SHARK
Photo :- google
There are more than 465 known species of sharks living in our oceans today. Sharks are an apex predator at or near the top of their marine food chains, and they regulate the populations of species below them. Research has shown that massive depletion of sharks has cascading effects throughout the ocean’s ecosystems.
Sharks belong to a family of fish that have skeletons made of cartilage, a tissue more flexible and lighter than bone. They breathe through a series of five to seven gill slits located on either side of their bodies. All sharks have multiple rows of teeth, and while they lose teeth on a regular basis, new teeth continue to grow in and replace those they lose.
Shark ‘skin’ is made up of a series of scales that act as an outer skeleton for easy movement and for saving energy in the water. The upper side of a shark is generally dark to blend in with the water from above and their undersides are white or lighter colored to blend in with the lighter surface of the sea from below. This helps to camouflage them from predators and prey.
HABITAT & RANGE
Sharks have adapted to living in a wide range of aquatic habitats at various temperatures. While some species inhabit shallow, coastal regions, others live in deep waters, on the ocean floor and in the open ocean. Some species, like the bull shark, are even known to swim in salt, fresh and brackish waters.
BEHAVIOR
Most sharks are especially active in the evening and night when they hunt. Some sharks migrate over great distances to feed and breed. This can take them over entire ocean basins. While some shark species are solitary, others display social behavior at various levels. Hammerhead sharks, for instance, school during mating season around seamounts and islands.
Some shark species, like the great white shark, attack and surprise their prey, usually seals and sea lions, from below. Species that dwell on the ocean floor have developed the ability to bottom-feed. Others attack schooling fish in a feeding frenzy, while large sharks like the whale and basking sharks filter feed by swimming through the ocean with their mouths open wide, filtering large quantities of plankton and krill.
DIET
Most species of shark eat things like fish, crustaceans, mollusks, plankton, krill, marine mammals and other sharks. Sharks also have a very acute sense of smell that allows them to detect blood in the water from miles away.
POPULATION
It is difficult to estimate population numbers since there are many different species spanning a large geographic area. However, overall shark numbers are on the decline due to the many threats they face in the wild.
REPRODUCTION
Sharks mature slowly, and reach reproductive age anywhere from 12 to 15 years. This, combined with the fact that many species only give birth to one or two pups at a time, means that sharks have great difficulty recovering after their populations have declined.
Soon after birth, sharks pups swim away to fend for themselves. They are born with fully-fledged sets of teeth and are able to feed and live on their own.
TYPE OF SHARKS
(All photos collected from google)● GREAT WHITE SHARK
The great white shark (Carcharodon carcharias), also known as the great white, white shark or white pointer, is a species of large mackerel shark which can be found in the coastal surface waters of all the major oceans. The great white shark is notable for its size, with larger female individuals growing to 6.1 m (20 ft) in length and 1,905 kg (4,200 lb) in weight at maturity.
● TIGER SHARK
The tiger shark (Galeocerdo cuvier) is a species of requiem shark and is a large macropredator, capable of attaining a length over 5 m (16 ft 5 in). Populations are found in many tropical and temperate waters, especially around central Pacific islands. Its name derives from the dark stripes down its body, which resemble a tiger's pattern, but fade as the shark matures.
● BULL SHARK
The bull shark (Carcharhinus leucas), also known as the Zambezi shark is a requiem shark commonly found worldwide in warm, shallow waters along coasts and in rivers. The bull shark is known for its aggressive nature, and presence in warm, shallow brackish and freshwater systems including estuaries and rivers.
● WHALE SHARK
The whale shark (Rhincodon typus) is a slow-moving, filter-feeding carpet shark and the largest known extant fish species. The largest confirmed individual had a length of 12.65 m (41.5 ft) and a weight of about 21.5 t (47,000 lb). The whale shark holds many records for size in the animal kingdom, most notably being by far the largest living nonmammalian vertebrate. It is the sole member of the genus Rhincodon
● OCEANIC WHITETIP SHARK
The oceanic whitetip shark (Carcharhinus longimanus), also known as Brown Milbert's sand bar shark, brown shark, lesser white shark, nigano shark, oceanic white-tipped whaler, and silvertip shark, is a large pelagic requiem shark inhabiting tropical and warm temperate seas. Its stocky body is most notable for its long, white-tipped, rounded fins.
