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Biology

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Despite being a rather small and slender shark, the strong swimming sharpnose sevengill shark is a voracious predator that is most active during the night (2) (4). It has a varied diet, feeding on a range of marine invertebrates, such as shrimp, lobsters, squid and cuttlefish, as well as small bony fish such as hake, small sharks and rays (2). This shark itself is thought to be preyed on by larger sharks (2). Although this shark is said to be quick to bite when captured, it is too small to be dangerous to humans (4). The sharpnose sevengill shark is an ovoviviparous species, a method of reproduction in which the young develop within eggs that remain inside the body until they hatch. Females give birth to between 9 and 20 young in a litter (4), each one measuring around 25 centimetres long (2)
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Conservation

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There are not known to be any conservation measures in place for the sharpnose sevengill shark (1).
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Description

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The large, florescent green eyes of this slender shark may be its most noticeable feature as it moves silently though the ocean depths. As its name describes, this shark has a narrow, pointed head, a long, narrow mouth and seven gill slits down each side; most sharks have only five (2). The slim body is brownish-grey to olive on the upper surface, and paler on the underside, and it has only one small dorsal fin (2), the fin situated on the shark's back that helps prevent it from rolling in the water (3). Juvenile sharpnose sevengill sharks differ a little in appearance from adults, having dark blotches on the lower sides, and dark tips to the dorsal and tail fins (2).
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Habitat

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The sharpnose sevengill shark is found near the sea bottom, usually at depths between 27 and 720 metres, although occasionally is may also be found in shallower coastal waters, or in water as deep as 1,000 metres (4))
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Range

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This shark has a very wide distribution, occurring in tropical and temperate seas worldwide (4), except the eastern north Pacific (1), although nowhere is it believed to be common (2).
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Status

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Classified as Near Threatened (NT) on the IUCN Red List (1).
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Threats

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Bycatch in fisheries is thought to be the greatest threat to the sharpnose sevengill shark, and may have caused populations to decline in areas where deepwater fisheries have been in operation for many years (1). It is captured in bottom trawls and by longlines, as fishermen target other, more commercially important, bottom-dwelling species, and is then eaten by humans or used for fishmeal (1). Although not considered to be threatened with extinction, an increase in fishing effort in deepwater regions inhabited by the sharpnose sevengill shark could have a detrimental affect on this slender species (1).
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Diagnostic Description

provided by FAO species catalogs
fieldmarks: A narrow-headed, big-eyed, small seven-gilled shark with one dorsal fin. Head narrow and pointed, with 7 pairs of gill slits; eyes very large; mouth very narrow and parabolic; large lower comblike teeth long and low, with a few short mesial cusplets, an abruptly high cusp, and up to 7 or 8 distal cusplets in adults. Caudal peduncle long, distance from dorsal fin insertion to upper caudal origin over twice length of dorsal fin base. Spots absent from body, dorsal fin and upper caudal lobe with black tips, faded or absent in adults but prominent in young.

References

  • Bigelow & Schroeder, 1948
  • Garrick & Paul, 1971

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bibliographic citation
FAO species catalogue Vol.4. Sharks of the world. An Annotated and Illustrated Catalogue of Shark Species Known to Date Part 1 - Hexanchiformes to Lamniformes. Compagno, L.J.V.1984FAO Fisheries Synopsis. , (125) Vol.4, Part 1.
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Distribution

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Wideranging in tropical and temperate seas; Western Atlantic: North Carolina, USA to Cuba and northern Gulf of Mexico, also southern Brazil and Argentina. Eastern Atlantic: From Morocco to Angola, also Mediterranean Sea. Indian Ocean: South Africa, southern Mozambique, Aldabra Island, southwestern India. Western Pacific: Japan (southeastern Honshu) and southern Sea of Japan to China, also Indonesia (Bali), Australia (New South Wales, Victoria, Tasmania, South Australia) and New Zealand. Eastern Pacific: off northern Chile.
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FAO species catalogue Vol.4. Sharks of the world. An Annotated and Illustrated Catalogue of Shark Species Known to Date Part 1 - Hexanchiformes to Lamniformes. Compagno, L.J.V.1984FAO Fisheries Synopsis. , (125) Vol.4, Part 1.
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Size

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Maximum total length about 137 cm, size at birth about 26 cm, size at maturity about 85 cm, for males and 89 to 93 cm for females; said to reach 214 cm, but possibly in error.
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FAO species catalogue Vol.4. Sharks of the world. An Annotated and Illustrated Catalogue of Shark Species Known to Date Part 1 - Hexanchiformes to Lamniformes. Compagno, L.J.V.1984FAO Fisheries Synopsis. , (125) Vol.4, Part 1.
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Brief Summary

provided by FAO species catalogs
Marine and benthic, on the continental and insular shelves and upper slopes;depth usually between 27 to 720 m, but sometimes in shallower water close inshore and down to 1000 m. A primarily deepwater species, probably strong-swimming. Ovoviviparous, number of young 9 to 20 in a litter. Feeds on bony fishes, including hake, and squid.
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FAO species catalogue Vol.4. Sharks of the world. An Annotated and Illustrated Catalogue of Shark Species Known to Date Part 1 - Hexanchiformes to Lamniformes. Compagno, L.J.V.1984FAO Fisheries Synopsis. , (125) Vol.4, Part 1.
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Benefits

