Broadnose sevengill shark

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Broadnose sevengill shark
Notorynchus cepedianus SI4.jpg
Broadnose sevengill shark at Aquarium of the Bay
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Subclass: Elasmobranchii
Subdivision: Selachimorpha
Order: Hexanchiformes
Family: Hexanchidae
Genus: Notorynchus
Species:
N. cepedianus
Binomial name
Notorynchus cepedianus
(Péron, 1807)
Notorynchus cepedianus distmap.png
Range of the broadnose sevengill shark
Synonyms

Heptranchias haswelli* Ogilby, 1897
Heptranchias pectorosusGarman, 1884
Heptranchias spilotusLahille, 1913
Notidanus feroxPerez Canto, 1886
Notidanus indicusAgassiz, 1838
Notidanus medinaePhilippi, 1902
Notidanus wolniczkyiPhilippi, 1902
Notorynchus macdonaldiWhitley, 1931
Notorynchus maculatusAyres, 1855
Notorhynchus borealisGill, 1864
Notorhynchus ocellatusDevincenzi, 1920
Squalus cepedianusPéron, 1807
Squalus platycephalusTenore, 1809

Contents

* ambiguous synonym

The broadnose sevengill shark (Notorynchus cepedianus) is the only extant member of the genus Notorynchus, in the family Hexanchidae. It is recognizable because of its seven gill slits, while most shark species have five gill slits, with the exception of the members of the order Hexanchiformes and the sixgill sawshark. This shark has a large, thick body, with a broad head and blunt snout. The top jaw has jagged, cusped teeth and the bottom jaw has comb-shaped teeth. Its single dorsal fin is set far back along the spine towards the caudal fin, and is behind the pelvic fins. In this shark the upper caudal fin is much longer than the lower, and is slightly notched near the tip. Like many sharks, this sevengill is counter-shaded. Its dorsal surface is silver-gray to brown in order to blend with the dark water and substrate when viewed from above. In counter to this, its ventral surface is very pale, blending with the sunlit water when viewed from below. The body and fins are covered in a scattering of small black & white spots. In juveniles, their fins often have white margins.

It is also known as sevengill shark or simply sevengill and was formerly known as cow shark and mud shark; it is called sevengill due to its seven gill slits. Because of this, it was listed along with the sharpnose sevengill shark (Heptranchias perlo) by Guinness World Records as having the most gill slits. [2] It is similar to the sharpnose sevengill shark but the latter has a pointed snout and lacks spots on its dorsal surface. [3] [4] The sevengill species are also related to ancient sharks as fossils from the Jurassic Period (200 to 145 million years ago) also had seven gills. As recently as the 1930s and 1940s, the shark was targeted by fisheries along the coast of California and, once the commercial fishery receded, recreational fishing of the shark started in the 1980s and 1990s. [5]

Taxonomy

Name

The genus name Notorynchus a portmanteau is derived from the Ancient Greek νῶτον (nôton, meaning "back") prefixed to the Ancient Greek ῥῠ́γχος (rhúnkhos, meaning "snout"). [6] It has been interpreted that this refers to the spots on the broadnose sevengill's dorsal. The specific epithet cepedianus is derived from a variation of the name Lacepede, which refers to Bernard Germain de Lacépède, a French naturalist during the late 18th and early 19th century. [7] Altogether, the scientific name as a whole literally means "Lacepede's back snout".

The common name "broadnose sevengill shark" refers to the seven gill slits the species possesses and the shape of its snout. Sometimes, the name is shortened to "sevengill shark" or simply "sevengill". However, a variety of other common names are known in many languages. Other known common names in English include the bluntnose sevengill shark, broad-snout, cowshark, ground shark, seven-gill cowshark, seven-gilled shark, spotted cow shark, spotted seven-gill shark, and Tasmanian tiger shark. Common names from other languages include cação-bruxa (Portuguese), cañabota gata, gatita, tiburón de 7 gallas, tiburón pinto, and tollo fume (Spanish), ebisuzame and minami-ebisuzame (Japanese), gevlekte zevenkieuwshaai (Dutch), Kammzähner and Siebenkiemiger Pazifischer Kammzähner (German), koeihaai (Afrikaans), k'wet'thenéchte (Salish), platneus-sewekiefhaai (Afrikaans), platnez and requin malais (French), siedmioszpar plamisty (Polish), and tuatini (Maori). [3] [5]