● BLACKTIP SHARK
The blacktip shark (Carcharhinus limbatus) is a species of requiem shark, and part of the family Carcharhinidae. It is common to coastal tropical and subtropical waters around the world, including brackish habitats. Genetic analyses have revealed substantial variation within this species, with populations from the western Atlantic Ocean isolated and distinct from those in the rest of its range. The blacktip shark has a stout, fusiform body with a pointed snout, long gill slits, and no ridge between the dorsal fins. Most individuals have black tips or edges on the pectoral, dorsal, pelvic, and caudal fins. It usually attains a length of 1.5 m (4.9 ft).
● HAMMERHEAD SHARK
The hammerhead sharks are a group of sharks in the family Sphyrnidae, so named for the unusual and distinctive structure of their heads, which are flattened and laterally extended into a "hammer" shape called a cephalofoil. Most hammerhead species are placed in the genus Sphyrna, while the winghead shark is placed in its own genus, Eusphyra. Many, but not necessarily mutually exclusive, functions have been proposed for the cephalofoil, including sensory reception, manoeuvering, and prey manipulation. Hammerheads are found worldwide in warmer waters along coastlines and continental shelves. Unlike most sharks, hammerheads usually swim in schools during the day, becoming solitary hunters at night.
● BASKING SHARK
The basking shark (Cetorhinus maximus) is the second-largest living shark, after the whale shark, and one of three plankton-eating shark species, along with the whale shark and megamouth shark. Adults typically reach 6–8 m (20–26 ft) in length. They are usually greyish-brown, with mottled skin. The caudal fin has a strong lateral keel and a crescent shape.
● GOBLIN SHARK
The goblin shark (Mitsukurina owstoni) is a rare species of deep-sea shark. Sometimes called a "living fossil", it is the only extant representative of the family Mitsukurinidae, a lineage some 125 million years old. This pink-skinned animal has a distinctive profile with an elongated, flattened snout, and highly protrusible jaws containing prominent nail-like teeth. It is usually between 3 and 4 m (10 and 13 ft) long when mature, though it can grow considerably larger.
● BLUE SHARK
The blue shark (Prionace glauca) is a species of requiem shark, in the family Carcharhinidae, that inhabits deep waters in the world's temperate and tropical oceans. Preferring cooler waters, blue sharks migrate long distances, such as from New England to South America.
● ANGEL SHARK
The angelsharks are a group of sharks in the genus Squatina in the family Squatinidae, which are unusual in having flattened bodies and broad pectoral fins that give them a strong resemblance to rays. This genus is the only one in its family and order Squatiniformes. They occur worldwide in temperate and tropical seas. Most species inhabit shallow temperate or tropical seas, but a few species inhabits deeper water, down to 1,300 m (4,300 ft).
● COOKIECUTTER SHARK
The cookiecutter shark (Isistius brasiliensis), also called the cigar shark, is a species of small dogfish shark in the family Dalatiidae. This shark occurs in warm, oceanic waters worldwide, particularly near islands, and has been recorded as deep as 3.7 km (2.3 mi). It migrates vertically up to 3 km (1.9 mi) every day, approaching the surface at dusk and descending with the dawn. Reaching only 42–56 cm (16.5–22 in) in length, the cookiecutter shark has a long, cylindrical body with a short, blunt snout, large eyes, two tiny spineless dorsal fins, and a large caudal fin. It is dark brown, with light-emitting photophores covering its underside except for a dark "collar" around its throat and gill slits.
● SHORTFIN MAKO SHARK
The shortfin mako shark (Isurus oxyrinchus), also known as the blue pointer or bonito shark, is a large mackerel shark. It is commonly referred to as the mako shark, as is the longfin mako shark (Isurus paucus). The shortfin mako is on record as the fastest-swimming shark, capable of bursts of speed up to 18.8 metres per second (68 km/h; 42 mph).
