Six Gill Sharks - Hexanchus griseus

RESEARCH

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.

DESCRIPTION

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 Clark, 1995).

REPRODUCTION

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.