coastal waters.
The onset of maturity in basking sharks is not known but is thought to be between the age of 6 and 13 and at a length of between 4.6 and 6 m. Breeding frequency is also unknown, but is thought to be 2 to 4 years.
The seemingly useless teeth of basking sharks may play a role in courtship behaviour, possibly as a means for the male to keep hold of the female during mating.

Importance to humans
Historically, the basking shark has been a staple of fisheries because of its slow swimming speed, unaggressive nature and previously abundant numbers. Commercially it was put to many uses: the flesh for food and fishmeal, the hide for leather, and its large liver (which has a high squalene content) for oil. It is currently fished mainly for its fins (for shark fin soup). Parts (such as cartilage) are also used in traditional Chinese medicine and as an aphrodisiac in Japan, further adding to demand.
As a result of rapidly declining numbers, the basking shark has been protected and trade in its products restricted in many countries. It is fully protected in the UK, Malta, Florida and US Gulf and Atlantic waters. Targeted fishing for basking sharks is illegal in New Zealand.
It is tolerant of boats and divers approaching it and may even circle divers, making it an important draw for dive tourism in areas where it is common.

Basking sharks and cryptozoology
On several occasions, "globster" corpses initially thought to be sea serpents or plesiosaurs have later been identified as likely to be the decomposing carcasses of basking sharks, as in the Stronsay beast and the Zuiyo Maru cases.

Blacktip Reef Shark

The blacktip reef shark, Carcharhinus melanopterus, is a shark of tropical and warm temperate seas. It is often confused with the blacktip shark, Carcharhinus limbatus.

Distribution
One of the most common sharks found in shallow (sometimes as shallow as 30 cm) water around coral reefs of Indo-Pacific waters. The water they swim in is usually between 20 and 27 degree C (70 to 80? F). Blacktip reef sharks do not venture into tropical lakes and rivers far from the ocean.

Appearance
As its name suggests, the tips of the shark's pectoral fins and dorsal fin are black, with a white underside. Its skin is brownish in color on the top half of its body. It has been recorded at up to 190 cm (6 ft) in length. Its snout is blunt and rounded. The gray reef shark looks similar, and is also common, but is distinguished by its stockier and grey body and its lack of a black tip on the dorsal fin. Blacktip reef sharks are not considered a real threat because they are usually small

Diet
A blacktip reef shark's diet consists mainly of reef fish, but they will also feed on sturgeon and mullet.

Reproduction, behavior, and interaction with humans
Reproduction is viviparous, with 2 to 4 pups in a litter. Before giving birth, female blacktip reef sharks will incubate their young for 16 months. The pups' length at birth ranges from 33 to 52 cm.
This species is not considered social, but can been seen in small groups. While generally shy, they often are curious about snorkelers and scuba divers. As with most sharks, the body is bent into a sort of "S" shape when the shark feels threatened. Blacktip reef sharks are harmless unless provoked. Incidents generally involve hand feeding or spear fishing, possibly in combination with low visibility.
The blacktip is one of only a few sharks that can jump fully out of the water, a behaviour called breaching. They have also been observed surfacing to look around (spy-hopping).

Population decline
Blacktip reef sharks are often the bycatch from other fisheries and are often wasted. Their populations are declining, and so are the population of many other shark species. Their fins are used for shark fin soup which is a major factor in the population decline in recent years.

Blue Shark

The blue shark, Prionace glauca, is a carcharhinid shark which is found in the deep waters of the world's temperate and tropical oceans. They prefer cooler waters and are not found, for example, in the Yellow Sea or in the Red Sea. Blue sharks are known to migrate long distances, from New England to South America for example. Although generally lethargic, they are capable of moving very quickly if the need arises. Blue sharks are viviparous and are noted for their large litters of 25 to over 100 pups. They feed primarily on small fish and squid, although they are perfectly capable of taking larger prey should the opportunity present itself. Also, they may pose considerable danger to humans if they are encountered in large groups. They are often found in schools segregated by sex and size, and this behavior has led to their being nicknamed the "wolves of the sea".

Distribution and habitat
The blue shark is an oceanic and epipelagic shark found worldwide in deep temperate and tropical waters from the surface to about 350 meters. In temperate seas it may come closer to shore where it can be observed by divers, while in tropical waters it occurs at greater depths. It is found from as far north as Norway to as far south as Chile. Blue sharks are found off the coasts of every continent, except for Antarctica. In the Pacific its greatest concentrations occur between 20 degree and 50 degree North but with strong seasonal fluctuations. In the tropics it is uniformly distributed between 20 degree N and 20 degree S. It prefers waters with a temperature range of 7 to 16 degreeC but will tolerate temperatures of 21 degreeC or above. It is highly migratory with records from the Atlantic showing a regular clockwise migration within the prevailing currents.

Anatomy and appearance
Blue sharks are light-bodied with long pectoral fins. The top of the body is deep blue, lighter on the sides, and the underside is white. The animal grows to 3.8 m (12.5 ft) or more. The shark's typical weight is 136 kg (300 lb) to 182 kg (400 lb) and can grow to 205 kg (450 lb). The largest recorded specimen weighed 240 kg. They are not typically confused with any other species.

Ecology
Squid are an important prey item for blue sharks, but their diet also comprises other invertebrates such as cuttlefish and pelagic octopuses, as well as lobster, shrimp, crab, a large number of bony fishes, small sharks, mammalian carrion and occasional sea birds. Whale and porpoise blubber and meat have been retrieved from the stomachs of captured specimens and they are known take cod from trawl nets. Apparently, blue sharks do not or only very rarely eat tuna.
Adult blue sharks do not suffer predation on a regular basis, except by humans. Young and smaller individuals may get eaten by any sufficiently large carnivore. However, they are host to several species of parasites. For example, the blue shark is the definite host of the tetraphyllidean tapeworm, Pelichnibothrium speciosum (=Prionacestus bipartitus). They become infected by eating the intermediate hosts, probably Opah, Lampris guttatus, and/or longnose lancetfish, Alepisaurus ferox (Scholz et al. 1998).

Reproduction
They are vivaporous, with a yolk-sac placenta, delivering 4 to 135 pups per litter. The gestation period is between 9 and 12 months. Females mature at 5 to 6 years of age and males at 4 to 5. Courtship is believed to involve biting by the male, as mature specimens can be accurately sexed according to the presence or absence of bite scarring. Female blue sharks have adapted to the rigours of the mating ritual by developing skin 3 times as thick as that of males.

Importance to humans
Blue sharks are the most heavily fished sharks in the world mainly as result of bycatch. It is estimated that 10 to 20 million individuals are killed each year as a result of fishing. The flesh is edible, but not widely sought after; it is utilized fresh, dried, smoked and salted and for fishmeal. The skin is used for leather, the fins for shark-fin soup and the liver for oil. Blue sharks are occasionally sought as game fish and they are frequent accidental catches by commercial fisherman seeking swordfish or tuna. Most interaction between blue sharks and humans takes place in deep water as they rarely venture close to shore.

Attacks on humans
Blue sharks are known to attack people who are in small boats, and divers. The most common victims in blue shark attacks are commercial fishermen. They leave chum and dead fish near their boats and the sharks become aggressive because of the lack of food nearby.

Bull Shark

The bull shark, Carcharhinus leucas, also known as the bull whaler, Zambezi shark or informally Zambi in Africa and Nicaragua shark in Nicaragua, is common worldwide in warm, shallow waters along coasts and in rivers. The bull shark is well known for its unpredictable, often aggressive behavior. Many scientists agree that since bull sharks often dwell in shallow waters, they may be more dangerous to humans than any other species of sharks.
Unlike most other marine sharks, bull sharks tolerate fresh water. They can travel far up rivers. As a result, they are probably responsible for the majority of shark attacks on humans that take place near the shore, including many attacks attributed to other species. However, bull sharks are not true freshwater sharks (unlike the river sharks of the genus Glyphis).

Taxonomy
The name, "bull shark", comes from the shark's stocky shape, broad, flat snout and aggressive unpredictable behavior. In India, the bull shark is often called the Sundarbans or Ganges shark and is considered a delicacy for Bengali fish curries. In Africa it is also commonly called the Zambezi River shark or just Zambi. Its wide range and diverse habitats result in many other local names, for example Lake Nicaragua shark, Fitzroy Creek whaler, Van Rooyen's shark, cub shark, shovelnose shark, freshwater whaler.

Distribution and habitat
The bull shark is found all over the world in many different areas and has been known to travel long distances. The bull shark is common in the coastal areas of warm oceans, in rivers and lakes, and occasionally streams if they are deep enough in both salt and fresh water. It is found to a depth of 150 m, but does not usually swim deeper than 30 m. In the Atlantic it is found from Massachusetts, to Southern Brazil and from Morocco to Angola. In the Indian Ocean it is found from South Africa to Kenya, India, Vietnam to Australia. It is estimated that there are more than 500 bull sharks in the Brisbane River and greater numbers still in the canals of the Gold Coast in Queensland, Australia. In the Pacific Ocean, it can be found from Baja California to Ecuador.
The shark has been reported 2,220 miles (4000 km) up the Amazon River at Iquitos in Peru, and has been recorded as far up the Mississippi River as Illinois. It is also found in the fresh water Lake Nicaragua and the Ganges and Brahmaputra rivers of West Bengal and Assam in eastern India and adjoining Bangladesh. It can live in almost any water including water with a high salt content as in St. Lucia Estuary in South Africa. After Hurricane Katrina hit in 2005, a large number of bull sharks were sighted in Lake Ponchartrain. Although rare there, bull sharks have made their way through the Great Lakes as far as Lake Michigan. The Lake Michigan encounter occurred off the coast of Chicago, Illinois in 1955.