● NURSE SHARK
The nurse shark (Ginglymostoma cirratum) is an elasmobranch fish within the family Ginglymostomatidae. They are directly targeted in some fisheries and considered as bycatch in others. The conservation status of the nurse shark is globally assessed as being data deficient in the IUCN List of Threatened Species owing to the lack of information across its range in the eastern Pacific Ocean and eastern Atlantic Ocean. They are considered to be a species of least concern in the United States and in The Bahamas, but considered to be near threatened in the western Atlantic Ocean because of their vulnerable status in South America and reported threats throughout many areas of Central America and the Caribbean.
● SPOT JAKSON SHARK
The Port Jackson shark (Heterodontus portusjacksoni) is a nocturnal, oviparous (egg laying) type of bullhead shark of the family Heterodontidae, found in the coastal region of southern Australia, including the waters off Port Jackson. It has a large, blunt head with prominent forehead ridges and dark brown harness-like markings on a lighter grey-brown body, and can grow up to 1.65 metres (5.5 ft) long.
● SAND TIGER SHARK
The sand tiger shark (Carcharias taurus), grey nurse shark, spotted ragged-tooth shark, or blue-nurse sand tiger is a species of shark that inhabits subtropical and temperate waters worldwide. It inhabits the continental shelf, from sandy shorelines (hence the name sand tiger shark) and submerged reefs to a depth of around 191 m (627 ft).
● SPINY DOGFISH SHARK
The spiny dogfish, spurdog, mud shark, or piked dogfish (Squalus acanthias) is one of the best known species of the Squalidae (dogfish) family of sharks, which is part of the Squaliformes order. While these common names may apply to several species, Squalus acanthias is distinguished by having two spines (one anterior to each dorsal fin) and lacks an anal fin. It is found mostly in shallow waters and further offshore in most parts of the world, especially in temperate waters.
● THRESHER SHARK
Thresher sharks are large lamniform sharks of the family Alopiidae found in all temperate and tropical oceans of the world; the family contains four species, all within the genus Alopias.
● WOBBEGONG SHARK
Wobbegong is the common name given to the 12 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. The word wobbegong is believed to come from an Australian Aboriginal language, meaning "shaggy beard", referring to the growths around the mouth of the shark of the western Pacific.
● ZEBRA SHARK
The zebra shark (Stegostoma fasciatum) is a species of carpet shark and the sole member of the family Stegostomatidae. It is found throughout the tropical Indo-Pacific, frequenting coral reefs and sandy flats to a depth of 62 m (203 ft). Adult zebra sharks are distinctive in appearance, with five longitudinal ridges on a cylindrical body, a low caudal fin comprising nearly half the total length, and a pattern of dark spots on a pale background. Young zebra sharks under 50–90 cm (20–35 in) long have a completely different pattern, consisting of light vertical stripes on a brown background, and lack the ridges. This species attains a length of 2.5 m (8.2 ft).
● LEOPARD SHARK
The leopard shark (Triakis semifasciata) is a species of houndshark, in the family Triakidae. It is found along the Pacific coast of North America, from the U.S. state of Oregon to Mazatlán in Mexico. Typically measuring 1.2–1.5 m (3.9–4.9 ft) long, this slender-bodied shark is immediately identifiable by the striking pattern of black saddle-like markings and large spots over its back, from which it derives its common name. Large schools of leopard sharks are a common sight in bays and estuaries, swimming over sandy or muddy flats or rock-strewn areas near kelp beds and reefs. They are most common near the coast, in water less than 4 m (13 ft) deep.
● TRIAKIS SHARK
Triakis is a genus of houndsharks in the family Triakidae. The name comes from the Greek word τρι, tri meaning "three", and the Latin word acis meaning "sharp" or "pointed", in reference to the three-pointed teeth of these sharks.
● CARIBBEAN REEF SHARK
The Caribbean reef shark (Carcharhinus perezii) is a species of requiem shark, belonging to the family Carcharhinidae. It is found in the tropical waters of the western Atlantic Ocean from Florida to Brazil, and is the most commonly encountered reef shark in the Caribbean Sea. With a robust, streamlined body typical of the requiem sharks, this species is difficult to tell apart from other large members of its family such as the dusky shark (C. obscurus) and the silky shark (C. falciformis). Distinguishing characteristics include dusky-colored fins without prominent markings, a short free rear tip on the second dorsal fin, and tooth shape and number.