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Generally caught in some numbers as a bycatch of fisheries utilizing bottom trawls and longlines, but of small importance.
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FAO species catalogue Vol.4. Sharks of the world. An Annotated and Illustrated Catalogue of Shark Species Known to Date Part 1 - Hexanchiformes to Lamniformes. Compagno, L.J.V.1984FAO Fisheries Synopsis. , (125) Vol.4, Part 1.
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Diagnostic Description

provided by Fishbase
A narrow-headed, big-eyed small seven-gilled shark (Ref. 247). Body fusiform and slender; dorsal fin small, originating over inner margins of pelvic fins; anal fin small (Ref. 6871). Teeth wide, low and comb-shaped (Ref. 6871). Brownish grey above, paler below, sometimes with indistinct dark blotches on body; juveniles with dark-tipped dorsal and caudal fins, adults with light fin margins (Ref. 5578, 6574, 6871). Live specimens with fluorescent green eyes (Ref. 6871).
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Recorder
Cristina V. Garilao
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Life Cycle

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Ovoviviparous, number of young 9 to 20 in a litter (Ref. 247). Size at birth about 25 cm (Ref. 6871). Distinct pairing with embrace (Ref. 205). No apparent seasonality in its reproduction cycle (Ref.58048).
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Morphology

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Dorsal spines (total): 0; Dorsal soft rays (total): 0; Analspines: 0; Analsoft rays: 0; Vertebrae: 125 - 161
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Trophic Strategy

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Found on the outer continental and insular shelves and upper slopes in depths of 100 to 400 (Ref. 11230, 13573, 75154), also inshore and down to 1,000 m (Ref. 6871, 11230). Feeds on small sharks and rays, small bony fish, shrimps, crabs, lobsters, squid, and cuttlefish (Ref. 5578).
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Biology

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Found on the outer continental and insular shelves and upper slopes in depths of 100 to 400 (Ref. 13573, 11230), also inshore and down to 1,000 m (Ref. 6871, 11230). Feeds on small sharks and rays, small bony fish, shrimps, crabs, lobsters, squid, and cuttlefish (Ref. 5578). Ovoviviparous (Ref. 205), with 9-12 young born per litter (Ref. 247). Very active and aggressive when captured and quick to bite but too small to be very dangerous to people (Ref. 247). Liver utilized as a source of oil. Maximum length may reach 214 cm, but this is uncertain.
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Importance

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fisheries: minor commercial; price category: unknown; price reliability:
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分布

provided by The Fish Database of Taiwan
廣泛分布於除了東北太平洋外之世界各溫帶及熱帶海域。臺灣東北部及東部海域曾發現。
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利用

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偶由延繩釣、流刺網或底拖網捕獲,肝具豐富之油脂,但非重要之食用魚,一般以加工食之。
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描述

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體延長,前部亞圓筒形,後部稍側扁。頭稍平扁;尾基上下方無凹窪。吻中長,前緣尖突。眼大,長橢圓形,無瞬膜。鼻孔小,近於吻端。口裂寬,深弧形;上下唇褶不發達。頜齒側齒而尖銳;上頜無正中齒,每側9-10個,每齒均具一細長鉤狀齒頭,具小齒頭1-3,愈往後側具較多小齒頭;下頜正中具一齒,中央齒頭大,側齒頭細小,每側5齒,長方形,內外側具1-5小齒頭。噴水孔細小,位於眼後緣上方。鰓孔7個。背鰭一個,小而後位,起點與腹鰭後緣相對,後緣凹入,上角鈍圓,下角延長尖突;胸鰭寬大,鐮刀狀,後緣凹入,外角鈍尖,內角鈍圓;尾鰭狹長,尾椎軸低平,上葉不發達,下葉前部具顯著三角形突出,中、後部間具缺刻。體背側暗褐色;吻腹側及腹部淡色;各鰭灰褐色;背鰭上部及尾鰭末端灰黑色。
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棲地

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棲息於大陸棚或島嶼棚斜坡外緣的近、外海底棲大型鯊類,一般棲息深度在100-400公尺附近,但最深可達1,000公尺,偶被捕獲於水表層。主要以其它小型鮫類、小型硬骨魚類、甲殼類及烏賊等為食。卵胎生,一胎可產下9-20尾幼鯊,剛出生之幼鯊體長可達26公分。
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Sharpnose sevengill shark