Freshwater tolerance
Only 43 species of elasmobranch in ten genera and four families have been reported to enter fresh water, of which the bull shark is the best known. Other species that enter rivers include the stingrays (Dasyatidae, Potamotygonidae and others) and sawfishes (Pristidae). Some skates (Rajidae), smooth dogfishes (Triakidae), and sandbar sharks (Carcharhinus plumbeus) regularly enter estuaries. The ability of elasmobranchs to enter fresh water is limited because their blood is normally at least as salty (in terms of osmotic strength) as seawater, through the accumulation of urea and trimethylamine oxide, but bull sharks living in fresh water reduce the concentration of these solutes by up to 50%. Even so, bull sharks living in fresh water need to produce twenty times more urine than those in salt water.
Until the 1970s, researchers thought the sharks in Lake Nicaragua were a separate species because there was no way for the sharks to move in or out. It was discovered that they were jumping along the rapids just like salmon. Bull sharks tagged inside the lake were later caught in the open ocean.

Anatomy and appearance
Bull sharks are large and stout. Males can reach 2.1 meters (6.9 ft) and weigh 90 kilograms (198.4 lbs). Females can be much larger:up to 3.49 metres (11.5 ft) and 318 kg (700 lb). Bull sharks are wider than other sharks of comparable length, and are grey on top and white below. The second dorsal fin is smaller than the first.

Diet
The diet of bull shark includes fish, other sharks, rays, dolphins, turtles, birds, molluscs, echinoderms, crustaceans, and even terrestrial mammals. Bull sharks have been known to use the bump-and-bite technique when attacking their prey. This type of hunting behaviour has been observed when researchers entered the water with relatively calm bull sharks, and the sharks suddenly became violent and began to bump the researchers. This behaviour was seen in the documentary Anatomy of a Sharkbite, which aired on the Discovery Channel in 2003, during Shark Week. Dr. Erich Ritter was severely wounded by a bull shark using this attack technique. This attack was not listed as being a case of mistaken identity, because the waters during the time of the attack were clear, and no noticeable weather patterns were affecting the sharks. This attack may have been a case of territoriality, in which the bull sharks were very fierce toward intruders. Recently, Dr. Ritter concluded that the attack was provoked by a piece of chum that had been thrown away from him, but was taken by a remora and brought back in his direction. The remora caused the bull sharks to get excited and swirl up the sand. In the resulting cloud of sand, one of the sharks bit him.

Behavior
Bull sharks are solitary hunters. They often cruise through shallow waters. They can suddenly burst into speed and can be highly aggressive, even attacking a racehorse in the Brisbane River in the Australian state of Queensland. They are extremely territorial and will attack other animals - including humans - that enter their territory. Along with the great white, tiger and oceanic whitetip sharks, bull sharks are among the four species considered the most dangerous to humans, and is probably the most dangerous of the four species. One or more bull sharks are most likely responsible for the Jersey Shore shark attacks of 1916 that were originally attributed to a great white, and which inspired the movie Jaws..
Many experts think the bull shark is responsible for most of the deaths around the Sydney Harbour inlets in the past. Most of these attacks were previously thought to be great whites. In India the bull shark cruises up the Ganges River where it has killed and attacked a large number of people. It also eats the corpses that the Indians float on the river. Many of these attacks have been wrongly blamed on the Ganges shark Glyphis gangeticus, a fairly rare species that is probably the only other shark that can live comfortably in both saltwater and freshwater. The grey nurse shark was also blamed in the sixties and seventies.

Reproduction
Bull sharks breed in the summer, often in the brackish water of river mouths. After gestating for about a year, a bull shark may give birth to as many as 13 live young (they are viviparous). The young are about 70 centimetres (28 in) at birth and take 10 years to reach maturity.

Enemies
Bull sharks are apex predators, and rarely have to fear being attacked by other animals. Humans are their biggest threat. Larger sharks, such as the tiger shark and great white, may attack them. Crocodiles may also eat them if they enter their freshwater territories.

Cookiecutter Shark

The cookie-cutter shark, Isistius brasiliensis, also known as the cigar shark or luminous shark, is a small rarely-seen dogfish shark.

Anatomy and morphology
Cookie-cutters are a small 50 cm (20 in )shark with a cigar shaped body. It has large eyes with green pupils, and prominent triangular teeth used for feeding on the lower jaw. The upper jaw of the shark consists of small teeth. In addition to the sharp teeth, the cookie-cutter shark bears rather fleshy lips. The creature has 2 small dorsal fins located toward the tail. The underside of the shark is bioluminescent, glowing a pale blue-green that matches the background light from the ocean's surface that serves as camouflage to creatures beneath it. However, a small non-luminescent patch appears black, deceiving the shark's prey, smaller predatory fish (like tuna), into thinking the shark is an even smaller fish. When the predatory fish tries to strike at the shark, the shark strikes back, scoring itself another meal . This is the only known instance whereby a bioluminescent lure is created by the absence of luminescence (contrast with anglerfish).

Distribution
Worldwide in deep water. The cookie-cutter shark has been found at depths of about 1,000 m (3,300 ft).

Ecology and life history

Feeding ecology
It derived its name from its habit of removing small circular chunks of flesh from cetaceans and large fish. It is hypothesized that the shark seizes its much larger prey with its jaws, then rotates its body to achieve a highly symmetrical cut. They are considered parasites.

Life history
Cookie-cutter sharks reproduce through aplacental viviparity in the same way as great white sharks. Little else is known about their reproduction.

Etymology and taxonomic history
Its name comes from its feeding style in which almost perfectly circular "cookie-cutter" shaped plugs are removed from the skin of marine mammals and larger fish and sharks.

Interaction with humans
There has been little interaction between humans and the cookie-cutter shark. However, there was an incident in which a cookie-cutter shark took a bite out of the rubber sonar dome of a US Navy submarine, causing damage to the housing, and forcing the submarine out of service until the rubber could be replaced. Though this is not considered a "true" interaction, cookie-cutters' distinct marks can be seen on some fish in some supermarkets.

Goblin Shark

The goblin shark, Mitsukurina owstoni, is a deep-sea shark, the sole living species in the family Mitsukurinidae. The most distinctive characteristic of the goblin shark is the unorthodox shape of its head. It has a long, trowel-shaped, beak-like rostrum or snout, much longer than other sharks' snouts. Some other distinguishing characteristics of the shark are the color of its body, which is mostly pink, and its long, protrusible jaws. When the jaws are retracted, the shark resembles a pink grey nurse shark, Carcharias taurus, with an unusually long nose.
Mitsukurina owstoni is found in the deep ocean, far below where the sun's light can reach at depths greater than 200 m. They can be found throughout the world, from Australia in the Pacific Ocean to the Gulf of Mexico in the Atlantic Ocean. They are best known from the waters around Japan, where the species was first discovered by modern science.
Goblin sharks feed on a variety of organisms that live in deep waters. Among some of their known meals are deep-sea squid, crabs and deep-sea fishes. Very little is known about the species' life history and reproductive habits, as encounters with them have been relatively rare. As seemingly rare as they are however, there seems to be no real threat to their populations and so they are not classified as endangered species by the IUCN.

Taxonomy
The goblin shark was originally described in 1898 by Jordan as Mitsukurina owstoni, from a specimen obtained in the Sagami Sea, near Yokohama, Japan.
Another specimen caught was described in 1909 as Scapanorhynchus jordoni by Louis Hussakof. For a time, the species was moved to the genus Scapanorhynchus and was referred to as Scapanorhynchus owstoni, a scientific name now invalid.
The fossil record includes another two dozen or so related species in two (extinct) genera, Scapanorhynchus and Anomotodon.
The genus' name Mitsukurina is named after Kakichi Mitsukuri, a Japanese zoologist from the University of Tokyo who was responsible for bringing the then-unidentified specimen to David Jordan for proper taxonomic identification and description. The species itself was named by Jordan in honor of avid wildlife collector Allan Owston, who acquired the first specimen from a Japanese fisherman.
The shark's common name is a translation of the Japanese name tenguzame, which was the original term that Japanese fishermen used to refer to the shark prior to its description. It refers to the goblin-like tengu of Japanese folklore, which has a long nose reminiscent of the goblin shark's snout.

Distribution and habitat
Mitsukurina owstoni is a bathydemersal deep-water shark usually found near the sea bottom, at depths of around 250 m. The deepest specimen ever caught was found at 1,300 m.
Only about 45 specimens of Mitsukurina owstoni have been described in the scientific literature.
Most goblin sharks that have been caught were from Japan (where it was first discovered), specifically in an area between Tosa Bay and Boso Peninsula. The species' Pacific range is rather large. M. owstoni specimens have been found in the waters off South Africa, from various sites throughout the western Pacific Ocean. Goblin sharks have also been found off the coasts of Australia and New Zealand.
In the Atlantic Ocean, they have been found in the western Atlantic off French Guiana, in the eastern Atlantic in the Bay of Biscay and off Madeira and Portugal. On the other side of the Atlantic, goblin sharks have been found in the Gulf of Mexico.

