Notorynchus cepedianus

Geographic Range

With the exception of the northern Atlantic Ocean and the Mediterranean Sea, broadnose sevengill sharks can be found in all oceans. The distribution extends from Southern Brazil to Northern Argentina in the Southwestern region of the Atlantic Ocean, from Nambia to South Africa in the Southeastern region of the Atlantic Ocean, from Southern Japan to New Zealand in the Western Pacific zone, and from Canada to Chile in the Eastern Pacific Region. Sitings of the sevengill shark have been recorded in the Indian Ocean, however, the validity of this information is uncertain.

• Biogeographic Regions
• indian ocean
  • native native
• atlantic ocean atlantic ocean
  • native native
• pacific ocean pacific ocean
  • native native

Habitat

Sevengill sharks are a marine benthic animals associated with continental shelves. Sevengill sharks inhabit different depth ranges depending on size. Large sevengill sharks prefer to inhabit deep ocean waters offshore at depths of up to 570 m and reside in deep channels in bays. Smaller individuals prefer to inhabit shallow, coastal waters at depths of less than 1 m and are common in shallow bays near shore and estuaries. In general, sevengill sharks show a preference for rocky bottom habitats although they commonly appear in muddy and sandy environments. Sevengill sharks prefer swimming slowly at the bottom but occasionally swim at the surface.

• Habitat Regions
• temperate temperate
• tropical tropical
• saltwater or marine saltwater or marine

• Aquatic Biomes
• benthic benthic
• coastal coastal

• Other Habitat Features
• intertidal or littoral intertidal or littoral

Physical Description

Broadnosed sevengill sharks have seven gill slits (most sharks have only five) in front of the pectoral fins, have a broadly rounded head with a short blunt nose, a wide mouth beneath the snout, a single dorsal fin (most sharks have two) located far back on the body, small eyes, a heterocercal caudal fin, and an anal fin smaller than the dorsal fin. There are numerous small, black spots on the body. The back and sides of these sharks are either redish-brown to silvery grey or olive-brown and the underside is cream colored. Broadnosed sevengills have teeth in their lower jaw that are comb-shaped and teeth in their upper jaw that are jagged. Maximum reported length is 300 cm and the maximum reported weight is 107 kg. Size at birth ranges between 45 and 53 cm with males reaching maturity between 150 and 180 cm in length and females reaching maturity between 192 and 208 cm. Females are generally larger than males.

• Other Physical Features
• ectothermic ectothermic
• heterothermic heterothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• female larger

Reproduction

Courtship in sevengill sharks is complex. The exact form of courtship is unknown, but it involves the male continuously biting the female to attract her attention. Eventually, the male lies side-by-side with the female, inserts his claspers and holds on during mating by grasping onto the gill opening or pectoral fins by biting into them. What leads to courtship is unknown because it has rarely been observed.

• Mating System
• polygynandrous (promiscuous) polygynandrous (promiscuous)

The mode of reproduction is ovoviparous. Spawning frequency for broadnose sevengill sharks occurs in one clear seasonal peak per year. Females move to shallow bays to give birth after a gestation period of 12 months, which occurs during spring and early summer. Sevengill sharks have large litters of 82 to 95 young each about 40 to 45 cm in length. For the first few years, young pups remain in coastal shallow bays, which provide protection from predators, until they are mature enough to migrate to offshore environments. The average reproductive age is not known but is believed to be between 20 to 25 years in females. Females give birth every two years (every 24 months) after consecutive year-long ovarion and gestation cycles meaning the reproductive cycle is biennial.I n general, this species has low fecundity, is slow growing, gives birth to large young, matures late, lives long, and has high survival rates.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• fertilization fertilization
  • internal internal
• ovoviviparous ovoviviparous

The young are nurtured internally. The eggs hatch within the females body and the young are nourished via an independent yolk sac located within the female's uterus. Upon depletion of the yolksac, the embryo obtains nutrients from uterine secretions until birth occurs. After birth, young feed independently lacking maternal or paternal assistance, there is no post-birth parental care.

• Parental Investment
• pre-fertilization
  • provisioning
  • protecting
    • female
• pre-hatching/birth
  • provisioning
    • female
  • protecting
    • female

Lifespan/Longevity

There is little information available about the lifespan of Notorynchus cepedianus . Unfortunately, although there are significant numbers of N. cepedianus available in the wild to study, information regarding these sharks is scarce. The life expectancy of this species is expected to be about 50 years.

Behavior

Little is known about the migratory behaviors of N. cepedianus . They seem to associate in groups with other individuals of the same sex and similar size. Their movements in bays seems to be correlated with tides. In the spring and summer seasons, N. cepedianus move into bays and estuaries to mate and give birth. They leave in the fall. Tagged individuals returned to specific nursery sites seasonally.

• Key Behaviors
• natatorial natatorial
• motile motile
• migratory migratory
• social social

Communication and Perception

Although N. cepedianus is wide-spread, little is known about communication and perception among sevengill sharks. Sharks, in general, have a well-developed chemical sensory abilities, as well as being able to detect changes in water pressure and electrical currents.

