|Scientific Name:||Hexanchus griseus|
|Species Authority:||(Bonnaterre, 1788)|
Squalus griseus Bonnaterre, 1788
|Red List Category & Criteria:||Near Threatened ver 3.1|
|Assessor(s):||Cook, S.F. & Compagno, L. J.V.|
|Reviewer(s):||Musick, J.A. & Fowler, S.L. (Shark Red List Authority)|
This assessment is based on the information published in the 2005 shark status survey (Fowler et al. 2005).
The Bluntnose Sixgill Shark (Hexanchus griseus) is wide ranging, although patchily distributed, in boreal, temperate and tropical seas. It is a deep-benthic, littoral and semipelagic shark, not known to be epipelagic. Young are often found close inshore, adults often in deeper water, although adults and sub¬adults are known to enter shallow water in bays with adjacent deepwater canyons. In tropical areas it tends not to penetrate coastal waters. Largely caught as a bycatch of other fisheries, this is also a valuable food and sports fish that appears very vulnerable to overfishing, unable to sustain intensive, targeted fisheries for long periods. Some regional populations have been severely depleted, e.g. in the Northeast Pacific. However, population and fisheries data are lacking from many regions.
|Range Description:||This species is widely but disjunctly distributed in temperate and tropical seas of the continental and insular shelves of the Pacific, Atlantic (including the type locality in the Mediterranean Sea) and Indian Oceans. It occurs from the surface to at least 2,000 m, on continental and insular shelves and upper slopes (including sea mounts).|
Native:Bermuda; Canada (British Columbia); United States (California, Oregon, Washington)
|FAO Marine Fishing Areas:||
Atlantic – northeast; Atlantic – eastern central; Atlantic – southwest; Atlantic – southeast; Atlantic – northwest; Atlantic – western central; Indian Ocean – western; Indian Ocean – eastern; Mediterranean and Black Sea; Pacific – southeast; Pacific – northeast; Pacific – northwest; Pacific – eastern central; Pacific – southwest
|Range Map:||Click here to open the map viewer and explore range.|
|Habitat and Ecology:||
A capable predator, the Bluntnose Sixgill Shark feeds on a wide variety of animals including other sharks (it is known to attack hooked conspecifics, which it sometimes follows to the surface from depth), skates, rays, chimaeras, dolphinfish, small swordfish and marlins, herring, grenadiers, antimoras (codlings), rockfishes, cod, lingcod, hake, flounders, halibut, turbot, gurnards and anglerfish, as well as many types of invertebrates including squid, crabs, sea cucumbers and shrimp. It also eats carrion and sometimes seals (Ebert 1994). The bluntnose sixgill shark has not been involved in shark bite incidents on humans, but has been known to swim up to and examine divers (off southern Vancouver Island, British Columbia, Canada) and rarely surfers (Cannon Beach, Oregon, USA) without threat or physical contact (C. Bond pers. comm. 1985). Small specimens thrash and snap when captured, but large individuals offer little resistance. This shark appears to become increasingly sensitive to light with increasing size. Adults may become highly agitated when exposed to even moderately intense light. However, this phenomenon needs much more investigation, since the species has been observed and/or photographed from research submersibles off Bermuda and California in well-lighted situations (floodlights) without undue agitation or avoidance of lighted areas (B. Lea pers. comm.).
The species is ovoviviparous, bearing very large litters numbering from 22-108 young, size at birth 65-74 cm. Males mature at about 315 cm and females at about 420 cm. Longevity, pupping interval and mating behaviour are unknown. Pupping grounds apparently occur on the upper slopes and outer continental shelves. Since this species preys on conspecifics opportunistically, some mechanism of separation of larger and smaller individuals undoubtedly occurs (Ebert 1994). Young tend to be found in shallow waters often just off the shore, but as they grow they move into successively deeper waters. Adults tend to follow diurnal patterns of vertical distribution, sitting deep on the bottom by day and coming toward or to the surface at night to feed. As for many species of deep-water sharks, it is unknown whether this species segregates by sex.
|Major Threat(s):||Due to its broad depth range and relative sluggishness, this shark has often been captured incidentally in fisheries for other species. It is taken by handline, longline, gillnet, traps, trammel net, and both pelagic and bottom-trawls. When captured it is often smoked in the Pacific Northwest U.S. (Washington State) and Italy to produce a fine cured product, usually for export to European markets. It is occasionally used for meat and liver oil in Australia (Last and Stevens 1994). Additionally, it has been used for salted and dried food products, as well as fish meal and pet foods. Uses of fins may exist but are unreported. This species has been sought for sport fisheries in deeper parts of San Francisco Bay, California, USA (beneath the Golden Gate Bridge), as well as in deeper bays of Oregon and Washington States (Compagno in prep. a). This species is widely believed not to be capable of sustaining either sport or commercial fisheries efforts. Attempts to develop directed fisheries for the bluntnose sixgill shark have rapidly collapsed in California waters, usually lasting less than three years (Compagno in prep. a). Attempts to manage the sport fishery for the hexanchids in San Francisco Bay have been hampered by unusual rules that did not regulate the catch of these sharks per boat, but rather set the quotas at fish per person-pole. It has not been uncommon to see boats on the Bay loaded "to the gunwales" with fishermen to justify the number of poles aboard. The sixgill shark population in San Francisco and Humboldt Bays of California and Puget Sound complex of Washington was considered to be in serious decline in 1995 as a result of fishery activity. Development of a fishery for bluntnose sixgill in British Columbia is being explored, as a replacement for other traditional bony fish and elasmobranch fisheries that are now in decline. This has proceeded despite strong concerns voiced by fishery biologists as to the unsustainability of such fisheries historically (K. Wolf pers. comm.).|
|Citation:||Cook, S.F. & Compagno, L. J.V. 2005. Hexanchus griseus. The IUCN Red List of Threatened Species. Version 2015.2. <www.iucnredlist.org>. Downloaded on 31 July 2015.|
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