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Spinner shark

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Carcharhinus brevipinna
Scientific classificationEdit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Subclass: Elasmobranchii
Subdivision: Selachimorpha
Order: Carcharhiniformes
Family: Carcharhinidae
Genus: Carcharhinus
Species:
C. brevipinna
Binomial name
Carcharhinus brevipinna
Range of the spinner shark
Synonyms

Aprionodon capartiPoll, 1951
Carcharhinus johnsoniSmith, 1951
Carcharias brevipinnaMüller & Henle, 1839
Isogomphodon maculipinnisPoey, 1865
Longmania calamariaWhitley, 1944
Uranga nasutaWhitley, 1943

Thespinner shark(Carcharhinus brevipinna) is a type ofrequiem shark,in thefamilyCarcharhinidae, named for the spinning leaps it makes as a part of its feeding strategy. This species occurs in tropical and warm temperate waters worldwide, except for in the easternPacific Ocean.It is found from coastal to offshore habitats to a depth of 100 m (330 ft), though it prefers shallow water. The spinner shark resembles a larger version of theblacktip shark(C. limbatus), with a slender body, long snout, and black-marked fins. This species can be distinguished from the blacktip shark by the firstdorsal fin,which has a different shape and is placed further back, and by the black tip on theanal fin(in adults only). It attains a maximum length of 3 m (9.8 ft).

Spinner sharks are swift and gregariouspredatorsthat feed on a wide variety of smallbony fishesandcephalopods.When feeding onschoolsofforage fish,they speed vertically through the school while spinning on their axis, erupting from the water at the end. Like other members of its family, the spinner shark isviviparous,with females bearing litters of three to 20 young every other year. The young are born in shallow nursery areas near the coast, and are relatively fast-growing. This species is not usually dangerous to humans, but may become belligerent when excited by food. Spinner sharks are valued bycommercial fisheriesacross their range for their meat, fins,liver oil,and skin. They are also esteemed as strong fighters byrecreational fishers.TheInternational Union for Conservation of Naturehas assessed this species asVulnerableworldwide.

Taxonomy and phylogeny

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The spinner shark was originally described asCarcharias (Aprion) brevipinnabyJohannes Peter MüllerandFriedrich Gustav Jakob Henlein their 1839Systematische Beschreibung der Plagiostomen,based on the mounted skin of a 79-cm-long specimen collected offJava.[2]This species was subsequently moved to the generaAprion,Squalus,andAprionodonbefore being placed within the genusCarcharhinus.[3]The tooth shape and coloration of this species varies significantly with age and between geographical regions, which caused much taxonomic confusion.[2]Other common names include black-tipped shark, great blacktip shark, inkytail shark, large blacktip shark, long-nose grey shark, longnose grey whaler, and smoothfang shark.[4]

Based on similarities inmorphology,tooth shape, and behavior, the closest relatives of the spinner shark were originally believed to be theblacktip sharkand thegraceful shark(C. amblyrhynchoides).[5]However, this interpretation was not supported by Gavin Naylor's 1992allozymeanalysis, which suggested that these similarities are the product ofconvergent evolutionand that the closest relative of the spinner shark is thecopper shark(C. brachyurus).[6]In a 2007ribosomal DNAstudy, the spinner shark was found to be the mostgenetically divergentof all the requiem shark species examined save for thetiger shark(Galeocerdo cuvier), being less related to otherCarcharhinusspecies than thelemon shark(Negaprion brevirostris).[7]

Distribution and habitat

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Some uncertainty exists in the distribution data for the spinner shark due to confusion with the blacktip shark. In the Western Atlantic Ocean, it occurs fromNorth Carolinato the northernGulf of Mexico,including theBahamasandCuba,and from southernBraziltoArgentina.In the Eastern Atlantic, it occurs from offNorth AfricatoNamibia.In theIndian Ocean,it is found fromSouth AfricaandMadagascar,to theRed Seaand theGulf of Aden,toIndiaand nearby islands, toJavaandSumatra.In thePacific Ocean,it occurs offJapan,Vietnam,Australia,and possibly thePhilippines.[2][3]Parasitological evidence suggests that Indian Ocean spinner sharks have passed through theSuez Canalinto theMediterranean Sea,becomingLessepsian migrants.[8]

The spinner shark has been reported from the ocean surface to a depth of 100 m (330 ft), though it prefers water less than 30 m (98 ft) deep, and occupies all levels of the water column. This species may be found from coastal waters to well offshore, over continental and insular shelves. Juveniles have been known to enter bays, but avoidbrackishconditions. The northwest Atlantic subpopulation is known to bemigratory;in spring and summer, they are found in warm inshore waters, and in winter, they move south into deeper water.[2][3]

Description

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The average spinner shark is 2 m (6.6 ft) long and weighs 56 kg (123 lb); this species attains a maximum known length and weight of 3 m (9.8 ft) and 90 kg (200 lb). Indo-Pacific sharks are generally larger than those from the northwest Atlantic.[3]This species has a slim, streamlined body with a distinctive, long, pointed snout. The eyes are small and circular. Prominent, forward-pointing furrows occur at the corners of the mouth. The tooth rows number 15–18 in each half of the upper jaw and 14–17 in each half of the lower jaw, with two and one tiny symphysial (central) teeth, respectively. The teeth have long, narrow central cusps and are finely serrated in the upper jaw and smooth in the lower jaw. The five pairs ofgill slitsare long.[2]

