Portal:Sharks

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Sharks are a group of elasmobranch cartilaginous fishes characterized by a ribless endoskeleton, dermal denticles, five to seven gill slits on each side, and pectoral fins that are not fused to the head. Modern sharks are classified within the division Selachii and are the sister group to the Batomorphi (rays and skates). 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 (Selachii) 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 placoid scales (denticles) that protects the skin from damage and parasites in addition to improving their fluid dynamics. They have numerous sets of replaceable teeth.

Several shark species are apex predators, which are organisms that are at the top of their food chain with select examples including the bull shark, tiger shark, great white shark, mako sharks, thresher sharks and hammerhead sharks. Some sharks are filter-feeding planktivores, such as the whale shark and basking shark, which are among the largest fish ever lived. (Full article...)

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The Philadelphia Inquirer reported the capture of a "man-eating" shark off the Jersey Shore after the attacks

The Jersey Shore shark attacks of 1916 were a series of shark attacks along the coast of New Jersey between July 1 and July 12, 1916, in which four people were killed and one injured. Since 1916, scholars have debated which shark species was responsible and the number of animals involved, with the great white shark and the bull shark most frequently being blamed. The attacks occurred during a deadly summer heat wave and polio epidemic in the northeastern United States that drove thousands of people to the seaside resorts of the Jersey Shore. Shark attacks on the Atlantic Coast of the United States outside the semitropical states of Florida, Georgia, and the Carolinas were rare, but scholars believe that the increased presence of sharks and humans in the water led to the attacks in 1916.

Local and national reaction to the attacks involved a wave of panic that led to shark hunts aimed at eradicating the population of "man-eating" sharks and protecting the economies of New Jersey's seaside communities. Resort towns enclosed their public beaches with steel nets to protect swimmers. Scientific knowledge about sharks before 1916 was based on conjecture and speculation. The attacks forced ichthyologists to reassess common beliefs about the abilities of sharks and the nature of shark attacks.

The Jersey Shore attacks immediately entered into American popular culture, where sharks became caricatures in editorial cartoons representing danger. The attacks inspired Peter Benchley's novel Jaws (1974), an account of a great white shark that torments the fictional coastal community of Amity. Jaws was made into an influential film in 1975 by Steven Spielberg. The attacks became the subject of documentaries for the History Channel, Discovery Channel, and National Geographic Channel.

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Did you know (auto-generated)

... that a shark cost a competitor a silver medal in the spearfishing event at the 2014 Micronesian Games?
... that the parasitic copepod Driocephalus cerebrinoxius burrows into the brains of sharks through their noses?

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Credit: Zac Wolf

The whale shark is a slow moving filter feeding shark that is the largest living fish species. Four male and two female whale sharks are held in the Georgia Aquarium.

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... that the whitefin dogfish has light-producing organs on its upper eyelids?
... that the spinner shark is named for the spinning leaps it makes out of the water as part of its feeding strategy?
...that John Singleton Copley's painting, Watson and the Shark, was based on a real-life shark attack that occurred in Havana, Cuba in 1749?
... that, like the related cookiecutter shark, the kitefin shark sometimes feeds by taking bites out of animals larger than itself?
... that the first successful artificial insemination of a shark was performed in the cloudy catshark?

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General images

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

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