Brown Catshark

• Maximum lengthAbout 68 cm (27 in); adults mostly 45–60 cm
• WeightNo reliable maximum published; under 1 kg
• LifespanUnknown; no validated age data
• Depth range33–1,300 m (110–4,260 ft), mostly 300–1,000 m
• DietShrimps, krill, small squid, small fish
• IUCN statusLeast Concern (assessed 2024)

How to recognise a brown catshark

A brown catshark on the sorting table is unmistakable once you have handled one: the body is so soft that it drapes over a hand, the skin is velvety rather than rough, and the whole animal is a plain, even dark brown, with the trailing edges of the fins slightly paler and sometimes almost translucent. There are no spots or bars at any age.

The head is the giveaway for the genus. The snout is long, broad and flattened, shaped like a bell or a duck's bill when seen from above, with big nostrils and small oval eyes set well back. The mouth is wide and strongly arched, and the labial furrows at its corners are long, running forward to below the eye. The teeth are minute, in many rows, each with a tall central point and a smaller cusplet on either side, the kind of dentition built for holding shrimps rather than cutting.

Along the back, both dorsal fins are small, about equal in size and set far to the rear; the first begins over the rear half of the pelvic fin bases and the second sits over the back part of the anal fin. That anal fin is the feature to look for below: long, low and broad-based, it runs most of the way to the tail and is far larger than in any dogfish or houndshark of the same coast. The tail itself is long and low with a narrow upper lobe and no obvious lower lobe. The one local shark that resembles it, the filetail catshark, has a comb of enlarged, thorn-like denticles along the top edge of its tail; the brown catshark has none.

How big is a brown catshark?

The biggest brown catsharks reliably measured are about 68 cm (27 in) long, with occasional reports up to 70 cm. Most adults taken in trawl surveys off British Columbia and California are between 45 and 60 cm, and the sexes are much the same size: males mature at roughly 45–50 cm and females at about the same length, a little larger in some samples. There is no published maximum weight; a 60 cm animal with this watery, low-density build weighs well under a kilogram, most of it water and liver oil.

Hatchlings emerge from the egg case at only 7 to 9 cm (2.75–3.5 in), which means the shark grows roughly eight-fold in length between hatching and maturity. How long that takes is unknown, because nobody has validated growth rings for the species, but deep, cold water and a sparse food supply point to slow growth and a lifespan measured in decades rather than years (see how long sharks live).

The size bar below compares the 68 cm maximum with a 1.8 m diver.

Where brown catsharks live

The brown catshark is an eastern Pacific species with its heartland in the cold water of the North American continental margin. Its northern limit is Icy Point in south-east Alaska; from there it occurs along the coast of British Columbia in Canada, Washington, including the deep basins of Puget Sound, Oregon, California, and both sides of the Baja California peninsula into the Gulf of California in Mexico. Scattered specimens have been reported from the slopes of Panama, Ecuador and Peru; those southern records are treated with caution by taxonomists and may prove to be a related species.

The depth range is wide, from 33 m (110 ft) in the cold fjords of British Columbia to about 1,300 m (4,260 ft) on the open slope, but the species is most abundant between 300 and 1,000 m, on soft mud of the outer shelf and upper slope where the water is 4–9 °C, dark and, off California and Mexico, low in oxygen. It is a bottom-dweller by preference, yet trawlers fishing for Pacific hake in midwater catch it well above the seabed often enough to show that it also swims up into the water column, presumably to feed.

Off Washington, Oregon and British Columbia it is the most commonly caught shark in deep trawl surveys. The map and the list below show where SharkSider has confirmed records.

What brown catsharks eat and how they hunt

Stomachs from trawl-caught brown catsharks are filled with small animals of the mud and the water just above it: pandalid and other shrimps, krill, small squid, amphipods, and small fish such as lanternfish and juvenile hake. Nothing large, nothing armoured, nothing that can fight back. The tiny multi-cusped teeth hold prey while the shark swallows it whole, and the strongly arched mouth gives a surprisingly large gape for an animal with such a weak bite.

Hunting happens in near or total darkness, so sight plays a small part. The long snout is packed with ampullae of Lorenzini, which detect the electric fields of buried shrimps at close range, and the large nostrils and long nasal flaps give the shark an acute sense of smell for carrion and for the scent trails of prey drifting down-current. The lateral line senses the vibration of swimming krill. A brown catshark cruises slowly a few centimetres above the mud with its snout down, and its occasional presence in midwater trawls suggests it also rises to feed on the dense layers of krill and lanternfish that hang above the slope at night.

It is itself food for larger deep-water predators, including the Pacific sleeper shark, sablefish and large rockfish, and its egg cases are vulnerable to snails and other egg predators during their long incubation on the seabed.

Behaviour and adaptations

Remotely operated vehicles working the slopes of Monterey Bay and the fjords of British Columbia have given a rare look at this species alive, and what they show is an unhurried animal. Brown catsharks are usually seen resting on the mud or swimming slowly with an eel-like sway of the long tail, and they react to lights and the vehicle's wash by drifting away rather than bolting. In the low-oxygen water off California they are often seen lying still, which is what a fish that needs to conserve oxygen ought to do.

The body reflects the same economy. Thin, watery muscle, a lightly calcified skeleton and a large oily liver bring the shark close to neutral buoyancy, so it can hover over the bottom without the constant swimming a dense-bodied shark needs. The small gills and heart are consistent with a metabolic rate a fraction of that of a shallow-water shark of the same length.

