Cat Shark: Catshark ID, Egg Cases and Dogfish Names

A cat shark is a small, slender shark that spends its life on the seabed. Wikipedia gives the family's main marks:

• Eyes: elongated, cat-like eyes, which give the group its name.
• Dorsal fins: two small dorsal fins set far back on the body.
• Pattern: many species are boldly marked with stripes, spots or blotches.
• Size: most species are under 80 cm (31 in).
• Habits: nocturnal bottom feeders that eat invertebrates and small fish, and usually stay in a restricted range instead of migrating.

For a photo ID, photograph the whole animal from the side and from above so the pattern shows, plus a close shot of the eye and the positions of the two dorsal fins.

Sometimes by name, but not by biology. Wikipedia notes that some catsharks are still called dogfish because of older naming, and gives two practical differences: catsharks lay eggs while dogfish have live young, and dogfish lack an anal fin.

The small-spotted catshark, Scyliorhinus canicula, shows how tangled the names are. Wikipedia lists it as the sandy dogfish, lesser-spotted dogfish, rough-hound and, in Scotland and Cornwall, morgay. It grows to about 1 m, lives on the continental shelf from Norway and the British Isles south to Senegal and in the Mediterranean, at depths from a few metres to 400 m, and is listed as Least Concern. It was one of the fish sold in English and Scottish fish and chip shops as rock salmon, rock eel, huss or sweet william.

Most catsharks are oviparous. Wikipedia describes the eggs as laid in tough protective cases, often called mermaid's purses, with curly tendrils that anchor them, and says hatching takes nearly a year. A few species instead keep the embryos inside until they are ready and give birth to live young.

For the small-spotted catshark, Wikipedia gives an egg case usually about 4 cm by 2 cm, never more than 6 cm, with the embryo developing for 5 to 11 months depending on water temperature. SEA LIFE Orlando describes coral catshark females anchoring their cases to coral with the tendrils.

• Coral catshark (Atelomycterus marmoratus): FishBase gives a maximum length of 70 cm, and SEA LIFE Orlando an average of 24 to 28 inches. It lives on shallow coral reefs in the Indo-West Pacific, from Pakistan and India to Southeast Asia, southern China and north to Japan (FishBase). It rests in crevices and caves by day, is dark-and-light spotted for camouflage, and uses its strong pectoral fins almost to walk along the bottom (SEA LIFE Orlando). The IUCN lists it as Near Threatened (2020 assessment, via FishBase), with destructive fishing on reefs named as a likely cause.
• Swellsharks: can fill the stomach with water or air to about three times their normal girth when threatened (Wikipedia).
• Chain catshark: biofluorescent, which is unusual among sharks (Wikipedia).
• Nursehound: one of the largest catsharks at 1.6 m (Wikipedia).

Public aquariums keep them, which is why many people first meet one: SEA LIFE Orlando, for example, displays coral catsharks. For a home aquarium, the facts that matter are size and lifestyle. A coral catshark can reach about 70 cm (FishBase), it is a bottom-living, nocturnal hunter of small fish and crustaceans, and it is listed as Near Threatened. None of the sources we checked give home-care requirements, so we do not give tank sizes here. If you are considering one, talk to an experienced marine aquarist or a public aquarium first, make sure the animal is legally sourced, and check your local rules on keeping sharks.

Research and drafting for this page were assisted by AI and checked line by line against the sources listed below. Every number names the organisation it comes from, and where sources disagree we say so instead of picking one silently. Prices and rules are given with the date we checked them; they change, so confirm before you rely on them. If you find an error, tell us and we will correct it.