Field Guide - Pacific Sleeper Shark
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Pacific Sleeper Shark
Somniosus pacificus
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Order: Squaliformes
Family: Somniosidae
Genus: Somniosus
Species: pacificus
Description: In Alaskan waters, the Pacific sleeper shark is found in the Bering Sea, the Aleutian Islands, and the Gulf of Alaska. This species is closely related to the Greenland shark and there may be difficulty distinguishing between species in the Arctic where their ranges may overlap. It is usually found close to the surface in the Arctic, but can dive to depths as deep as 2,000 meters. Sleepers are not considered economically valuable to commercial fisheries.
Population status: The population stability of this species is currently unknown. Some sharks are caught as bycatch in trawls and long-line fisheries in the Arctic.
General characteristics: Black or blackish brown, averages 12 feet and 700–800 pounds, but can vary greatly, no anal fin and no dorsal spines, the upper teeth are long, narrow, and sharp, the lower teeth are short with low cusps, and most specimens have had infections from a large parasitic copepod that attaches to the cornea.
Female defining traits: No claspers.
Male defining traits: Has 2 claspers near the tail base for sperm transfer.
Juvenile defining traits: Smaller (young at birth ~1.3 feet) and found in shallower waters than adults.
Diet in the wild: Squid, octopus, various fish and crab species, amphipods, and some marine mammals such as harbor seals.
Reproductive cycle: Very little is known but evidence available suggests that females are not sexually mature until approximately 12 feet. Brood size is thought to be large.
Predators in the wild: Unknown.
Similar species: Greenland shark.
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Related Links & Sources
Assessment of the sharks in the Bering Sea and Aleutian Islands
The Sharks of North America
Castro, José