Anatomy and appearance
Mitsukurina owstoni is a medium-to-large shark. Typical specimens are two to three m (6.6 to 9.8 ft) in length. The largest specimen ever landed (caught of the coast of Tasmania) was 3.9 m. Their maximum length is estimated to be around 5.4 to 6.0 m.
Goblin sharks have the typical shark's semi-fusiform body. Unlike the common image of sharks, M. owstoni's fins are not pointed and instead are low and rounded, with the anal and pelvic fins significantly larger than the dorsal fins. Their heterocercal tails are similar to the thresher shark's, with the upper lobe significantly longer proportionately than other sharks'. In addition, the goblin shark's tail lacks a ventral lobe.
The pink coloration, unique among sharks, is due to blood vessels underneath a semi-transparent skin (which bruises easily), thereby causing the coloring. The fins have a bluish appearance. Goblin sharks lack a nictitating membrane. They have no precaudal pit and no keels. The front teeth are long and smooth-edged, while the rear teeth are adapted for crushing.
Up to 25% of the goblin shark's body weight can be its liver. It is currently not understood why the shark has such a large liver.

Behaviour
Goblin sharks hunt by sensing the presence of prey with electro-sensitive organs in the rostrum, or snout, due to the absence of light in the deep waters where it swims. Once a shark finds its prey, it suddenly protrudes its jaws, while using a tongue-like muscle to suck the victim into its sharp front teeth. Some prey they have been known to feed on include deep-sea rockfish, (Helicolenus dactylopterus was found in one specimen), cephalopods and crustaceans.

Reproduction
Next to nothing is known from the goblin sharks' reproductive habits. Even though a pregnant goblin shark has never been caught or found, as members of the order Lamniformes, they are hypothesized to be ovoviviparous; their eggs mature and hatch inside the mother's body and the shark "gives birth" to live young.

Importance to humans
Goblin sharks are most often encountered as fisheries' bycatch. As they stay near the sea bottom, they are usually caught via deep bottom-set gillnets and sea-bottom long line fishing. They are also sometimes caught by trawling. In addition, they are sometimes found entangled by deep-sea fishing lines.
There is a demand by some collectors for the skeletal jaws of goblin sharks. Prices of these jaws range from US$1,500 to US$4,000.

Specific occurrences
The first goblin shark discovered was caught by a Japanese fisherman in the Kuroshio Current off the coast of Yokohama, Japan in 1897. This specimen was later identified as a 3.5-ft male shark.
In 1985, a goblin shark was discovered in waters off eastern Australia. Several specimens have been caught in the vicinity of New South Wales and Tasmania and are preserved at the Australian Museum. A four-meter long specimen was caught in waters off Tasmania in 2004. The shark was taken to the national fish collection in Hobart. In nearby New Zealand, a goblin shark was also caught only a few years later, in 1988.
In 2003, more than a hundred goblin sharks were caught off the northwest coast of Taiwan, an area in which they have previously not been found. Reportedly, the sharks were caught a short time after an earthquake occurred in the area.
A goblin shark was kept by the Tokai University of Japan; the fish in question died after a week.
On January 25, 2007 a 1.3 m long goblin shark was caught alive in Tokyo Bay, in waters 150 to 200 m (500 to 650 ft) deep. It was taken to the Tokyo Sea Life Park to be displayed in an aquarium, but died two days later on January 27.
Later the same year in April, several animals were seen swimming in shallow waters in the Japanese Sea. A live one was caught near Tokyo Bay. It is the first time the animals have been seen swimming in such shallow waters.

Role in the ecosystem
The goblin shark is a upper-level carnivore in its natural habitat. As a macro-organism, it has its fair share of external and internal parasites. Two new species of tapeworm were discovered in a specimen captured off Australia, Litobothrium amsichensis and Marsupiobothrium gobelinus.

Conservation Status
In 2004, Mitsukurina owstoni was classified by the IUCN's Shark Red List Authority as a species of "Least Concern". The rationale given was that despite the fact that goblin shark sightings have been relatively rare, the worldwide distribution of the species, combined with the fact that it was not accidentally taken often as bycatch in fisheries ensured that the species is most probably not in any reasonable danger of extinction. The IUCN described the major threats to M. owstoni populations' as either harvesting (as an intentional target for fishing), accidental mortality (bycatch) and to a lesser-extent, water pollution. There are no active conservation efforts being made toward this specific species.

Appearances in popular culture
As obscure as it is in nature, Mitsukurina owstoni appears in some aspects of popular culture.
It can be seen in several video games released for a variety of gaming platforms. The goblin shark is one of twenty marine animals featured in the PC/Windows game, Zoo Tycoon 2: Marine Mania.
Miniature ornamental figurines of the shark have been made by various companies for decorative purposes (see image to the right).
Zigra, a foe from the Japanese kaiju series, Gamera, bears some resemblance to a goblin shark.
One of the bosses in G Darius, Eternal Triangle, is modeled on the goblin shark.
Guitarist Buckethead has a song named Goblin Shark on his album Pepper's Ghost.
In the Wii game Endless Ocean, a Goblin Shark can be found at the bottom of the Abyss at night.

Great White Shark

The great white shark, Carcharodon carcharias, also known as white pointer, white shark, or white death, is an exceptionally large lamniform shark found in coastal surface waters in all major oceans. Reaching lengths of about 6 m (20 ft) and weighing up to 2,250 kg (5,000 lb), the great white shark is the world's largest known predatory fish. It is the only surviving species of its genus, Carcharodon.

Taxonomy
Carolus Linnaeus gave the great white shark its first scientific name, Squalus carcharias in 1758. Sir Andrew Smith gave it the generic name Carcharodon in 1833, and in 1873 the generic name was identified with Linnaeus specific name and the current scientific name Carcharodon carcharias was finalised. Carcharodon comes from the Greek words karcharos, which means sharp or jagged, and odous, which means tooth.

Related species
The great white is classified as a mackerel (Lamnidae) shark. There are four other living species in this family, two mako and two Lamna sharks.
Dental features and the extreme size of both the great white and the prehistoric Megalodon lead many scientists to believe they were closely related, and the name Carcharodon megalodon was applied to the latter. At present there is considerable doubt about this hypothesis, as many scientists would place the megalodon and white shark as distant relatives - sharing the family Lamnidae but no closer relationship. Latest research suggests that the great white shark is more closely related to the mako shark than to the megalodon. According to this theory, the extinct broad tooth mako, Isurus hastalis, is considered to be the true ancestor of the great white, while the megalodon has strong ties with the sharks belonging to Carcharocles genus. In this case, Otodus obliquus is considered to be the ancient representative of the extinct Carcharocles lineage; indeed, Carcharocles megalodon is a popular alternative classification of the megalodon.
Megalodon is only known from its teeth and from a few cartilage remains, and probably reached sizes of 15 m (49 ft) or more, considerably larger than even the largest great white sharks. From time to time it is suggested that megalodon might still exist. Megalodon teeth have supposedly been found from as recently as 10,000 to 13,000 years ago, but these results appear to be based on misinterpretation of the evidence. However, while megalodon fossils are widespread and plentiful, no evidence has surfaced that the species is anything but extinct.

Distribution and habitat
Great white sharks live in almost all coastal and offshore waters which have a water temperature of between 12 and 24 degree C (54 degree to 75 degree F), with greater concentrations off the southern coasts of Australia, off South Africa, California, Mexico's Isla Guadalupe and to a degree in the Central Mediterranean and Adriatic Seas. One of the densest known populations is found around Dyer Island, South Africa where much research on the shark is conducted. It can be also found in tropical waters like those of the Caribbean, and has been recorded off Mauritius.
It is a pelagic fish, but recorded or observed mostly in coastal waters in the presence of rich game like fur seals, sea lions, cetaceans, other sharks and large bony fish species. It is considered an open-ocean dweller and is recorded from the surface down to depths of 1,280 m (4,199 ft), but is most often found close to the surface.
In a recent study great white sharks from California were shown to migrate to an area between Baja California and Hawaii, where they spend at least 100 days of the year before they migrate back to Baja. On the journey out, they swim slowly and dive down to around 900 m (2,953 ft). After they arrive, they change behaviour and do short dives to about 300 m (984 ft) for up to 10 minutes. It is still unknown why they migrate and what they do there; it might be seasonal feeding or possibly a mating area.
In a similar study a great white shark from South Africa was tracked swimming to the northwestern coast of Australia and back to the same location in South Africa, a journey of 20,000 km (12,428 mi) in under 9 months.

Anatomy and appearance
The great white shark has a robust large conical-shaped snout. It has almost the same size upper and lower lobes on the tail fin (like most mackerel sharks, but unlike most other sharks).
Great white sharks display countershading, having a white underside and a grey dorsal area (sometimes in a brownish or bluish shade) that gives an overall "mottled" appearance. The colouration makes it difficult for prey to spot the shark because it breaks up the shark's outline when seen from a lateral perspective. When viewed from above the darker shade blends in with the sea and when seen from below casts a minimal silloutte against the sunlight.
Great white sharks, like many other sharks, have rows of teeth behind the main ones, allowing any that break off to be rapidly replaced. A great white shark's teeth are serrated and when the shark bites it will shake its head side to side and the teeth will act as a saw and tear off large chunks of flesh. Great white sharks often swallow their own broken off teeth along with chunks of their prey's flesh.

