Hexanchus griseus (Bonnaterre, 1788)
Bluntnose sixgill shark
Hexanchus griseus
photo by Murch, A.

Family:  Hexanchidae (Cow sharks)
Max. size:  600 cm TL (male/unsexed); max.weight: 590 kg
Environment:  bathydemersal; marine; depth range 1 - 2500 m, oceanodromous
Distribution:  Circumglobal with patchy distribution and possibly absent from Arctic and Antarctic. Highly migratory species.
Diagnosis:  Dorsal spines (total): 0-0; Dorsal soft rays (total): 0-0; Anal spines: 0-0; Anal soft rays: 0-0. A heavily-bodied, broad-headed sixgill shark, mouth ventral with 6 rows of lower, bladelike, comb-shaped teeth on each side (Ref. 247). Snout broadly rounded, body fusiform (Ref. 6871). Anal fin smaller than dorsal fin (Ref. 6871). Brown or grey above, paler below, with a light stripe along side (Ref. 26346). Fins with white edges (Ref. 6574). Live specimens with fluorescent green eyes (Ref. 6871). Six gill slits are very long (Ref. 35388).
Biology:  Depth range reported at 0m-2500m (Ref. 125614). A deepwater species of the outer continental and insular shelves and upper slopes (Ref. 6871, 75154), islands, seamounts and mid-ocean ridges (Ref. 125614). Near bottom, occasionally pelagic, adults usually below 91 m (Ref. 58302). Juveniles may be found close inshore (Ref. 6871), while nursery areas are in very shallow waters (Ref. 125614). Found on the bottom by day, moving to the surface at night to feed, and where it may take longlines set for other species (Ref. 45445). Depth distribution related to growth and temperature, with juveniles having most shallow records and from colder, poleward regions (Ref. 58302). Generally occurs at a bottom temperature of 6 to 10°C (Ref. 125614). Feeds on a wide range of marine organisms, including other sharks, rays, chimaeras, bony fish, squids, crabs, shrimps, carrion, and even seals (Ref. 26969). Large sharks (at least 2m) take cetaceans and seals. Viviparous, very large litters of 47-108 pups (Ref. 125614). Give birth to almost 100 young (Ref. 35388). Young and adults may be segregated, with the young using inshore nursery grounds. Possibly long-lived (Ref. 125614). Is a eurytrophic predator that is capable of exploiting a wide range of prey species and habitats (Ref. 26969). A vertical migrant, it may sit on the bottom by day, and rise to the surface at night to feed (Ref. 247). It occurs alone or in groups. Adults are more sensitive to light than the juveniles and less seen in clear shallow waters, but more prevalent at night or areas with dense plankton blooms (Ref. 125614). It is locally common in bycatch and target fisheries for food, fishmeal and oil, and in sports fisheries, but vulnerable to overfishing and requires careful management (Ref. 125614). Marketed fresh, frozen, or dried salted (Ref. 247). Not known to have attacked people without provocation (Ref. 247).
IUCN Red List Status: Near Threatened (NT); Date assessed: 21 November 2019 (A2bd) Ref. (126983)
Threat to humans:  other
Country info:  Recorded from specimens taken from Bukana, Sikayab, Dapitan City; Pamilacan Islands (Ref. 47737). Occurrence based on map distribution (Ref. 125614). Also Ref. 280, 13573.

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