● LEMON SHARK
The lemon shark (Negaprion brevirostris) is a stocky and powerful shark. A member of the family Carcharhinidae, lemon sharks can grow to 3.4 metres (11 ft) in length. They are often found in shallow subtropical waters and are known to inhabit and return to specific nursery sites for breeding. Often feeding at night, these sharks use electroreceptors to find their main source of prey: fish. Lemon sharks enjoy the many benefits of group living such as enhanced communication, courtship, predatory behavior, and protection. This species of shark gives birth to live young, and the females are polyandrous and have a biennial reproductive cycle. Lemon sharks are not thought to be a large threat to humans.
● HORN SHARK
The horn shark (Heterodontus francisci) is a species of bullhead shark, in the family Heterodontidae. It is endemic to the coastal waters off the western coast of North America, from California to the Gulf of California. Young sharks are segregated spatially from the adults, with the former preferring deeper sandy flats and the latter preferring shallower rocky reefs or algal beds. A small species typically measuring 1 m (3.3 ft) in length, the horn shark can be recognized by a short, blunt head with ridges over its eyes, two high dorsal fins with large spines, and a brown or gray coloration with many small dark spots.
● MEGAMOUTH SHARK
The megamouth shark (Megachasma pelagios) is a species of deepwater shark. It is rarely seen by humans and is the smallest of the three extant filter-feeding sharks alongside the whale shark and basking shark. Since its discovery in 1976, few megamouth sharks have been seen, with fewer than 100 specimens being observed or caught.
● FRILLED SHARK
The frilled shark (Chlamydoselachus anguineus) is one of two extant species of shark in the family Chlamydoselachidae, with a wide but patchy distribution in the Atlantic and Pacific Oceans. This species is found over the outer continental shelf and upper continental slope, generally near the bottom, though there is evidence of substantial upward movements. It has been caught as deep as 1,570 m (5,150 ft), although it is uncommon below 1,200 m (3,900 ft). In Suruga Bay, Japan, it is most common at depths of 50–200 m (160–660 ft). Exhibiting several primitive features, the frilled shark has often been termed a living fossil. It reaches a length of 2 m (6.6 ft) and has a dark brown, eel-like body with the dorsal, pelvic, and anal fins placed far back. Its common name comes from the frilly or fringed appearance of its six pairs of gill slits, with the first pair meeting across the throat.
● MEGALODON
Megalodon (Carcharocles megalodon), meaning "big tooth", is an extinct species of shark that lived approximately 23 to 2.6 million years ago (mya), during the Early Miocene to the end of the Pliocene. It was formerly thought to belong to the family Lamnidae, making it closely related to the great white shark (Carcharodon carcharias). However presently there is near unanimous consensus that it belongs to the extinct family Otodontidae, which diverged from the ancestry of the great white shark during the Early Cretaceous.
● SAWSHARK
A sawshark or saw shark is a member of a shark order (Pristiophoriformes) bearing a unique long, saw-like rostrum (snout or bill) edged with sharp teeth, which they use to slash and disable their prey.
● BIGEYED SIXGILL SHARK
The bigeyed sixgill shark (Hexanchus nakamurai) is a cow shark of the family Hexanchidae. Its dorsal surface has a brownish-gray color, and is sharply separated from the light coloring of its ventral surface. The eyes are a fluorescent green while the shark is alive. The body of this shark is small, slim, and fusiform in shape. As the name suggests, this shark has six gill slits, unusual among most shark species. The head is narrow and somewhat flattened, and the mouth contains 5 rows of large, comb-shaped teeth. This shark's single dorsal fin is pushed back towards the caudal fin, and is behind the pelvic fins. The upper caudal fin is much longer than the lower, with a deep notch near the tip. All fins have thin white margins on the edge. In juveniles, the upper caudal fin has a black tip.
● GREY REEF SHARK
The grey reef shark (Carcharhinus amblyrhynchos, sometimes misspelled amblyrhynchus or amblyrhinchos) is a species of requiem shark, in the family Carcharhinidae. One of the most common reef sharks in the Indo-Pacific, it is found as far east as Easter Island and as far west as South Africa. This species is most often seen in shallow water near the drop-offs of coral reefs. The grey reef shark has the typical "reef shark" shape, with a broad, round snout and large eyes. This species can be distinguished from similar species by the plain or white-tipped first dorsal fin, the dark tips on the other fins, the broad, black rear margin on the tail fin, and the lack of a ridge between the dorsal fins. Most individuals are less than 1.9 m (6.2 ft) long.