• Perception Channels
• tactile tactile
• chemical chemical
• electric electric

Food Habits

An opportunistic predator, N. cepedianus feeds on many prey including sharks, rays, chimeras , dolphins , porpoises , seals , bony fish such as salmon , sturgeon , herring, anchovies and mammalian carrion, including rats and humans. N. cepedianus has many adaptations and tactics to catch prey. They hunt in groups and ambush prey by sneaking up on them and attacking at high speed. The lower jaw contains comb-shaped teeth and the teeth in the upper jaw are jagged, allowing these sharks to eat large prey. When N. cepedianus bites into its prey the jaw becomes anchored by the lower teeth and then the shark thrashes its head back and forth to saw off pieces of flesh with the upper teeth. This species slowly digest food for up to hours or days. This practice allows the shark to go for days without expending energy to hunt. As little as one-tenth of its body weight in food each month is consumed by an adult sevengill shark.

• Primary Diet
• carnivore carnivore
  • eats terrestrial vertebrates
  • piscivore piscivore

• Animal Foods
• mammals
• fish
• eggs
• carrion carrion
• mollusks

Predation

Broadnose sevengill sharks have few known predators, probably due to their large size and potential aggressiveness. Known predators are great white sharks and killer whales .

Ecosystem Roles

This species is a large predator which feeds on many prey but there little information on any ecological effects. Sevengill sharks are predators that feed at or near the top of the food chain and have few known predators ( white shark and killer whale ).

Economic Importance for Humans: Positive

Notorynchus cepedianus is a large shark and has high quality flesh which makes it a highly fished species. Sevengill sharks are used for human consumption, the skin is used for leather, and the liver is used as a source of oil.

• Positive Impacts
• food food
• body parts are source of valuable material

Economic Importance for Humans: Negative

Aggresive when provoked, N. cepedianus can potentially be considered dangerous to humans in open waters. It has been documented to have attacked divers when in captivity and may have been involved in various shark attacks off the coast of California and South Africa. However, it should be noted that these shark attacks have not been verified to have been caused by broadnosed sevengill sharks.

• Negative Impacts
• injures humans
  • bites or stings

Conservation Status

Notorynchus cepedianus is listed on the IUCN Red List as data deficient because there is not enough data to infer direct or indirect risk of extinction based on its distribution and/or population status. Therefore, more information is required before any further categorization may be employed.

Additional Links

Encyclopedia of Life

Contributors

Tanya Dewey (editor), Animal Diversity Web.

Zerrin Yilmaz (author), University of Michigan-Ann Arbor, Kevin Wehrly (editor, instructor), University of Michigan-Ann Arbor.

References

Bester, C. 2004. "Ichthyology at the Florida Museum of Natural History" (On-line). Accessed October 18, 2005 at http://www.flmnh.ufl.edu/fish/Gallery/Descript/Sevengill/Sevengill.html .

Col, J. 2005. "Enchanted Learning" (On-line). Accessed October 18, 2005 at http://www.enchantedlearning.com/subjects/sharks/species/Broadnosesevengill.shtml .

Compagno, L., D. Ebert, M. Smale. 2005. "Fishbase.org, Notorynchus cepedianus, broadnose sevengill shark" (On-line). Accessed October 18, 2005 at http://fishbase.org/Summary/SpeciesSummary.php?genusname=Notorynchus&speciesname=cepedianus .

Cox, G., M. Francis. 1997. Sharks and rays of New Zealand . Univ. of Canterbury: Canterbury Univ. Press.

Dulvy, N., J. Reynolds. 1997. "Evolutionary transitions among egg-laying, live-bearing and maternal inputs in sharks and rays" (On-line). Accessed October 19, 2005 at http://www.uea.ac.uk/bio/reynoldslab/documents/%20Dulvy_&_Reynolds_PRS_97.pdf .

Ebert, D. 2001. "California Department of Fish and Game" (On-line). Accessed October 18, 2005 at http://www.dfg.ca.gov/mrd/status/cow_sharks.pdf .

Martin, R. 2003. "Biology of Sharks and Rays" (On-line). Accessed October 18, 2005 at http://www.elasmo-research.org/education/shark_profiles/hexanchiformes.htm .

McGrouther, M. 2005. "Austrilian Museum Fish Site" (On-line). Accessed October 18, 2005 at http://www.amonline.net.au/fishes/fishfacts/fish/nceped.htm .

Pogonoski, J., D. Pollard, J. Paxton. 2002. "Conservation overview and action plan for Australian threatened and potentially threatened marine and estuarine fishes" (On-line). publications. Accessed October 19, 2005 at http://www.deh.gov.au/coasts/publications/marine-fish-action/hexanchidae2.html .

Van Sommeran, S. 2003. "Pelagic Shark Research Foundation" (On-line). Accessed October 18, 2005 at http://www.pelagic.org/montereybay/benthic/7gillshark.html .