Blackspot shark

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Blackspot shark
Carcharhinus sealei terengganu.jpg
Conservation status
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Subclass: Elasmobranchii
Order: Carcharhiniformes
Family: Carcharhinidae
Genus: Carcharhinus
Species: C. sealei
Binomial name
Carcharhinus sealei
(Pietschmann, 1913)[2]
Carcharhinus sealei distmap.png
Synonyms[2]
  • Carcharhinus menisorrah (Müller & Henle, 1839)
  • Carcharias borneensis Seale, 1910
  • Carcharias sealei Pietschmann, 1913
  • Platypodon coatesi Whitley, 1939

The blackspot shark (Carcharhinus sealei) is a small species of requiem shark in the family Carcharhinidae. It is found in the tropical Indo-West Pacific Ocean between latitudes 24° N and 30° S, from the surface to depths of about 40 metres (130 ft). Its length is a little under one metre (yard) and it is not considered dangerous to humans. It feeds mainly on fish, crustaceans and squid and is itself caught in small-scale fisheries for human consumption.

Description[edit]

The blackspot shark is a relatively slender species with a streamlined appearance growing to a length of about 95 centimetres (37 in). The snout is fairly long, pointed or slightly rounded at the tip. The eyes are large, oval and set horizontally and are protected by a nictitating membrane on the lower side. The flaps of skin beside the nostrils are triangular and the furrows on the upper lip are short. There are usually twelve tooth rows on either side of both top and bottom jaws, but the number can vary from eleven to thirteen. The upper teeth have strongly serrated oblique cusps and smooth-edged cusplets and the lower teeth have oblique cusps, either serrated or smooth. The hindermost of the five gill slits is above the origin of the pectoral fins and there are no spiracles. The first dorsal fin is long, narrow and curved (falcate) and has a short rear tip. It is either pointed or narrowly rounded at the apex and its origin is directly over the free posterior end of the pectoral fins. The second dorsal fin is relatively large. It also has a short rear tip and its origin is slightly behind the origin of the anal fin. The pectoral fins are falcate, long and narrow and taper to a blunt point. There is no fleshy keel along the sides of the caudal peduncle. The caudal fin is about one fifth of the total length of the shark, the dorsal lobe is elongated and has a notch in the lower margin near the tip and the ventral lobe is smaller, markedly falcate and has a more rounded tip. The body colour is brownish or silvery grey on the dorsal surface and pale grey on the ventral surface and there is an inconspicuous pale stripe running along the flank. There is a large, triangular black spot on the second dorsal fin which covers at least half of the fin. The other fins have no distinctive markings, but do have pale posterior edges.[3][4]

The blackspot shark can be confused with the whitecheek shark (Carcharhinus dussumieri),[5] but that species has a triangular first dorsal fin that is only slightly falcate, and a small second dorsal fin that merely has a dark margin.[6]

Distribution[edit]

The blackspot shark is native to the Indian and Pacific Oceans where it is found on the continental shelves and shallow water around islands from the surf line to depths of about 40 metres (130 ft). It is not usually found in estuaries and may be intolerant of low salinity water. In the Indian Ocean it is found along the east coast of Africa from South Africa and Madagascar to Kenya. It is present in the water around the Seychelles and Mauritius and further east, it is present around the coasts of Pakistan, India and Sri Lanka. In the eastern Pacific Ocean it is found along the coasts of Thailand, Viet Nam, China, Indonesia, New Guinea and northern and western Australia.[3] In South Africa the species seems to be resident but there is some increase in numbers during the summer months.[3]

Biology[edit]

The blackspot shark feeds on small fish, crustaceans and squid and is not dangerous to man.[3] It is a fast-growing, short-lived species. It is mature at about one year old at a length of about 70 centimetres (28 in) and can live for five years or more. Like other members of its genus, the blackspot shark is viviparous. The period of gestation is about nine months and one or two offspring develop at one time in the uterus. At first, the embryos are sustained by a yolk sac, but later a placenta develops. Off the coast of Natal, the juvenile sharks are born in spring.[7]

Status[edit]

The blackspot shark is listed as "Near Threatened" by the International Union for Conservation of Nature in its Red List of Threatened Species. Detailed surveys of population size have not been done but it is believed that the population is in decline. The shallow waters in which the fish lives are intensively fished with longlines and gillnets and the blackspot shark may be overexploited through overfishing. It is sold in local markets and its flesh is used for human consumption.[1]

References[edit]

  1. ^ a b White, W. T. (2003). "Carcharhinus sealei". IUCN Red List of Threatened Species. Version 2012.2. IUCN. Retrieved 2013-06-18. 
  2. ^ a b Bailly, Nicolas (2013). "Carcharhinus sealei (Pietschmann, 1913)". World Register of Marine Species. Retrieved 2013-06-18. 
  3. ^ a b c d "Blackspot shark (Carcharhinus sealei)". Sharks of the World. Marine Species Identification Portal. Retrieved 2013-06-18. 
  4. ^ "Carcharhinidae: Requiem sharks". Encyclopedia of Life. Retrieved 2013-06-18. 
  5. ^ Carpenter, Kent E. "Carcharhinus sealei (Pietschmann, 1913)". FishBase. Retrieved 2013-06-18. 
  6. ^ "Whitecheek shark (Carcharhinus dussumieri)". Sharks of the World. Marine Species Identification Portal. Retrieved 2013-06-18. 
  7. ^ Van Der Elst, Rudy (1993). A Guide to the Common Sea Fishes of Southern Africa. Struik. p. 367. ISBN 9781868253944.