Size
A typical adult great white shark measures 4 to 4.8 m (13 to 16 ft) with a typical weight of 680 to 1,100 kg (1,500 to 2,450 lb), females generally being larger than males. The maximum size of the great white shark has been subject to much debate, conjecture, and misinformation. Richard Ellis and John E. McCosker, both academic shark experts, devote a full chapter in their book, The Great White Shark (1991), to analysing various accounts of extreme size.
Today, most experts contend that the great white shark's "normal" maximum size is about 6 m (20 ft), with a "normal" maximum weight of about 1,900 kg (4,189 lb).
For several decades, many ichthyological works, as well as the Guinness Book of World Records, listed two great white sharks as the largest individuals caught: an 11 m (36 ft) great white captured in Southern Australian waters near Port Fairy in the 1870s, and an 11.3 m (37 ft) shark trapped in a herring weir in New Brunswick, Canada in the 1930s. While this was the commonly accepted maximum size, reports of 7.5 to 10 metre (25 to 33.3 ft) great white sharks were common and often deemed credible.
Some researchers questioned the reliability of both measurements, noting they were much larger than any other accurately-reported great white shark. The New Brunswick shark may have been a misidentified basking shark, as both sharks have similar body shapes. The question of the Port Fairy shark was settled in the 1970s, when J.E. Reynolds examined the shark's jaws and "found that the Port Fairy shark was of the order of 5 m (17 ft) in length and suggested that a mistake had been made in the original record, in 1870, of the shark's length.
Ellis and McCosker write that "the largest White Sharks accurately measured range between 19 and 21 ft (6.4 m) [about 5.8 to 6.4 m], and there are some questionable 23-footers [about 7 m] in the popular - but not the scientific - literature". Furthermore, they add that "these giants seem to disappear when a responsible observer approaches with a tape measure." (For more about legendary exaggerated shark measurements, see the submarine).
The largest specimen Ellis and McCosker endorse as reliably measured was 6.4 m (21 ft) long, caught in Cuban waters in 1945; though confident in their opinion, Ellis and McCosker note other experts have argued this individual might have been a few feet shorter. There have since been claims of larger great white sharks, but, as Ellis and McCosker note, verification is often lacking and these extraordinarily large great white sharks have, upon examination, all proved under the 20-21 ft limit. For example, a much-publicized female great white said to be 7.13 m (23 ft) was fished in Malta in 1987 by Alfredo Cutajar. In their book, Ellis and McCosker agree this shark seemed to be larger than average, but they did not endorse the 7.13 metres measurement. In the years since, experts eventually found reason to doubt the claim, due in no small part to conflicting accounts offered by Cutajar and others. A BBC photo analyst concluded that even "allowing for error ... the shark is concluded to be in the 18.3 ft (5.6 m) [5.5 m] range and in no way approaches the 23 ft (7.0 m) [7 m] reported by Abela." (as in original)
According to the Canadian Shark Research Centre, the largest accurately measured great white shark was a female caught in August 1988 at Prince Edward Island off the Canadian (North Atlantic) coast and measured 6.1 m (20 ft). The shark was caught by David McKendrick, a local resident from Alberton, West Prince.
The question of maximum weight is complicated by the unresolved question of whether or not to account for the weight of a shark's recent meals when weighing the shark itself. With a single bite, a great white can take in up to 14 kg (31 lb) of flesh, and can gorge on several hundred kilograms or pounds of food.
Ellis and McCosker write in regards to modern great white sharks that "it is likely that [Great White] sharks can weigh as much as 2 tons", but also note that the largest recent scientifically measured examples weigh in at about 2 tonnes (1.75 short tons).
The largest great white shark recognized by the International Game Fish Association (IGFA) is one landed by Alf Dean in south Australian waters in 1959, weighing 1,208 kg (2,663 lb). Several larger great white sharks caught by anglers have since been verified, but were later disallowed from formal recognition by IGFA monitors for rules violations.

Adaptations
Great white sharks, like all other sharks, have an extra sense given by the Ampullae of Lorenzini, which enables them to detect the electromagnetic field emitted by the movement of living animals. Every time a living creature moves it generates an electrical field and great whites are so sensitive they can detect half a billionth of a volt. Most fish have a less developed but similar ability in the horizontal line along their body.
To more successfully hunt fast moving and agile prey such as sea lions, the poikilothermic great white shark has developed adaptations that allow it to maintain a body temperature warmer than the surrounding water. One of these adaptations is a "rete mirabile" (Latin for "wonderful net"). This close web-like structure of veins and arteries, located along each lateral side of the shark, conserves heat by warming the cooler arterial blood with the venous blood that has been warmed by the working muscles. This keeps certain parts of the body (particularly the brain) at temperatures up to 14 degreeC above the surrounding water, while the heart and gills remain at sea-temperature. When conserving energy (a great white shark can go weeks between meals), the core body temperature can drop to match the surroundings. A great white shark's success in raising its core temperature is an example of gigantothermy. Therefore, the great white shark can be considered an endothermic poikilotherm, because its body temperature is not constant but is internally regulated.

Diet and hunting
White sharks are carnivorous, and primarily eat fish (including rays, tuna, and smaller sharks), dolphins, porpoises, whale carcasses and pinnipeds such as seals, fur seals and sea lions and sometimes sea turtles. Sea otters and penguins are attacked at times although rarely, if ever, eaten. Great whites have also been known to eat objects that they are unable to digest. In great white sharks above 3.41 meters (11 ft, 2 in) a diet consisting of a higher proportion of mammals has been observed. These sharks prefer prey with high contents of energy-rich fat. Shark expert Peter Klimley used a rod-and-reel rig and trolled carcasses of a seal, a pig, and a sheep to his boat in the South Farallons. The sharks attacked all three baits but rejected the lower fat content sheep carcass.
The great white is regarded as an apex predator with its only real threats from humans and, in at least one incident, the Orca. Although their diets overlap greatly, there are few reports of encounters between orcas and great whites, and they don't seem to directly compete with each other. Great whites are also sometimes preyed on by larger specimens.
A great white shark primarily uses its extra senses (i.e, electrosense and mechanosense) to locate prey from far off. Then, the shark uses smell and hearing to further verify that its target is food. At close range, the shark utilizes sight for the attack.
Great white sharks' reputation as ferocious predators is well-earned, yet they are not (as was once believed) indiscriminate "eating machines". They typically hunt using an "ambush" technique, taking their prey by surprise from below. Near the now-famous Seal Island, in South Africa's False Bay; studies have shown that the shark attacks most often occur in the morning, within 2 hours after sunrise. The reason for this is that it is hard to see a shark close to the bottom at this time. The success rate of attacks is 55% in the first 2 hours, it falls to 40% in late morning and after that the sharks stop hunting.
The hunting technique of the white shark varies with the species it hunts. When hunting Cape fur seals off Seal Island, South Africa; the shark will ambush it from below at high speeds and hit the seal at mid-body. They go so fast that they actually breach out of the water. They have also been observed chasing their prey after a missed attack. The prey is usually attacked at the surface.
When hunting Northern elephant seals off California, the shark immobilizes the prey with a large bite to the hindquarters (which is the main source of the seal's mobility) and waits for the seal to bleed to death. This technique is especially used on adults which are large and dangerous. Prey is normally attacked sub-surface. Harbour seals are simply grabbed from the surface and pulled down until they stop struggling. They are then eaten near the bottom. California sea lions are ambushed from below and struck in mid-body before being dragged and eaten.
When hunting dolphins and porpoises, white sharks attack them from above, behind or below to avoid being detected by their echolocation. Among the species targeted are dusky dolphins, harbour porpoises, Risso's dolphins and Dall's porpoises.
A new study from the University of New South Wales in Sydney, Australia, is using CT scans of a shark's skull and complex computer models to measure the maximum bite force of the great white. The study will reveal what forces and behaviours the carnivore's skull is adapted to handle and will help resolve competing theories about its feeding behaviour.

Behaviour
The behaviour and social structure of the white shark is not well understood but recent research shows that white sharks are more social than previously thought. In South Africa, white sharks seem to have a dominance hierarchy depending on size, sex and squatter's rights. Females dominate over males, larger sharks dominate smaller sharks, and residents dominate newcomers. When hunting the white sharks tend to space out between each other and resolve conflicts with rituals and displays. White sharks rarely resort to combat although some individuals have been found with bite marks that match that of other white sharks. This suggests that when their personal space is intruded upon, a white shark will give the intruder a warning bite. Another possibility is that white sharks may softly bite other individuals as a way of showing their dominance. Also, as noted above, white sharks can be cannibalistic.
The great white shark is one of only a few sharks known to regularly lift its head above the sea surface to gaze at other objects such as prey; this is known as "spy-hopping". This behaviour has also been seen in at least one group of blacktip reef sharks, but this might be a behaviour learned from interaction with humans (it is theorized that the shark may also be able to smell better this way, because smells travel through air faster than through water). They are very curious animals, and can display a high degree of intelligence and personality when conditions permit (such as in the clear waters off of Isla Guadalupe, Mexico).

Reproduction
There is still a great deal that is unknown about great white shark behaviour, such as their mating habits. Birth has never been observed, but several pregnant females have been examined. Great white sharks are ovoviviparous, the eggs developing in the female's uterus, hatching there and continuing to develop until they are born, at which point they are perfectly capable predators. The embryos can feed off unfecundated eggs. The delivery takes place in the period transitioning spring and summer. When giving birth, the female has to fast to prevent herself from eating her young after they are born.
The young, which number 8 or 9 (with a maximum of perhaps 14) for a single delivery, are about 1.5 metres (5 ft) long when born. Their teeth are provided with small side cusps. They grow rapidly, reaching 2 metres of length in the first year of life. Almost nothing, however, is known about how and where the great white mates. There is some evidence that points to the near-soporific effect resulting from a large feast (such as a whale carcass) possibly inducing mating.
Great white sharks can also mate when a male is twelve-years old and a female is around fourteen. A great white's lifespan has not been definitively established, though many sources estimate that great whites live 30 to 40 years. It would not be unreasonable to expect such a slow maturing animal to live longer however.

