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, 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 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 Caribbean reef shark (Carcharhinus perezi, often misspelled perezii) is a species of requiem shark, 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. 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.

Measuring up to 3 m (10 ft) long, the Caribbean reef shark is one of the largest apex predators in the reef ecosystem, feeding on a variety of fishes and cephalopods. They have been documented resting motionless on the sea bottom or inside caves, unusual behavior for an active-swimming shark. If threatened, it may perform a threat display in which it frequently changes direction and dips its pectoral fins. Like other requiem sharks, it is viviparous with females giving birth to 4–6 young every other year. Caribbean reef sharks are of some importance to fisheries as a source of meat, leather, liver oil, and fishmeal, but recently they have become more valuable as an ecotourist attraction. In the Bahamas and elsewhere, bait is used to attract them to groups of divers in controversial "shark feedings". This species is responsible for a small number of attacks on humans.

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Did you know (auto-generated)

... 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 "the Hurricane Shark is real"?
... that the ampullae of Lorenzini enable sharks to sense electric fields?
... that Hixxy and Sharkey created a schism in the UK rave music scene in 1995?
... that since 2018, IKEA's stuffed toy shark Blåhaj has become a popular Internet meme and an icon of the online transgender community?
... that Alexis Sharkey's last Instagram post before her murder documented her travels to Tulum, Mexico?

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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 when captured, the tawny nurse shark often spits a jet of water into the faces of its captors?
... that the swellshark bends its body in a U-shape and sucks in water to double in size and avoid attacks from predators?
...that shark threat display is an exaggerated swimming style exhibited by some sharks when they perceive they are in danger?
... that almost a quarter of the brown lanternsharks found in Suruga Bay, Japan, have both male and female organs?
... that the blacktip shark can reproduce asexually?

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General images

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

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