Cat Shark: Species, Habitats, and What to Know

A catshark is any member of the family Scyliorhinidae, a group of small, bottom-dwelling sharks named for the vertical, cat-like shape of their pupils. With roughly 150 species spread across temperate and tropical seas, it is the largest shark family on Earth. Most species stay under one meter long at maturity and spend daylight hours tucked into reef crevices, kelp, or rocky shelves.

This guide walks through the defining traits, species diversity, habitats, and behaviors of catsharks, offering practical context for divers, marine students, and aquarium hobbyists curious about these small, bottom-dwelling fish.

Defining the Catshark Family and Its Place Among Sharks

The catshark family, Scyliorhinidae, sits inside the order Carcharhiniformes, the same large group that includes houndsharks, requiem sharks, and hammerheads. That order houses more than 270 species in total, and its account for well over half of them, which makes the family unusually important to ocean food webs.

Most members share a few giveaway traits: a slender, cylindrical body, two small dorsal fins set far back on the tail, a pattern of spots, stripes, or saddles, and eyes with a nictitating membrane that slides up to protect the eye during feeding. Many species also have a pair of barbels near the nostrils and a mouth set on the underside of the head, classic features of a benthic hunter that sniffs out prey hiding in sand and gravel.

Where the Name Causes Trouble

Not every shark sold under the label “catshark” belongs to Scyliorhinidae. Pet stores often call bamboo sharks, epaulette sharks, and a few other carpet sharks “its” because they are small, gentle, and patterned. Those animals sit in different families, Hemiscylliidae and the genus Hemiscyllium, and they reproduce by laying eggs, but their skeletons, fin placement, and behavior separate them from true its. Keeping that distinction in mind is the single biggest step toward accurate identification, both in the wild and on a dealer’s price list.

Feature	True Catshark (Scyliorhinidae)	Pet-Store “Catshark” (Bamboo, Epaulette)
Family	Scyliorhinidae	Hemiscylliidae
Body shape	Slender, cylindrical	Stout, eel-like or flattened head
Eye	Cat-like vertical pupil	Rounder pupil, no nictitating membrane
Typical max length	0.4–1.6 m (1.3–5.2 ft)	0.7–1.2 m (2.3–3.9 ft)
Range	Temperate and tropical seas worldwide	Indo-Pacific reefs and tide pools

Key Species and How to Tell Them Apart

Field guides identify most catsharks by pattern and proportion rather than size, because adults of different species can overlap in length. Spot shape, the number of dark saddles across the back, and the position of the first dorsal fin relative to the pelvic fins are the most reliable markers. The species below show how varied that pattern can be, and they form the backbone of any working it identification key.

Common European and Atlantic Species

The small-spotted catshark (Scyliorhinus canicula) is the textbook example, with a slender tan body covered in small dark spots. It rarely exceeds 1 meter (3.3 ft) and ranks among the most abundant sharks in the northeastern Atlantic and Mediterranean. The nursehound (Scyliorhinus stellaris) is its larger, bolder-spotted cousin, often reaching 1.5 meters (4.9 ft) and showing fewer but larger dark blotches. Both species appear in European fish markets, where they are often sold as “rock salmon” or “huss.”

Indo-Pacific and Tropical Species

The coral it (Atelomycterus marmoratus) carries a striking marbled pattern of black and white bands and rarely grows past 70 cm (28 in). It rests in reef crevices from India to Japan. The swellshark (Cephaloscyllium ventriosum), native to the eastern Pacific, gulps water and inflates to roughly twice its resting size, a defense that wedges it into cracks and discourages predators. The chain dogfish (Scyliorhinus retifer) is a deep-water western Atlantic species with a lattice of dark chains over a light background, often photographed during deep reef surveys.