Description

The length at birth is 40–45 cm (15.5–17.5 in) while the mature male length is 1.5 m (4.9 ft) and mature female length is around 2.2 m (7.2 ft). [1] The maximum length found is 3.3 metres (11 ft). [8] The maximum recorded weight is 182 kg (401 lb) for a 2.91-metre (9.5 ft) individual. [9] The shark is large and active and has a large head but small eyes and snout. [5] The mouth is broad and prominent. [10] The shark has one dorsal fin at the back of the body that spans from the insertion to the tops of the pelvic fins. [5] The mottled grey and white body is covered in a variable number of small black spots. [10]


Range and habitat

Range of the broadnose sevengill Notorynchus cepedianus distmap.png
Range of the broadnose sevengill

The broadnose sevengill has so far been found in the western Pacific Ocean off China, Japan, Australia, New Zealand, the eastern Pacific Ocean off Canada, United States and Chile, and the southern Atlantic Ocean off Argentina and South Africa. It is significantly found in the San Francisco Bay particularly near the Golden Gate Bridge and Alcatraz Island. [11] Large, old individuals tend to live in deep offshore environments as far down as 446 feet (136 m). However, most individuals live in either the deep channels of bays, or in the shallower waters of continental shelves and estuaries. These sharks are mainly benthic in nature, cruising along the sea floor and making an occasional foray to the surface. [12] Individuals that live closer to the coast in South Africa tend to prefer more open areas with a sandy sea floor and sparse clumps of kelp. [10]

Behavior

A broadnose sevengill shark in "Shark Alley", South Africa 170121-Sevengill-02 DSC0627 (1).jpg
A broadnose sevengill shark in "Shark Alley", South Africa

An opportunistic predator, the broadnose sevengill preys on a great variety of animals, and has been found at depths of 1,870 feet (570 meters), in offshore waters. [5] It has been found to feed on other sharks (including the gummy shark, one of its main prey choices, [13] and cowsharks), rays, chimaeras, cetaceans, pinnipeds, bony fishes and animal falls (seafloor carrion). It will also feed on anything that fits in its mouth, such as shark egg cases, sea snails, crustaceans and any remains of rats, seabirds, and even deceased drowned humans. Research in 2003 found that its diet consisted of 30% mammals, with a frequency of occurrence of 35%. [14] It is a frequent top predator in shallow waters, [15] and has comb-like teeth, [16] with the upper teeth having slender, smooth edged cusps to swallow small enough prey whole and lower teeth that are broad enough to bite flesh into pieces. [17] These sharks occasionally hunt in packs to take larger prey, using tactics such as stealth to succeed. [18] After feeding, it slowly digests for several days, and can go weeks until eating again. [19] Larger, predatory sharks (such as the great white shark) can be a threat, and cannibalism among this species has also been recorded. The species has also been observed being preyed upon by orcas in False Bay, South Africa. [20] When not actively hunting, it patrols the water, stealthily, while making very little movement except for moving its caudal fin; when prey is detected, they conserve their energy until ready to make an accelerated dash to attack. [5]

It can be one of the most abundant predators in coastal waters in summer; for example, in southeastern Tasmania, there is a high abundance of elasmobranches (including the gummy shark) in coastal regions in summer. In New Zealand, it is also one of the most common inshore sharks. [21] While it is mainly a nocturnal forager, it may opportunistically feed on prey casually found during the day; however, research in 2010 noted even amounts of activity during day and night. During this research, the shark was consistently detected at many depths, from bottom to near the surface, although it was mainly near the seafloor during the day. It also found that, as Norfolk Bay does not have adequate shelter cover, this species may use group formation to avoid predation. [13]

The sevengill, like all other members of Hexanchiformes, is ovoviviparous. The broadnose sevengill lives for about 30 years, [1] although the Washington State Department of Fish and Wildlife lists a maximum of 49 years, [22] with the males maturing at 4 to 5 years and the female 11 to 21 years; the average reproductive age for a female is 20 to 25 years. [23] After a 12-month gestation period, the female moves to a shallow bay or estuary to give birth between April and May [24] to a large litter of between 82 and 95 pups, measuring 40–45 cm (15.5–17.5 in).

