Finetooth shark

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Finetooth shark

Near Threatened  (IUCN 3.1)[1]
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. isodon
Binomial name
Carcharhinus isodon
Range of the finetooth shark
Synonyms

Aprionodon punctatus Gill, 1861
Carcharias isodon Valenciennes in J. P. Müller & Henle, 1839

The finetooth shark (Carcharhinus isodon) is a

viviparous with females giving birth to two to six pups in estuarine
nursery areas every other year.

Valued for its meat, the finetooth shark forms an important component of the

gillnet shark fishery operating off the southeastern United States
. Population assessments suggest that this fishery does not currently pose a threat to U.S. populations of the species. This shark is not known to pose a danger to humans, though it snaps vigorously when captured and should be handled with caution.

Taxonomy and phylogeny

The finetooth shark was originally described as Carcharias (Aprionodon) isodon by French

type specimen is a 65-cm (26-in) juvenile male, possibly caught off New York. This species was later moved to the genus Carcharhinus.[2] The specific epithet isodon means "equal teeth" in Greek, and refers to the similar number of teeth in the upper and lower jaws.[3] This species may also be referred to as the eventooth shark, smoothtooth shark, or night shark (usually used for C. signatus).[4]

As is the case for most Carcharhinus species, attempts to analyze the finetooth shark's

allozyme analysis found that the finetooth shark is the second-most basal member of the genus next to the blacknose shark (C. acronotus).[5] Mine Dosay-Akbulut's 2008 study, based on ribosomal DNA, suggested that the closest relative of the finetooth shark is the smalltail shark (C. porosus), and that the two species form a clade apart from other Carcharhinus species.[6]

Description

The body of the finetooth shark is slender and streamlined. The snout is long and pointed, with the

nares preceded by short, broadly triangular flaps of skin. The eyes are large and round, with nictitating membranes (protective third eyelids). The mouth is broad with well-defined furrows at the corners. Twelve to 15 tooth rows occur on either side of the upper jaw and 13–14 tooth rows on either side of the lower jaw. Each tooth is small and needle-like, with a narrow central cusp and smooth to minutely serrated edges. The five pairs of gill slits are long, measuring about half the length of the dorsal fin base.[2]

The first dorsal fin is high and triangular with a pointed apex, originating forward of the free rear tips of the

dermal denticles are small and overlapping, each bearing three horizontal ridges leading to marginal teeth. Living finetooth sharks are a distinctive dark bluish-gray above and white below, with a faint pale stripe on the flanks and no prominent fin markings.[3] Some individuals from Florida have green eyes.[7] Males average 1.6 m (5.2 ft) in length and females 1.7 m (5.4 ft); the largest shark on record was 1.9 m (6.2 ft) long.[3]

  • Distinguishing traits of the finetooth shark include its long gill slits and slender teeth
    Distinguishing traits of the finetooth shark include its long gill slits and slender teeth
  • Jaws
    Jaws
  • Upper teeth
    Upper teeth
  • Lower teeth
    Lower teeth

Distribution and habitat

In North American waters, the finetooth shark is common and found from North Carolina to the northern Gulf of Mexico, and very occasionally straying as far north as New York. In Central and South American waters, it is rare, but may occur more widely than presently known, having been reported off Trinidad and Guyana, infrequently from the Caribbean Sea, and off southern Brazil from São Paulo to Santa Catarina. The northwestern Atlantic, Gulf of Mexico, and South America populations are distinct, with little interchange between them.[1][8] Old records exist of this species in the eastern Atlantic off Senegal and Guinea-Bissau, but these likely represent misidentifications of spinner sharks (C. brevipinna).[2]

The finetooth shark is often found near

estuaries. It inhabits extremely shallow waters, no deeper than 10 m (33 ft) in the summer and 20 m (66 ft) deep in the winter.[8] Historically, it was known to venture into rivers in the Gulf Coastal Plain of Texas, though most of paths into this area are now blocked by dams.[9] The northwestern Atlantic population of this species is strongly migratory: juveniles, followed by adults, arrive off South Carolina from late March to early May, when the water temperature rises above 20 °C (68 °F). They remain until September to mid-October, until the water temperature drops and they move south to Florida. The movements of other populations are unknown.[8]

Biology and ecology

The Atlantic menhaden is the most important prey of finetooth sharks in the northwestern Atlantic.

Adult and juvenile finetooth sharks form large

tapeworm Triloculatum geeceearelensis,[11] and unidentified species in the genera Anthobothrium, Paraorygmatobothrium, and Phoreiobothrium.[12]

Life history

Like other requiem sharks, the finetooth shark is

spermatozoa are embedded. Called a "spermatozeugma", the function of this short-lived structure is unknown. Newborn finetooth sharks measure 48–64 cm (19–25 in) long.[2][8] Shallow bays and estuaries, such as Bull's Bay in South Carolina, serve as critical nursery areas for newborns and juveniles.[13]

Female finetooth sharks grow much more slowly and to a larger ultimate size than males.

maximum lifespan has been estimated to be at least 9 years for males and 14 years for females.[14]

Human interactions

The finetooth shark is caught for meat off the southeastern United States.

The finetooth shark has never been implicated in an attack on humans.

habitat degradation due to its inshore habits.[1]

Substantial numbers of finetooth sharks are caught in drift

Near Threatened
overall and off the U.S. and Mexico. Concern existsfor this species in South America, where its numbers seem naturally low and it is potentially under heavy pressure by widespread, intensive coastal fisheries.

References

  1. ^
    doi:10.2305/IUCN.UK.2021-1.RLTS.T161524A890428.en. Retrieved 19 November 2021.{{cite journal}}: CS1 maint: multiple names: authors list (link
    )
  2. ^
    ISBN 92-5-101384-5
    .
  3. ^ a b c d e Bester, C. Biological Profiles: Finetooth Shark Archived 2011-07-07 at the Wayback Machine. Florida Museum of Natural History Ichthyology Department. Retrieved on May 5, 2009.
  4. ^ Froese, Rainer; Pauly, Daniel (eds.) (2009). "Carcharhinus isodon" in FishBase. May 2009 version.
  5. S2CID 39697113
    .
  6. PMID 18558373
    .
  7. ^ Grace, M.A. (2001). "Field guide to requiem sharks (Elasmobranchiomorphi: Carcharhinidae) of the Western North Atlantic." NOAA Technical Report NMFS 153. pp. 21.
  8. ^
    S2CID 29587318
    .
  9. ISBN 0-292-78058-3
    .
  10. ISBN 0-89587-195-5
    .
  11. S2CID 31178927
    .
  12. PMID 20026125
    .
  13. ^ a b Ulrich, G.F. Finetooth Shark Carcharhinus isodon Archived 2011-09-28 at the Wayback Machine. South Carolina Department of Natural Resources. Retrieved on May 5, 2009.
  14. ^ a b c d Carlson, J.K.; Cortés, E. & Bethea, D.M. (2003). "Life history and population dynamics of the finetooth shark (Carcharhinus isodon) in the northeastern Gulf of Mexico". Fisheries Bulletin. 101: 281–292.
  15. ^ Carlson, J.K., Drymon, J.M. and Neer, J.A. (2007). "Life history parameters for finetooth sharks, Carcharhinus isodon, from the United States South Atlantic Ocean and northern Gulf of Mexico". SEDAR 13 Small Coastal Sharks Data Workshop, Working Document SEDAR 13-DW-11.
  16. ISBN 1-57806-827-4
    .

External links

Wikimedia Commons has media related to Carcharhinus isodon.
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