Finetooth shark: Difference between revisions
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==Taxonomy and phylogeny== |
==Taxonomy and phylogeny== |
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The |
The dylan and connor shark was originally described as ''Carcharias (Aprion) isodon'' by [[Achille Valenciennes]], in [[Johannes Müller|Müller]] and [[Friedrich Henle|Henle]]'s 1839 ''Systematische Beschreibung der Plagiostomen''; the [[type specimen]] is a 65 cm (26 in) juvenile male, possibly caught off [[New York]], USA. The name was later changed to the currently-accepted ''Carcharhinus isodon''.<ref name="compagno">{{cite book |author=Compagno, L.J.V. |date=1984 |title=Sharks of the World: An Annotated and Illustrated Catalogue of Shark Species Known to Date |place=Rome |publisher=Food and Agricultural Organization |isbn=9251013845 |pages=477–478}}</ref> The [[specific epithet]] ''isodon'' means "equal teeth" in Greek, and refers to the similar number of teeth in the upper and lower jaws.<ref name="bester">Bester, C. [http://www.flmnh.ufl.edu/fish/gallery/descript/finetoothshark/finetoothshark.html Biological Profiles: Finetooth Shark]. ''Florida Museum of Natural History Ichthyology Department''. Retrieved on May 5, 2009.</ref> A [[phylogenetic]] study based on [[ribosomal DNA]], published by Mine Dosay-Akbulut in 2008, suggests 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.<ref>{{cite journal |author=Dosay-Akbulut, M. |title=The phylogenetic relationship within the genus ''Carcharhinus'' |journal=Comptes Rendus Biologies |volume=331 |date=2008 |pages=500–509}}</ref> |
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==Distribution and habitat== |
==Distribution and habitat== |
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Revision as of 00:58, 14 May 2009
| Finetooth shark | |
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| Species: | C. isodon
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| Binomial name | |
| Carcharhinus isodon (Valenciennes, 1839)
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| Range of the finetooth shark | |
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Aprionodon punctatus Gill, 1861 | |
Template:FixHTML Template:Sharksportal Template:FixHTML The finetooth shark, Carcharhinus isodon, is a species of requiem shark, family Carcharhinidae, found in the western Atlantic Ocean from North Carolina to Brazil. It forms large schools in shallow, coastal waters and migrates seasonally following warm water. A relatively small, slender-bodied shark, the finetooth shark can be identified by its needle-like teeth, dark blue-gray dorsal coloration, and long gill slits. It attains a maximum length of 1.9 m (6.2 ft). The diet of this species consists primarily of small bony fishes, in particular menhaden. Like other members of its family, it exhibits a viviparous mode of reproduction; females give birth to 2–6 pups in estuarine nursery areas every other year. The finetooth shark is of significance to the gillnet shark fishery operating off the southeastern United States, with the meat sold for human consumption. Its population has not yet been depleted, but the US National Marine Fisheries Service (NMFS) has determined that fishing is occuring at unsustainable levels.
Taxonomy and phylogeny
The dylan and connor shark was originally described as Carcharias (Aprion) isodon by Achille Valenciennes, in Müller and Henle's 1839 Systematische Beschreibung der Plagiostomen; the type specimen is a 65 cm (26 in) juvenile male, possibly caught off New York, USA. The name was later changed to the currently-accepted Carcharhinus isodon.[1] The specific epithet isodon means "equal teeth" in Greek, and refers to the similar number of teeth in the upper and lower jaws.[2] A phylogenetic study based on ribosomal DNA, published by Mine Dosay-Akbulut in 2008, suggests 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.[3]
Distribution and habitat
The finetooth shark is found in the western Atlantic from North Carolina south to the Gulf of Mexico, and is rare in the Caribbean Sea. It also occurs off southern Brazil and on rare occasions it strays as far north as New York.[4] There are old records of this species in the eastern Atlantic off Senegal and Guinea-Bissau, but these may represent misidentifications of spinner sharks (C. brevipinna).[1] This shark inhabits coastal waters less than 10 m (30 ft) deep in the summer and 20 m (70 ft) deep in the winter.[4] Historically they were known to venture into rivers in the Gulf Coastal Plain of Texas, though most of paths into this area are now blocked by dams.[5]
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, when the water temperature drops and they move south to Florida. The movements of the Gulf of Mexico population are unknown.[4]
Description
The body of the finetooth shark is slender and streamlined, with a long, pointed snout and large eyes. The mouth is broad with well-defined furrows at the corners. There are 12–15 tooth rows 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.[1]
The first dorsal fin is of moderate size while the second dorsal fin is relatively large; there is no ridge running between them. The pectoral fins are small and falcate (sickle-shaped), with pointed tips.[1] The dermal denticles are small and overlapping, each bearing three horizontal ridges leading to marginal teeth. The coloration in live specimens is a distinctive dark bluish-gray above and white below, with a faint pale stripe on the flanks.[2] Some individuals from Florida have green eyes.[6] The fins lack prominent markings. Male finetooth sharks average 1.6 m (5.2 ft) long and females 1.7 m (5.4 ft) long; the maximum length on record is 1.9 m (6.2 ft).[2]
