Portal:Sharks

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Sharks are a group of elasmobranch fish characterized by a cartilaginous skeleton, five to seven gill slits on the sides of the head, and pectoral fins that are not fused to the head. Modern sharks are classified within the clade Selachimorpha (or Selachii) and are the sister group to the Batoidea (rays and kin). Some sources extend the term "shark" as an informal category including extinct members of Chondrichthyes (cartilaginous fish) with a shark-like morphology, such as hybodonts. Shark-like chondrichthyans such as Cladoselache and Doliodus first appeared in the Devonian Period (419–359 million years), though some fossilized chondrichthyan-like scales are as old as the Late Ordovician (458–444 million years ago). The earliest confirmed modern sharks (selachimorphs) are known from the Early Jurassic around 200 million years ago, with the oldest known member being Agaleus, though records of true sharks may extend back as far as the Permian.

Sharks range in size from the small dwarf lanternshark (Etmopterus perryi), a deep sea species that is only 17 centimetres (6.7 in) in length, to the whale shark (Rhincodon typus), the largest fish in the world, which reaches approximately 12 metres (40 ft) in length. They are found in all seas and are common to depths up to 2,000 metres (6,600 ft). They generally do not live in freshwater, although there are a few known exceptions, such as the bull shark and the river sharks, which can be found in both seawater and freshwater, and the Ganges shark, which lives only in freshwater. Sharks have a covering of dermal denticles that protects their skin from damage and parasites in addition to improving their fluid dynamics. They have numerous sets of replaceable teeth.

Several species are apex predators, which are organisms that are at the top of their food chain. Select examples include the bull shark, tiger shark, great white shark, mako sharks, thresher sharks, and hammerhead sharks. (Full article...)

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The kitefin shark or seal shark, Dalatias licha, is a species of dogfish shark in the family Dalatiidae, and the only species in its genus. It is found sporadically around the world, usually close to the sea floor at depths of 200–600 m (660–2,000 ft). This shark has a slender body with a very short, blunt snout, large eyes, and thick lips. Its teeth are highly differentiated between the upper and lower jaws, with the upper teeth small and narrow and the lower teeth large, triangular, and serrated. Its typical length is 1.0–1.4 m (2.5–4.0 ft).

With a sizable oil-filled liver to maintain neutral buoyancy, the kitefin shark is able to cruise slowly through the water while expending little energy. Armed with large teeth and a strong bite, it is a powerful, solitary predator that takes many different types of prey, ranging from bony fishes, sharks and rays, to cephalopods, crustaceans, polychaete worms, siphonophores, and possibly carrion. It also takes bites out of animals larger than itself, similar to its smaller relative, the cookiecutter shark (Isistius brasiliensis). This shark is ovoviviparous and gives birth to 10–14 young. The kitefin shark is fished commercially for its meat, skin, and liver oil, primarily by Portugal and Japan. A fishery targeting this species existed off the Azores from the 1970s to the 1990s, but collapsed due to overfishing and falling liver oil prices; the rapid depletion of the Azores stock is often cited as an example of the susceptibility of deep-sea sharks to human exploitation. The World Conservation Union does not yet have sufficient data to assess the global conservation status of this species.

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Did you know (auto-generated)

... that the ampullae of Lorenzini enable sharks to sense electric fields?
... that a shark cost a competitor a silver medal in the spearfishing event at the 2014 Micronesian Games?
... that "the Hurricane Shark is real"?
... that Timo Meier became the first player in San Jose Sharks franchise history to score five goals in one game when he was 25?
... that Hixxy and Sharkey created a schism in the UK rave music scene in 1995?

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Credit: Matthew Field

The leopard shark is a species of houndshark found along the Pacific coast of North America from the U.S. state of Oregon to Mazatlán in Mexico.

