Bluntnose sixgill shark (Hexanchus griseus) COSEWIC assessment and status report: chapter 5

Habitat

Habitat requirements

The bluntnose sixgill shark is considered to be primarily a deepwater benthic species found in waters below 91 metres (m), but is known to occur from the surface to depths of 2500 m (Ebert 2003). The species is primarily found over the outer continental and insular shelves as well as upper slopes associated with areas of upwelling and high biological productivity (Ebert 2003). 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 (Ebert 2003). Newborn pups and juveniles may often stray close to shore and occasionally occur in bays and harbours (Ebert 2003). Adult males typically remain in deeper water, where mating and courtship take place. In British Columbia, a single tagging study (n=214) in inlets along the west coast of Vancouver Island found primarily juveniles of both sexes with no mature females and a mean length for both sexes of 205 centimetres (cm) (Figures 7 and 8).  A video surveillance study in the Strait of Georgia has also observed only immature animals with a mean length of 240 cm (n=35) (Dunbrack personal communication 2006).

Figure 7. Tagging locations (red circles) of bluntnose sixgill shark along the west coast of Vancouver Islandduring a 1994 tagging survey.

Figure 7.  Tagging locations (red circles) of bluntnose sixgill shark along the west coast of Vancouver Islandduring a 1994 tagging survey. (See long description below)
Long description of Figure 7

Figure 7 is a detailed image of the Pacific Marine Fisheries Commission (PMFC) groundfish management areas within Canadian Pacific waters along the British Columbia coast. It illustrates the location of each area (3C, 3D, 4B, 5A, 5B, 5C, 5D, 5E) in varying shades of grey.

Figure 8. Length frequency distribution of male (top panel) and female (bottom panel) bluntnose sixgill sharks caught on a research survey along the west coast of Vancouver Islandin 1994. Source: Department of Fisheries and Oceans (DFO) Unpublished data.

Figure 8. Length frequency distribution of male (top panel) and female (bottom panel) bluntnose sixgill sharks caught on a research survey along the west coast of Vancouver Islandin 1994. Source: DFO Unpublished data.

Habitat trends

There are no known habitat trends of the bluntnose sixgill shark in British Columbia waters.

Habitat protection/ownership

No habitat has been specifically protected for the purpose of conserving bluntnose sixgill sharks. There are several Rockfish Conservation Areas which restrict most fishing activities; however, the use of these areas by bluntnose sixgill sharks is unknown. In the past there have been various proposals to protect areas with known high concentrations and dive tourism values but to date none have been successfully implemented (Harvey-Clark 1995).

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