In 2004 and 2005, along with research for the sand tiger shark, there was research for the broadnose sevengill shark for development techniques for semen collection and artificial insemination to potentially increase breeding and lower overreliance on natural mating. [25] Research in 2010 found that this shark has very poorly calcified vertebrae that cannot be used for age and growth estimations. [26] Research in 2009 in Ría Deseado (RD) and Bahía San Julián (SJ), Argentina found that females were larger in RD than SJ and the heaviest female in RD was 70 kg while it was 36.9 kg in SJ. For the males, the heaviest in RD was 40 kg while it was 32.5 in SJ. Both locations also found the most significant to occur December and January. [27]

Research in 2014 also found that for the first time, reproductive hormones levels were found in the broadnose sevengill shark. [28] for a few years before venturing out. The probable predators of this species are larger sharks. Research from 2002 showed that although juvenile sevengill sharks utilize nursery areas in a similar way, males mature faster than females even if they are the same size and thus males are more likely to leave the nursery area before females. [29]

In 2004, John G Maisey of the American Museum of Natural History published a detailed analysis of the broadnose sevengill shark including imagery such as CT scans and morphology of its braincase. [30]

A broadnose sevengill shark in the Aquarium of the Bay Notorynchus cepedianus.png
A broadnose sevengill shark in the Aquarium of the Bay

Conservation and relationship to humans

Painting by Frederick Schoenfeld Frederick Schoenfeld06.jpg
Painting by Frederick Schoenfeld

The broadnose sevengill is listed by the IUCN Red List as Vulnerable throughout its range. [5] This species likely suffers great ongoing pressure [1] from various types of fisheries, and from frequently being caught as bycatch. In Argentina, it's fished by rod and reel and broadnose sevengill shark fishing competitions have been occurring since the 1960s. [27] It is also threatened by water pollution and is hunted for its liveroil and hide which is considered good quality in places such as China. In the early 1980s, intense fishing in the San Francisco Bay caused a local decline. In June 2018 the New Zealand Department of Conservation classified the broadnose sevengill shark as "Not Threatened" with the qualifiers "Data Poor" and "Secure Overseas" under the New Zealand Threat Classification System. [31]

Its meat and fins are in demand in countries such as the US, Brazil, Spain, Germany, Netherlands and Israel, and is packaged for frozen food. [32] The broadnose sevengill is also a source of vitamin A and utilized by South African sport anglers for winter tournaments, however, this shark is not easy to land despite being readily hooked. [4]

It is frequently seen by tourists [33] and in temperate water aquariums and can adapt to captivity. [34] One of the aquariums that houses the broadnose sevengill shark, Oregon Coast Aquarium in Newport, Oregon, has featured it as a "keynote species". [35] There is also an app Sevengill Shark Tracking "Shark Observers" that allows divers to log sightings that are added to the Shark Observation Network, where the information supports "environmental awareness, assessment and policy making, and public participation at a global level". [36]

Not many conservation measures are known but it has been recorded from one marine reserve in South Africa and it occurs in La Jolla Cove, La Jolla, San Diego, California with the latter having an apparent population increase in 2013. [37] 2009 research also suggested that Bahía Anegada be made a conservation area given the high number of sharks there. [27] In Washington state, recreational fishing of broadnose sevengill shark is closed on all state waters. [22] In Victoria, Australia, the Department of Environment and Primary Industries sets a one bag limit and must be whole or in carcass form. [38]

