Outline of sharks

A great white shark at Isla Guadalupe, Mexico

Sharks (superorder Selachimorpha) are a type of fish with a full cartilaginous skeleton and a highly streamlined body. The earliest known sharks date from more than 420 million years ago, before the time of the dinosaurs.^[1]

Since that time, sharks have diversified into more than 440 species, ranging in size from the small dwarf lanternshark, Etmopterus perryi, a deep sea species of only 17 centimetres (6.7 in) in length, to the whale shark, Rhincodon typus, the largest fish, which reaches approximately 12 metres (39 ft 4 in) and which feeds only on plankton, squid, and small fish by filter feeding. Sharks are found in all seas and are common down to depths of 2,000 metres (6,600 ft). They generally do not live in freshwater, with a few exceptions such as the bull shark and the river shark which can live both in seawater and freshwater.^[2] They breathe through five to seven gill slits and have a covering of dermal denticles that protect their skin from damage and parasites. Denticles also improve their fluid dynamics by maintaining turbulent flow over the animals body, this means that the shark can move faster. They have several sets of replaceable teeth.^[3]

Some well-known species such as the great white shark, tiger shark, and the hammerhead are apex predators, at the top of the underwater food chain. Their skills as predators fascinate and frighten humans, even as their survival is under serious threat from fishing and other human activities.

The following outline is provided as an overview of and topical guide to sharks:

Fields

• Ichthyology – branch of zoology devoted to fish (including sharks)
• Meristics – branch of ichthyology that relates to counting features of fish, such as the number of fins or scales

Biological classification

Further information: Biological classification

• Kingdom: Animalia
• Phylum: Chordata
• Class: Chondrichthyes
• Subclass: Elasmobranchii
• Superorder: Selachimorpha

Types

Main article: List of sharks

Subdivisions of the biological classification Selachimorpha include:

• Carcharhiniformes – groundsharks
• Heterodontiformes – bullhead sharks
• Hexanchiformes – the five extant species of the most primitive types of sharks
• Lamniformes – mackerel sharks
• Orectolobiformes – includes carpet sharks, including zebra sharks, nurse sharks, wobbegongs and whale shark
• Pristiophoriformes – includes sawsharks
• Squaliformes – includes gulper sharks, bramble sharks, lantern sharks, rough sharks, sleeper sharks and dogfish sharks
• Squatiniformes – angel sharks
• † Symmoriida
• † Cladoselachiformes
• † Xenacanthida (Xenacantiformes)
• † Iniopterygia
• † Eugeneodontida
• † Hybodontiformes

Behavior

The Philadelphia Inquirer report of Jersey Shore shark attack.

• Predation
• Apex predator
• Shark threat display – Behaviour shown by some sharks when threatened
• Spy hopping – Raising the head out of the water

Attacks

Main article: Shark attack

• International Shark Attack File
• List of fatal, unprovoked shark attacks in the United States
• Jersey Shore shark attacks of 1916 – series of shark attacks along the coast of New Jersey between July 1 and July 12, 1916^[4]
• Summer of the Shark – the name given to the summer of 2001 by American media outlets capitalizing on a bull shark attack and subsequent shark attacks ^[5]

Range and habitats

Range

• Bodies of water in which sharks can be found include:
  • Seas: all
  • Freshwater – some species of shark can live both in seawater and freshwater, and include:
    • Bull shark
    • River shark
    • Sandbar shark
• Depths: from the surface down to depths of 2,000 metres (6,600 ft).

