Great hammerhead: Difference between revisions
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| name = Great hammerhead |
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It is easy to confuse the great hammerhead with the [[smooth hammerhead]], ''Sphyrna zygaena'', since both are very large hammerhead sharks. |
It is easy to confuse the great hammerhead with the [[smooth hammerhead]], ''Sphyrna zygaena'', since both are very large hammerhead sharks. |
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The great hammerhead has a thick head in which the eyes are located at the margins. It has a dark brown to light grey dorsal surface: this colour can be olive as it fades into the underside of the sharks which is a lighter off-white color. |
The great hammerhead has a thick head in which the eyes are located at the margins. It has a dark brown to light grey [[dorsum (biology)|dorsal]] surface: this colour can be olive as it fades into the underside of the sharks which is a lighter off-white color. |
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The average great hammerhead shark is up to |
The average great hammerhead shark is up to 3.5 m (11.5 ft) long. The largest reported was 6 m (20 ft) long and of unknown weight. These large sharks average about 230 [[kilogram|kg]] (500 [[pound (mass)|lb]] but can weigh as much as 450 kg (1,000 lb). The heaviest ever caught weighed 580 kg (1,280 lb) but was only 4.4 m (14.5 ft) long, caught in [[Boca Grande, Florida]]<ref name="WR">[http://www.firstcoastnews.com/news/florida/news-article.aspx?storyid=58228 Firstcoastnews.com | Jacksonville, St. Augustine and Brunswick | Port Charlotte Man Catches 1,280 Pound Hammerhead Shark<!-- Bot generated title -->]</ref>. However, this was a pregnant specimen, bearing 55 near-[[Birth|natal]] pups, which have obviously added to the weight. |
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Expected life span of this species is approximately 20 to 30 years |
Expected life span of this species is approximately 20 to 30 years. |
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<ref name="flmnh">[http://www.flmnh.ufl.edu/fish/Gallery/Descript/GreatHammerhead/GHammerhead.html Florida Museum of natural history]</ref> |
<ref name="flmnh">[http://www.flmnh.ufl.edu/fish/Gallery/Descript/GreatHammerhead/GHammerhead.html Florida Museum of natural history]</ref> |
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==Reproduction== |
==Reproduction== |
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Great hammerheads are [[viviparous]]. They give birth to a litter of between 6 and 55 young, typically 20 to 40.[http://www.sptimes.com/2006/06/30/State/Catch_is_a_big_inside.shtml] The gestation period is 11 months. Size at birth is about 60 to 70 cm. Females mature at about 2.1 to 2.5 m and males at about 2.25 to 2.7 m. |
Great hammerheads are [[viviparous]]. They give birth to a litter of between 6 and 55 young, typically 20 to 40.[http://www.sptimes.com/2006/06/30/State/Catch_is_a_big_inside.shtml] The gestation period is 11 months. Size at birth is about 60 to 70 cm. Females mature at about 2.1 to 2.5 m and males at about 2.25 to 2.7 m. |
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==The Great Hammerhead Shark== |
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Great Hammerheads grow up to six metres and have an odd head with keen senses that can pick up distress signals from panicing fish. They are the largest of all hammerheads and the only one to lead a solitary life. They prefer open oceans. |
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==References== |
==References== |
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Revision as of 04:09, 7 August 2008
| Great hammerhead | |
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| Species: | S. mokarran
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| Binomial name | |
| Sphyrna mokarran (Rüppell, 1837)
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Template:FixBunching Template:Sharksportal Template:FixBunching
The great hammerhead, Sphyrna mokarran, is the largest species of hammerhead shark. It is found worldwide in coastal areas and above continental shelves in warm and tropical waters to depths of 80 m (260 ft).
Anatomy and appearance
It is easy to confuse the great hammerhead with the smooth hammerhead, Sphyrna zygaena, since both are very large hammerhead sharks.
The great hammerhead has a thick head in which the eyes are located at the margins. It has a dark brown to light grey dorsal surface: this colour can be olive as it fades into the underside of the sharks which is a lighter off-white color.
The average great hammerhead shark is up to 3.5 m (11.5 ft) long. The largest reported was 6 m (20 ft) long and of unknown weight. These large sharks average about 230 kg (500 lb but can weigh as much as 450 kg (1,000 lb). The heaviest ever caught weighed 580 kg (1,280 lb) but was only 4.4 m (14.5 ft) long, caught in Boca Grande, Florida[2]. However, this was a pregnant specimen, bearing 55 near-natal pups, which have obviously added to the weight.
Expected life span of this species is approximately 20 to 30 years. [3]
Diet
Great hammerheads eat small sharks, rays and sting rays, squid and bony fish. The great hammerhead has a defense against the venom of sting rays, which seem to be a particular favorite in their diet. They will kill stingrays by using their hammer shaped head to pin them down while they bite the wings off the ray. They often skim the bottoms of oceans and stir up the sand with their heads, mouths open, to consume their prey. They also hunt alone.
Behavior
When encountered by divers, the great hammerhead is usually quite shy and normally not aggressive. The International Shark Attack File classifies the great hammerhead as one of the least dangerous sharks with only one reputed attack, but an unspecified hammerhead which might include the great hammerhead is on tenth place, so this shark is to be considered dangerous but not extremely aggressive. [4]
Reproduction
Great hammerheads are viviparous. They give birth to a litter of between 6 and 55 young, typically 20 to 40.[1] The gestation period is 11 months. Size at birth is about 60 to 70 cm. Females mature at about 2.1 to 2.5 m and males at about 2.25 to 2.7 m.
References
- "Sphyrna mokarran". Integrated Taxonomic Information System. 23 January.
{{cite web}}: Check date values in:|date=and|year=/|date=mismatch (help) - Froese, Rainer; Pauly, Daniel (eds.). "Sphyrna mokarran". FishBase. September 2005 version.
- Great Hammerhead shark, Sphyrna mokarran at marinebio.org
External links
- Great Hammerhead Shark Pictures - Great Hammerhead Shark Pictures at Shark-Pictures.com
- ARKive - images and movies of the great hammerhead (Sphyrna mokarran)