Species Profile

Bluntnose Sixgill Shark

Scientific Name: Hexanchus griseus
Taxonomy Group: Fishes
Range: Pacific Ocean
Last COSEWIC Assessment: April 2007
Last COSEWIC Designation: Special Concern
SARA Status: Schedule 1, Special Concern


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Quick Links: | Description | Habitat | Biology | Threats | Protection | National Recovery Program | Documents

Image of Bluntnose Sixgill Shark

Description

The bluntnose sixgill shark, with a maximum reported length 4.8 m, is the largest predatory shark regularly encountered in Canada’s Pacific waters. It is one of four species belonging to the family Hexanchidae, sometimes called cow sharks. The name, sixgill, refers to the presence of six gill slits whereas most other shark species have only five. It is easily distinguished from other sharks as it has only a single dorsal fin, compared to two in all other shark species normally found on Canada’s Pacific coast. Its colour is a dark brown or grey to black on their back dorsal side with the colour becoming lighter towards their underside. Its head is broad and depressed with a blunt snout and its eyes are bright green.

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Distribution and Population

The bluntnose sixgill shark is one of widest ranging shark species in the world. It is widely distributed over continental and insular shelves in temperate and tropical seas across the planet. Bluntnose sixgill sharks are likely well distributed throughout much of Canada’s Pacific waters including inlets, continental shelf and slope and the Strait of Georgia. There are presently no reliable indicators for understanding bluntnose sixgill shark population in Canadian waters. The historic population size for bluntnose sixgill shark in the northeast Pacific was estimated based on genetic techniques to be about 8000, but this estimate has wide uncertainty and cannot be used to estimate current abundance. Encounter rates with immature bluntnose sixgill sharks at a shallow site in the Strait of Georgia have decreased by more than 90% over the last five years based on video surveillance and anecdotal diving records. It is unlikely the decline monitored at this site is related to by-catch mortality, but may be a distributional change related to major changes in environmental conditions such as increased water temperatures in the Strait. In Atlantic Canada this species has only been sighted twice: two immature individuals from Nova Scotia in 1989 and 1990, suggesting the species is rare in these waters, or only occurs as a vagrant.

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Habitat

Although the bluntnose sixgill shark is found from the surface to depths of 2500 m, it is primarily a deepwater species found in waters below 91 m. The species is mostly found over the outer continental and insular shelves. Young bluntnose sixgill sharks are thought to remain in shallower waters of the continental shelf and uppermost slope until they reach adolescence, at which time they move further down the slope and into deeper water. In Canada’s Pacific waters immature bluntnose sixgill sharks regularly make forays into shallow waters in some locales allowing the opportunity for scuba divers to observe them.

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Biology

Mating and courtship is believed to take place in deepwater. Bluntnose sixgill sharks are ovoviviparous, meaning the young hatch within the female’s body before being released. Females have a two-year reproductive cycle with an estimated 12-24 month gestation. The number of pups carried by females is known from only three credible accounts ranging from 47-70 pups and 61-73 cm in size. With this species females grow larger than males. Length at maturity has been reported for females to be 421-482 cm. For males length at maturity is 310 cm. Mature animals are rarely found with only one mature female recorded from northeast Pacific waters. Age of maturity is widely reported at 11-14 years for males and 18-35 years for females as is an estimated longevity of up to 80 years, but these values have not been confirmed through valid aging studies. The bluntnose sixgill shark is a generalist feeder primarily foraging nocturnally on a wide variety of prey items. Overall, movement patterns include a migration of mature individuals to shallower nursing areas to give birth. Juveniles appear to use shallower coastal waters and have extended residency in relatively small areas. Migratory behaviour on a seasonal and/or latitudinal basis has not been recorded.

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Threats

Fishing presents the only known proximate (or imminent) threat to bluntnose sixgill shark populations in Canada. Recent observer data indicates that this species is caught regularly as bycatch by fisheries pursuing halibut and spiny dogfish. There is no current bluntnose sixgill shark fishery, although the species has been the focus of at least three known directed fisheries in Canadian waters. The first occurred in the early 1920s with a focus on skins used to make shark leathers. The second took place between 1937 and 1946 with a focus on the shark livers for vitamin A. The third commercial fishery for bluntnose sixgill sharks commenced under an experimental basis in the late 1980s to early 1990s but was terminated due to conservation concerns.

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Protection

Federal Protection

More information about SARA, including how it protects individual species, is available in the Species at Risk Act: A Guide.

ProtectionThe IUCN has assessed the bluntnose sixgill shark as lower risk/near threatened (LR/nt) (Shark Specialist Group 2000). Retention and selling of bluntnose sixgill shark captured by hook and line fisheries, both commercial and recreational, in British Columbia is prohibited. In Puget Sound waters, there has been a permanent closure on the recreational and commercial take of Sixgill Sharks since 2001. Beginning in April 2006 all commercial hook and line fisheries operating in Canada’s Pacific waters became subjected to 100% at-sea monitoring coverage in the form of observers and electronic monitoring (video surveillance). Monitoring will allow for highly reliable catch estimates of non-target species including bluntnose sixgill sharks in the future. (Current observer coverage currently does not identify sharks at the species level.)