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The sharpnose sevengill shark (Heptranchias perlo), also known as one-finned shark, perlon shark, sevengill cow shark, sharpsnouted sevengill or slender sevengill, is a species of shark in the family Hexanchidae, and the only living species in the genus Heptranchias.[3] Found almost circumglobally in deep water, it is one of the few species of sharks with seven pairs of gill slits as opposed to the usual five. The other shark species with seven gill slits is the broadnose sevengill shark. Though small, this shark is an active, voracious predator of invertebrates and fish. When caught, this species is notably defensive and will attempt to bite. It is of minor commercial importance.[4]

Taxonomy

The genus name Heptranchias is from the Greek heptra meaning "seven arms", and agchein meaning "throttle", referring to this shark's seven pairs of gill slits. Other common names for this species include one-finned shark, perlon shark, sevengill cow shark, sevengilled Mediterranean shark, sevengilled shark, sharpnose seven-gill shark, snouted sevengill shark and slender sevengill shark.[5] Some authors believe this species is distinct enough to merit its own family, Heptranchiidae.[6]

Distribution and habitat

The sharpnose sevengill shark is uncommon, but widely distributed in the tropical and temperate regions of all oceans except for the northeastern Pacific Ocean. It is found from North Carolina to Cuba, including the northern Gulf of Mexico, and from Venezuela to Argentina in the western Atlantic. In the eastern Atlantic, it occurs from Morocco to Namibia, including the Mediterranean Sea. It is reported from the Indian Ocean off southwestern India, Aldabra Island, southern Mozambique, and South Africa. In the Pacific Ocean, it is known from Japan to China, Indonesia, Australia, New Zealand, and northern Chile.[5]

This is a demersal to semipelagic species usually captured at a depth of 300–600 m (980–1,970 ft), but is occasionally found close to the surface (though these reports may represent misidentifications) or down to 1,000 m (3,300 ft). It is mainly found on the outer continental shelf and upper continental slope, and may aggregate around seamounts.[2]

Description

Usually measuring 60–120 cm (2.0–3.9 ft) long, sharpnose sevengill sharks attain a maximum length of 1.4 m (4.6 ft). This species has a slender, fusiform body with a narrow, pointed head. The eyes are very large and fluoresce green in live specimens. The mouth is narrow and strongly curved, containing 9-11 teeth on either side of the upper jaw and five teeth on either side of the lower. The upper teeth are narrow and hook-shaped with small lateral cusps, while the lower teeth are broad and comb-shaped (except for a symmetrical symphysial tooth). Unlike most other sharks, there are seven pairs of gill slits that extend onto the throat.[5][7]

A single small dorsal fin is located behind the pelvic fins, with a straight front margin, narrowly rounded tip, and concave rear margin. The pectoral fins are small with a weakly convex outer margin. The anal fin is small with nearly straight margins. The caudal peduncle is long, and the distance between the dorsal fin origin and the caudal fin is more than twice the dorsal fin base. The closely overlapping dermal denticles are very thin and transparent; each is longer than it is broad, bearing a distinct median ridge and two lateral ridges ending in marginal teeth. The coloration is brownish gray to olive above and lighter below; some individuals have dark blotches on the body or light posterior fin margins. Juveniles have dark blotches on the flank and dark tips on the dorsal fin and upper caudal lobe.[4][5]

Biology and ecology

Despite its relatively small size, the sharpnose sevengill shark is considered a top predator in the ecosystem it inhabits. At the Great Meteor Seamount in the eastern Atlantic, this species feeds primarily on teleosts and cephalopods, and to a lesser extent on small cartilaginous fishes. Off Tunisia, crustaceans are the second-most common prey taken after teleosts. Off Australia, this species consumes mostly teleosts, with smaller individuals taking mainly Lepidorhynchus denticulatus and larger individuals taking increasing numbers of snake mackerels and cutlassfishes.[8] It is a strong-swimming species, with feeding and activity level increasing at night. This species may be preyed upon by larger sharks. Known parasites of the sharpnose sevengill shark include nematodes in the genera Anisakis and Contracaecum, and the cestode Crossobothrium dohrnii.[5]

Reproduction is ovoviviparous, with no apparent reproductive season. The females give birth to litters of 9–20 pups; the newborns measure about 26 cm (10 in) long. Males mature at 75–85 cm (2.46–2.79 ft) long and females at 90–100 cm (3.0–3.3 ft). The onset of sexual maturation in males may be marked by the formation of mucus on the tips of the claspers.[4][5]

