Broadnose sevengill shark
| Broadnose sevengill shark | |
|---|---|
 | |
| Conservation status | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Chondrichthyes |
| Subclass: | Elasmobranchii |
| Superorder: | Selachimorpha |
| Order: | Hexanchiformes |
| Family: | Hexanchidae |
| Genus: | Notorynchus Ayres, 1855 |
| Species: | N. cepedianus |
| Binomial name | |
| Notorynchus cepedianus (Péron, 1807) | |
 | |
| Range of the broadnose sevengill shark | |
| Synonyms | |
|
Heptranchias haswelli* Ogilby, 1897
* ambiguous synonym | |
The broadnose sevengill shark (Notorynchus cepedianus) is the only extant member of the genus Notorynchus, in the family Hexanchidae. It is recognizable because of its seven gill slits, while most shark species have five gill slits, with the exception of the members of the order Hexanchiformes and the sixgill sawshark. This shark has a large, thick body, with a broad head and blunt snout. The top jaw has jagged, cusped teeth and the bottom jaw has comb-shaped teeth. Its single dorsal fin is set far back along the spine towards the caudal fin, and is behind the pelvic fins. In this shark the upper caudal fin is much longer than the lower, and is slightly notched near the tip. Like many sharks, this sevengill is counter-shaded. Its dorsal surface is silver-gray to brown in order to blend with the dark water and substrate when viewed from above. In counter to this, its ventral surface is very pale, blending with the sunlit water when viewed from below. The body and fins are covered in a scattering of small black & white spots. In juveniles, their fins often have white margins.
Measurements
Length at birth: 40–45 cm. Mature Male Length: 1.3-1.7 m. Mature Female Length: Around 2 m. Max. Length Found: 2.9 m.
Range and habitat
The broadnose sevengill has so far been found in the western Pacific Ocean off China, Japan, Australia, New Zealand, the eastern Pacific Ocean, and the southern Atlantic Ocean off Argentina and South Africa. Large, old individuals tend to live in deep offshore environments as far down as 136 m. However, most individuals live in either the deep channels of bays, or in the shallower waters of continental shelves and estuaries. These sharks are mainly benthic in nature, cruising along the sea floor and making an occasional foray to the surface.[1]
Behavior
An opportunistic predator, the broadnose sevengill preys on a great variety of animals. It has been found to feed on sharks, rays, chimaeras, cetaceans, pinnipeds, bony fishes, and carrion. These sharks occasionally hunt in packs to take down larger prey, using tactics such as stealth to succeed. This sevengill, like all other members of Hexanchiformes, is ovoviviparous. After a 12-month gestation period, the female moves to a shallow bay or estuary to give birth to a large litter of up to 82 pups. The juveniles remain in this nursery for a few years before venturing out. The probable predators of this species are larger sharks.
Conservation
The broadnose sevengill is listed by the IUCN Red List as Data Deficient throughout most of its range, and as possibly Vulnerable in the northeast Pacific. This species likely suffers great pressure from various types of fisheries, and from frequently being caught as bycatch. The International Shark Attack File considers this shark to be potentially dangerous because of its proximity to humans, and because of its aggressive behavior when provoked. Six attacks on humans by the broadnose sevengill, the latest being in 2013 in New Zealand, have been recorded since the 16th century, with no known fatalities. [2][3]
References
- ↑ Compagno, Leonardo, Dando, Marc and Fowler, Sarah. Sharks of the World. Princeton University Press. 2005. p. 67-68
- ↑ Shark Attacks Diver in Fiordland - national | Stuff.co.nz
- ↑ accessed 13 July 2010
- Compagno (2000). Notorynchus cepedianus. 2006. IUCN Red List of Threatened Species. IUCN 2006. www.iucnredlist.org. Retrieved on 12 May 2006. Database entry includes justification for why this species is listed as data deficient
- "Notorynchus cepedianus". Integrated Taxonomic Information System. Retrieved 23 January 2006.
- Froese, Rainer and Pauly, Daniel, eds. (2005). "Notorynchus cepedianus" in FishBase. 10 2005 version.
- http://www.stuff.co.nz/national/8197600/Shark-grabs-diver-by-the-head
External links
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