The firstdorsal finis relatively small and usually originates behind the free rear tip of thepectoral fins.No ridge exists between the first and second dorsal fins. The pectoral fins are moderately short, narrow, and falcate (sickle-shaped).[2]The body is densely covered with diamond-shapeddermal denticleswith seven (rarely five) shallow horizontal ridges. The coloration is gray above, sometimes with a bronze sheen, and white below, with a faint white band on the sides. Young individuals have unmarked fins; the tips of the second dorsal fin, pectoral fins, anal fin, and lower caudal fin lobe (and sometimes the other fins, as well) are black in larger individuals. The spinner shark differs from the blacktip shark in that its first dorsal fin is slightly more triangular in shape and is placed further back on the body. Adults can also be distinguished by the black tip on the anal fin.[2][3]

  • Gill slits
    Gill slits
  • Jaws
    Jaws
  • Upper teeth
    Upper teeth
  • Lower teeth
    Lower teeth

Biology and ecology

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The spinner shark is a fast, active swimmer that sometimes forms largeschools,segregated by age and sex. Young individuals prefer cooler water temperatures than adults.[9]Off South Africa, females are found close to shore year-round, while males only appear during the summer.[10]Smaller spinner sharks may be preyed upon by larger sharks. Knownparasitesof the spinner shark include thecopepodsKroyeria deetsi,Nemesis pilosus,andN. atlantica,which infest the shark's gills,Alebion carchariae,which infests the skin,Nesippus orientalis,which infests the mouth andgill arches,andPerissopus dentatus,which infests thenaresand the rear margins of the fins.[3]

Feeding

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Spinner sharks feed primarily on small bony fish, includingtenpounders,sardines,herring,anchovies,sea catfish,lizardfish,mullets,bluefish,tunas,bonito,croakers,jacks,mojarras,andtongue-soles.They have also been known to eatstingrays,cuttlefish,squid,andoctopus.[2]Groups of spinner sharks are often found pursuing schools of prey at high speed.[11]Individual prey are seized and swallowed whole, as this shark lacks cuttingdentition.[10]This species employs an unusual tactic when feeding on schools of small fish; the shark charges vertically through the school, spinning on its axis with its mouth open and snapping all around it. The shark's momentum at the end of these spiraling runs often carries it into the air, giving it its common name.[2][12]The blacktip shark also performs this behavior, though not as often.[3]Off Madagascar, spinner sharks follow migrating schools of mackerel, tunas, and jacks. Like blacktip sharks, they congregate aroundshrimptrawlersto feed on the discardedbycatch,and may be incited intofeeding frenzies.[2]

Life history

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Claspers(external male copulatory parts) of a youngCarcharhinus brevipinna

Like other requiem sharks, the spinner shark isviviparous.Adult females have a single functionalovaryand two functionaluteri;each uterus is divided into compartments, one for eachembryo.The embryos are initially sustained by ayolk sac.When the embryo grows to around 19 cm (7.5 in) long, the supply of yolk has been exhausted and the empty yolk sac develops into aplacentalconnection through which the mother provides nutrients for the remainder ofgestation.This species has the smallestovarelative to the fully developed embryo of any viviparous shark known.[13]Females give birth to three to 20 (usually seven to 11) pups every other year, after a gestation period of 11–15 months. Mating occurs from early spring to summer, and parturition in August off North Africa, from April to May off South Africa, and from March to April in the northwestern Atlantic.[13][14]Young are birthed in coastal nursery areas such as bays, beaches, and high-salinity estuaries in water deeper than 5 m (16 ft).[14]

The length at birth is 66–77 cm (26–30 in) in the northwestern Atlantic,[14]61–69 cm (24–27 in) off Tunisia,[13]and 60 cm (24 in) off South Africa.[10]Spinner sharks are relatively fast-growing sharks: 30 cm (12 in) per year for newborns, 25 cm (9.8 in) per year for one-year-olds, 10 cm (3.9 in) per year for adolescents, and 5 cm (2.0 in) per year for adults. In the northwestern Atlantic, males mature at 1.3 m (4.3 ft) long and females at 1.5–1.6 m (4.9–5.2 ft) long, corresponding to ages of 4–5 years and 7–8 years, respectively.[14]Off South Africa, males mature at 1.8 m (5.9 ft) and females at 2.1 m (6.9 ft).[10]Spinner sharks generally do not reproduce until they are 12–14 years old. Themaximum lifespanhas been estimated at 15–20 years or more.[14]

Human interactions

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The spinner shark is valued by both commercial and recreational fisheries.