There is no evidence of schooling, though trawls sometimes bring up many at once from a productive patch of slope, and there are no documented seasonal migrations along the coast. A seasonal shift up and down the slope has been suggested from survey catches but not confirmed. Egg cases are laid in clusters on the same hard structures year after year, which hints that females return to particular spots to lay, but whether that is fidelity or simply a shortage of suitable anchor points on a muddy slope nobody has tested.

Reproduction and lifespan

The brown catshark is oviparous, and its egg cases are better known than the shark itself because they turn up in trawls and on the anchor lines and cables of moored equipment. A female produces one egg from each oviduct at a time, so eggs are laid in pairs. Each case is a flattened, translucent pouch about 5 cm long and 2.5 cm wide, olive to pale brown, with long coiled tendrils at the corners that snag on sea whips, sponges, rocks and man-made structures and hold the case in place through the current. Off British Columbia females carrying cases have been recorded from February to August, indicating a long spring-and-summer laying season.

Development inside the case is slow. The best estimate is that the embryo takes about a year to use up its yolk and hatch, and in the coldest parts of the range it may take longer; captive relatives kept in cold water have needed well over a year. The hatchling is a 7–9 cm replica of the adult, dark and soft, and it starts feeding on tiny crustaceans immediately. How many eggs a female lays in a season is not known.

Nobody has aged a brown catshark. The vertebrae of deep-water catsharks are so poorly calcified that the growth bands used for other sharks are unreadable, and no tagging study has followed individuals for years. Slow growth, a year in the egg and maturity at 45–50 cm from an 8 cm hatchling all point to a life of a decade or more, but the honest entry in the table above is "unknown".

Are brown catsharks dangerous to people?

No. The SharkSider database has no incident attributed to the brown catshark, and there is no plausible way one could occur. The species lives on deep mud where no swimmer or recreational diver goes, its jaws are weak and its teeth are the size of grains of rice, and a specimen lifted from a net hangs limp in the hand. The only people who touch it are trawler crews and survey biologists, and the only harm in that exchange is to the shark, which rarely survives the trip to the surface.

The sharks that account for the eastern Pacific's bite record, summarised on our California page, are the white shark and, far behind it, a few others; the catsharks of the deep slope are not among them. If a brown catshark ever features in a human injury it will be a fisherman's cut from the hooks in the same net, not from the fish.

The SharkSider database has no incident attributed to this species. The database draws on the International Shark Attack File, the Global Shark Attack File and verified local reports, and is updated weekly.

Conservation status

The IUCN Red List currently lists the brown catshark as Least Concern, having previously placed it in Data Deficient when almost nothing was known of its catch rates. The change reflects the volume of survey data now available from Canada and the United States, which shows a widespread species at stable abundance across a large depth range, much of it below the reach of commercial gear.

That does not mean it is unfished. The brown catshark is a routine bycatch of bottom trawls for Dover sole, thornyheads, sablefish and other deep groundfish along the whole North American coast, of midwater trawls for Pacific hake, and of deep shrimp trawls. It has no commercial value and is discarded, but a soft-bodied animal brought up from several hundred metres suffers barotrauma and crushing in the cod-end, and its survival after release is probably poor (see bycatch). Egg cases attached to the seabed are also torn loose by trawl doors and ground gear. Trawl footprints on the US and Canadian slope have shrunk since the 2000s under groundfish closures and the protection of deep coral and sponge habitat, and those measures benefit the catshark and its eggs.

The species is not listed on CITES or the Convention on Migratory Species and has no protection of its own in any country. The main gap is knowledge: without age data, fecundity or a resolved taxonomy for the southern records, nobody can say how quickly it could recover from a decline, which is the same blind spot that affects most deep-sea sharks (see why sharks are endangered).

Similar species and close relatives

The brown catshark belongs to Apristurus, the most species-rich shark genus, whose members are so alike that new ones are still being separated by vertebral counts and DNA. Its nearest neighbours in the eastern Pacific are the longnose catshark of the Gulf of California, with an even longer snout, and the tiny Panama ghost catshark, known from a few specimens off Panama and perhaps the identity behind the doubtful southern records of the brown catshark. Across the Pacific and Atlantic the genus continues with the ghost catshark, white ghost catshark, Iceland catshark and longfin catshark, all built to the same soft, dark, long-snouted pattern.

On its own coast it shares the slope with two other small catsharks that are not Apristurus: the filetail catshark, told by the crest of enlarged denticles on its tail and its larger eyes, and, in the Gulf of California, the lollipop catshark, whose swollen, gill-packed head is unlike anything else. The dogfishes of the same waters are stiff, rough-skinned and have no anal fin at all.

• Longnose Catsharkspecies profile
• Panama Ghost Catsharkspecies profile
• Filetail Catsharkspecies profile
• Lollipop Catsharkspecies profile
• Ghost Catsharkspecies profile
• Iceland Catsharkspecies profile

Written and reviewed by

SharkSider Editorial Team

A small team focused on researching sharks and making marine biology easy to understand. Every page is reviewed against current species records and the SharkSider attack database, and updated when new incidents or research appear.

Published August 27, 2022 · Last updated September 22, 2026 · No incident attributed to this species in the SharkSider attack database, which is updated weekly.