Blacktip shark

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Not to be confused with Blacktip reef shark.

Blacktip 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. limbatus
Binomial name
Carcharhinus limbatus
Range of the blacktip shark
Synonyms
  • Carcharias abbreviatus Klunzinger, 1871
  • Carcharias aethalorus Jordan & Gilbert, 1882
  • Carcharias ehrenbergi Klunzinger, 1871
  • Carcharias maculipinna Günther, 1868
  • Carcharias microps Lowe, 1841
  • Carcharias muelleri Steindachner, 1867
  • Carcharias phorcys Jordan & Evermann, 1903
  • Carcharias pleurotaenia Bleeker, 1852
  • Carcharhinus natator Meek & Hildebrand, 1923

The blacktip shark (Carcharhinus limbatus) is a

caudal fins
. It usually attains a length of 1.5 m (4.9 ft).

Swift, energetic

viviparous
; females bear one to 10 pups every other year. Young blacktip sharks spend the first months of their lives in shallow nurseries, and grown females return]

Normally wary of humans, blacktip sharks can become aggressive in the presence of food and have been responsible for a number of attacks on people. This species is of importance to both commercial and recreational fisheries across many parts of its range, with its meat, skin, fins, and liver oil used. It has been assessed as Vulnerable by the IUCN, on the basis of its low reproductive rate and high value to fishers.

Taxonomy

The blacktip shark was first described by French zoologist

type specimens were two individuals caught off Martinique, both of which have since been lost. Later authors moved this species to the genus Carcharhinus.[2][3] The specific epithet limbatus is Latin for "bordered", referring to the black edges of this shark's fins.[4] Other common names used for the blacktip shark include blackfin shark, blacktip whaler, common or small blacktip shark, grey shark, and spotfin ground shark.[5]

Phylogeny and evolution

The closest relatives of the blacktip shark were originally thought to be the graceful shark (C. amblyrhynchoides) and the spinner shark (C. brevipinna), due to similarities in morphology and behavior. However, this interpretation has not been borne out by studies of mitochondrial and ribosomal DNA, which instead suggest affinity with the blacknose shark (C. acronotus). More work is required to fully resolve the relationship between the blacktip shark and other Carcharhinus species.[6]

Analysis of mitochondrial DNA has also revealed two distinct lineages within this species, one occupying the western Atlantic and the other occupying the eastern Atlantic, Indian, and Pacific Oceans. This suggests that Indo-Pacific blacktip sharks are descended from those in the eastern Atlantic, while the western Atlantic sharks became isolated by the widening Atlantic Ocean on one side and the formation of the

Ma) deposits in Delaware and Florida.[8][9]

Description

The blacktip shark has a robust, streamlined body with a long, pointed snout and relatively small eyes. The five pairs of

pectoral fins are falcate and pointed.[2]

The coloration is gray to brown above and white below, with a conspicuous white stripe running along the sides. The pectoral fins, second dorsal fin, and the lower lobe of the caudal fin usually have black tips. The pelvic fins and rarely the anal fin may also be black-tipped. The first dorsal fin and the upper lobe of the caudal fin typically have black edges.

coccolithophores.[10] This species attains a maximum known length of 2.8 m (9.2 ft), though 1.5 m (4.9 ft) is more typical, and a maximum known weight of 123 kg (271 lb).[5]

  • The blacktip shark has black markings on most of its fins.
    The blacktip shark has black markings on most of its fins.
  • Lower teeth
    Lower teeth
  • Upper teeth
    Upper teeth

Distribution and habitat

A blacktip shark swimming in murky water off Oahu, Hawaii

The blacktip shark has a worldwide distribution in tropical and subtropical waters. In the Atlantic, it is found from

Galápagos.[2]

Most blacktip sharks are found in water less than 30 m (98 ft) deep over continental and insular shelves, though they may dive to 64 m (210 ft).

mangrove swamps. Although an individual may be found some distance offshore, blacktip sharks do not inhabit oceanic waters.[2] Seasonal migration has been documented for the population off the east coast of the United States, moving north to North Carolina in the summer and south to Florida in the winter.[12]

Biology and ecology

The blacktip shark is an extremely fast, energetic predator that is usually found in groups of varying size.

parasites of the blacktip shark include the copepods Pandarus sinuatus and P. smithii, and the monogeneans Dermophthirius penneri and Dionchus spp., which attach the shark's skin.[3][15][16] This species is also parasitized by nematodes in the family Philometridae (genus Philometra), which infest the ovaries.[17]

Behaviour

Blacktip sharks are social and usually found in groups.

