Six Gill Sharks - Hexanchus griseus
Depth telemetry, diet studies and surveys of basic biological aspects
of the sixgill have been conducted. However, relatively few data exist
concerning this shark, probably due to its deep water habitat.
The sixgill shark (Hexanchus griseus) is a common species of
deep water shark and one of the largest nonplankton feeding sharks. Sixgills
are distributed worldwide in temperate and tropical seas and are typically
found below depths of 100 meters. Several reports have identified sixgills
at depths greater than 2500m. Adults reach a total length of at least 4m.
Color ranges from dark brown to dark silvery gray, and they posess large,
opalescent eyes. Although unconfirmed, it is suspected that sixgills have
the ability to change their color for short periods of time (Ebert, 1994).
Such a characteristic would be advantageous to these slow swimming and
wide ranging predators in order to camouflage themselves in different habitats
and approach fast swimming fish undetected. Sixgills feed on a wide variety
of prey. A diet study of sixgills conducted off southern Africa revealed
that the most important prey items include cephalopods, crustaceans, bony
and cartilaginous fish, and marine mammals (South African fur seals, hake,
dolphins; Ebert, 1994); though the marine mammals may have been scavenged.
They are not considered dangerous to humans unless provoked (Carey and
Females reach maturity at approximately 450cm and may give birth to
up to 108 pups. At birth the size of the pups is 65-70cm (Ebert, 1986).
RELATIONSHIP TO MAN
Though edible, there have been no large-scale fisheries developed for
this species, probably because of its deep-water habitat.