Biology and ecology
Despite being common in the northwestern Atlantic and the Gulf of Mexico, the finetooth shark is one of the least-known requiem sharks off the southeastern United States.[7] Both adults and juveniles form large schools.[1] The finetooth shark feeds mainly on small bony fishes, and often enter the surf zone during the day to hunt.[8] The most important prey of this species off the US East Coast is the Atlantic menhaden (Brevoortia tyrannus), which the sharks swallow whole after removing the head. Other known food items include spot, mackerel, mullet, shrimp, and in one case a juvenile Atlantic sharpnose shark (Rhizoprionodon terraenovae), which may have been scavenged from the bycatch discard of a shrimp trawler.[4] The finetooth shark may be preyed upon by larger sharks.[2]
Like other requiem sharks, the finetooth shark is viviparous, with the females bearing litters of 2–6 pups every other year. Courtship involves the male biting the female to hold her for copulation. The semen exuded by the male congeals into a large spongy mass called a "spermatozeugma", in which the individual spermatozoa are embedded, inside the female's uterus; the function of this short-lived structure is unknown.[4] Mating occurs from early May to early June, with the young born the following year at around the same time, after a gestation period of about a year. The embryos are sustained by a yolk sac for the first fifteen weeks, after which the depleted yolk sac develops into a placental connection through which the mother provides nourishment. Females make use of shallow nursery areas, such as Bull's Bay, South Carolina, to give birth.[4] The newborns measure 48–64 cm (19–25 in) long [1][4] Estuaries are critical habitat for newborns and juveniles.[7]
Females grow at a slower rate and to a larger ultimate size than males.[9] The life history characteristics of this species differs between the northwestern Atlantic and Gulf of Mexico populations, with sharks in the northwestern Atlantic being larger and slower to mature. In the northwestern Atlantic, males mature at a fork length (length from snout tip to tail fin fork) of 99 cm (39 in) and females at 102 cm (40 in), corresponding to ages of 5 and 6 years respectively. In the Gulf of Mexico, males mature at a fork length of 94 cm (37 in) and females at 99 cm (39 in), corresponding to ages of 4 and 5 years respectively.[10] The lifespan is estimated to be at least 9 years for males and 14 years for females.[9]
Relationship to humans
The finetooth shark has never been implicated in an attack on humans.[2] However, when caught this shark will thrash and snap at anything within range, and people have been bitten attempting to handle it.[11] Finetooth sharks are utilized for human consumption fresh or dried and salted. Other than off the southeastern United States, this species is of little commercial importance: it is small and occurs in water too shallow for most commercial and recreational fisheries, and is too fast-swimming to be caught by shrimp trawlers. Small numbers are taken incidentally by floating longlines and on hook-and-line.[4]
Substantial numbers of finetooth sharks are caught in drift gillnets operated by the shark fishery off southeastern United States, which peaked in 1999 at about 129 short tons landed. This fishery is managed under the US National Marine Fisheries Service (NMFS) 1993 Fisheries Management Plan (FMP) for Atlantic and Gulf of Mexico sharks. The finetooth shark is classified as a "Small Coastal Shark" (SCS) for the purposes of commercial quotas and recreational bag limits.[9] In 2002, the NMFS determined that the finetooth shark population was not yet overfished, but also that the catch rate had exceeded sustainable levels and additional conservation measures were needed.[7] The conservation status of this species has not been evaluated by the World Conservation Union.[12]
References
- ^ a b c d e f Compagno, 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. 477–478. ISBN 9251013845.
- ^ a b c d e Bester, C. Biological Profiles: Finetooth Shark. Florida Museum of Natural History Ichthyology Department. Retrieved on May 5, 2009.
- ^ Dosay-Akbulut, M. (2008). "The phylogenetic relationship within the genus Carcharhinus". Comptes Rendus Biologies. 331: 500–509.
- ^ a b c d e f g h Castro, J.I. (1993). "The biology of the finetooth shark, Carcharhinus isodon". Environmental Biology of Fishes. 36: 219–232.
- ^ Vines, R.A. (1984). Trees of Central Texas. University of Texas Press. p. 133. ISBN 0292780583.
- ^ Grace, M.A. (2001). "Field guide to requiem sharks (Elasmobranchiomorphi: Carcharhinidae) of the Western North Atlantic." NOAA Technical Report NMFS 153. pp. 21.
- ^ a b c Ulrich, G.F. Finetooth Shark Carcharhinus isodon. South Carolina Department of Natural Resources. Retrieved on May 5, 2009.
- ^ Goldstein, R.J. (2000). Coastal fishing in the Carolinas: From Surf, Pier, and Jetty (third ed.). John F. Blair. p. 129. ISBN 0895871955.
- ^ a b c Carlson, J.K., Cortés, E. and 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.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ 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.
- ^ Parsons, G.R. (2006). Sharks, Skates, and Rays of the Gulf of Mexico: A Field Guide. University Press of Mississippi. p. 64. ISBN 1578068274.
- ^ Froese, Rainer; Pauly, Daniel (eds.). "Carcharhinus isodon". FishBase. May 2009 version.