Like the spinner shark, the blacktip shark is known to leap out of the water and spin three or four times about its axis before landing. Some of these jumps are the end product of feeding runs, in which the shark corkscrews vertically through schools of small fish and its

hydrodynamic shape.[18] The speed attained by the shark during these jumps has been estimated to average 6.3 m/s (21 ft/s).[19]

Blacktip sharks have a timid disposition and consistently lose out to

agonistic display: the shark swims towards the threat and then turns away, while rolling from side to side, lowering its pectoral fins, tilting its head and tail upwards, and making sideways biting motions. The entire sequence lasts around 25 seconds. This behavior is similar to the actions of a shark attempting to move a sharksucker; one of these behaviors possibly is derived from the other.[20]

Feeding

Fish make up some 90% of the blacktip shark's diet.

smoothhounds and sharpnose sharks. Crustaceans and cephalopods are occasionally taken.[2] In the Gulf of Mexico, the most important prey of the blacktip shark is the Gulf menhaden (Brevoortia patronus), followed by the Atlantic croaker (Micropogonias undulatus).[21] Off South Africa, jacks and herring are the most important prey.[22] Hunting peaks at dawn and dusk.[21] The excitability and sociability of blacktip sharks makes them prone to feeding frenzies when large quantities of food are suddenly available, such as when fishing vessels dump their refuse overboard.[2]

Life history

As with other requiem sharks, the blacktip shark is

philopatric and return to their original nursery areas to give birth. This results in a series of genetically distinct breeding stocks that overlap in geographic range.[23][25]

Mating occurs from spring to early summer, and the young are born around the same time the following year after a

gestation period of 10–12 months.[2] Females have one functional ovary and two functional uteri; each uterus is separated into compartments with a single embryo inside each.[26] The embryos are initially sustained by a yolk sac; in the 10th or 11th week of gestation, when the embryo measures 18–19 cm long (7.1–7.5 in), the supply of yolk is exhausted and the yolk sac develops into a placental connection that sustains the embryo until birth.[12] The length at birth is 55–60 cm (22–24 in) off the eastern United States and 61–65 cm (24–26 in) off North Africa.[12][26] The mortality rate in the first 15 months of life is 61–91%, with major threats being predation and starvation.[27] The young remain in the nurseries until their first fall, when they migrate to their wintering grounds.[12]

The growth rate of this species slows with age: 25–30 cm (9.8–11.8 in) in the first six months, then 20 cm (7.9 in) a year until the second year, then 10 cm (3.9 in) a year until maturation, then 5 cm (2.0 in) a year for adults.[28][29] The size at maturity varies geographically: males and females mature at 1.4–1.5 m (4.6–4.9 ft) and 1.6 m (5.2 ft), respectively, in the northeastern Atlantic,[12] 1.3–1.4 m (4.3–4.6 ft) and 1.5–1.6 m (4.9–5.2 ft), respectively, in the Gulf of Mexico,[28][30] 1.5 and 1.6 m (4.9 and 5.2 ft) respectively off South Africa,[31] and 1.7 and 1.8 m (5.6 and 5.9 ft), respectively, off North Africa.[26] The age at maturation is 4–5 years for males and 7–8 years for females.[28][30] The lifespan is at least 12 years.[2]

In 2007, a 9-year-old female blacktip shark at the

fertilization. Along with an earlier case of parthenogenesis in the bonnethead (Sphyrna tiburo), this event suggests that asexual reproduction may be more widespread in sharks than previously thought.[32]

Human interactions

The blacktip shark usually poses little danger to divers.
Blacktip shark in UShaka Sea World

Blacktip sharks showing curiosity towards divers has been reported, but they remain at a safe distance. Under most circumstances, these timid sharks are not regarded as highly dangerous to humans. However, they may become aggressive in the presence of food, and their size and speed invite respect.[2] As of 2008, the International Shark Attack File lists 28 unprovoked attacks (one fatal) and 13 provoked attacks by this species.[33] Blacktip sharks are responsible annually for 16% of the shark attacks around Florida. Most attacks by this species result in only minor wounds.[3]