A whale shark in the Georgia Aquarium

Habitats

• White Shark Cafe – remote mid-Pacific Ocean area noted as a winter and spring habitat of otherwise coastal great white sharks

In captivity

Main article: Sharks in captivity

• Shark tank
• Shark tunnel – underwater tunnel that passes through an aquarium that keeps sharks

Anatomy

• Physical characteristics of sharks – shark skeleton, respiration and skin
  • Dermal denticle – small outgrowths which cover the skin of sharks
  • Ampullae of Lorenzini – sensing organ that helps sharks and fish to sense electric fields
  • Electroreception – the biological ability to perceive electrical impulses (see also Ampullae of Lorenzini)
  • Lateral line – sense organ that detects movement and vibration in the surrounding water
  • Shark cartilage – material that a sharks' skeleton is composed of
  • Shark teeth
  • Spiracle – pumps water across gills
  • Clasper – the anatomical structure that male sharks use for mating
  • Fish anatomy – generic description of fish anatomy

Protective equipment

Simplified diagram of shark net

• Drum lines
• Shark net – submerged net placed around beaches to reduce shark attacks on swimmers
• Shark proof cage – cage from which a SCUBA diver can examine sharks more safely
• Shark repellent – method of driving sharks from an area, object, person, or animal
  • Magnetic shark repellent – use of permanent magnet to repel sharks
  • Protective Oceanic Device – first successful electronic shark repellent
• Shark suit

Fishing

• Drivers of the shark trade
• Land-based shark fishing – fishing for sharks from land such as a beach, shoreline, jetty, pier, or bridge
• Shark finning–the removal of shark fins for commercial purposes

Conservation

• 1992 Cageless shark-diving expedition – 1st publicized cageless dive with great white sharks which contributed to changing public opinions about the supposed "killing machine"
• Shark Alliance – coalition of non-governmental organizations dedicated to restoring and conserving shark populations by improving European fishing policy
• Shark Conservation Act – Proposed US law to protect sharks
• Shark sanctuary – Palau's first-ever attempt to prohibit taking sharks within its territorial waters
• Shark tourism – form of ecotourism showcasing sharks
• Shark Trust – A UK organisation for conservation of sharks

Notable sharks

• Stronsay Beast – large, dead creature washed ashore on Stronsay, in the Orkney Islands, after a storm in 1808, later presumed to be a basking shark

Notable researchers and people

Hans Hass, diving pioneer

• Peter Benchley – author of the novel Jaws, later worked for shark conservation
• Jacques-Yves Cousteau – French naval officer, explorer, ecologist, filmmaker, innovator, scientist, photographer, author and researcher who studied the sea and all forms of life in water including sharks
• Eugenie Clark–American ichthyologist researching poisonous fish and the behavior of sharks; popularly known as The Shark Lady
• Leonard Compagno–international authority on shark taxonomy, best known for 1984 catalog of shark species (FAO)
• Ben Cropp–Australian former shark hunter, who stopped in 1962 to produced some 150 wildlife documentaries
• Richard Ellis – American marine biologist, author, and illustrator.
• Rodney Fox – South Australian film maker, conservationist, survivor of great white shark attack and one of the world's foremost authorities on them
• Andre Hartman – South African diving guide best known for free-diving unprotected with great white sharks
• Hans Hass – diving pioneer, known for shark documentaries
• Mike Rutzen – great white shark expert and outspoken champion of shark conservation; known for free diving unprotected with great white sharks
• Ron & Valerie Taylor – ex-spearfishing champions who switched from killing to filming underwater documentaries

References

1. ^ Martin, R. Aidan. "Geologic Time". ReefQuest. http://www.elasmo-research.org/education/evolution/geologic_time.htm. Retrieved 2006-09-09. 
2. ^ Allen, Thomas B. (1999). The Shark Almanac. New York: The Lyons Press. ISBN 1-55821-582-4. OCLC 39627633. 
3. ^ Budker, Paul (1971). The Life of Sharks. London: Weidenfeld and Nicolson. SBN 297003070. 
4. ^ Fernicola, Twelve Days of Terror
5. ^ "Summer of the Shark". Time. July 30, 2001. http://www.time.com/time/2001/sharks/. Retrieved May 20, 2010. 

See also

Sharks portal

• List of ichthyology terms
• List of megamouth shark specimens and sightings
• List of prehistoric cartilaginous fish
• List of Red Sea sharks