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 rays. However, the term "shark" is also used to refer to extinct shark-like members of the subclass Elasmobranchii, such as hybodonts, that lie outside the modern group.

Modern sharks first diversified during the Jurassic period. Since then, sharks have diversified into over 500 species. They 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. Sharks 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 shark, which can be found in both seawater and 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 tiger shark, blue shark, great white shark, mako shark, thresher shark, and hammerhead shark. (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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... that the greeneye spurdog, Sydney skate, grey skate and whitefin swellshark are at risk of extinction by trawling, according to a 2021 report?
... that in 2014, judge William Orrick III upheld the constitutionality of a California law banning the possession and sale of shark fin?

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Credit: Didier Descouens

The jaw of a shortfin mako shark. The species feeds mainly upon cephalopods, bony fishes including mackerel, tuna, bonito, and swordfish, but it may also eat other sharks, porpoises, sea turtles, and seabirds.

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... that the spadenose shark exhibits the most advanced form of placental reproduction in fishes?
... that the dark, puffadder, brown, and Natal shysharks of South Africa are so named because they curl into a ring when threatened and "shyly" cover their eyes with their tails?
... that the daggernose shark can adjust the timing of events in its reproductive cycle by several months?
... that the lollipop catshark is shaped like a tadpole and has an almost gelatinous body?
... that the Australian swellshark can survive out of water for more than a day?

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General images

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

Image 1The major features of sharks (from Shark anatomy)
Image 2The 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 3BranchiostomaLanceolatum PioM (from Shark anatomy)
Image 4Shark cage diving (from Shark tourism)
Image 5Shark Anatomy (50693674756) (from Shark anatomy)
Image 6Postural configuration of a Gray Reef Shark as it displays agonistic behaviour, in a sculpture (from Shark agonistic display)
Image 7Sharksucker (Echeneis naucrates) (from Shark agonistic display)
Image 8Depiction of shark anatomy including eggs, pups, and the liver (from Shark anatomy)
Image 9Dorsal fin diagram with landmarks labeled. (from Shark anatomy)
Image 10White shark cage diving near Gansbaai in South Africa (2015) (from Shark cage diving)
Image 11A sign at Pyramid Rock Beach in Hawaii warning about a shark sighting, 2015 (from Shark tourism)
Image 12Lateral and Cross Section View of Shark Red and White Locomotor Muscles (from Shark anatomy)
Image 13Sharks swimming outside shark-proof cage with people inside. (from Shark cage diving)
Image 14A ventral dissection of a pregnant female dogshark exposing its internal gill slits and internal spiracles. (from Shark anatomy)
Image 15Distribution of highly sensitive ampullae of Lorenzini across the shark's head and rostrum. (from Shark agonistic display)
Image 16This grey reef shark demonstrates countershading, with its darker dorsal surface and lighter ventral surface. (from Shark anatomy)
Image 17The gill slits of a whale shark flaring as it expels water from its pharyngeal cavity. (from Shark anatomy)
Image 18A dissected view of the unique four-chambered heart of the sharkChambers: Sinus Venosus, Atrium, Ventricle, Conus Ateriosus (from Shark anatomy)
Image 19Postural elements of the agonistic display of the Gray Reef Shark (from Shark agonistic display)
Image 20In 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 21Placoid Scale (from Shark anatomy)
Image 22Anti-cull protesters on Perth's Cottesloe Beach in Western Australia in 2014 (from Shark culling)
Image 23Great white shark cages at Isla Guadalupe, Mexico (from Shark cage diving)
Image 24A 14-foot (4.3 m), 1,200-pound (540 kg) tiger shark caught in Kāne'ohe Bay, Oahu, in 1966
Image 25Great white shark at Isla Guadalupe, Mexico, August 2006. Shot with Nikon D70s in Ikelite housing, in natural light. Animal estimated at 11-12 feet (3.3 to 3.6 m) in length, age unknown (from Shark tourism)
Image 26Clear agonistic behaviour observed in Great White Shark (from Shark agonistic display)

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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