Portal:Sharks

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Welcome to the shark portal

Welcome to the shark portal!
Welcome to the shark portal!

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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A wild horn shark
The horn shark, Heterodontus francisci, is a species of bullhead shark, family Heterodontidae. It is endemic to the coastal waters off the western coast 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 venomous spines, and a brown or gray coloration with many small dark spots.

Slow-moving, generally solitary predators, horn sharks hunt at night inside small home ranges and retreat to a favored shelter during the day. Their daily activity cycles are controlled by environmental light levels. Adult sharks prey mainly on hard-shelled molluscs, echinoderms, and crustaceans, which they crush between powerful jaws and molar-like teeth, while also feeding opportunistically on a wide variety of other invertebrates and small bony fishes. Juveniles prefer softer-bodied prey such as polychaete worms and sea anemones. The shark extracts its prey from the substrate using suction and, if necessary, levering motions with its body. Reproduction is oviparous, with females laying up to 24 eggs from February to April. After laying, the female picks up the auger-shaped egg cases and wedges them into crevices to protect them from predators.

Horn sharks are harmless unless harassed, and are readily maintained in captivity. They are not targeted by either commercial or recreational fisheries, though small numbers are caught as bycatch. In Mexico this species is used for food and fishmeal, and in California its spines are made into jewelry. The International Union for Conservation of Nature (IUCN) does not yet have enough information to determine the horn shark's conservation status. It faces few threats off the coast of the United States.

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Credit: Albert kok
The lemon shark is a shark belonging to the family Carcharhinidae that can grow 10 feet (3.0 m) long. It is a popular choice for study, as it survives well in captivity.

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General images

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

Topics


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)



Shark biology


Shark-human interaction

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