Relationship with humans

Shark attacks
More than any documented attack, Steven Spielberg's 1975 film Jaws provided the great white shark with the image of a "man eater" in the public mind. While great white sharks have been responsible for fatalities in humans, they typically do not target humans as prey: for example, in the Mediterranean Sea there were 31 confirmed attacks against humans in the last two centuries, only a small number of them deadly. Many incidents seem to be caused by the animals "test-biting" out of curiosity. Great white sharks are known to perform test-biting with buoys, flotsam, and other unfamiliar objects as well, and might grab a human or a surfboard with their mouth in order to determine what kind of object it might be.
Other incidents seem to be cases of mistaken identity, in which a shark ambushes a bather or surfer, usually from below, believing the silhouette it sees on the surface is a seal. Many attacks occur in waters with low visibility, or other situations in which the shark's senses are impaired. It has been speculated that the species typically does not like the taste of humans, or at least that the taste is unfamiliar.
However some researchers have hypothesized that the reason the proportion of fatalities is low is not because sharks do not like human flesh, but because humans are often able to get out of the water after the shark's first bite. In the 1980s John McCosker noted that divers who dived solo and were attacked by great whites were generally at least partially consumed, while divers who followed the buddy system were normally pulled out of the water by their colleagues before the shark could finish its attack. Tricas and McCosker suggest that a standard attack modus operandi for great whites is to make an initial devastating attack on its prey, and then wait for the prey to weaken before going in to consume the wounded animal. A human's ability to get to land (or onto a boat) with the help of others is unusual for a great white's prey, and thus the attack is foiled.
Humans, in any case, are not healthy for great white sharks to eat because the sharks' digestion is too slow to cope with the human body's high ratio of bone to muscle and fat. Accordingly, in most recorded attacks, great whites have broken off contact after the first bite. Fatalities are usually caused by loss of blood from the initial limb injury rather than from critical organ loss or from whole consumption.
Biologist Douglas Long and Tyler B. write that the great white shark's "role as a menace is exaggerated; more people are killed in the U.S. each year by dogs than have been killed by great white sharks in the last 100 years." However, such comments should be taken in context; interaction between humans and canines takes place far more regularly and in greater numbers than it does between humans and sharks.
Many "shark repellents" have been tested, some using scent, others using protective clothing, but to date the most effective is an electronic beacon (POD) worn by the diver/surfer that creates an electric field which disturbs the shark's sensitive electro-receptive sense organs, the ampullae of Lorenzini.

Attacks on boats
Great white sharks infrequently attack and sometimes even sink boats, in a few cases they have attacked boats up to 10 meters in length. They have bumped or knocked people overboard, usually 'attacking' the boat from the stern. In one case (in 1936), a large shark leapt completely into the South African fishing boat Lucky Jim, knocking a crewman into the sea. Tricas and McCosker's underwater observations suggest that sharks are attracted to boats due to the electrical fields they generate.

Great white sharks in captivity
All attempts to keep a great white shark in captivity prior to August 1981 lasted 11 days or less. However, that month a great white broke previous records by lasting 16 days in captivity at SeaWorld San Diego before being released into the wild.
In 1984, shortly before opening day, the Monterey Bay Aquarium in Monterey, California housed its first great white shark, which died after 10 days. In July 2003, Monterey researchers captured a small female and kept it in a large, netted pen off Malibu for five days, where they had the rare success of getting the shark to feed in captivity before it was released. It was not until September 2004 that the aquarium was the first to place a great white on long-term exhibit. The young female, who was caught off the coast of Ventura, was kept in the aquarium's massive 1 million-gallon (3,800,000 litres) Outer Bay exhibit for 198 days before her successful release back to the wild in March 2005. She was tracked for 30 days after her early morning release. On the evening of August 31, 2006 the aquarium introduced a second shark to the Outer Bay exhibit. The juvenile male, caught outside Santa Monica Bay on August 17 , had its first official meal in captivity (a large salmon steak) on September 8, 2006 and as of that date, the shark was estimated to be 1.72 metres (5 ft 8 in) and to weigh approximately 47 kilograms (104 lb). He was released on January 16, 2007 after 137 days in captivity.
Probably the most famous great white shark to be kept in captivity was a female named "Sandy", which in August 1980 became the first and only great white shark to be housed at the Steinhart Aquarium in San Francisco, California. She was returned to the wild because she would not eat anything given to her and constantly bumped against the walls.

Shark tourism and cage diving
Shark cage-diving is when a group of tourists, or those who wish to study the sharks up close are lowered into the water beside a boat, protected by a steel cage. From this view point it is easier to view the sharks up close without the dangers of being bitten. Cage diving is most common off the coasts of Australia, South Africa, and Guadalupe Island off the coast of Baja California as these are places where great white sharks are most likely to be seen.
Viewing sharks from the safety of a cage gives tourists an adrenaline rush and has become a booming industry. A common practice is to chum the water to draw in sharks for the tourists to view. These practices have raised the fear that sharks may be becoming more accustomed to people in their environment and beginning to associate human activity with food - a potentially dangerous situation. It is claimed that certain methods of chumming, such as when bait on a wire is drawn towards the divers in the cage, which may result in the shark striking the cage, exacerbate this problem. Other operators purposefully draw the bait away from the cage causing the shark to swim past the divers.
Companies respond that they are being made the scapegoats, as people try to find someone to blame for shark attacks on humans. Most point out that lightning tends to strike humans more often than sharks bite humans. Their position is that further research needs to be done before banning practices such as chumming which are said to alter sharks' natural behaviour.
It has been advised that all dive boats should only use chum in areas in which Whites are known to actively patrol anyway, and these should be far enough away from human leisure areas so as not to draw the sharks towards them. Also, responsible dive operators will not feed the sharks; only sharks that are willing to scavenge will follow the chum trail, and if they find no food at the end then the shark will soon swim off and not associate chum with a meal. It has been suggested that government licensing strategies may help enforce these suggested advisories.
The shark tourist industry has some financial leverage in conserving this animal. For a fisherman with limited income, a single set of White jaws can fetch up to ?20,000, a very substantial amount of money for a day's fishing. However, the value of the dead animal is a fraction of the value of viewing a live shark, which can become a more viable and sustainable economic activity to the local community. For example, the dive industry in Gaansbai South Africa, consists of about six boat operators with each boat taking around 30 people out to sea a day; if each person pays anywhere between ?50 to ?150, then in a single day a solitary live shark that visits each boat can create anywhere between ?9,000 to ?27,000 of revenue daily.

Conservation status
It is unclear how much a concurrent increase in fishing for great white sharks had to do with the decline of great white shark population from the 1970s to the present. No accurate numbers on population are available, but populations have clearly declined to a point at which the great white shark is now considered endangered. Their reproduction is slow, with sexual maturity occurring at about nine years of age, the population, therefore, can take a long time to rise.
The Convention on International Trade in Endangered Species (C.I.T.E.S.) has put the great white shark on its 'Appendix II' list of endangered species. The shark is targeted by fishermen for its jaws, teeth, and fins, and as a game fish. The great white shark, however, is rarely an object of commercial fishing, although its flesh is considered valuable. If casually captured (it happens for example in some tonnare in the Mediterranean), it is sold as smooth-hound shark.
From April 2007 great white sharks are fully protected within 200 nautical miles (370 km) of New Zealand and additionally from fishing by New Zealand-flagged boats outside this range.

Hammerhead Shark

Hammerhead sharks of the genus Sphyrna are members of the family Sphyrnidae. The only other genus of Sphyrnidae, Eusphyra, contains only one species, Eusphyra blochii, the winghead shark.

Physical description
The nine known species of hammerhead range from 0.9 to 6 m long (3 to 20 feet). All the species have a projection on each side of the head that gives it a resemblance to a flattened hammer. The shark's eyes and nostrils are at the tips of the extensions.
The hammer shape of the head was once thought to help sharks get food, aiding in close-quarters maneuverability and allowing the shark to turn sharply without losing stability. However, it was found that the special design of its vertebrae allowed it to make the turns correctly, more than its head. But as a wing the hammer would also provide lift; hammerheads are one of the most negatively buoyant of sharks. Like all sharks, hammerhead have electrolocation sensory pores called ampullae of Lorenzini. By distributing the receptors over a wider area, hammerheads can sweep for prey more effectively. These sharks have been able to detect an electrical signal of half a billionth of a volt. The hammer-shaped head also gives these sharks larger nasal tracts, increasing the chance of finding a particle in the water by at least 10 times as against the ability of other 'classical' sharks.
Wider spacing between sensory organs better enables an organisms to detect gradients and therefore the location of a gradient source such as food or a mate. The peculiar head of this shark can be thought of as analogous to the antennae of an insect.
The hammerheads are aggressive predators, eating fish, rays, cephalopods, and crustaceans. They are found in warmer waters along coastlines and continental shelves.
Hammerheads have disproportionately small mouths and seem to do a lot of bottom-hunting. They are also known to form schools during the day, sometimes in groups of over 100. In the evening, like other sharks, they become solitary hunters.
Hammerheads are notably the only creature in the animal kingdom besides humans to acquire a tan from prolonged exposure to sunlight. Tanning occurs when a hammerhead is in shallow waters or close to the surface for long periods.
It's also noted that in recent studies that when large groups of hammerheads gather, they usully communicate with other individuals by creating pressure waves by thrashing their heads more sharply than usual, causing pressure waves that other individuals pick up and respond to.