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... that the milk shark is so named because of a belief in India that eating its meat improves lactation?
... that the silky shark is the most common source of ornamental shark jaws sold to tourists in the tropics?
... that the southern African frilled shark preys mainly on smaller sharks, which it swallows whole with its greatly distensible mouth?
... that more than 90 percent of the night sharks caught off northeastern Brazil contain mercury concentrations higher than that considered safe by the local government?
... that the largetooth cookiecutter shark has the largest teeth relative to its body of any living shark?

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General images

The following are images from various shark-related articles on Wikipedia.

Image 1Postural elements of the agonistic display of the Gray Reef Shark (from Shark agonistic display)
Image 2Great white shark cages at Isla Guadalupe, Mexico (from Shark cage diving)
Image 3The gill slits of a whale shark flaring as it expels water from its pharyngeal cavity. (from Shark anatomy)
Image 4Branchiostoma lanceolatum (from Shark anatomy)
Image 5Shark cage diving (from Shark tourism)
Image 6The major features of sharks (from Shark anatomy)
Image 7Clear agonistic behaviour observed in Great White Shark (from Shark agonistic display)
Image 8The whale shark, the world's largest fish, is classified as Endangered.

Binding legislation and harvest management strategies... are urgently needed to address the disproportionate impact of fisheries on cartilaginous fishes.

– IUCN global study 2010

(from List of threatened sharks)
Image 9Postural configuration of a Gray Reef Shark as it displays agonistic behaviour, in a sculpture (from Shark agonistic display)
Image 10A ventral dissection of a pregnant female dogshark exposing its internal gill slits and internal spiracles. (from Shark anatomy)
Image 11Placoid Scale (from Shark anatomy)
Image 12Dorsal fin diagram with landmarks labeled. (from Shark anatomy)
Image 13White shark cage diving near Gansbaai in South Africa (2015) (from Shark cage diving)
Image 14Anti-cull protesters on Perth's Cottesloe Beach in Western Australia in 2014 (from Shark culling)
Image 15Sharksucker (Echeneis naucrates) (from Shark agonistic display)
Image 16Sharks swimming outside shark-proof cage with people inside (from Shark cage diving)
Image 17Great white shark at Isla Guadalupe, Mexico, August 2006. Animal estimated at 11–12 feet (3.3 to 3.6 m) in length, age unknown. (from Shark tourism)
Image 18In a milestone decision in 2013, CITES prohibited international trade in the fins of the scalloped hammerhead (pictured) and four other shark species. (from List of threatened sharks)
Image 19Shark Anatomy (50693674756) (from Shark anatomy)
Image 20A 14-foot (4.3 m), 1,200-pound (540 kg) tiger shark caught in Kāne'ohe Bay, Oahu, in 1966
Image 21Depiction of shark anatomy including eggs, pups, and the liver (from Shark anatomy)
Image 22A sign at Pyramid Rock Beach in Hawaii warning about a shark sighting, 2015 (from Shark tourism)
Image 23A dissected view of the unique four-chambered heart of the sharkChambers: Sinus Venosus, Atrium, Ventricle, Conus Ateriosus (from Shark anatomy)
Image 24Lateral and cross section view of shark's red and white locomotor muscles (from Shark anatomy)
Image 25Distribution of highly sensitive ampullae of Lorenzini across the shark's head and rostrum. (from Shark agonistic display)
Image 26This grey reef shark demonstrates countershading, with its darker dorsal surface and lighter ventral surface. (from Shark anatomy)

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Topics

Shark · Outline of sharks

Shark orders

Carcharhiniformes (groundsharks) · Cladoselachiformes (extinct) · Eugeneodontida (extinct) · Heterodontiformes (bullhead sharks) · Hexanchiformes (most primitive sharks) · Hybodontiformes (extinct) · Iniopterygia (extinct) · Lamniformes (mackerel sharks) · Orectolobiformes (carpet sharks and relatives) · Pristiophoriformes (sawsharks and relatives) · Squaliformes (gulper sharks, bramble sharks, lantern sharks, rough sharks, sleeper sharks, dogfish sharks and relatives) · Squatiniformes (angel sharks) · Symmoriida (extinct) · Xenacanthida (also known as Xenacantiformes, extinct)

Major species