Atlantic Sawtail Catshark

• Maximum length45 cm (18 in); males mature at about 38–42 cm, females 40–45 cm
• WeightNo published maximum; a few hundred grams
• LifespanUnknown; no ageing study exists
• Depth rangeAbout 330–800 m (1,080–2,600 ft), mostly 400–600 m
• DietShrimps and other crustaceans, small bony fishes, squid
• IUCN statusNear Threatened (assessed 2020)

How to recognise an Atlantic sawtail catshark

At first glance you are looking at a small blackmouth catshark, and that is exactly the problem. Both are slender, soft-skinned sharks with a flattened head, a long narrow snout, large oval eyes with a nictitating lower lid, and a back marked with a row of dark saddles and blotches on a grey or fawn ground, white below. Both have the mouth lining pigmented black, and both carry the mark of the genus Galeus: a crest of enlarged, tooth-like denticles along the upper edge of the caudal fin, the "saw" of sawtail. The two dorsal fins are small and roughly equal with pale rear margins, the first over the pelvic fins and the second over the rear of the long, low anal fin.

The characters that separate the Atlantic sawtail are subtle and best seen on the underside of the head. The furrows at the corners of the mouth are pigmented dark in G. atlanticus and pale in the blackmouth; the nostrils sit slightly further back from the snout tip; and the crest of denticles on the tail differs in detail. Size helps: a blackmouth catshark grows to 90 cm, twice the Atlantic sawtail, so any mature Galeus under 45 cm in the Alborán Sea deserves a second look. The clincher is genetic: a 2007 study of mitochondrial DNA showed the two are distinct lineages, ending a century of confusion since Léon Vaillant described the species in 1888 from a specimen taken off north-west Morocco.

The teeth are tiny, each with a central cusp flanked by one or two small cusplets on each side, set in many rows in both jaws.

How big does the Atlantic sawtail catshark get?

It is one of the smaller sharks in European waters. The largest specimen reliably measured was 45 cm (18 in) total length, and most adults trawled in the Alborán Sea are between 35 and 42 cm. The old figure that mature males run 38 to 42 cm and females 40 to 45 cm is about right, although the smallest mature individuals in a large Spanish sample were nearer 33 cm for males and 37 cm for females, so maturity begins earlier than the averages suggest. Females are only slightly the larger sex.

Hatchlings have not been measured directly, but the egg cases are only a few centimetres long, and by analogy with the blackmouth catshark a newly hatched pup is probably 8 to 10 cm. Nobody has published a weight for the species; a 40 cm catshark of this slim build weighs in the region of 200 to 300 g.

Beside the great catsharks of the same slopes the Atlantic sawtail is a minnow: the blackmouth reaches 90 cm and even the shallow-water small-spotted catshark tops 1 m. On the size bar below, its 45 cm maximum reaches roughly the knee of a 1.8 m diver.

Where Atlantic sawtail catsharks live

The Atlantic sawtail has one of the smallest confirmed ranges of any shark. Its centre is the Alborán Sea, the westernmost basin of the Mediterranean between southern Spain and Morocco, where Spanish trawl surveys catch it regularly on the slopes around the island of Alborán and off Málaga and Almería. From there it extends west through the Strait of Gibraltar into the Gulf of Cádiz, off southern Portugal, and south along the Moroccan and Western Saharan slope to Mauritania. Scattered records from Algeria and further east in the Mediterranean exist but need checking, because any small saddle-marked catshark there was until recently logged as a blackmouth.

Within that range it is a bottom-dwelling shark of the upper continental slope. Most captures come from 400 to 600 m, with the extremes at roughly 330 and 800 m, on soft mud and muddy sand where deep-water shrimps burrow. The bottom water there is a stable 13 °C or so in the Mediterranean and a little cooler on the Atlantic side. The old description of the species as "commonly found on the continental shelf" is wrong: the shelf ends at about 200 m and the sawtail lives well below it, which is why divers never see one and why it does not feature on SharkSider's coastal country lists.

What Atlantic sawtail catsharks eat

Stomachs examined from the Alborán Sea show a diet dominated by crustaceans, above all decapod shrimps and prawns, including the same deep-water species that the local trawl fleet targets, together with mysids and other small swimming crustaceans. Small bony fishes, mainly lanternfish and the juveniles of hake and other slope species, come second, and squid and cuttlefish third. Worms and fish offal turn up too, so the shark also scavenges what the trawlers discard.

This is the diet of a slow, methodical bottom hunter, not a chaser. A catshark cruises a few centimetres above the mud at night, sweeping the snout from side to side. The nostrils, with their large flaps, sample the water for scent; the ampullae of Lorenzini under the snout sense the faint electric field of a shrimp hidden in the sediment; and the big eyes, backed by a reflective layer, use whatever faint bioluminescence the slope provides. Once prey is located the shark simply pins it with a quick downward thrust of the head and swallows it whole or in a couple of bites. The small multi-cusped teeth are for gripping slippery, hard-shelled animals, not for cutting.

The sawtail is in turn eaten by larger slope predators, including the blackmouth catshark and hake.

Behaviour and adaptations

Almost everything about the Atlantic sawtail's behaviour is inferred from trawl data and from its better-studied relatives, because no one has watched one alive for more than a few minutes on a ship's deck. Catches show it is a demersal shark that stays close to the bottom and does not undertake the long vertical migrations of the oceanic dogfishes. The same trawl tracks yield the species year after year, so it appears to be sedentary, living out its life on a small patch of slope, which fits a range this restricted and means local populations cannot be replenished quickly from elsewhere.

