Common
Names: Bigeye sixgill shark, Sixgill shark,
bigeyed sixgill, cow shark.
Latin
Name:
Hexanchus nakamurai
Family:
Hexanchidae
Identification:
Six gill slits.
Sender body (compared to H.griseus). Single
dorsal fin
set well back above anal fin.
Caudal fin with distinct lower lobe and deeply notched upper lobe.
Large round pupils reflect a
luminous green. Five rows of large comb shaped teeth.
Size:
180cm maximum.
Size at birth 40-43cm.
Habitat:
Temperate and tropical seas. Usually at great depth (90 to 620m). Long line
collection in Cape Eleuthera by Edd Brooks (Cape Eleuthera Institute) indicates
that bigeye sixgill sharks may inhabit greater depths than previously recorded.
Abundance
and distribution:
Found worldwide - Western Atlantic from Florida, Bahamas, Northern Caribbean,
Atlantic Panama and Costa Rica and Venzuela to Northern Brazil. Eastern Atlantic
from Southern Europe to North Africa including much of the Mediterranean Sea.
Indian Ocean off of East Africa and Western Australia and in the Western Pacific
from Japan and the Philippines and Eastern Australia. Not recorded in the
Eastern Pacific. Distribution records are patchy because the bigeye sixgill shark is
a rarely caught species. Many isolated pockets in this species' range may
eventually be linked once more catch data becomes available.
Red List Status: Data deficient. Sometimes taken as bi-catch in
line fisheries and as part of the artisanal shark fishery in the Gulf of Mexico.
Diet:
Small to medium sized bony
fishes and crustaceans.
Reproduction:
Ovoviviparous.
13-26 pups per
litter.
Photographs:
Cape Eleuthera, Bahamas. Photographed during a tagging study conducted by Edd
Brooks of the
Cape Eleuthera Institute.
Similar species: Bluntnose
sixgill Hexanchus griseus. The bluntnose sixgill shark can be identified
by its generally larger size and stockier body, its indistinct lower caudal lobe
and lack of a notch in the upper caudal lobe.
Reaction to divers:
Not applicable however a captured specimen showed aggressive behavior when
manhandled during release.
Diving
logistics: Not applicable
References
and further
reading:
IUCN
Red List of Endangered Species:
http://www.iucnredlist.org/apps/redlist/details/161352/0
Cape
Eleuthera Institute Shark Ecology Program
http://www.ceibahamas.org/shark-ecology.aspx
