Animal Database

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Animal Database
Animal Database
Pacific Sleeper Shark
Range Continental shelves and slopes in temperate waters between latitudes 70°N and 22°N, from the surface to 2,000 metres (6,600 ft).
Scientific Classification
Kingdom Animalia
Phylum Chordata
Class Chondrichthyes
Order Squaliformes
Family Somniosidae
Genus Somniosus
Species S. pacificus
Conservation Status
Data Deficient

The Pacific sleeper shark, (Somniosus pacificus), is a sleeper shark of the family Somniosidae, found circumglobally on continental shelves and slopes in temperate waters between latitudes 70°N and 22°N, from the surface to 2,000 metres (6,600 ft). Its length is up to 4.4 m (14 ft), although fishbase accepts that it could possibly reach lengths in excess of 7 m (23 ft).

Feeding Habits[]

Pacific sleeper sharks, which are also known scavengers, can glide through the water with little body movement and little hydrodynamic noise making them successful predators. They feed by suction and cutting of their prey. They have large mouths that can inhale prey and their teeth cut up any pieces that are too large to swallow. They show a characteristic rolling motion of the head when feeding. Only in Alaska has the shark’s diet been studied - most sharks' stomachs contain remains of giant pacific octopus. They are also known to feed on bottom-dwelling teleost fishes as well as soles, rockfishes, shrimps, hermit crabs, and even marine snails. Larger Pacific sleeper sharks are also found to feed on fast swimming prey such as squids, pacific salmon, and harbor porpoises. The diet of the Pacific sleeper shark seems to broaden as they increase in size. For example, a 3.7 m female shark found off Trinidad, California was found to have fed mostly on giant squid. Sleeper sharks found in Alaskan waters from 2 to 3 m (6.6 to 9.8 ft) seem to feed mostly on flounder, pollock, and cephalopods, while sleeper sharks 3.3 to 4.25 m (11 to 13.9 ft) long seem to consume teleosts and cephalopods, as well as marine mammals.


There is very little known about the early life of Pacific sleeper sharks. Pacific sleeper sharks are believed to produce eggs that hatch inside the female’s body (reproduction is ovoviviparous), but gestation time is unknown and litter sizes are thought to be about 10 pups. Its length at birth is approximately 42 cm (1.38 ft) or less.


Pacific sleeper sharks are reported to reach lengths of up to 25 feet. The average mature size is 3.65 m (12.0 ft) and 318–363 kg (700–800 lb). The largest Pacific sleeper shark verified in size measured 4.4 m (14 ft) long and weighed 888 kg (1,960 lb), although FishBase accepts that it could possibly reach 7 m or more. In 1989, an enormous Pacific sleeper shark was attracted to a bait in deep water outside Tokyo Bay, Japan and filmed. The shark was estimated by Eugenie Clark to be about 7 m (23 ft) long.


Due to living in frigid depths the sleeper shark's liver oil contains no squalene because it would solidify into a dense, non-buoyant mass. Rather than squalene, the low-density compounds in the sharks' liver are diacylglyceryl ethers (DAGE) and triacylglycerol (TAG) which maintain their fluidity even at the lowest temperatures. Also, they store very little urea in their skin (like many deep sea sharks) but store high concentrations of trimethylamine oxide (a nitrogenous waste product). This helps the sleeper shark stabilize proteins that make up swimming muscles, digestive and reproductive hormones against the crushing pressure and intense cold of the deep sea. Because food is relatively scarce on the deep sea floor the sleeper shark is able to store food in its capacious stomach. The sleeper shark’s jaws are able to produce a powerful bite due to their short and transverse size. The upper jaw teeth of the sleeper shark are spike-like, while the lower jaw teeth are oblique cusps and overlapping bases. This arrangement allows grasping and sawing of food too large to swallow. Pacific sleeper sharks have a short caudal fin which allows them to store energy for fast and violent bursts of energy to catch prey.

Known Predators[]

Sleeper sharks are preyed upon by the offshore eco-type of killer whales off British Columbia.