Pacific sleeper shark
The Pacific sleeper shark, Somniosus pacificus, is a sleeper shark of the family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

Somniosidae is a family of sharks in the order Squaliformes, commonly known as sleeper sharks.-Genera:* Centroscymnus Barbosa du Bocage & Brito Capello, 1864...

, found circumglobally on continental shelves and slopes in temperate
In geography, temperate or tepid latitudes of the globe lie between the tropics and the polar circles. The changes in these regions between summer and winter are generally relatively moderate, rather than extreme hot or cold...

 waters between latitude
In geography, the latitude of a location on the Earth is the angular distance of that location south or north of the Equator. The latitude is an angle, and is usually measured in degrees . The equator has a latitude of 0°, the North pole has a latitude of 90° north , and the South pole has a...

s 70°N
70th parallel north
The 70th parallel north is a circle of latitude that is 70 degrees north of the Earth's equatorial plane, in the Arctic. It crosses the Atlantic Ocean, Europe, Asia and North America, and passes through some of the southern seas of the Arctic Ocean....

 and 47°S
47th parallel south
The 47th parallel south is a circle of latitude that is 47 degrees south of the Earth's equatorial plane. It crosses the Atlantic Ocean, the Indian Ocean, Australasia, the Pacific Ocean and South America....

, from the surface to 2000 metres (6,561.7 ft). Its length is up to 4.4 metres (14.4 ft), although FishBase
FishBase is a comprehensive database of information about fish species . It is the largest and most extensively accessed online database on adult finfish on the web...

 accepts that it could possibly reach 7 metres (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
Alaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...

 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 sole
Sole (fish)
Sole is a group of flatfish belonging to several families. Generally speaking, they are members of the family Soleidae, but, outside Europe, the name sole is also applied to various other similar flatfish, especially other members of the sole suborder Soleoidei as well as members of the flounder...

s, flounder
The flounder is an ocean-dwelling flatfish species that is found in coastal lagoons and estuaries of the Northern Atlantic and Pacific Oceans.-Taxonomy:There are a number of geographical and taxonomical species to which flounder belong.*Western Atlantic...

s, pollock
Pollock is the common name used for either of the two species of marine fish in the Pollachius genus. Both P. pollachius and P. virens are commonly referred to as pollock. Other names for P...

s, rockfishes, shrimp
Shrimp are swimming, decapod crustaceans classified in the infraorder Caridea, found widely around the world in both fresh and salt water. Adult shrimp are filter feeding benthic animals living close to the bottom. They can live in schools and can swim rapidly backwards. Shrimp are an important...

s, hermit crab
Hermit crab
Hermit crabs are decapod crustaceans of the superfamily Paguroidea. Most of the 1100 species possess an asymmetrical abdomen which is concealed in an empty gastropod shell that is carried around by the hermit crab.-Description:...

s, and even marine snail
Snail is a common name applied to most of the members of the molluscan class Gastropoda that have coiled shells in the adult stage. When the word is used in its most general sense, it includes sea snails, land snails and freshwater snails. The word snail without any qualifier is however more often...

s. Larger Pacific sleeper sharks are found to also feed on fast swimming prey such as squid
Squid are cephalopods of the order Teuthida, which comprises around 300 species. Like all other cephalopods, squid have a distinct head, bilateral symmetry, a mantle, and arms. Squid, like cuttlefish, have eight arms arranged in pairs and two, usually longer, tentacles...

s, Pacific salmon, and harbor porpoise
Porpoises are small cetaceans of the family Phocoenidae; they are related to whales and dolphins. They are distinct from dolphins, although the word "porpoise" has been used to refer to any small dolphin, especially by sailors and fishermen...

s. The diet of the Pacific sleeper shark seems to broaden as they increase in size. For example a 3.7 ft female shark found off Trinidad, California
Trinidad, California
Trinidad is a seaside city in Humboldt County, located on the Pacific Ocean north of the Arcata-Eureka Airport and north of the college town of Arcata...

 was found to have fed mostly on Giant Squid
Giant squid
The giant squid is a deep-ocean dwelling squid in the family Architeuthidae, represented by as many as eight species...