● SILVERTIP REEF SHARK
The silvertip shark (Carcharhinus albimarginatus) is a large species of requiem shark, in the family Carcharhinidae, with a fragmented distribution throughout the tropical Indian and Pacific Oceans. This species is often encountered around offshore islands and coral reefs, and has been known to dive to a depth of 800 m (2,600 ft). The silvertip shark resembles a smaller yet bulkier grey reef shark (C. amblyrhynchos), and can be easily identified by the prominent white margins on its fins. It attains a maximum length of 3 m (10 ft).
FACTS
With fossil records dating back 400 million years, sharks have outlived the dinosaurs and many other forms of life currently on earth. There are more than 1,000 species of sharks, with new species discovered every year.
These majestic top predators that are so essential to the natural order of marine ecosystems now face their most severe threat from overfishing. Many species are threatened with extinction, with some families of rays such as sawfishes in peril. While sharks have been an irreplaceable resource for coastal communities in the developing world for centuries, this unique balance is in danger of being lost forever.
With our oceans severely degraded, restoring sharks is key to improving the resilience of these water bodies to climate change. While sharks' diverse range of species adds complexity to our conservation efforts, the dwindling numbers of these amazing creatures from overfishing and demand for their fins and meat increases the urgency of the task.
THREATS
Overfishing and illegal fishing of sharks for their fins is depleting populations worldwide. There is often a general lack of even basic management monitoring, control, and surveillance of many fisheries. Improving the capacity to combat pirate fishing (illegal, unreported and unregulated fishing) of sharks is a key factor in ensuring that shark fishing and shark populations are sustainable.
DEMAND FOR SHARK FIN
The growing trade in shark fins –often used to make an expensive Asian soup—has become a serious threat to many shark species. The latest research suggests that around 100 million sharks may be killed annually, often targeted for their fins. This practice affects many different shark species, including whale sharks.
OVERFISHING
The overfishing of sharks happens because of the huge demand—mainly for shark fins—and a lack of management to ensure shark fisheries are sustainable. Some species, such as spiny dogfish and porbeagle, are targeted primarily for their meat.
Millions of these sharks continue to be fished annually to supply the persistent demand for their fins and meat. Controls on fishing are woefully insufficient. As a result, the oceanic whitetip, porbeagle, and the smooth hammerhead are classified as vulnerable by the IUCN, while scalloped and great hammerhead sharks are classified as endangered.
1. Threats to pelagic sharks
Overfishing is the overwhelming threat, with open ocean longlines using hundreds if not thousands of hooks each catching the greatest volume of sharks globally. While these fisheries may be primarily targeting tuna and billfishes such as marlin, the sharks caught are an important source of income, particularly their fins. Tuna purse-seiners also catch sharks, although these have a better chance of being released alive, while gill nets are an ecological disaster, catching almost anything in their path, including whales, dolphins, turtles and sharks.
While the oceans are vast, there are few refuges from industrial fishing, and some pelagic species, such as the oceanic whitetip have suffered massive population losses due to their inability to reproduce more quickly. Seventeen out of the 39 pelagic shark species are threatened with extinction.
2. Threats to reef sharks
As with most shark species, overfishing is by far the biggest threat to most larger reef sharks, while damage to reef and other key habitats is also having an impact. The clearance of mangroves has a negative impact on species whose young use these as nursery grounds. The loss of living coral reefs due to sedimentation and fertilizer run-off from farmland, and climate change, will often reduce the amount of prey for sharks. Many kinds of food fishes that humans like to eat inhabit reefs, and so reefs are targeted by fishers, using types of fishing that also catch sharks.
Some 25% of all the 494 sharks inhabiting coastal continental shelves, which includes all reef sharks, are threatened with extinction. There may be many more as the conservation status of 35% is not yet known.
BYCATCH
Sharks are often caught incidentally by fishing gear set for other types of fish—such as tuna longlines, trawls and seine nets—and many will simply be discarded. This contributes to the decline of many species of sharks.