Provincial and Territorial Protection

To know if this species is protected by provincial or territorial laws, consult the provinces' and territories' websites.

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Documents

PLEASE NOTE: Not all COSEWIC reports are currently available on the SARA Public Registry. Most of the reports not yet available are status reports for species assessed by COSEWIC prior to May 2002. Other COSEWIC reports not yet available may include those species assessed as Extinct, Data Deficient or Not at Risk. In the meantime, they are available on request from the COSEWIC Secretariat.

9 record(s) found.

COSEWIC Status Reports

  • COSEWIC Assessment and Status Report on the Bluntnose Sixgill Shark (Hexanchus griseus) in Canada (2007)

    The bluntnose sixgill shark (Hexanchus griseus) is one of four species belonging to the family Hexanchidae sometimes referred to as cow sharks. The name, sixgill, refers to the presence of six gill slits whereas most other shark species have only five. The population structure of bluntnose sixgill sharks in Canada’s Pacific waters is unknown. For the purposes of this report, bluntnose sixgill sharks are considered as one designatable unit throughout Canadian waters.

COSEWIC Assessments

Response Statements

  • Response Statement - Bluntnose Sixgill Shark (2007)

    This large (maximum reported length 4.8 m), heavy-bodied shark is a benthic species that is widely distributed over continental and insular shelves in temperate and tropical seas throughout the world.  In Canadian Pacific waters, it is found in inlets and along the continental shelf and slope typically at depths greater than 91 m (range 0-2500 m).  In the absence of information about population structure, it is treated as a single population for assessment purposes.  The present population size and abundance trends are not known.  The only available abundance index, encounter rates with immature sharks at a shallow site in the Strait of Georgia, has decreased significantly (>90%) in the last five years.  This index is not likely representative of the overall abundance trend because only immature sharks are encountered and the site is shallow relative to the preferred depth range.  The principal known threat to the species is fishing.  This shark has been the focus of at least three directed fisheries in Canadian waters, most recently in the late 1980s and early 1990s.  It continues to be caught as bycatch, but survival of released sharks is unknown.  Sharks observed by divers sometimes show scars from entanglement in fishing gear.  Because of its late age of maturity (18-35 yr for females), it is likely susceptible to overfishing even at low levels of mortality.  Little is known about the abundance and movement patterns of this species elsewhere in the world, so the potential for a rescue effect is unknown.

Action Plans

  • Multi-species Action Plan for Gwaii Haanas National Park Reserve, National Marine Conservation Area Reserve, and Haida Heritage Site (2016)

    The Multi-species Action Plan for Gwaii Haanas National Park Reserve, National Marine Conservation Area Reserve, and Haida Heritage Site meets the requirements for an action plan set out in the Species at Risk Act (SARA (s.47)) for species requiring an action plan that occur inside the boundary of the site. This action plan will be updated to more comprehensively include measures to conserve and recover the marine species at risk once the first integrated Land, Sea, People management plan for Gwaii Haanas National Park Reserve, National Marine Conservation Area Reserve & Haida Heritage Site (hereafter called Gwaii Haanas) is complete. Measures described in this plan will also provide benefits for other species of conservation concern that regularly occur in Gwaii Haanas.
  • Multi-species Action Plan for Pacific Rim National Park Reserve of Canada (2017)

    Backed by the Insular Mountain Range of Vancouver Island and facing the open Pacific Ocean, Pacific Rim National Park Reserve of Canada (Pacific Rim NPR) protects and presents the rich natural and cultural heritage of Canada's west coast. Pacific Rim NPR consists of three distinct units, the Long Beach Unit, Broken Group Islands Unit, and West Coast Trail Unit, each offering a range of unique visitor experiences. With significant areas (51,216 ha in total) of old growth, temperate rainforest, coastal dune systems, wetlands and foreshore, and marine habitats, the park demonstrates the interconnectedness between land, sea, and people. These natural wonders are interwoven with the Nuu-chah-nulth First Nations culture (past and present), and that of European explorers and settlers.

Management Plans

  • Management Plan for the Bluntnose Sixgill Shark (Hexanchus griseus) and Tope Shark (Galeorhinus galeus) in Canada (2012)

    The Bluntnose Sixgill Shark (Hexanchus griseus) and Tope Shark (Galeorhinus galeus) are marine fish which were both listed as species of “special concern” under the Species at Risk Act (SARA) in March 2009. This followed the 2007 assessment of both species as “special concern” by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC). The Bluntnose Sixgill Shark is an opportunistic predator widely distributed throughout temperate and tropical seas around the world. It is likely well distributed within a wide depth range (surface to 2500 m) throughout much of Canadian Pacific waters including inlets, continental shelf and slope waters, and the Strait of Georgia.  Age of maturity is estimated to be 11-14 years for males and 18-35 years for females, with an estimated longevity of up to 80 years, and a maximum length of 350 cm (males) and 480 cm (females). Current abundance in Canadian Pacific waters is unknown.

Orders

COSEWIC Annual Reports

  • COSEWIC Annual Report - 2007 (2007)

    2007 Annual Report to the The Minister of the Environment and the Canadian Endangered Species Conservation Council (CESCC) from the Committee on the Status of Endangered Wildlife in Canada.