Relationship to humans

The sharpnose sevengill shark is reasonably small and is located in generally deep water, and these characteristics classify this shark as harmless to humans.[3] Small to moderate numbers of sharpnose sevengill sharks are captured as bycatch in certain deepwater commercial fisheries on longlines or in trawls.[2] They are used for fishmeal and liver oil; the meat is said to be of good quality, but the flesh is considered to be mildly poisonous when consumed.[5][7] When captured, it is very active and quick to bite, but it does not pose a substantial threat to people due to its small size.[4] It has occasionally been kept in captivity in Japan.[2]

Conservation status

Some concern exists that populations of this slow-reproducing species may be declining in areas of sustained deepwater fishing, and it has been assessed as Near Threatened by the World Conservation Union.[2] In June 2018 the New Zealand Department of Conservation classified the sharpnose sevengill shark as "At Risk – Naturally Uncommon" with the qualifiers "Data Poor" and "Secure Overseas" under the New Zealand Threat Classification System.[9]

Curiosity

On 26 September 2019, in the morning, a dead carcass was found on Torre Pali's beach, one small locality in Salento (Italy).

See also

References

Wikimedia Commons has media related to Sharpnose sevengill shark.
  1. ^ Sepkoski, Jack (2002). "A compendium of fossil marine animal genera (Chondrichthyes entry)". Bulletins of American Paleontology. 364: 560. Archived from the original on February 23, 2008. Retrieved January 9, 2008.
  2. ^ a b c d e Paul, L. & Fowler, S. (SSG Australia & Oceania Regional Workshop, March 2003). Heptranchias perlo. The IUCN Red List of Threatened Species doi:10.2305/IUCN.UK.2003.RLTS.T41823A10572878.en
  3. ^ a b "Heptranchias perlo :: Florida Museum of Natural History". www.flmnh.ufl.edu. Retrieved 2016-04-04.
  4. ^ a b c d Compagno, Leonard J.V. (1984). Sharks of the World: An Annotated and Illustrated Catalogue of Shark Species Known to Date. Rome: Food and Agriculture Organization. ISBN 92-5-101384-5.
  5. ^ a b c d e f g Bester, C. Biological Profiles: Sharpnose Sevengill Shark. Florida Museum of Natural History Ichthyology Department. Retrieved on February 16, 2009.
  6. ^ Martin, R.A. Hexanchiformes: Cow Sharks. ReefQuest Centre for Shark Research. Retrieved on February 17, 2009.
  7. ^ a b Froese, Rainer; Pauly, Daniel (eds.) (2009). "Heptranchias perlo" in FishBase. February 2009 version.
  8. ^ Braccini, J.M. (November 19, 2008). "Feeding ecology of two high-order predators from south-eastern Australia: the coastal broadnose and the deepwater sharpnose sevengill sharks". Marine Ecology Progress Series. 371: 273–284. doi:10.3354/meps07684.
  9. ^ Duffy, Clinton A. J.; Francis, Malcolm; Dunn, M. R.; Finucci, Brit; Ford, Richard; Hitchmough, Rod; Rolfe, Jeremy (2018). Conservation status of New Zealand chondrichthyans (chimaeras, sharks and rays), 2016 (PDF). Wellington, New Zealand: Department of Conservation. p. 10. ISBN 9781988514628. OCLC 1042901090.
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Sharpnose sevengill shark: Brief Summary

provided by wikipedia EN

The sharpnose sevengill shark (Heptranchias perlo), also known as one-finned shark, perlon shark, sevengill cow shark, sharpsnouted sevengill or slender sevengill, is a species of shark in the family Hexanchidae, and the only living species in the genus Heptranchias. Found almost circumglobally in deep water, it is one of the few species of sharks with seven pairs of gill slits as opposed to the usual five. The other shark species with seven gill slits is the broadnose sevengill shark. Though small, this shark is an active, voracious predator of invertebrates and fish. When caught, this species is notably defensive and will attempt to bite. It is of minor commercial importance.

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Description

provided by World Register of Marine Species
Found on outer continental and insular shelves and upper slopes in depths of 100 to 400 m, also inshore and down to 400 m. Feeds on bony fishes, sharks (Ref.6574), hake, and squid. Ovoviviparous, number of young 9 to 20 in a litter. Probably strong-swimming. Generally, very active and aggresive. Quick to bite when captured, but too small to be very dangerous to people. Livers used in Japan for oil. Maximum lengh may reach 214 cm, but this is uncertain.

Reference

Froese, R. & D. Pauly (Editors). (2023). FishBase. World Wide Web electronic publication. version (02/2023).

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Distribution

provided by World Register of Marine Species
off southern Virginia (36° 59' N, 74° 37 ' W), and south to Argentina

Reference

North-West Atlantic Ocean species (NWARMS)

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Habitat

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benthic

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North-West Atlantic Ocean species (NWARMS)

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Habitat

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Known from seamounts and knolls

Reference

Stocks, K. 2009. Seamounts Online: an online information system for seamount biology. Version 2009-1. World Wide Web electronic publication.

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