Bigeye sixgill shark

A shark with 6 gills formerly named Hexanchus vitulus

The Bigeye Sixgill shark (Hexanchus nakamurai) is a Cow shark of the family Hexanchidae. It is a small shark with 6 gills found in the Indian and western Pacific Oceans.


Family: Hexanchidae – Cow Sharks

Genus: Hexanchus 

Species: nakamurai


Phylum– Chordata

Class– Chondrichthyles



Common Name– Cow and Frilled Sharks

Family– Hexanchidae

Common NameCow Sharks




Average Size and Length: Length at birth for this species is 1.1-1.5 feet. Mature males average 4 feet, while mature females average 4.7 feet. The maximum recorded length is 5.9 feet.

Average Weight: Mature adults weigh around 44 pounds.

Teeth and Jaw: The mouth is narrow and ventral, and contains 5 rows of large, comb-shaped teeth in the lower jaw on each side.

Head: The head is narrow and somewhat flattened. The eyes are a fluorescent green while the shark is alive.

Tail: The upper caudal fin is much longer than the lower, with a deep notch near the tip. There is a short, ventral caudal lobe.

Demographic, Distribution, Habitat, Environment and Range: Bigeye Sixgill sharks are found in the Indian Ocean and the western Pacific Ocean in temperate and tropical seas. They live near the sea floor between 295-2,037 feet deep but may move closer to the surface at night to take advantage of prey there. They make their home on continental shelves, insular shelves, and upper slopes, occasionally inshore.

Diet: Based on the few stomach examinations of Bigeye Sixgill sharks, they are thought to feed mainly on small to moderately sized bony fish and crustaceans.

Research suggests that larger sharks may prey upon the Bigeye Sixgill shark.

Aesthetic Identification: The dorsal surface of the Bigeye Sixgill shark has a brownish-gray color and is counter-shaded ventrally. The body is small, slim, and fusiform in shape. It has 6 gill slits. This shark’s single dorsal fin is pushed back towards the caudal fin and is behind the pelvic fins. All fins have thin white margins on the edge. In juveniles, the upper caudal fin has a black tip. The body and fins are firm.

Biology and Reproduction: Bigeye Sixgill sharks have several parasite species of Monogeneans that have been found only on the gills.

Bigeye Sixgill sharks are ovoviviparous. After an unknown gestation period, it gives birth to litters of between 13 and 26 pups.

Behavioral Traits, Sensing and Intelligence: Unknown.

Bigeye Sixgill Shark Future and Conservation: Not evaluated.

Bigeye Sixgill Shark Recorded Attacks on Humans: Not a threat to humans.