Pacific sleeper shark
Large deep-sea shark of the North Pacific
The Pacific sleeper shark is a large predatory fish found in temperate and subarctic waters. It lives in deep oceans and hunts using stealth. The species grows slowly and faces threats from accidental capture in commercial fishing nets.
- Largest confirmed length is 4.65 metres
- Lives at depths up to 2000 metres
- Classified as Near Threatened by IUCN
- Feeds on salmon, squid and marine mammals
- Reaches sexual maturity at 3.5 metres
What it is
This shark belongs to the sleeper shark family. It has a robust body adapted for cold, high-pressure environments. Adults average 3.65 metres in length and weigh over 300 kilograms. The largest confirmed specimen measured 4.65 metres. Its liver contains special oils that remain fluid in freezing temperatures. The jaws are short and broad, allowing powerful bites. Upper teeth are spike-like while lower teeth have overlapping bases for sawing prey.
Where it lives
The species inhabits the North Pacific Ocean, ranging from Arctic to temperate zones. It is found between latitudes 70 degrees north and 22 degrees north. Records also exist from the western tropical Pacific near Palau and the Solomon Islands. These sharks live on continental shelves and slopes. They occupy depths from the surface down to 2000 metres. Most individuals spend their time between 200 and 600 metres deep. Water temperatures in these zones range from 3.3 to 11.0 degrees Celsius.
How it lives
Pacific sleeper sharks are generalist predators and scavengers. They hunt using stealth, gliding with minimal movement to avoid detection. Their diet includes fast-swimming fish like salmon and tuna, as well as squid and octopus. Larger sharks may eat marine mammals such as harbour porpoises. They perform vertical migrations, moving closer to the surface at night to feed. This behaviour helps them find prey in different water layers. Killer whales are known to prey on them in some regions.
Breeding and life cycle
Reproduction details remain scarce. The sharks are ovoviviparous, meaning eggs hatch inside the female. A mother may carry up to 300 eggs, but only a small fraction develop into embryos. Newborns are about 42 centimetres long and have lighter skin than adults. Sexual maturity is reached when the shark exceeds 3.5 metres in length. This late maturity contributes to their vulnerability to population declines.
Fish and people
Fisheries do not typically target this species, but it is frequently caught as bycatch. Bottom trawl and longline gear used for pollock and halibut often capture these sharks. In some areas, fishers cut lines to release entangled animals, though survival rates are uncertain. Historically, some fishers valued the liver oil. The species is classified as Near Threatened due to fishing pressure and slow reproductive rates. Most caught individuals are immature, which threatens future breeding stocks.
Status and threats
The International Union for Conservation of Nature lists the species as Near Threatened. This status reflects evidence of regional population declines and vulnerability to fishing. Slow growth and late maturity make recovery from overfishing difficult. While biomass estimates increased in the Bering Sea during the 1990s, the capture of immature sharks remains a concern. Depth separation offers some protection, as mature sharks live deeper than most commercial fishing operations.
Questions people ask about Pacific sleeper shark
How big does the Pacific sleeper shark get?
The average adult measures 3.65 metres. The longest confirmed specimen was 4.65 metres. Unconfirmed reports suggest they may reach seven metres or more, which would make them one of the largest predatory sharks.
What does the Pacific sleeper shark eat?
It is a generalist feeder. Diet includes teleost fish, cephalopods like squid and octopus, and salmon. Larger individuals may consume marine mammals such as harbour porpoises and juvenile sea lions.
Is the Pacific sleeper shark dangerous to humans?
There are no recorded attacks on humans. They live in deep, cold waters far from typical swimming areas. Their sluggish reputation and deep habitat mean interactions with people are extremely rare.
Why is the Pacific sleeper shark Near Threatened?
It grows slowly and matures late. Commercial fishing gear often catches them accidentally as bycatch. Since most captured sharks are immature, this reduces the number of animals able to reproduce.
Good reading and sources
- Pacific sleeper shark on WikipediaEncyclopedia
- More photos on Wikimedia CommonsPhotos
- Wikidata recordOpen data
The facts on this page come from the Wikipedia article "Pacific sleeper shark", written by its contributors and used under the CC BY-SA 4.0 licence, and from its Wikidata record (CC0). EveryFish rewrote the text in its own words, with AI assistance, and compares every page with the article to make sure no passage is copied. It may be reused under the same CC BY-SA 4.0 licence with a link back.
It may contain mistakes, and figures change over time. Nothing here is investment or buying advice. If something is wrong, tell us. Last refreshed 2026-11-15.
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