Somniosus pacificus, Pacific Sleeper Shark [+]
Kingdom Animalia
Phylum Chordata
Class Elasmobranchii
Order Squaliformes
Family Somnosidae
Genus Somniosus
species: Somniosus pacificus [+ITIS +WoRMS]
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Description & Behavior
The Pacific sleeper shark, Somniosus pacificus (Bigelow and Schroeder, 1944), is a large deep-water shark reaching about 4.4 m in length for males and 4.3 m for females. It is thought that this species can reach up to 7 m. The Pacific sleeper shark is dark gray to black with blue-black fins. The snout is short and rounded, the body is cylindrical, and the 2 dorsal fins are equal in size. The first dorsal fin is closer to the pelvic fins than the pectoral fins. Small precaudal fins are also present and the caudal fin is asymmetrical with a well-developed ventral lobe.
World Range & Habitat
The Pacific sleeper shark, Somniosus pacificus, can be found in temperate waters between 70°N-47°S in the North Pacific from Japan, along the Siberian coast to the Bering Sea and in southern California USA, Baja California, and Mexico. There are some sightings reported in the South Pacific. In Australasian waters, the Pacific sleeper shark is found from the seamounts south of Tasmania to the Challenger Plateau off eastern New Zealand, and possibly to Macquarie Island. In the southwest Atlantic they are seen off the coast of Uruguay.
This species prefers to inhabit continental shelves and slopes. At higher latitudes, the Pacific sleeper shark can be found in littoral and even intertidal areas; in lower latitudes its depth ranges down to at least 2,000 m.
Feeding Behavior (Ecology)
The Pacific sleeper shark, Somniosus pacificus, feeds on bottom fishes, octopuses, squids (including the giant squid and their even bigger relative, the colossal squid), crabs and tritons; and occasionally on harbor seals and carrion.
Life History
The Pacific sleeper shark, Somniosus pacificus, is thought to be ovoviviparous. Pups measure about 42 cm or less.
Ovoviviparous: eggs are retained within the body of the female in a brood chamber where the embryo develops, receiving nourishment from a yolk sac. This is the method of reproduction for the "live-bearing" fishes where pups hatch from egg capsules inside the mother's uterus and are born soon afterward. Also known as aplacental viviparous.
Conservation Status/Additional Comments
The Pacific sleeper shark, Somniosus pacificus, is harmless to humans. The flesh of this species contains a toxin which can cause symptoms of intoxication.
References & Further Research
BioOne ~ CITES ~ Discover Life ~ GBIF ~ Google Scholar ~ ITIS ~ IUCN RedList ~ MarineBio Network ~ NCBI ~ SCIRIS ~ SIRIS ~ Tree of Life Web Project ~ Wikipedia
Arctic Science Journeys Radio: Sleeper Sharks Not So Sleepy
Pacific Sleeper Sharks - CONSERVATION SCIENCE INSTITUTE
Antarctic jaws: cephalopod prey of sharks in Kerguelen waters, Deep Sea Research Part I: Oceanographic Research Papers, Volume 51, Issue 1, January 2004, Pages 17-31, Yves Cherel and Guy Duhamel
Primary photo above: Sleeper shark observed by ROV Tiburon at about 1076 meters depth on the Patton Escarpment, MBARI Seamounts Cruise, May 7, 2004
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