Species	Scientific Name	Range	Adult Length	Distinctive Mark
Small-spotted it	Scyliorhinus canicula	NE Atlantic, Mediterranean	0.6–1.0 m	Dense small dark spots
Nursehound	Scyliorhinus stellaris	NE Atlantic, Mediterranean	1.0–1.6 m	Large scattered dark spots
Coral it	Atelomycterus marmoratus	Indo-Pacific reefs	0.5–0.7 m	Marbled black-and-white bands
Swellshark	Cephaloscyllium ventriosum	Eastern Pacific	0.8–1.1 m	Brown blotches, can inflate body
Chain dogfish	Scyliorhinus retifer	Western Atlantic deep reefs	0.4–0.5 m	Chain-like dark pattern

Where Catsharks Live, What They Eat, and How They Behave

Almost every species in the family is a benthic bottom-dweller, spending daylight hours tucked into caves, kelp holdfasts, rocky crevices, or coral rubble. Most range from the intertidal zone down to roughly 2,000 meters (6,560 ft), though the majority cluster on continental shelves between 50 and 500 meters deep. They prefer rough, structured habitat where their patterned backs break up their outline against predators.

Feeding happens mostly after dark, when the sharks glide out over sand and gravel to hunt. Prey lists read like a sampler of the seafloor: small bony fish, shrimp, crabs, squid, octopuses, marine worms, and small crustaceans. Scyliorhinus canicula alone has been documented eating more than 140 prey taxa across its range, which helps explain why it sustains such high population numbers in heavily fished European waters.

Sensing the Dark

its rely on a dense network of electroreceptors called ampullae of Lorenzini, pores scattered across the snout that detect the faint bioelectric fields of hidden prey. Combine that sense with low-light vision, a strong sense of smell, and barbels near the mouth in some species, and the shark can pinpoint a buried crustacean without ever seeing it. The same receptor grid also picks up approaching predators, which is why these sharks often freeze against the bottom when divers get close.

Biofluorescence

In 2014, researchers reported widespread biofluorescence in Scyliorhinidae. Under blue or ultraviolet light, several species glow a vivid green across their skin, a pattern invisible in normal daylight. The function remains debated, with current hypotheses ranging from camouflage at depth to species recognition during courtship. For divers and aquarium keepers, that glow is a useful diagnostic tool, because the intensity and pattern differ between species.

Size, Growth, and Reproduction in the Wild

Most its stay modest in size, and that single trait shapes how populations handle fishing pressure. The largest species in the family top out near 1.6 meters (5.2 ft); the smallest mature at less than 30 cm (12 in). Sexual maturity arrives slowly compared with bony fish of similar size, often between 4 and 12 years depending on the species, and adults may live two decades or more in stable populations.

Reproduction across the family is overwhelmingly oviparous. Females lay eggs in tough, leathery cases commonly called mermaid’s purses, each one equipped with long tendrils at the corners that anchor to seaweed, coral, gorgonians, or rock. Inside the case, an embryo develops for several months on yolk alone, slowly taking the shape of a miniature adult before hatching fully formed.

From Egg Case to Hatchling

Incubation periods vary with temperature and species, ranging from about 4 months in warm tropical water to over a year in cold temperate seas. Hatchlings emerge at roughly 10–15 cm (4–6 in) and immediately adopt the benthic lifestyle of the adults, hiding in the same crevices their parents used. Empty egg cases often wash ashore after storms, and citizen-science programs run by groups like the Shark Trust use those cases to map where adults are laying.

Why Slow Growth Matters

Because females produce only a handful of eggs per year, often one or two at a time per oviduct, and reach maturity late, populations cannot rebound quickly from overfishing. A small-spotted it removed from the Mediterranean is replaced, on average, only after many years of successful breeding. That is the core reason the IUCN and NOAA flag the family as a priority for bycatch monitoring in mixed fisheries, even when individual species are still listed as Least Concern.

Catshark Safety and How They Compare to Dogfish

No it species is considered dangerous to people. Their small, multi-cusped teeth are built for gripping slippery prey like squid and small fish, not for delivering a serious bite. Documented incidents are rare and almost always involve a shark that was handled, cornered, or stepped on in shallow water, situations where any small predator will defend itself with whatever teeth it has.

Swimmers and divers encounter these sharks more often than they realize, especially in temperate reef systems at night, and negative interactions are essentially unheard of. Standard sense still applies: avoid grabbing a resting shark by the tail, watch your step on rocky bottoms in clear water, and never corner a fish in a tide pool.