Like other catsharks it is almost certainly more active at night. The body is built for economical cruising rather than speed: a long, low-slung tail with a weak lower lobe, small paired fins and a flexible, eel-like trunk that lets the shark thread through burrow-pocked mud and rest on the bottom without effort. The denticle crest on the tail is puzzling; suggestions include protection of the tail from the teeth of other sharks, or a role in the courtship of a genus in which males bite females during mating, but there is no evidence either way.

For the anatomy the sawtail shares with every other shark, from the spiral valve to the cartilage skeleton, see do sharks have bones and the wider evolution of sharks.

Reproduction and lifespan

The Atlantic sawtail catshark lays eggs. It is oviparous like every catshark, and, unusually, it practises what biologists call multiple oviparity: instead of forming one egg case in each oviduct and laying the pair before starting the next, a female builds up several cases at once and holds them until they are ready to be laid together. Spanish workers have found females carrying up to nine developing egg cases at a time. Each case is a few centimetres long, vase-shaped with a rounded base, reddish-brown when fresh, with short coiled tendrils at the corners to anchor it to sponges, sea pens or rubble on the otherwise featureless mud. Read more about this reproductive mode under the ways sharks reproduce.

Reproductively active males and females are found in every month, so there is no defined breeding season, although the proportion of females carrying cases seems to peak in spring and summer. Hatching time is unknown; blackmouth catshark eggs take many months in the same cold water, and the sawtail's are unlikely to be faster.

Males mature at about 38 to 42 cm and females at 40 to 45 cm, the smallest mature animals a few centimetres below that. No one has aged the species. Small catsharks of cold deep water generally live 10 to 15 years or more, and the sawtail, with a maximum length reached slowly, probably falls in that band (see how long sharks live).

Is the Atlantic sawtail catshark dangerous to people?

No. SharkSider's attack database lists nothing under this species, and no incident is possible in practice. The animal is under half a metre long, weighs a few hundred grams, has teeth the size of grains of rice and lives 400 m or more below the surface, far beyond any diver. The only humans it meets are the crews of Spanish and Moroccan trawlers, who see it come up dead or dying in the cod-end among the shrimps.

Even in the hand it is inoffensive. A live catshark will twist and may close its mouth on a finger, but the sawtail's teeth cannot break skin in any meaningful way, and unlike the dogfishes it has no dorsal spines. The Spanish attack record on this site contains no catshark of any species. For the sharks that do bite, see how to survive a shark attack.

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 assesses the Atlantic sawtail catshark as Near Threatened, first in 2009 and again in its 2020 reassessment. The reasoning is simple and uncomfortable: the species' entire known range lies within the footprint of one of the most intensive deep-water trawl fisheries in the Mediterranean and eastern Atlantic. The Alborán Sea fleets fishing for red shrimp, Norway lobster and hake work exactly the 400 to 600 m mud where the sawtail lives, and every haul brings up catsharks that are thrown back dead or dying. Nobody wants them: the species has no commercial value and is not listed on any CITES appendix or by the Convention on Migratory Species.

The damage is therefore incidental but constant. A shark with a range measured in a few hundred kilometres, no known migration and low fecundity cannot absorb a bycatch mortality that continues year after year, and because the sawtail was recorded as "blackmouth catshark" in fishery statistics until recently, there is no long time series showing whether it has declined. That absence of data, not evidence of recovery, is why the listing is Near Threatened and not worse.

Two measures help indirectly. The General Fisheries Commission for the Mediterranean banned bottom trawling below 1,000 m in 2005, and the European Union has since 2016 closed depths beyond 800 m to trawlers in Atlantic waters; both protect the deepest part of the sawtail's range but not the 400 to 600 m core. No country protects the species by name. It belongs on any honest list of why sharks are endangered: not hunted, just in the way.

Similar species and close relatives

The one species that matters is the blackmouth catshark (Galeus melastomus), which shares the whole of the sawtail's range and much of its depth, looks nearly identical and grows twice as large. Until 2007 the two were treated as one by most fishery observers, and older records of "G. melastomus" from the Alborán Sea certainly include sawtails. The dark labial furrows, the slightly more rearward nostrils and the small adult size are the field marks; DNA is the proof. The genus Galeus holds about 18 sawtail catsharks worldwide, from the roughtail catshark of the western Atlantic to several Pacific species, all with the same denticle crest on the tail.

Within the deepwater catshark family the sawtail's nearer cousins in European waters are the ghost catsharks of the genus Apristurus, such as the mouse catshark and Iceland catshark: plain-coloured, soft-bodied sharks of deeper water, without saddles or a tail crest. Further afield the family includes the Arabian catshark and the quagga catshark of the Indian Ocean. The familiar inshore catsharks of Europe, the small-spotted catshark and the nursehound, belong to the separate family Scyliorhinidae; they are spotted rather than saddled, live on the shelf rather than the slope, and have a smooth-edged tail. See how many teeth sharks have for the multi-cusped dentition they all share.

• Blackmouth Catsharkspecies profile
• Mouse Catsharkspecies profile
• Iceland Catsharkspecies profile
• Arabian Catsharkspecies profile
• Quagga Catsharkspecies profile
• Small-Spotted 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 October 6, 2022 · Last updated September 22, 2026 · No incident attributed to this species in the SharkSider attack database, which is updated weekly.