Silvertip shark

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Silvertip shark
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Subclass: Elasmobranchii
Subdivision: Selachimorpha
Order: Carcharhiniformes
Family: Carcharhinidae
Genus: Carcharhinus
Species:
C. albimarginatus
Binomial name
Carcharhinus albimarginatus
(
Rüppell
, 1837)
Range of the silvertip shark
Synonyms

Carcharias albimarginatus Rüppell, 1837
Eulamia platyrhynchus Gilbert, 1892

The silvertip shark (Carcharhinus albimarginatus) is a large species of requiem shark, in the family Carcharhinidae, with a fragmented distribution throughout the tropical Indian and Pacific Oceans. It is often encountered around offshore islands and coral reefs, and has been known to dive to a depth of 800 m (2,600 ft). The silvertip shark resembles a larger and bulkier grey reef shark (C. amblyrhynchos), but can be easily identified by the prominent white margins on its fins. It attains a maximum length of 3 m (10 ft).

An aggressive, powerful

viviparous, with females giving birth to one to 11 pups in the summer. Silvertip sharks are regarded as potentially dangerous to humans, as they often approach divers quite closely. This slow-reproducing species is taken by commercial fisheries for its meat, fins, skin, cartilage, and jaws and teeth, which has apparently led to local population declines or extirpations
.

Taxonomy and phylogeny

The silvertip shark was originally described as Carcharias albimarginatus by German naturalist

allozyme data.[6]

Distribution and habitat

Silvertip sharks are most often found on or near coral reefs.

The silvertip shark is widely but not continuously distributed in the tropical Indian and Pacific Oceans. In the western Indian Ocean, this species occurs from the Red Sea to

Galapagos, and Revillagigedo Islands. Its presence in the Gulf of Mexico and the Caribbean Sea is unconfirmed.[2]

Silvertip sharks are found over continental and insular shelves at a depth of 30–800 m (98–2,625 ft), occupying all levels of the water column. They are most common around isolated islands, coral banks, and reef drop-offs.[2][7] Juveniles frequent coastal shallows or lagoons, while adults occur in deeper water, with little overlap between the two age groups.[3][8]

Description

The silvertip shark is a robust and streamlined species with a moderately long, broad snout and large, round eyes. The five pairs of

pectoral fin tips. A ridge occurs between the first and second dorsal fins. The pectoral fins are proportionately longer than in most requiem sharks and falcate (sickle-like) in shape, with pointed tips.[2][9]

The coloration is blue-gray above with a bronze sheen, and white below. A subtle white band runs along the sides, with distinctive white tips and borders on all fins. Silvertip sharks can grow up to 3 m (9.8 ft) long, but typically measure 2.0–2.5 m (6.6–8.2 ft) in length. The maximum reported weight is 162.2 kg (358 lb).[3] Females are larger than males.[8]

  • The silvertip shark can be recognized by its white-edged fins.
    The silvertip shark can be recognized by its white-edged fins.
  • Jaws
    Jaws
  • Upper teeth
    Upper teeth
  • Lower teeth
    Lower teeth

Biology and ecology

A silvertip shark at New Hanover Island, Papua New Guinea - individual sharks usually stay at particular reefs.

Though silvertip sharks are quite mobile, they exhibit fidelity to certain areas, with reports of

parasites.[12] They sometimes follow marine mammals such as bottlenose dolphins (Tursiops sp.) in open water, and are themselves followed by pilot fish (Naucrates ductor).[13]

Like the grey reef shark, the silvertip shark sometimes perform a

threat display if pursued by divers, warning that it is prepared to attack. The display begins with the shark accelerating away to a distance of 15 m (49 ft), before turning and charging towards the perceived threat. At a distance of two body lengths, the shark brakes, turns broadside, drops its pectoral fins, gapes its jaws, lowers the posterior two-thirds of its body, and "shivers". The last two elements of this display are unique to this species; the "shivering" may serve to emphasize its white fin markings. If the diver persists, the shark may rapidly close in and slash with its upper teeth.[14][15]

