Long-nosed saw shark
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Long-nosed saw shark ( Pristiophorus cirratus ) |
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| Pristiophorus cirratus | ||||||||||||
| ( Latham , 1794) |
The long-nosed saw shark ( Pristiophorus cirratus ) is a shark from the family of saw sharks (Pristiophoridae). Like its relatives, the shark is characterized by a long saw-like snout, which makes up up to 30 percent of the body length of this species. He lives off the southern coast of Australia.
features
The long-nosed saw shark reaches a body length of up to 137 cm. The body is long, cylindrical and slim. The head is flattened and has a very elongated and flattened snout with a saw-like rostrum typical of saw sharks , which makes up between 26 and 30 percent of the body length of this species. The rostrum has a distinctive pair of barbels in front of the nostrils and 19 to 21 distinctive teeth on the side edge of the "saw". The barbels of this species are very far in front of the nostrils and thus closer to the saw tip than to this; 9 to 11 teeth are in front of the barbels and 9 to 10 behind them. Young animals also have two to three small teeth between the larger saw teeth.
The color of the top of its body ranges from pale yellow to gray-brown with dark spots and stripes, the underside is white. There is a dark center line on the rostrum, at the same time the sides are colored darker and the sawtooth bases are black.
The eyes are on the side of the head, behind them the large suction holes . Like other species of the genus, the sawshark has five gill slits . Like all saw sharks, it has two dorsal fins without a thorn and no anal fin. The tail stalk has clear keels, the tail consists only of a large upper lobe while the lower lobe is absent in all sawsharks.
Way of life
The long-nosed saw shark is a ground shark that occurs mainly in deeper water areas around 300 meters. It feeds on various types of predatory fish , and it also hunts crustaceans , snails and cuttlefish . The long rostrum is used to search for food, which is equipped with barbels and other sensory organs and can therefore perceive movements and probably also electrical fields and chemical impressions in the sea floor. The prey is tracked down with a saw, dug up and probably also partly killed. In addition, the saw shark also uses them against attackers and conspecifics. The shark forms schools or groups of animals hunting together.
The sharks are viviparous and do not form a placenta (aplacentally viviparous ). The females get between six and 19 young animals with a length of about 30 to 35 cm in one litter. The birth takes place annually in winter. With a body length of about 97 cm, the animals are sexually mature.
distribution
The long-nosed saw shark can be found off the southern coast of Australia from Jurien Bay in Western Australia to Eden in New South Wales . The main concentration of the species is believed to be in the Bass Strait .
Its habitat is in the area of the continental shelf near the sea floor in water depths of about 310 meters, less often in the tidal area near the coast.
Danger
The long-nosed saw shark is classified in the IUCN Red List as not endangered ("least concern"). In 2000, the shark was listed as a type of warning list; the downgrading was based, among other things, on a detailed study of age structure, growth rates and reproduction. In addition, data from the fishery over the past 25 years and data from a 12-year monitoring program were evaluated.
Individual evidence
- ↑ a b Pristiophorus cirratus in the endangered Red List species the IUCN 2006. Posted by: Walker, TI & Simpfendorfer, C. (SSG Australia & Oceania Regional Workshop, March 2003), 2003. Accessed June 24 of 2009.
literature
- Leonard Compagno , Marc Dando, Sarah Fowler: Sharks of the World. Princeton Field Guides, Princeton University Press , Princeton and Oxford 2005; P. 132, ISBN 978-0-691-12072-0 .
