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. (Bester, 2004; Compagno, et al., 2005)
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. (Compagno, et al., 2005; Ebert, 2001)
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. (Bester, 2004; Compagno, et al., 2005; Ebert, 2001)
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. (Compagno, et al., 2005; Ebert, 2001)
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. (Bester, 2004; Compagno, et al., 2005; Cox and Francis, 1997; Dulvy and Reynolds, 1997; Pogonoski, et al., 2002)
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. (Bester, 2004; Compagno, et al., 2005; Ebert, 2001)
An opportunistic predator, sharks, rays, chimeras, dolphins, porpoises, seals, bony fish such as salmon, sturgeon, herring, anchovies and mammalian carrion, including rats and humans. 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 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. (Bester, 2004; Col, 2005; Compagno, et al., 2005; Cox and Francis, 1997; Ebert, 2001; Martin, 2003; McGrouther, 2005)feeds on many prey including
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. (Bester, 2004; Col, 2005; Compagno, et al., 2005; Ebert, 2001; Martin, 2003; Bester, 2004; Col, 2005; Compagno, et al., 2005; Ebert, 2001; Martin, 2003)
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). (Bester, 2004; Col, 2005; Compagno, et al., 2005; Ebert, 2001)
Tanya Dewey (editor), Animal Diversity Web.
Zerrin Yilmaz (author), University of Michigan-Ann Arbor, Kevin Wehrly (editor, instructor), University of Michigan-Ann Arbor.
the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.
body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.
Referring to an animal that lives on or near the bottom of a body of water. Also an aquatic biome consisting of the ocean bottom below the pelagic and coastal zones. Bottom habitats in the very deepest oceans (below 9000 m) are sometimes referred to as the abyssal zone. see also oceanic vent.
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
an animal that mainly eats meat
flesh of dead animals.
uses smells or other chemicals to communicate
the nearshore aquatic habitats near a coast, or shoreline.
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
uses electric signals to communicate
union of egg and spermatozoan
A substance that provides both nutrients and energy to a living thing.
having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.
fertilization takes place within the female's body
the area of shoreline influenced mainly by the tides, between the highest and lowest reaches of the tide. An aquatic habitat.
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
makes seasonal movements between breeding and wintering grounds
having the capacity to move from one place to another.
specialized for swimming
the area in which the animal is naturally found, the region in which it is endemic.
reproduction in which eggs develop within the maternal body without additional nourishment from the parent and hatch within the parent or immediately after laying.
an animal that mainly eats fish
the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.
mainly lives in oceans, seas, or other bodies of salt water.
breeding is confined to a particular season
reproduction that includes combining the genetic contribution of two individuals, a male and a female
associates with others of its species; forms social groups.
uses touch to communicate
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
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.