Bottomfish
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Bottomfish Identification: Sharks, Skates and Ratfishes

Bluntnose Sixgill Shark
Hexanchus griseus

Caught incidentally in the commercial fishery off the outer Washington coast with longline and jig handline gear.  Recreational fishing for bluntnose sixgill sharks is closed in all Washington waters.

Description: The bluntnose sixgill shark has a heavy, powerful body with a broad head and small florescent green-blue eyes. They range in color from brown to tan to black, with darker colored spots on the sides.  This species has a light colored lateral line down the sides and on the fins’ edges.  They have one dorsal fin located near the base of the tail. The pectoral fins are broad with rounded edges. This species has six gill slits, rather than the five of most other shark species, which gives the species its name. The mouth of this species is ventral with 6 rows of lower, bladelike, comb-shaped teeth on each side.  Teeth in the upper jaw have one strong cusp and several smaller cusps, and are used for gripping food while the lower jaw saws pieces away.  As an adult the bluntnose sixgill shark can grow to a massive size, with females generally growing larger than males.

Maximum Size: To at least 550 cm (18 ft) in length, and 590 kg (1,300 lbs) in weight.  Males average between 309–330 cm (10.14–10.8 ft) in length, and females are larger, averaging between 350 and 420 cm (11.5–13.8 ft) in length. Female weight varies greatly with reproductive stage due to large litter size.

Maximum Age:  80 years old, though typical aging techniques for this species perform poorly due to low levels of calcification in most body structures.

Range/Habitat: The bluntnose sixgill shark is circumglobal: both in tropical and temperate waters. In the Eastern Pacific, they are found from the Aleutian Islands, Alaska to Baja California, Mexico. They are a highly migratory species that typically inhabits water depths greater than 90 m (300 ft), and has been recorded as deep as 1,875 meters (6,152 ft). This species is a deepsea shark, but like most fish that prefer the deep, they may move to shallower depths to feed.  In some areas, such as Puget Sound, females move into shallow water to give birth, at which time they may be encountered by divers.

Fun Fish Facts: The litter size for bluntnose sixgill sharks ranges from 22 to 108 pups!  Due to their prevalence in deepwater habitat, evidence indicates this is one of the most widespread shark species in the world.

Sources: 

  • Compagno, L.J.V., 1984. FAO Species Catalogue. Vol. 4. Sharks of the world. An annotated and illustrated catalogue of shark species known to date. Part 1 - Hexanchiformes to Lamniformes. FAO Fish. Synop. 125(4/1):1-249. Rome: FAO.
  • Humann, P. and H. Hall, 1996. Coastal fish identification: California to Alaska. New World Pubns Inc.
  • McFarlane, G. A., J. R. King, and M.W.  Saunders, 2002. Preliminary study on the use of neural arches in the age determination of bluntnose sixgill sharks (Hexanchus griseus). Fishery Bulletin – National Oceanic and Atmospheric Administration, 100(4), 861-864.
  • http://www.arkive.org/bluntnose-six-gill-shark/hexanchus-griseus/#ref3
  • http://www.fishbase.org/summary/Hexanchus-griseus.html

Photos: Veronica Von Allworden