Bigeyed Sixgill Shark

About the Bigeyed Sixgill Shark

The Bigeyed Sixgill Shark is a rare deepwater cow shark often misidentified as the larger Bluntnose Sixgill Shark. Very little is known about this shark, with a poor knowledge of its distribution and no knowledge of population trends.

Description and Biology

The species can be identified by its narrow, pointed head, large eyes, six gill slits and single dorsal fin. Its body is generally slender, with a dark brownish-gray or gray upper surface that becomes lighter underneath.

Adults can reach approximately 180 cm (5.9 ft) in total length. Males mature at approximately 123–157 cm (4.0–5.2 ft) and females at around 142–178 cm (4.7–5.8 ft). The species feeds on bony fishes, tuna and crustaceans.

Habitat

The Bigeyed Sixgill Shark is found in tropical and warm-temperate waters in the Atlantic Ocean, the Mediterranean Sea, the western Pacific Ocean and the Indian Ocean. They are found at depths ranging from 0 to 702 m (0–2,303 ft), but mostly occur between 60 and 620 m (197–2,034 ft).

Reproduction

The species is ovoviviparous, meaning that the embryos develop inside the mother without a placenta. Females produce between 13 and 26 pups per litter, with newborns measuring approximately 40 to 43 cm (15.7–16.9 in) in total length at birth.

Conservation

Although it is infrequently reported as bycatch in bottom trawls, longlines and other fishing gear, its possible misidentification with other sixgill sharks makes the extent of its interaction with fisheries difficult to assess. The Bigeyed Sixgill Shark is listed as Near Threatened by the IUCN partly because of suspected population declines associated with its overlap with fishing pressure.

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