The International Shark Attack File considers this shark to be potentially dangerous because of its proximity to humans, and because of its aggressive behavior when provoked. It has also been noted as being aggressive towards divers and spearfishermen in both public aquariums and the wild. In 2013, in Fiordland, New Zealand, a sevengill bit a diver's regulator and then her head. [5] [39] Human remains were also supposedly found in one specimen's stomach. Seven attacks on humans by the broadnose sevengill have been recorded since the 16th century, with no known fatalities [ citation needed ]. In 2020 a 13 year old girl was bitten while surfing at Oreti Beach in New Zealand. The girl continued to surf for an hour before realizing her leg was bleeding. [40]

Related Research Articles

<span class="mw-page-title-main">Hexanchiformes</span> Order of sharks

The Hexanchiformes are a primitive order of sharks, that numbering just seven extant species in two families. Fossil sharks that were apparently very similar to modern sevengill species are known from Jurassic specimens.

<span class="mw-page-title-main">Frilled shark</span> Species of shark

The frilled shark, also known as the lizard shark, is one of the two extant species of shark in the family Chlamydoselachidae. The frilled shark is considered a living fossil, because of its primitive, anguilliform (eel-like) physical traits, such as a dark-brown color, amphistyly, and a 2.0 m (6.6 ft)–long body, which has dorsal, pelvic, and anal fins located towards the tail. The common name, frilled shark, derives from the fringed appearance of the six pairs of gill slits at the shark's throat.

<span class="mw-page-title-main">Cow shark</span> Family of sharks

Cow sharks are a shark family, the Hexanchidae, characterized by an additional pair or pairs of gill slits. Its 37 species are placed within the 10 genera: Gladioserratus, Heptranchias, Hexanchus, Notidanodon, Notorynchus, Pachyhexanchus, Paraheptranchias, Pseudonotidanus, Welcommia, and Weltonia.

<span class="mw-page-title-main">Cookiecutter shark</span> Species of shark

The cookiecutter shark, also called the cigar shark, is a species of small squaliform shark in the family Dalatiidae. This shark occurs in warm, oceanic waters worldwide, particularly near islands, and has been recorded as deep as 3.7 km (2.3 mi). It migrates vertically up to 3 km (1.9 mi) every day, approaching the surface at dusk and descending with the dawn. Reaching only 42–56 cm (16.5–22 in) in length, the cookiecutter shark has a long, cylindrical body with a short, blunt snout, large eyes, two tiny spineless dorsal fins, and a large caudal fin. It is dark brown, with light-emitting photophores covering its underside except for a dark "collar" around its throat and gill slits.

<span class="mw-page-title-main">Prickly shark</span> Species of shark

The prickly shark is one of the two species of sharks in the family Echinorhinidae, found in the Pacific Ocean over continental and insular shelves and slopes, and in submarine canyons. Bottom-dwelling in nature, it generally inhabits cool waters 100–650 m (330–2,130 ft) deep, but it also frequently enters shallower water in areas such as Monterey Bay off California. This stocky, dark-colored shark grows up to 4.0 m (13.1 ft) long, with two small dorsal fins positioned far back on its body and no anal fin. It is characterized by a dense covering of thorn-like dermal denticles, hence its common name.

<span class="mw-page-title-main">Tetraphyllidea</span> Order of flatworms

Tetraphyllidea is a large tapeworm order that contains some 60 genera and about 800 described species. Tetraphyllideans are remarkable for their scolex morphologies, which are the most varied and morphologically complex amongst all tapeworm orders.

<span class="mw-page-title-main">Sharpnose sevengill shark</span> Species of shark

The sharpnose sevengill shark, 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.

<span class="mw-page-title-main">Port Jackson shark</span> Species of shark

The Port Jackson shark is a nocturnal, oviparous type of bullhead shark of the family Heterodontidae, found in the coastal region of southern Australia, including the waters off Port Jackson. It has a large, blunt head with prominent forehead ridges and dark brown harness-like markings on a lighter grey-brown body, and can grow up to 1.65 metres (5.5 ft) long. They are the largest in the genus Heterodontus.

<span class="mw-page-title-main">Draughtsboard shark</span> Species of shark

The draughtsboard shark is a species of catshark, and part of the family Scyliorhinidae, so named for its "checkerboard" colour pattern of dark blotches. It is endemic to New Zealand, where it is also known as the carpet shark. This shark typically reaches 1 m (3.3 ft) in length and has a thick body with a broad, flattened head and a capacious mouth. Its two dorsal fins are placed far back on the body, with the first much larger than the second.