Ordinarily, spinner sharks do not pose a substantial danger to humans; they do not perceive largemammalsas prey, as their small, narrow teeth are adapted for grasping rather than cutting. However, they can become excited by the presence of food, so caution is warranted if this species is encountered whilespearfishing.[2]As of 2008, theInternational Shark Attack Filelisted 16 unprovoked attacks and one provoked attack attributable to the spinner shark, none of them fatal.[15]

The meat of the spinner shark is of high quality and sold fresh or dried and salted. In addition, the fins are used forshark fin soupinEast Asia,theliver oilis processed forvitamins,and the skin is made intoleatherproducts. Spinner sharks are an important catch of the US commercial shark fisheries operating in the northwestern Atlantic and the Gulf of Mexico. The meat is marketed under the name "blacktip shark" in the United States, due to that species being considered superior in quality by consumers. It is likely also caught by other fisheries across its range, going unreported owing to confusion with the blacktip shark.[14]The spinner shark is also highly regarded by recreational fishers, being described as a "spectacular fighter" that often leaps out of the water.[16]

The IUCN has assessed the spinner shark asVulnerableworldwide; its frequent use of coastal habitats renders it vulnerable to human exploitation andhabitat degradation.[1]The Northwest Atlantic fishery for this species is managed under the USNational Marine Fisheries Service1999 Fishery Management Plan for Atlantic Tunas, Swordfish, and Sharks. For the purposes of commercial quotas and recreational bag limits, the spinner shark is categorized as a "large coastal shark".[14]

References

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  1. ^abRigby, C.L.; Carlson, J.; Smart, J.J.; Pacoureau, N.; Herman, K.; Derrick, D.; Brown, E. (2020)."Carcharhinus brevipinna".IUCN Red List of Threatened Species.2020:e.T39368A2908817.doi:10.2305/IUCN.UK.2020-3.RLTS.T39368A2908817.en.Retrieved19 November2021.
  2. ^abcdefghijkCompagno, L.J.V. (1984).Sharks of the World: An Annotated and Illustrated Catalogue of Shark Species Known to Date.Rome: Food and Agricultural Organization. pp. 466–468.ISBN92-5-101384-5.
  3. ^abcdefgBester, C.Biological Profiles: Spinner SharkArchived2010-04-16 at theWayback Machine.Florida Museum of Natural History Ichthyology Department. Retrieved on May 7, 2009.
  4. ^Froese, Rainer;Pauly, Daniel (eds.)."Carcharhinus brevipinna".FishBase.May 2009 version.
  5. ^Garrick, J.A.F. (1982)."Sharks of the genusCarcharhinus".NOAA Technical Report, NMFS CIRC-445.
  6. ^Naylor, G.J.P. (1992)."The phylogenetic relationships among requiem and hammerhead sharks: inferring phylogeny when thousands of equally most parsimonious trees result"(PDF).Cladistics.8(4): 295–318.doi:10.1111/j.1096-0031.1992.tb00073.x.hdl:2027.42/73088.PMID34929961.S2CID39697113.
  7. ^Dosay-Akbulut, M. (2008)."The phylogenetic relationship within the genusCarcharhinus".Comptes Rendus Biologies.331(7): 500–509.doi:10.1016/j.crvi.2008.04.001.PMID18558373.
  8. ^Castri, F.; Hansen, A.J. & Debussche, M. (1990).Biological Invasions in Europe and the Mediterranean Basin(second ed.). Springer. p. 300.ISBN0-7923-0411-X.
  9. ^Compagno, L.J.V; Dando, M. & Fowler, S. (2005).Sharks of the World.Princeton University Press. pp. 293–294.ISBN978-0-691-12071-3.
  10. ^abcdVan der Elst, R. & Borchert, P. (1993).A Guide to the Common Sea Fishes of Southern Africa(third ed.). Struik. p.36.ISBN1-86825-394-5.
  11. ^Heemstra, E. (2004).Coastal Fishes of Southern Africa.NISC (PTY) LTD. p.58.ISBN1-920033-01-7.
  12. ^"Carcharhinus brevipinna,Spinner Shark ".MarineBio.org.RetrievedMay 9,2009.
  13. ^abcCapape, C.; Hemida, F.; Seck, A.A.; Diatta, Y.; Guelorget, O. & Zaouali, J. (2003). "Distribution and reproductive biology of the spinner shark,Carcharhinus brevipinna(Muller and Henle, 1841) (Chondrichthyes: Carcharhinidae) ".Israel Journal of Zoology.49(4): 269–286.doi:10.1560/DHHM-A68M-VKQH-CY9F.
  14. ^abcdefgFowler, S.L.; Cavanagh, R.D.; Camhi, M.; Burgess, G.H.; Cailliet, G.M.; Fordham, S.V.; Simpfendorfer, C.A. & Musick, J.A. (2005).Sharks, Rays and Chimaeras: The Status of the Chondrichthyan Fishes.International Union for Conservation of Nature and Natural Resources. pp. 106–109, 287–288.ISBN2-8317-0700-5.
  15. ^ISAF Statistics on Attacking Species of Shark.International Shark Attack File, Florida Museum of Natural History, University of Florida. Retrieved on May 7, 2009.
  16. ^Goldstein, R.J. (2000).Coastal Fishing in the Carolinas: From Surf, Pier, and Jetty(third ed.). John F. Blair. p. 129.ISBN0-89587-195-5.
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