Pacific Sleeper Shark Images in
the Shark Picture Database
Pacific Sleeper Shark, Mud Shark.
Somniosidae - Sleeper sharks.
A large, heavy bodied shark. Very low
first and second dorsal fins set well back on body. No dorsal spines. Snout
broadly rounded. A network of small white pores (probably electro-receptors or
pressure sensors) are present around the snout and behind the eyes. Light blue
eyes are often covered by a parasite. Dorsal coloration dark reddish-brown. No
counter-shading. Ventrum uniformly brown. A small spiracle is present
towards the back of the head; well behind and above eye level.
Maximum recorded length is 440cm but there are unconfirmed reports of 7m
individuals that have been seen by deepwater submersibles. If those reports are
correct, the Pacific sleeper shark would be the fifth largest shark; slightly
smaller than its Atlantic cousin the Greenland shark. Estimated size at birth is
Boreal and temperate oceans on continental shelves and slopes. A mostly demersal
species. Adults are usually found close to the substrate, whereas neonates are
often caught in mid-water implying that they inhabit this region until the grow
larger and settle onto the bottom. The Pacific sleeper shark is confined to deep
water in the warmer parts of its range. It is known to migrate vertically after
dark, occasionally entering shallow bays at night in polar regions. One
individual was found trapped in a tide pool. Maximum depth at least 2000m.
North Pacific. Found from Japan in the west, through the Kuril Islands, Sea of
Okhotsk, Bering Sea, Chukchi Sea, Coastal Alaska and southward as far as Baja
California. Reports of Pacific sleeper sharks from the southern hemisphere are
likely misidentifications of Somniosus antarcticus. Its distribution
above the arctic circle is unclear. Reports may be attributed to S.
Diet and feeding behavior:
Feeds on flatfishes, Pacific salmon, rockfish, harbor seals, octopi, squid,
crabs, tritons, and carrion. It is unclear if the Pacific sleeper shark is
capable of catching fast moving prey or if it scavenges for carcasses that have
fallen to the bottom. ts long head and oral cavity imply that it has a powerful
suction capability but the use of this attribute has not been observed in the
Pregnant females have yet to be found. This suggests that either pregnant
females reside at great depth (below the range of commercial fisheries), or
Pacific sleeper sharks have an extremely low fecundity.
Listed as Data
Deficient by the IUCN. However, this species is taken as bycatch in several
fisheries and usually discarded. It is notably affected by bottom trawl
fisheries in the western Bering Sea (Orlov 2005), by longline fisheries for
sablefish and Pacific halibut in the eastern North Pacific (Courtney et al.
2006a, b). Incidental catch in US waters in 2006 was 435 mt, in some years it
has reached ~ 1,400 mt (Courtney et al. 2006a, b).
From 1997–2001 in the Bering Sea Aleutian Islands area, Pacific sleeper sharks
were caught primarily by the Pacific cod longline fishery (30%), walleye pollock
pelagic trawl fishery (26%), Greenland turbot longline fishery (17%), flatfish
trawl fishery (12%), and sablefish longline fishery (10%). From 1997–2002 in the
Bering Sea Aleutian Islands area, Pacific sleeper sharks were caught primarily
in two statistical areas, which made up 57% and 20% of the total sleeper shark
catch. There has been an increasing trend in catch of Pacific sleeper sharks
from two statistical areas in the eastern Bering Sea between 1997-2002, however,
this may reflect a change in fishing effort as opposed to any increase in the
Fisheries in the western Bering Sea catch mainly juveniles of this species,
present at shallower depths than adults. Greater depths that are not currently
fished may provide some refuge for adult Pacific sleeper sharks, however the
situation should be monitored.
Port Fidalgo, Prince William Sound,
The Pacific sleep shark's range may overlap with the
Shark inside the arctic circle. However, it is unclear if the Pacific
sleeper is present within that region.
Reaction to divers:
Although its nightly vertical migrations make contact with divers feasible,
there are no accounts of it being encountered. During a catch and release
experimental dive in Port Fidalgo, a 4m specimen showed no interest in the diver
(me). Once released, it immediately swum back into deep water.
None. Please send any reports of encounters by divers to elasmodiver.
Ebert, D.A., Goldman, K.J. & Orlov, A.M. 2009. Somniosus
pacificus. The IUCN Red List of Threatened Species 2009: e.T161403A5416294.
on 23 June 2018.