<span class="mw-page-title-main">Australian swellshark</span> Species of shark

The Australian swellshark or draughtboard shark, is a species of catshark, and part of the family Scyliorhinidae, endemic to southern Australia. This bottom-dwelling species can be found on the continental shelf down to a depth of 220 m (720 ft). Usually measuring 1 m long, it is a stout-bodied, broad-headed shark with a short tail and a first dorsal fin much larger than the second. It can be identified by its variegated dorsal coloration of brown or grey patches and numerous spots.

<span class="mw-page-title-main">Pyjama shark</span> Species of shark

The pyjama shark or striped catshark is a species of catshark, and part of the family Scyliorhinidae, endemic to the coastal waters of South Africa. This abundant, bottom-dwelling species can be found from the intertidal zone to a depth of around 100 m (330 ft), particularly over rocky reefs and kelp beds. With a series of thick, parallel, dark stripes running along its stout body, the pyjama shark has an unmistakable appearance. It is additionally characterized by a short head and snout with a pair of slender barbels that do not reach the mouth, and two dorsal fins that are placed far back on the body. It can grow up to a length of 1.1 m (3.6 ft) long.

<span class="mw-page-title-main">Leopard catshark</span> Species of shark

The leopard catshark is a species of catshark, and part of the family Scyliorhinidae, endemic to the coastal waters of South Africa. Abundant in inshore waters under 20 m (66 ft) deep, this bottom-dweller favors rocky reefs, kelp beds, and sandy flats. Growing to a length of 84 cm (33 in), the leopard catshark has a stout body with two dorsal fins placed well back, and a short head and tail. It is extremely variable in color and pattern, with individuals ranging from almost white to black and covered by diverse patterns of black spots, blotches, rosettes, and/or lines. The color pattern changes with age and some forms seem to be location-specific, suggesting the presence of multiple distinct, local populations. In the past, some of the more distinct color forms have been described as different species.

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<span class="mw-page-title-main">Puffadder shyshark</span> Species of shark

The puffadder shyshark, also known as the Happy Eddie, is a species of catshark, belonging to the family Scyliorhinidae, endemic to the temperate waters off the coast of South Africa. This common shark is found on or near the bottom in sandy or rocky habitats, from the intertidal zone to a depth of 130 m (430 ft). Typically reaching 60 cm (24 in) in length, the puffadder shyshark has a slender, flattened body and head. It is strikingly patterned with a series of dark-edged, bright orange "saddles" and numerous small white spots over its back. The Natal shyshark, formally described in 2006, was once considered to be an alternate form of the puffadder shyshark.

<span class="mw-page-title-main">Dark shyshark</span> Species of shark

The dark shyshark or pretty happy is a species of catshark, belonging to the family Scyliorhinidae, endemic to the temperate waters off southern Namibia and western South Africa. It is benthic in nature and inhabits shallow, inshore waters and favors rocky reefs and kelp forests. Growing to 60 cm (24 in) long, this small, stocky shark has a wide, flattened head with a rounded snout and a large flap of skin extending from before the nostrils to the mouth. Its dorsal coloration is extremely variable and may feature black-edged orange to blackish saddles and/or white spots on a light brown to nearly black background.

<span class="mw-page-title-main">Tiger catshark</span> Species of shark

The tiger catshark is a species of catshark, belonging to the family Scyliorhinidae. It is found over sandy areas and near reef peripheries off South Africa and perhaps Mozambique, from close to shore to usually no deeper than 100 m (330 ft). Reaching a length of 50 cm (20 in), this small, slim shark has a broad, flattened head with an upturned snout tip. It can additionally be identified by its dorsal colour pattern of ten dark brown saddles on a yellowish brown background.

