Sharks and rays in U.S. zoos

What sharks and rays have in common

Sharks and rays are cartilaginous fish. Together they form the subclass Elasmobranchii, from Greek words for "plate" and "gill," a nod to their broad, flattened gills. Their skeletons are made of cartilage rather than bone, and their skin is covered in tiny placoid scales.

They share several other features. Each has five to seven pairs of gill slits that open separately to the outside, rather than under a single gill cover. None has a swim bladder; instead, a large liver rich in oil helps keep them buoyant. All reproduce by internal fertilization, though some lay eggs and others give birth to live young.

How to tell them apart

Rays are the flattened branch of the family, with well over 600 species. Their pectoral fins are enlarged into wings fused to the head, and their gill slits lie on the underside. Most sharks have a spindle-shaped body with gill slits on the sides of the head.

Bottom-dwelling rays breathe differently from most fish. Their eyes and spiracles sit on top of the head, so they can draw in water from above while lying flat on the sea floor. The southern stingray uses this to rest half-buried in sediment. It flushes prey out of the sediment by spraying water from its mouth or flapping its fins, and it carries a venomous tail spine for defense.

Many rays have heavy, rounded teeth for crushing shells. The cownose ray specializes in hard-shelled prey such as scallops and clams, and gets its name from the two lobes at the front of its head.

Bamboo sharks up close

Bamboo sharks are small, bottom-dwelling carpet sharks with a tail longer than the rest of the body. The brownbanded bamboo shark is nocturnal and sedentary, and it can survive out of water for up to 12 hours. The white-spotted bamboo shark has a white body crossed with dark bands and dotted with purple and pink spots, a pattern unique in its family.

Both are egg-layers. White-spotted bamboo shark egg cases are about 13 cm (5 in) long and hatch after 14 or 15 weeks. Females of both species have surprised keepers by producing eggs after years without a male, possibly through parthenogenesis.

Conservation picture

In 2026, the IUCN Red List counted 38% of shark and ray species as threatened with extinction. Fishing affects them in less obvious ways too: capture often triggers premature birth or abortion in live-bearing sharks and rays, something documented in at least 88 species but rarely considered in fisheries management.

The cownose ray was listed as Vulnerable in 2019, mainly because of overfishing; it matures late and has a long pregnancy, so its numbers recover slowly. Both bamboo sharks are Near Threatened, and the white-spotted bamboo shark is caught for food in Madagascar and Taiwan.