. A 12 foot female caught off the coast of Chile
Chile ,officially the Republic of Chile , is a country in South America occupying a long, narrow coastal strip between the Andes mountains to the east and the Pacific Ocean to the west. It borders Peru to the north, Bolivia to the northeast, Argentina to the east, and the Drake Passage in the far...

 had a whole Southern Rightwhale Dolphin in its stomach. Sleeper sharks found in Alaskan waters from 6.5 to 10 feet seem to feed mostly on flounder, pollock, and cephalopods, while sleeper sharks 11 to 14 feet long seem to consume teleosts and cephalopods, as well as marine mammals. It is one of two creatures (along with the Sperm Whale
Sperm Whale
The sperm whale, Physeter macrocephalus, is a marine mammal species, order Cetacea, a toothed whale having the largest brain of any animal. The name comes from the milky-white waxy substance, spermaceti, found in the animal's head. The sperm whale is the only living member of genus Physeter...

) that feed on mature giant squid
Giant squid
The giant squid is a deep-ocean dwelling squid in the family Architeuthidae, represented by as many as eight species...

 and colossal squid
Colossal Squid
The colossal squid , sometimes called the Antarctic or giant cranch squid, is believed to be the largest squid species in terms of mass. It is the only known member of the genus Mesonychoteuthis...

, as research on the stomach contents of this shark has shown. Since the 7 m (23 ft) shark might have problems catching and devouring a 12 to 14 m (39 to 46 ft) squid, it is believed that the shark may feed on squid carcasses rather than live squid. However, it is also entirely possible that it may be able to catch live squid that are either sick or malnourished, given the squid's reduced ability to fight back under such circumstances.


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
Ovoviviparity, ovovivipary, or ovivipary, is a mode of reproduction in animals in which embryos develop inside eggs that are retained within the mother's body until they are ready to hatch...

), but gestation time is unknown and litter sizes are thought to be about 300. Its length at birth is approximately 42 centimetres (1.4 ft) or less.


Pacific sleeper sharks are reported to reach lengths of up to 25 feet. The average size is 12 feet and 700 to 800 pounds. The largest reported captured Pacific sleeper shark is 4.4 m (14 ft), although FishBase
FishBase is a comprehensive database of information about fish species . It is the largest and most extensively accessed online database on adult finfish on the web...

 accepts that it could possibly reach 7 m. In 1989, an enormous Pacific sleeper shark was attracted to a bait in deep water outside Tokyo Bay
Tokyo Bay
is a bay in the southern Kantō region of Japan. Its old name was .-Geography:Tokyo Bay is surrounded by the Bōsō Peninsula to the east and the Miura Peninsula to the west. In a narrow sense, Tokyo Bay is the area north of the straight line formed by the on the Miura Peninsula on one end and on...

, Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

 and filmed. The shark was estimated by Eugenie Clark
Eugenie Clark
Eugenie Clark , popularly known as The Shark Lady, is an American ichthyologist known for her research on poisonous fish of the tropical seas and on the behaviour of sharks.-Academic life:...

 to be about 7 m (23 ft) long.


Due to living in frigid depths the sleeper shark's liver oil
Shark liver oil
Shark liver oil is obtained from sharks that are caught for food purposes and are living in cold, deep oceans. The liver oil from sharks has been used by fishermen for centuries as a folk remedy for general health...

 contains no squalene
Squalene is a natural organic compound originally obtained for commercial purposes primarily from shark liver oil, though plant sources are used as well, including amaranth seed, rice bran, wheat germ, and olives. All plants and animals produce squalene, including humans...

 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
A triglyceride is an ester derived from glycerol and three fatty acids. There are many triglycerides, depending on the oil source, some are highly unsaturated, some less so....

 (TAG) which maintain their fluidity even at the lowest temperatures. Also, they store very little urea
Urea or carbamide is an organic compound with the chemical formula CO2. The molecule has two —NH2 groups joined by a carbonyl functional group....

 in their skin (like many deep sea sharks) but store high concentrations of trimethylamine oxide
Trimethylamine N-oxide
Trimethylamine N-oxide, also known by several other names and acronyms, is the organic compound with the formula 3NO. This colorless solid is usually encountered as the dihydrate. It is an oxidation product of trimethylamine and a common metabolite in animals. It is an osmolyte found in saltwater...

 (a nitrogenous waste product). This helps the sleeper shark stabilize protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...

s 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 known to be eaten in the wild by offshore Orca whales on British Columbia's Pacific coastline.

External links

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