<i>Callorhinchus</i> Genus of cartilaginous fishes

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<span class="mw-page-title-main">Crossback stingaree</span> Species of cartilaginous fish

The crossback stingaree or banded stingaree is a species of stingray in the family Urolophidae. It is endemic to southeastern Australia, mainly off Victoria and Tasmania but also marginally to New South Wales and South Australia. This bottom-dwelling fish generally inhabits sand and reef habitats deeper than 100 m (330 ft) off Victoria, and muddy habitats in shallow bays and estuaries off Tasmania. Befitting its name, the crossback stingaree has a distinctive dark pattern on its back, consisting of a midline stripe that is crossed by three transverse bars. It has an oval pectoral fin disc with a blunt snout and a skirt-shaped curtain of skin between the nostrils. Its tail is short with no skin fold along the sides, and a deep, leaf-shaped caudal fin. The youngest rays may have a small dorsal fin in front of the stinging tail spine. This species reaches 50 cm (20 in) in length.

<span class="mw-page-title-main">Onefin electric ray</span> Species of cartilaginous fish

The onefin electric ray or Cape numbfish is a common but little-known species of electric ray in the family Narkidae, native to South Africa and Namibia. It is a benthic fish found in shallow coastal bays over sandy or muddy bottoms. This small species reaches 38 cm (15 in) in length, and has a nearly circular pectoral fin disc and a short, muscular tail that supports a large caudal fin. It can be identified by its single dorsal fin, which is located over the large pelvic fins. Its dorsal coloration is yellowish to dusky brown.

<span class="mw-page-title-main">Tasmanian numbfish</span> Species of cartilaginous fish

The Tasmanian numbfish is a species of electric ray in the family Narcinidae. Endemic to southeastern Australia, this common ray inhabits shallow continental shelf waters in the southern portion of its range and deeper continental slope waters in the northern portion of its range. It prefers sand and mud habitats. This species can be identified by its spade-shaped pectoral fin disc with concave anterior margins, long tail with well-developed skin folds along either side, and plain dark brown dorsal colouration. Its maximum known length is 47 cm (19 in).