Reproduction
Reproduction in the hammerhead shark occurs once a year with each litter containing 20 to 40 pups. Hammerhead shark mating courtship is a violent affair. The male will bite the female until she acquiesces, allowing mating to occur. Unlike many other shark species, the hammerhead shark has internal fertilization which creates a safe environment for the sperm to unite with the egg. The embryo develops within the female inside a placenta and is fed through an umbilical cord, similar to mammals. The gestation period is 10 to 12 months. Once the pups are born the parents do not stay with them and they are left to fend for themselves. Young hammerheads are often born headfirst, with the tip of their hammerhead folded backward to make them more streamlined for birth. A world-record 1,280 pound (580 kg) pregnant female hammerhead shark was caught off Boca Grande, Florida on May 23, 2006. The shark was carrying 55 pups, which suggests scientists had previously underestimated the number of pups per gestation.
In May 2007 scientists discovered that Hammerhead sharks can reproduce asexually through a rare method known as parthenogenesis, as they have the ability to fertilize their own eggs. At first the announcement was considered skeptically, due to the fact that a female shark can store sperm inside her for months, even years, but it was confirmed through DNA testing that the pup lacked any paternal DNA. This is the first documented case of any shark doing this.

Species
Of the nine known species of hammerhead, three can be dangerous to humans: the scalloped, great, and smooth hammerheads.
Genus Sphyrna
Subgenus Sphyrna
Scalloped hammerhead, Sphyrna (Sphyrna) lewini (Griffith & Smith, 1834)
"Cryptic scalloped hammerhead" - Scalloped hammerheads turn out to be divided into two separate species, which have not been officially reclassified with separate names.
Great hammerhead, Sphyrna (Sphyrna) mokarran (R?ppell, 1837)
Smooth hammerhead, Sphyrna (Sphyrna) zygaena (Linnaeus, 1758)
Whitefin hammerhead, Sphyrna (Sphyrna) couardi Cadenat, 1951
Subgenus Mesozygaena
Scalloped bonnethead, Sphyrna (Mesozygaena) corona Springer, 1940
Squarehead shark Sphyrna (Mesozygaena) sp. listed on elasmo-research's list
Subgenus Platysqualus
Scoophead, Sphyrna (Platysqualus) media Springer, 1940
Bonnethead or shovelhead, Sphyrna (Platysqualus) tiburo (Linnaeus, 1758)
Smalleye hammerhead, Sphyrna (Platysqualus) tudes (Valenciennes, 1822)
Announcements in June, 2006 reported the discovery of a possible new species of hammerhead off the shores of South Carolina. The possible new species is referred to simply as a cryptic species until it receives an official designation. This is prolonged, in part, because the discovery is really that the "scalloped hammerhead" is possibly two different species, not that a new species has been sighted, in the normal way. The discovery that scalloped hammerheads are possibly two species is purely a result of genetic testing, not identification of physical differences.
Since sharks do not have mineralized bones and rarely fossilize, it is their teeth alone that are commonly found as fossils. The hammerheads seem closely related to the carcharhinid sharks that evolved during the mid-Tertiary Period. Because the teeth of hammerheads resemble those of some carcharhinids, it has been difficult to determine when hammerheads first appeared. It is probable that the hammerheads evolved during the late Eocene, Oligocene or early Miocene.
Geneticist Andrew Martin used DNA to study all of the hammerhead species and he concluded that the first hammer appeared on the winghead shark, which has the largest hammer, and the rest of the hammerhead sharks evolved one at a time from the original winghead shark each with a smaller hammer .

Mako Shark

The shortfin mako shark, Isurus oxyrinchus, ("sharp nose") is a large shark of the Lamnidae family. Along with the closely related longfin mako, Isurus paucus, it is commonly called just mako shark. They are known to be incredibly fast swimmers with superior lateral movements.

Anatomy and appearance
With an average full-grown length of 1.82-2.42 m (6-8 ft), it can also grow to 3.9 m (13 feet) long and has been reported to weigh up to 800 kg (1,750 lb). It has a bluish back and white underside. Although the sexes grow at about the same rate, females are thought to have a longer life span, and grow larger and weigh more than the males. Shortfin makos are renowned for their speed and their ability to leap out of the water. In fact, there are cases when an angry mako will jump out of the water and into the boat after it has been caught on the hook. Mako sharks have a better hydrodynamic shape than all other sharks, and this, combined with the lamnidae's typical high aerobic muscle mass, reflects in the spectacular speed and agility of both the longfin and shortfin makos.
The shortfin mako shark is a sleek spindle shaped shark with a long conical snout. This shark has short pectoral fins and a crescent shaped caudal (tail) fin. There is a distinct caudal keel on the caudal base. Its second dorsal fin is much smaller than the first. The teeth are slender and slightly curved with no lateral cusps, and are visible even when the mouth is closed. There is marked countershading on this shark: dorsally it is a metallic indigo blue while ventrally it is white.

Naming
The name "mako" comes from the M?ori language, but the etymology is unclear. A typical gloss given for "mako" is "large blue shark". The term entered the English language in 1727. It can also mean "man-eater".

Diet
The shortfin mako feeds mainly upon bony fishes including mackerels, tunas, bonitos and swordfish, but may also eat other sharks, porpoises and sea turtles.

Distribution
The shortfin mako is found in temperate and tropical seas worldwide. The closely related longfin mako shark, Isurus paucus, is found in the Gulf Stream or warmer offshore waters.
Shortfin mako sharks live in tropical and temperate offshore waters. They are a pelagic species that occur from the surface down to depths of 150 meters (490 feet). This shark is seldom found in waters colder than 16 degrees Celsius (61 degrees Fahrenheit).
The shortfin mako is found worldwide. In the western Atlantic it can be found from Argentina and the Gulf of Mexico to Browns Bank off of Nova Scotia. In Canadian waters these sharks are not abundant as they prefer warm waters, but neither are they rare. Shortfin makos are often found in the same waters as swordfish as they are a source of food and both fish prefer similar environmental conditions.

Behavior
The shortfin mako's speed has been recorded at 50 km/h (31 mph) and there are reports that it can achieve bursts of up to 74 km/h (46 mph). Shortfin makos can jump up to 9 m (28 ft) in the air. Due to its speed and agility, this high-leaping fish is sought as game worldwide. This shark is highly migratory. They are also one of four warm-blooded sharks which helps them in their speed.
There is still some uncertainty about its life-span, but it is suspected to reach ages of between 11-23 years.

Reproduction
The shortfin mako shark is a yolk-sac ovoviviparous shark, meaning it gives birth to live young who feed from a sac full of yolk in the womb. The gestation period for a mako shark is 15 to 18 months. Shortfin mako embryos in the female's body consume each other to get nutrients. This is called intrauterine cannibalism.
Female shortfin makos usually become sexually mature at a length of 3 meters. Developing embryos feed on unfertilized eggs in the uterus during the gestation period of 15-18 months. The 4-18 surviving young are born live in the late winter and early spring at a length of about 70 cm, but have no placental connection during development (ovoviviparity). It is believed that females may rest for 18 months after birth before the next batch of eggs are fertilized.
Male shortfin makos reach sexual maturity within 4 years.

Distinguishing characteristics
Teeth are visible even when the mouth is closed
Teeth are long and slender with smooth-edged cusps
Distinct countershading, dorsally blue and ventrally white
Moderately short pectoral fins
Underside of the snout is white
Lunate tail and caudal keel

Mako sharks in popular culture
Three genetically engineered mako sharks are the chief antagonists of 1999 science fiction/horror film Deep Blue Sea.
A female mako shark also starred in Mathias Bradley's novel, Mako: Journey of Discovery as the human-friendly Sunyui. In the sequel, Mako: Journey of Discovery 2: Sunyui's Family, Sunyui becomes the main star at SeaWorld, Japan, along with her mate, Rio. In the end, Sunyui mates with Rio and she has two litters of three pups during her two pregnancies.
A Mako shark is also seen on Jackass 2:The Movie, one of the stars kicks one in the head while being used as human bait in a skit.
A Mako shark appeared in Ernest Hemmingway's novella, "The Old Man and The Sea"
Mako sharks were mentioned in Life of Pi, by Yann Martel.

Nurse Shark

The nurse shark, Ginglymostoma cirratum, is a shark in the nurse sharks family, the only member of its genus Ginglymostoma. It may reach a length of 4.3 m.

Taxonomy
The name nurse shark is thought to be a corruption of nusse, a name which once referred to the catsharks of the family Scyliorhinidae. The nurse shark family name, Ginglymostomatidae, derives from the Greek.

Distribution and habitat
The nurse shark is a common inshore bottom-dwelling shark, found in tropical and subtropical waters on the continental and insular shelves. It is frequently found at depths of 1 metre or less but may occur down to 12 m. Its common habitats are reefs, channels between mangrove islands and sand flats. It occurs in the Western Atlantic from Rhode Island down to southern Brazil;in the Eastern Atlantic from Cameroon to Gabon (and possibly ranges further north and south); in the Eastern Pacific from the southern Baja California to Peru; and around the islands of the Caribbean.

Behaviour and diet
Nurse sharks are nocturnal animals, spending the day in large inactive groups of up to 40 individuals. Hidden under submerged ledges or in crevices within the reef, the nurse sharks seem to prefer specific resting sites and will return to them each day after the night's hunting. By night, the sharks are largely solitary; they spend most of their time rifling through the bottom sediments in search of food. Their diet consists primarily of crustaceans, molluscs, tunicates, and other fish, particularly stingrays.
Their diet consists of a large number of marine invertebrates - spiny lobsters, crabs, shrimps, sea urchins, octopuses, squid, and marine snails and bivalves.
They are thought to take advantage of dormant fish which would otherwise be too fast for the sharks to catch; although their small mouths limit the size of prey items, the sharks have large throat cavities which are used as a sort of bellows valve. In this way nurse sharks are able to suck in their prey. Nurse sharks are also known to graze algae and coral.
Nurse sharks have been observed resting on the bottom with their bodies supported on their fins, possibly providing a false shelter for crustaceans which they then ambush and eat.

