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 oldest confirmed modern sharks (selachimorphs) are known from the Early Jurassic, about 200 million years ago, 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 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 grey reef shark, Carcharhinus amblyrhynchos (sometimes misspelled amblyrhynchus or amblyrhinchos), is a species of requiem shark, family Carcharhinidae. what 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 a 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.

Grey reef sharks are fast-swimming, agile predators that feed primarily on free-swimming bony fishes and cephalopods. Their aggressive demeanor enables them to dominate many other shark species on the reef, despite their moderate size. Many grey reef sharks have a home range on a specific area of the reef, to which they will return time and again. However, they are not territorial but rather quite social. During the day, these sharks often form aggregations of 5–20 individuals near coral reef drop-offs, and then split up in the evening as the sharks begin to hunt. Adult female grey reef sharks also form groups in very shallow water, where the higher water temperature may accelerate their growth or that of their unborn young. Like other members of its family, the grey reef shark is viviparous, meaning that the mother nourishes her embryos through a placental connection. Litters of 1–6 pups are born every other year.

Grey reef sharks were the first shark species known to perform a threat display, a stereotyped behavior warning that it is prepared to attack. The display involves a "hunched" posture with characteristically dropped pectoral fins, and an exaggerated, side-to-side swimming motion. Grey reef sharks will often perform the display if they are followed or cornered by divers to indicate that they perceive a threat. This species has been responsible for a number of attacks on humans and should be treated with caution, especially if they begin to display. Grey reef sharks are caught by many fisheries and are susceptible to local population depletion due to their low reproductive rate and limited dispersal. As a result, the World Conservation Union has assessed this species as Near Threatened.

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... that since 2018, IKEA's stuffed toy shark Blåhaj has become a popular Internet meme and an icon of the online transgender community?
... that Timo Meier became the first player in San Jose Sharks franchise history to score five goals in one game when he was 25?

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Credit: John Singleton Copley

Watson and the Shark, a 1778 oil-on-canvas painting by John Singleton Copley, depicts the rescue of Brook Watson from a shark attack in Havana, Cuba.

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... that the zebra shark is striped when young and spotted when mature?
... that the blurred and smooth lanternsharks form a species group distinguished from the rest of their family by the shape and arrangement of their dermal denticles?
... that the leopard shark feeds on anchovies by swimming into their schools with its mouth open and waiting for them to accidentally enter?
... that relative to its body size, the horn shark has the strongest known bite of any shark?
... that the title for Peter Benchley's best-selling 1974 novel Jaws was not agreed until 20 minutes before it went into production?

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General images

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

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

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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