References

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  8. ↑ "The Pelagic Shark Research Foundation - The Sharks of the Monterey Bay - Benthic Sharks". www.pelagic.org. Retrieved 2023-11-17.
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  11. ↑ "Fascinating Facts About Sevengill Sharks". kqed.org. August 2, 2013. Retrieved June 23, 2015.
  12. ↑ Compagno, Leonardo, Dando, Marc and Fowler, Sarah. (2005) Sharks of the World. Princeton University Press. pp. 67–68. ISBN   9780691120720
  13. 1 2 Barnett, Adam; Abrantes, Kátya G.; Stevens, John D.; Bruce, Barry D.; Semmens, Jayson M. (2010). "Fine-Scale Movements of the Broadnose Sevengill Shark and Its Main Prey, the Gummy Shark". PLOS ONE. 5 (12): e15464. Bibcode:2010PLoSO...515464B. doi: 10.1371/journal.pone.0015464 . PMC   2997065 . PMID   21151925.
  14. ↑ Crespi-Abril, A. C.; García, N. A.; Crespo, E. A.; Coscarella, M. A. (2003). "Consumption of marine mammals by broadnose sevengill shark Notorynchus cepedianus in the northern and central Patagonian shelf". Latin American Journal of Aquatic Mammals. 2 (2). doi:10.5597/lajam00038. hdl: 11336/30393 . Retrieved June 22, 2015.
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  16. ↑ Lubke, Roy; De Moor, Irene J. (1998). Field Guide to the Eastern and Southern Cape Coasts. Juta and Company Ltd. p. 139. ISBN   1919713034.
  17. ↑ Rathbone, Jim; Rathbone, LeAnn (2009). Sharks Pasta and Present. DomoAji Publications (self-published). p. 26. ISBN   978-1607029601.
  18. ↑ Ebert, D. A. (December 1991). "Observations on the predatory behaviour of the sevengill shark Notorynchus cepedianus". South African Journal of Marine Science. 11 (1): 455–465. doi: 10.2989/025776191784287637 .
  19. ↑ "Broadnose sevengill shark". montereybayaquarium.org. Retrieved June 22, 2015.
  20. ↑ Qukula, Qama (5 February 2019). "Shark-eating killer whales lurking in Cape Town's waters". capetalk.co.za.
  21. ↑ "Summer Series 6: Broadnose Sevengill Shark". National Institute of Water and Atmospheric Research. January 31, 2012. Retrieved June 22, 2015.
  22. 1 2 "Bottomfish – Broadnose sevengill shark". wdfw.wa.gov. Archived from the original on June 23, 2015. Retrieved June 22, 2015.
  23. ↑ Fowler, Sarah L. (2005). Sharks, Rays and Chimaeras: The Status of the Chondrichthyan Fishes : Status Survey. IUCN. p. 224. ISBN   2831707005.
  24. ↑ Helfman, Gene; Burgess, George H. (2014). Sharks. Johns Hopkins University. p. 121. ISBN   978-1421413105.
  25. ↑ "Grey Nurse Shark Research". waza.org. Archived from the original on June 24, 2015. Retrieved June 23, 2015.
  26. ↑ Braccini, J. M.; Troynikov, V. S.; Walker, T. I.; Mollet, H. F.; Ebert, D. A.; Barnett, A.; Kirby, N. (2010). "Incorporating heterogeneity into growth analyses of wild and captive broadnose sevengill sharks Notorynchus cepedianus". Moss Landing Marine Laboratories/California State University. Retrieved June 22, 2015.
  27. 1 2 3 Cedrola, Paula V.; Caille, Guillermo M.; Chiaramonte, Gustavo E.; Pettovello, Alejandro D. (2009). "Demographic structure of broadnose seven-gill shark, Notorynchus cepedianus, caught by anglers in southern Patagonia, Argentina". Marine Biodiversity Records. 2. doi:10.1017/S1755267209990558. hdl: 11336/103416 .
  28. ↑ Awruch, C. A.; Jones, S. M.; Asorey, M. G.; Barnett, A. (2014). "Non-lethal assessment of the reproductive status of broadnose sevengill sharks (Notorynchus cepedianus) to determine the significance of habitat use in coastal areas". Conservation Physiology. 2 (1): cou013. doi:10.1093/conphys/cou013. PMC   4806732 . PMID   27293634.
  29. ↑ "Long-term trends in catch composition from elasmobranch derbies in Elkhorn Slough, California". Marine Fisheries Review. January 1, 2007. Retrieved June 19, 2015.
  30. ↑ Maisey, John G. (February 27, 2004). "Morphology of the Braincase in the Broadnose Sevengill Shark Notorynchus (Elasmobranchii, Hexanchiformes), Based on CT Scanning" (PDF). American Museum of Natural History. Retrieved August 9, 2015.
  31. ↑ 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.
  32. ↑ Vannuccini, Stefania (1999). Shark Utilization, Marketing, and Trade. Food and Agriculture Organization. p. 282. ISBN   9251043612.
  33. ↑ Techera, Erika J.; Klein, Natalie (2014). Sharks: Conservation, Governance and Management. Routledge. p. 242. ISBN   978-1135012618.
  34. ↑ Michael, Scott W. (2005). Reef Sharks and Rays of the World. ProStar Publications. p. 341577855388. ISBN   1577855388.
  35. ↑ "Swimming with sharks: 'You're going to be in their space'". kval.com. March 31, 2012. Archived from the original on June 18, 2015. Retrieved June 18, 2015.
  36. ↑ "Shark Observation Network". scientificamerican.com. Retrieved June 23, 2015.
  37. ↑ "Sharks Attracting Attention In San Diego Waters". kpbs.org. June 4, 2013. Retrieved June 22, 2015.
  38. ↑ "Shark". depi.vic.gov.au. Archived from the original on June 26, 2015. Retrieved June 23, 2015.
  39. ↑ Turner, Anna (January 19, 2013). "Shark Attacks Diver in Fiordland". stuff.co.nz. Retrieved 21 Apr 2020.
  40. ↑ Rowe, Damian (January 17, 2020). "Girl continues to surf after possible shark bite at Oreti Beach". stuff.co.nz. Retrieved 21 Apr 2020.
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