Catshark vs. Dogfish at a Glance

The it and dogfish names get used interchangeably in casual conversation, but they point to different branches of Carcharhiniformes. Dogfish generally refers to spiny dogfish (Squalidae) or to certain requiem sharks like the smooth-hound, while its belong to Scyliorhinidae. The two groups share small size and benthic habits, but the differences show up in body shape, fin spines, and life history.

Feature	Catshark (Scyliorhinidae)	Spiny Dogfish (Squalidae)
Body	Slender, soft skin	Sleeker, slightly rougher skin
Spines	No dorsal spines	Sharp spine in front of each dorsal fin
Eye	Vertical cat-like pupil	Larger, rounder eye
Reproduction	Egg cases (oviparous)	Live birth (viviparous)
Range	Mostly continental shelves	Open temperate seas, migratory
Commercial use	Local food, bycatch	Major commercial fishery

“Handling a wild it is roughly equivalent to handling a large grouper: careful hands, wet gloves, and support under the belly. Pinch points are the snout and tail base, not the teeth.

Keeping Catsharks in Home Aquariums and Their Conservation Outlook

The first question to settle before buying any shark labeled a “it” is which family it actually belongs to. Bamboo and epaulette sharks are the species most often sold under that name, and they sit outside Scyliorhinidae. Among true its, only a handful enter the aquarium trade with any regularity, primarily coral it juveniles and a few chain dogfish imports, and even those are usually destined for public aquariums rather than home tanks.

A suitable shark system needs space, flow, and stability. The minimum setup that lets a small it thrive sits around 750 liters (roughly 180 US gallons), with a soft sand substrate so the shark can rest on the bottom without abrading its belly, plus ample live rock or PVC caves for daytime shelter. Temperature depends on species: tropical its do well at 24–26°C (75–79°F), while temperate species like the small-spotted it prefer 16–20°C (61–68°F). Ammonia and nitrite must stay near zero, and a protein skimmer rated above the tank’s water volume is non-negotiable.

Stocking and Sourcing

Buying captive-bred juveniles is the responsible path, and it also produces hardier fish because they are already eating prepared foods. Wild-caught juveniles often refuse to feed in captivity and may carry internal parasites. Ask the breeder for documentation of parentage, recent feeding records, and a health check that includes a fecal float. Expect to pay between roughly $300 and $1,500 for a small, captive-bred coral it in 2025, with rarer species climbing well past that range.

Conservation Status of Common Species

The IUCN Red List currently classifies most common its, including Scyliorhinus canicula, Atelomycterus marmoratus, and Cephaloscyllium ventriosum, as Least Concern. That status can mask local depletion, however, because the family is heavily caught as bycatch in trawl and longline fisheries throughout its range. Deep-water species are especially poorly assessed, and a meaningful share of the family’s true diversity has not been evaluated at all. NOAA and regional fishery management organizations track bycatch rates for the most-frequent species because that is the metric most likely to flag trouble before the global assessment changes.

• ▸Plan tank size for adult length: A 15 cm (6 in) juvenile coral it will approach 70 cm (28 in) within three years and needs room to turn around comfortably.
• ▸Match temperature to species: Keep Mediterranean species cool and Indo-Pacific species in stable tropical ranges; mixing the two is a common cause of slow decline.
• ▸Provide a sand bed: Bare glass or sharp gravel wears down the belly and opens the door to infection.
• ▸Buy captive-bred only: Wild-caught juveniles often starve in captivity and pull from already-pressured wild populations.
• ▸Quarantine before display: A separate 4–6 week quarantine with copper-treated water and observation cuts the odds of introducing parasites to your display tank.

Final Takeaways

its are a real, well-defined family of small, patterned bottom-dwellers with vertical pupils, slender bodies, and tough egg cases, not a marketing term for any shark sold as a pet. The roughly 150 species span temperate and tropical seas, mostly hunt at night, and pose no real threat to swimmers. Remember the difference between Scyliorhinidae and the bamboo sharks that share the pet-trade label, and the rest of the identification puzzle falls into place quickly.

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