Reproduction
The mating season runs from late June to the end of July. Nurse sharks are ovoviviparous, meaning the eggs develop and hatch within the body of the female where the hatchlings develop further until live birth occurs. The gestation period is six months, with a typical litter of 21 - 28 pups. The mating cycle is biennial, as it takes 18 months for the female's ovaries to produce another batch of eggs. The young nurse sharks are born fully developed at about 30 centimetres long in Ginglymostoma cirratum. They possess a spotted coloration which fades with age.

Interaction with humans
The nurse shark is not widely commercially fished, but because of its sluggish behaviour it is an easy target for local fisheries. Its skin is exceptionally tough and is prized for leather; its flesh consumed fresh and salted and its liver utilised for oil. It is not taken as a game fish. It has been reported in some unprovoked attacks on humans but is not generally perceived as a threat.

Popular Culture
A character in the cartoon Camp Lazlo named Nurse Leslie is a nurse shark.

Sandtiger Shark

The grey nurse (Australia), spotted ragged-tooth (Africa) or sand tiger (US and UK), Carcharias taurus, is a large shark inhabiting coastal waters worldwide, with many different names in different countries in the world. Despite a fearsome appearance and strong swimming abilities, it is a relatively placid and slow moving animal. It is considered not aggressive unless provoked.

Habitat and distribution
Research indicates that generally the shark remains within a kilometre of its aggregation site, and stays close to the ocean floor. Present throughout the world, in the Atlantic, Indian and Pacific Oceans, the shark is a common sight in many areas of the world.

Anatomy and appearance
Their bodies are stout, with two large dorsal fins and the tail is elongated and have a long upper lobe. The shark has a precaudal pit but no caudal keels. It grows to a length of 3.2 m (about 10' 6"). Male grey nurse sharks mature at 2.1 m (about 6' 11"); and females mature at 2.2 m (about 7' 3"). This shark weighs 200 to 350 pounds (90 to 160 kg).
The grey nurse shark usually has a grey back and white underside. In August 2007, an albino specimen was photographed off South West Rocks, Australia.

Diet
The diet of Carcharias taurus consists of bony fishes including jewfish and kingfish, other sharks and rays, squid, crabs and lobsters

Behaviour
The sharks typically congregate in coastal waters, at depths of 60-190 metres, although deeper depths have been recorded. Often they will shelter in caves or gutters during the day, and come out at night to feed. During the day they exhibit sluggish behavior, becoming more active during the night. The grey nurse shark is the only known shark to gulp and store air in its stomach in order to maintain neutral buoyancy while swimming.
Towards man, grey nurse sharks will not attack unless provoked, but when so they can be dangerous. The grey nurse comes directly after the bull shark, in place #5, on the list of most dangerous sharks. However, it can be calm during daytime and in aquariums it is a very common species.

Reproduction
The species is ovoviviparous, i.e. bearing live young from eggs which hatch inside the uterus. Female sharks have two uteruses. Inside the uterus the young sharks develop and eat each other, so typically only two young sharks are born for each gestation period, which lasts 6-9 months. This process, also known as intrauterine cannibalism, is making it harder for the shark population to rebound from the near extinction. As a result, scientists plan to artificially inseminate and breed the sharks, in order to increase their population. Another plan is to remove the shark embryos from the uterus before cannibalism can take place and then artificially gestate them.

Spiny Dogfish Shark

The spiny dogfish or piked dogfish, Squalus acanthias, is one of the best known of the dogfish, members of the family Squalidae in the order Squaliformes. There are actually several species to which the names are applied, but all are readily distinguished by their having two spines (one anterior to each dorsal fin) and their lack of an anal fin. It is found in shallow waters and offshore in most parts of the world, especially in temperate waters.

Morphology and behavior
The spiny dogfish has dorsal spines, no anal fin, and white spots along its back. The caudal fin has asymmetrical lobes, forming a heterocercal tail. Males mature at around 11 years of age, growing to 80-100 cm in length; females mature in 18-21 years and are slightly larger than males, reaching 100-124 cm. Both sexes are greyish brown in color and are countershaded. Males are identified by a pair of pelvic fins modified as sperm-transfer organs, or "claspers". The male inserts one clasper into the female cloaca during copulation.
The species name acanthias refers to the shark's two spines. These are used defensively; if captured, the shark can arch its back to pierce its captor. Glands at the base of the spines secrete a mild poison.
Reproduction is aplacental viviparous, which was before called ovoviviparity. Fertilization is internal. The male inserts one claspers into the female oviduct orifice and injects sperm along a groove on the clasper's dorsal section. Immediately following fertilization, the eggs are surrounded by thin shells called candles, with one candle usually surrounding several eggs. Mating takes place in the winter months, with gestation lasting 22-24 months (the longest of any vertebrate). Litters range between 2 and 11 but average 6 or 7.

Commercial use
Spiny dogfish are fished for food in Europe, the United States, Canada, New Zealand and Chile. The meat is primarily consumed in England, France, the Benelux countries and Germany. The fins and tails are processed into fin needles and are used in less expensive versions of shark fin soup in Chinese cuisine. In England it is sold in "fish and chip shops" as "rock salmon", in France it is sold as "small salmon" (saumonette) and in Belgium it is sold as "sea eel" (zeepaling). It is also used as fertilizer, liver oil, and pet food, and, because of its availability and manageable size, as a popular vertebrate dissection specimen, especially in high schools.

Whale Shark

The whale shark, Rhincodon typus, is a slow filter feeding shark that is the largest living fish species. This distinctively-marked shark is the only member of its genus Rhincodon and its family, Rhincodontidae (called Rhinodontes before 1984), which is grouped into the subclass Elasmobranchii in the class Chondrichthyes. The shark is found in tropical and warm oceans and lives in the open sea. The species is believed to have originated about 60 million years ago.

Naming
The species was first identified in April 1828 following the harpooning of a 4.6-metre (15.1 ft) specimen in Table Bay, South Africa. It was described the following year by Andrew Smith, a military doctor associated with British troops stationed in Cape Town. He proceeded to publish a more detailed description of the species in 1849. The name "whale shark" comes from the fish's physiology; that is, a shark as large as a whale that shares a similar filter feeder eating mode. Known as a deity in a Vietnamese religion, the whale shark is called "Ca Ong", which literally translates as "Sir Fish"

Distribution and habitat
The whale shark inhabits the world's tropical and warm-temperate oceans. While thought to be primarily pelagic, seasonal feeding aggregations of the sharks occur at several coastal sites such as Ningaloo Reef in Western Australia; ?tila in Honduras; Donsol and Batangas in the Philippines; off Isla Holbox in Yucatan Mexico; and the Tanzanian islands of Pemba and Zanzibar. Though it is often seen offshore, it has also been found closer to shore, entering lagoons or coral atolls, and near the mouths of estuaries and rivers. Its range is restricted to about 30 latitude. It is found to a depth of 700 metres (2,300 ft). The whale shark is solitary and rarely seen in groups unless feeding at locations with an abundance of food. Males range over longer distances than females (which appear to favour specific locations).

Anatomy and appearance
As a filter feeder, it has a capacious mouth which can be up to 1.5 metres (4.9 ft) wide and can contain between 300 and 350 rows of tiny teeth. It has five large pairs of gills. Two small eyes are located towards the front of the shark's wide, flat head. The body is mostly grey with a white belly; three prominent ridges run along each side of the animal and the skin is marked with a "checkerboard" of pale yellow spots and stripes. These spots are unique to each whale shark and because of this they can be used to identify each animal and hence make an accurate population count. Its skin can be up to 10 centimetres (3.9 in) thick. The shark has a pair each of dorsal fins and pectoral fins. A juvenile whale shark's tail has a larger upper fin than lower fin while the adult tail becomes semi-lunate (or crescent-shaped). The whale shark's spiracles are just behind the eyes. They can often be below the mouth.
The whale shark is not an efficient swimmer since the entire body is used for swimming, which is unusual for fish and contributes to an average speed of only around 5-kilometre-per-hour (3.1 mph). The largest specimen regarded as accurately recorded was caught on November 11, 1947, near the island of Baba, not far from Karachi, Pakistan. It was 12.65 metres (41.50 ft) long, weighed more than 21.5 tonnes (47,300 lb), and had a girth of 7 metres (23.0 ft). Stories exist of vastly larger specimens - quoted lengths of 18 metres (59 ft) are not uncommon in the popular shark literature - but no scientific records exist to support their existence. In 1868 the Irish natural scientist E. Perceval Wright spent time in the Seychelles, during which he managed to obtain several small whale shark specimens, but claimed to have observed specimens in excess of 15 metres (49.2 ft), and tells of reports of specimens surpassing 21 metres (68.9 ft).
In a 1925 publication, Hugh M. Smith describes a huge whale shark caught in a bamboo fish trap in Thailand in 1919. The shark was too heavy to pull ashore, but Smith estimated that the shark was at least 17 metres (56 ft) long, and weighed approximately 37 tonnes (81,500 lb), which have been exaggerated to an accurate measurement of 17.98 metres (58.99 ft) and weight 43 tonnes in recent years. There have even been claims of whale sharks of up to 23 metres (75 ft). In 1934 a ship named the Maurguani came across a whale shark in the Southern Pacific Ocean, rammed it, and the shark consequently became stuck on the prow of the ship, supposedly with 4.6 metres (15.1 ft) on one side and 12.2 metres (40.0 ft) on the other. No reliable documentation exists of those claims and they remain little more than "fish-stories".