As one of the more common large sharks in coastal waters, the blacktip shark is caught in large numbers by commercial fisheries throughout the world, using

fishmeal.[2] Blacktip sharks are one of the most important species to the northwestern Atlantic shark fishery, second only to the sandbar shark (C. plumbeus). The flesh is considered superior to that of the sandbar shark, resulting in the sandbar and other requiem shark species being sold under the name "blacktip shark" in the United States. The blacktip shark is also very significant to Indian and Mexican fisheries, and is caught in varying numbers by fisheries in the Mediterranean and South China Seas, and off northern Australia.[29]

The blacktip shark is popular with recreational anglers in Florida, the Caribbean, and South Africa. It is listed as a game fish by the International Game Fish Association. Once hooked, this species is a strong, steady fighter that sometimes jumps out of the water.[3] Since 1995, the number of blacktip sharks taken by recreational anglers in the United States has approached or surpassed the number taken by commercial fishing.[29] The International Union for Conservation of Nature has assessed the blacktip shark as Vulnerable, as its low reproductive rate renders it vulnerable to overfishing.[1] The United States and Australia are the only two countries that manage fisheries catching blacktip sharks. In both cases, regulation occurs under umbrella management schemes for multiple shark species, such as that for the large coastal sharks category of the US National Marine Fisheries Service Atlantic shark Fisheries Management Plan. No conservation plans specifically for this species have been implemented.[29]

References

  1. ^
    doi:10.2305/IUCN.UK.2021-2.RLTS.T3851A2870736.en
    . Retrieved 12 November 2021.
  2. ^
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  3. ^ a b c d e f Curtis, T. Biological Profiles: Blacktip Shark Archived 2007-06-29 at the Wayback Machine. Florida Museum of Natural History Ichthyology Department. Retrieved on April 27, 2009.
  4. ^
    ISBN 978-0-520-23484-0
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  5. ^ a b c Froese, Rainer; Pauly, Daniel (eds.) (2009). "Carcharhinus limbatus" in FishBase. April 2009 version.
  6. PMID 18558373
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  7. S2CID 24521217
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  8. ^ Benson. R.N., ed. (1998). Geology and Paleontology of the Lower Miocene Pollack Farm Fossil Site, Delaware: Delaware Geological Survey Special Publication No. 21. Delaware Natural History Survey. pp. 133–139.
  9. ISBN 978-1-56164-409-4
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  10. ^ Martin, R.A. Albinism in Sharks. ReefQuest Centre for Shark Research. Retrieved on April 28, 2009.
  11. S2CID 34885027
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  12. ^ a b c d e Castro, J.I. (November 1996). "Biology of the blacktip shark, Carcharhinus limbatus, off the southeastern United States". Bulletin of Marine Science. 59 (3): 508–522.
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  14. doi:10.1071/MF01132
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  19. PMID 16849197
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  20. S2CID 85900416
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  21. ^ a b c Barry, K.P. (2002). Feeding habits of blacktip sharks, Carcharhinus limbatus, and Atlantic sharpnose sharks, Rhizoprionodon terraenovae, in Louisiana coastal waters. MS thesis, Louisiana State University, Baton Rouge.
  22. doi:10.2989/025776193784287356
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  23. ^
    S2CID 83856507
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  24. doi:10.1590/s1679-87592008000400008
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  25. S2CID 8747023
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  26. ^ a b c Capapé, C.H.; Seck, A.A.; Diatta, Y.; Reynaud, C.H.; Hemida, F. & Zaouali, J. (2004). "Reproductive biology of the blacktip shark, Carcharhinus limbatus (Chondrichthyes: Carcharhinidae) off West and North African Coasts" (PDF). Cybium. 28 (4): 275–284.
  27. doi:10.1139/f02-036
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  28. ^
    JSTOR 1445560
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  29. ^
    ISBN 978-2-8317-0700-6
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  30. ^ a b Killam, K.A. & Parsons, G.R. (May 1989). "Age and Growth of the Blacktip Shark, Carcharhinus limbatus, near Tampa Bay" (PDF). Florida Fishery Bulletin. 87: 845–857. Archived from the original (PDF) on 2016-12-15. Retrieved 2016-11-10.
  31. ^ Wintner, S.P. & Cliff, G. (1996). "Age and growth determination of the blacktip shark, Carcharhinus limbatus, from the east coast of South Africa" (PDF). Fishery Bulletin. 94 (1): 135–144. Archived from the original (PDF) on 2016-12-16. Retrieved 2016-11-10.
  32. doi:10.1111/j.1095-8649.2008.02018.x
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  33. ^ ISAF Statistics on Attacking Species of Shark. International Shark Attack File, Florida Museum of Natural History, University of Florida. Retrieved on April 22, 2009.

External links

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