Feeding

The diet of the silvertip shark consists primarily of

benthic prey.[13] The differently shaped dentition in their upper and lower jaws allows them to tackle large prey, gripping and sawing off chunks of flesh with violent twists and turns.[8] Silvertip sharks have been observed swimming around the periphery of groups of feeding sharks of other species, occasionally dashing in to steal food.[2] This species often approaches ships, as they are attracted to certain artificial, low-frequency sounds.[16]

Life history

Like other requiem sharks, the silvertip shark is

sexually mature at 1.6–1.8 m (5.2–5.9 ft) or 1.9–2.0 m (6.2–6.6 ft) long, and females at 1.6–2.0 m (5.2–6.6 ft) long.[1]

Silvertip sharks often behave boldly towards divers.

Human interactions

Inquisitive and bold, especially in the presence of food, the silvertip shark is regarded as potentially dangerous to humans. Often, several sharks will rush up from deep water to inspect divers when they first enter the water, which can be a very intimidating experience, as they may approach quite close.[18][19] This species has also been known to circle or pursue divers.[16] In one experiment involving bait, a large silvertip shark tore the leg off a dummy dressed in SCUBA gear, demonstrating that this species is capable of inflicting lethal injuries.[2] As of 2008, the International Shark Attack File listed four provoked attacks attributable to this species, none of them fatal.[20]

The silvertip shark is caught by commercial and

pelagic fisheries, where it is often finned at sea. This species is susceptible to overfishing, due to its slow reproductive rate and tendency to stay in a certain area. It is believed to have been extirpated by Indonesian artisan fishers at Scott Reef off northern Australia, and is likely becoming rare in many other parts of its range. As a result, the International Union for Conservation of Nature has assessed the silvertip shark as vulnerable.[1]

References

  1. ^
    doi:10.2305/IUCN.UK.2016-3.RLTS.T161526A68611084.en
    . Retrieved 11 November 2021.
  2. ^
    ISBN 92-5-101384-5
    .
  3. ^ a b c Bester, Cathleen. Biological Profiles: Silvertip Shark, Florida Museum of Natural History Ichthyology Department. Retrieved on February 12, 2009.
  4. ^ Bray, Dianne J. (2011) Silvertip Shark, Carcharhinus albimarginatus (Rüppell 1837) Archived 2014-10-22 at the Wayback Machine, in Fishes of Australia
  5. ^ Garrick, J.A.F. (1982). Sharks of the genus Carcharhinus. NOAA Technical Report, NMFS CIRC-445.
  6. doi:10.1071/MF9920097
    .
  7. ISBN 0-8248-1808-3
    .
  8. ^
    ISBN 1-55209-629-7
    .
  9. ISBN 1-86825-394-5
    .
  10. S2CID 85954905
    .
  11. ^ a b Murch, A. Silvertip Shark. Elasmodiver.com. Retrieved on February 12, 2009.
  12. ISBN 0-8117-2875-7
    .
  13. ^
    ISBN 1-900724-36-7
    .
  14. doi:10.1080/10236240601154872
    .
  15. ^ Martin, R.A. Agonistic Display in Grey Reef Shark. ReefQuest Centre for Shark Research. Retrieved on February 12, 2009.
  16. ^
    ISBN 0-8047-2289-7
    .
  17. ^ Kato, S. & Hernandez Carvallo, A. (1967). "Shark tagging in the eastern Pacific Ocean, 1962–1965". In Gilbert, P.W.; Mathewson, R.F. & Rail, D.P. (eds.). Sharks, Skates, and Rays. Baltimore: The Johns Hopkins Press. pp. 93–109.
  18. ISBN 1-85974-239-4
    .
  19. ISBN 0-520-23917-2
    .
  20. ^ ISAF Statistics on Attacking Species of Shark. International Shark Attack File, Florida Museum of Natural History, University of Florida. Retrieved on May 9, 2009.
  21. ^ Froese, Rainer; Pauly, Daniel (eds.) (2009). "Carcharhinus albimarginatus" in FishBase. January 2009 version.

External links

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