Diet
The whale shark is a filter feeder - one of only three known filter feeding shark species (along with the basking shark and the megamouth shark). It feeds on phytoplankton, macro-algae, plankton, krill and small nektonic life, such as small squid or vertebrates. The many rows of teeth play no role in feeding; in fact, they are reduced in size in the whale shark. Instead, the shark sucks in a mouthful of water, closes its mouth and expels the water through its gills. During the slight delay between closing the mouth and opening the gill flaps, plankton is trapped against the dermal denticles which line its gill plates and pharynx. This fine sieve-like apparatus, which is a unique modification of the gill rakers, prevents the passage of anything but fluid out through the gills (anything above 2 to 3 mm in diameter is trapped). Any material caught in the filter between the gill bars is swallowed. Whale sharks have been observed "coughing" and it is presumed that this is a method of clearing a build up of food particles in the gill rakers.
Whale sharks congregate at reefs off the Belizean Caribbean coast, supplementing their ordinary diet by feeding on the roe of giant cubera snappers, which spawn in these waters between the full and quarter moons of May, June, and July.
The whale shark is an active feeder and targets concentrations of plankton or fish by olfactory cues. Rather than simply "vacuuming" constantly, it is able to pump water over its gills. The shark can circulate water at a rate up to 1.7 L/s (3.5 U.S. pint/s). The whale shark does not need to swim forward when feeding; it is often observed in a vertical position, "bobbing" up and down swallowing water and actively filtering it for food. This is in contrast to the basking shark, which is a passive feeder and does not pump water; it relies on its swimming to force water over its gills.

Behavior towards divers
This species, despite its enormous size, does not pose any significant danger to humans. It is a frequently cited example when educating the public about the popular misconceptions of all sharks as "man-eaters". They are actually quite gentle and can be playful with divers. There are unconfirmed reports of sharks lying still, upside down on the surface to allow divers to scrape parasites and other organisms from their bellies. Divers and snorkellers can swim with this giant fish without any risk apart from unintentionally being hit by the shark's large tail fin.
The shark is often seen by divers in The Bay Islands in Honduras, Thailand, the Philippines, the Maldives, the Red Sea, Western Australia (Ningaloo Reef), Gladden Spit Marine Reserve in Belize, Tofo Beach in Mozambique, Sodwana Bay (Greater St. Lucia Wetland Park) in South Africa and at the Galapagos Islands.
The highest concentration of whale sharks to be found anywhere in the world is in the Philippines. From January to May, they congregate in the shallow coastal waters of Sorsogon province (at Donsol). Lucky divers have also come across whale sharks in the Seychelles and in Puerto Rico. Between December and September, they are well known to swim along the bay of La Paz in Mexico's Baja California. Sometimes, they are accompanied by smaller fish, in particular, the remora. Recently, they have been seen in the vicinity of Tenggol Island, off the east coast of West Malaysia.They are also frequently spotted around other Coral Reefs along the West Malaysian coast including Kapas Island and Redang Island.

Reproduction
The reproductive habits of the whale shark are obscure. Based on the study of a single egg recovered off the coast of Mexico in 1956, it was believed to be oviparous, but the capture of a female in July 1996 which was pregnant with 300 pups indicates that they are ovoviviparous. The eggs remain in the body and the females give birth to live young which are 40 centimetres (15.7 in) to 60 centimetres (23.6 in) long. It is believed that they reach sexual maturity at around 30 years and the life span has been estimated to be over 100 years.

Conservation status
The whale shark is targeted by artisanal and commercial fisheries in several areas where they seasonally aggregate. The population is unknown and the species is considered vulnerable by the IUCN. All fishing, selling, importing and exporting of whale sharks for commercial purposes has been banned in the Philippines since 1998 , followed by Taiwan in May 2007 .

Whale sharks in captivity
A whale shark is featured as the main attraction of Osaka Aquarium Kaiyukan and as of 2005, three whale sharks are being studied in captivity at the Okinawa Churaumi Aquarium in Japan. Four whale sharks, two males, Taroko, and Yushan, and two females, Alice and Trixie, are held in the Georgia Aquarium, in Atlanta. Two male whale sharks, Ralph and Norton, died in captivity at the Georgia Aquarium on January 11, 2007 and June 13, 2007 respectively. The two males were added on June 3, 2006 in hopes that reproduction in whale sharks could be studied in captivity. All six whale sharks were imported from Taiwan, where whale sharks are dubbed as tofu sharks because of the taste and texture of the flesh.

White Tip Reef Shark

The whitetip reef shark, Triaenodon obesus, is a requiem shark of the family Carcharhinidae, the only member of the genus Triaenodon.

Habitat and distribution
The whitetip reef shark is one of the most common sharks found in shallow tropical and warm temperate water around coral reefs in the Indian and Pacific oceans. It occurs at depths down to 330 m.

Anatomy and appearance
As its name suggests, the tips of the shark's first dorsal fin and upper caudal fin are white. The upper body is grey/brownish. Their average length is about 140 to 160 cm and the maximum reported length is 244 cm. Its head is broad and flat.

Diet
The whitetip reef shark feeds primarily on crustaceans, octopuses and fish.

Behaviour
This bottom dwelling shark is nocturnal and is often seen resting on the bottom during the day, sometimes in small groups. It is not aggressive and will generally swim away if disturbed, although it may bite if harassed. At night it hunts among crevices in the reef.

Reproduction
Reproduction is viviparous, with 1 to 5 pups in a litter, the gestation period being at least 5 months. The shark's size at birth ranges from 50 to 60 cm. It is estimated that this shark can live for about 25 years and it reaches maturity after about 5 years.

Wobbegong Shark

Wobbegong is the common name given to the eight species of carpet sharks in the family Orectolobidae. They are found in shallow temperate and tropical waters of the western Pacific Ocean and eastern Indian Ocean, chiefly around Australia and Indonesia, although one species (the Japanese wobbegong, Orectolobus japonicus) occurs as far north as Japan.
Wobbegongs are bottom-dwelling sharks which spend much of their time resting on the sea floor, often among rocks or under ledges. The largest species, the spotted wobbegong, Orectolobus maculatus, grows up to 3.2 m long. Wobbegongs are well camouflaged with a symmetrical pattern of bold markings which resembles carpet. Because of this striking pattern, wobbegongs and their close relatives are often referred to as carpet sharks. The camouflage is improved by the presence of small vegetation-like flaps of skin around the wobbegong's mouth. Wobbegongs make use of their relative invisibility to hide among rocks and ambush smaller fish which swim too close (animals which feed in this way are called ambush predators).
Wobbegongs are generally not dangerous unless they are provoked. They have bitten people who accidentally step on them in shallow water; they may also bite scuba divers or snorkellers who poke or handle them, or who block their escape route. Wobbegongs are very flexible and can easily bite a hand that is holding on to their tail. They have many small but sharp teeth and their bite can be severe, even through a wetsuit; having once bitten, they have been known to hang on and can be very difficult to remove. To avoid being bitten, divers should avoid accidental contact.
Although wobbegongs do not eat humans, humans frequently eat wobbegongs; the flesh of a wobbegong or other shark is called flake and it is often used in fish and chips in Australia. Wobbegong skin is also used to make leather.
The word wobbegong is believed to come from an Australian Aboriginal language.

Genera and species
Orectolobus
Orectolobus halei Whitley, 1940.
Orectolobus hutchinsi Last, Chidlow & Compagno, 2006.
Tasselled wobbegong, Orectolobus dasypogon (Bleeker, 1867)
Japanese wobbegong, Orectolobus japonicus Regan, 1906
Spotted wobbegong , Orectolobus maculatus (Bonnaterre, 1788)
Ornate wobbegong, Orectolobus ornatus (De Vis, 1883)
Northern wobbegong, Orectolobus wardi Whitley, 1939
Western wobbegong, Orectolobus sp. A
Sutorectus
Cobbler wobbegong, Sutorectus tentaculatus (Peters, 1864)

Zebra Shark

The zebra shark, Stegostoma fasciatum, is a common carpet shark of inshore Indo-Pacific waters notable for its very long caudal fin, nearly as long as its body. It is the only species in the family Stegostomatidae and the genus Stegostoma.

Common name
The name zebra shark is given because as a juvenile the shark has zebra-like stripes. When it matures these stripes change to cheetah-like spots. Because of this change in its coloration, it may also be sometimes known as the leopard shark, a name widely used to refer to Triakis semifasciata, a small benthic shark found in the Eastern Pacific coastline of North America.

Distribution and habitat
The zebra shark is found in the tropical Western Pacific and Indian oceans at depths of about 5 to 30 m.

Anatomy and appearance
It is a very sleek and slender shark, about 3.5m (11.5 ft) long. In addition to the long tail, the zebra shark has distinctive ridges running down its body. As its names suggest, it is patterned; young sharks are dark with yellowish stripes, changing to an adult pattern of a tan color with dark spots, found all over including the fins. The snout is rather rounded, with small barbels (whiskers).

Behavior
The zebra shark is a slow-moving type, often just sitting on the seafloor in the vicinity of coral reefs, on sandy or rocky bottoms. Unlike most types of sharks, it does not need to move, and instead pumps water through its gills. This is known as the ram-jet effect.

Diet
It feeds on mollusks, crustaceans, and small fish that it sucks out of the sand at night, and is capable of wiggling through small holes and crevices in its search for food.

Importance to humans
Zebra sharks do well in captivity, and a number of aquariums around the world have them on display. They are fished commercially on a small scale. They are often seen by scuba divers, and will lay still on the bottom as long as a diver does not come too close. They are harmless to divers as long as they are not disturbed. In addition several aquariums have shown them to be easy learners, even teaching them to respond to touch by flapping their gills. Due to its large caudal fins, this species are a prized catch for fishermen to make shark fin soup.

In popular culture
The male lead of Margaret Drabble's The Sea Lady is an expert on zebra sharks, which plays a substantial part in the plot.