Common
Names:
Sixgill shark, Sixgilled shark, Bluntnose sixgill shark, Cow shark.
Latin
Name:
Hexanchus griseus
Family:
Hexanchidae
Identification:
Six gill slits.
Single
dorsal fin position
set well back above anal fin.
Heavy
set body.
Round pupils reflect a
luminous green.
Size:
4.8m maximum. Possibly exceeding 1500lb.
Habitat:
Temperate and tropical seas. Usually at great depth (down to 2000m) but
occasionally encountered on shallow shelves close to deeper water.
Abundance
and distribution:
Found worldwide but seldom encountered
outside of Pacific Northwest North America.
Behavior:
Habits little known. Aiden Martin reports to have seen one individual stalking a
lingcod from below a shelf until it rose up and pinned the fish from behind onto
the reef and devoured it.
Reproduction:
Observations:
I have witnessed this shark
approaching divers from behind apparently out of curiosity as no aggressive
behaviour has been observed.
Photographs:
Henderson Point, Saanich Inlet, Vancouver Island, Canada.
Similar species:
Reaction to divers:
A slow moving species that rarely reacts aggressively to divers but will swim
away when closely approached. Baited encounters at the Seattle Aquarium report
that in these situations the Bluntnose sixgill changes into a lightning fast
predator.
Diving
logistics: The
sixgill is a difficult shark to encounter outside of the Pacific Northwest as it
remains at great depth. From Washington State up to Northern Vancouver Island it
can be encountered mainly in the summer months. Hornby Island in the Straits of
Georgia between Vancouver Island and the BC mainland is the place best known for
encounters but many divers return frustrated by this illusive shark. Another
good spot for encounters is the fiord north of Victoria known as the Saanich
Inlet. On the west side of the Saanich Peninsula are 3 well known entry points
that each are responsible for Sixgill sightings. Amongst these Henderson Point
has probably seen the most sharks with 15 or more sightings occurring during the
summer of 2004. Shore diving information and air can be had from various dive
shops around Victoria including Ogden Point Dive Centre located at the
Breakwater close to town.
Other diving locations submitted by
readers:
References
and further
reading:
Reef
Sharks and Rays of the World. Scott W. Michael. Sea Challengers.
Sharks
and Rays - Elasmobranch Guide of the World. Ralf M. Hennemann. IKAN.
