Rays

Rays are closely related to sharks. Like sharks, they too have skeletons made of cartilage, smooth or raspy skin instead of scales, and exposed gill openings on their belly.

Stingrays are common on the Great Barrier Reef

Reticulated whip ray / Himantura uarnak / Family - Dasyatidae

Rays are typically shaped like large flattened discs and have a long tail. There is great variety in position and size of fins in the different species.

Most rays swim by waving the edges of their very wide pectoral fins. This creates an S-shaped wave which moves vertically from head to tail. Although the manta ray weighs up to two tonnes, it moves gracefully in the water waving its enormous wing-like fins.

Habitat

Most rays stay on or near the seabed and are well adapted to bottom-living conditions. They have gill openings on their underside and a small round opening, a spiracle, just behind each eye on their upper surface. The spiracles enable them to take clear water into their gill chambers if their gills become clogged with sand or mud from the sea floor.

Reproduction

Most rays give birth to live young. Rays produce fewer and larger eggs than fish. Fertilisation is internal and the survival rate is much higher. Internal fertilisation is achieved by the paired claspers of the male, which are modifications of the pelvic fin used for transferring sperm to the female. Rays have a number of reproductive methods, varying from simple egg laying to the advanced live bearing.

Rays grow more slowly than fish. Growth is measured by estimating from the growth rings in hard skeletal parts such as the vertebrae or dorsal-fin spines.

Feeding

Rays glide along the sea bottom looking for, and sometimes digging for, molluscs and crustaceans in the sand. They have moveable eyes and good eyesight. Rays use electro-receptors to locate their prey. Their mouth, which is horny in appearance, lies on their underside. Their teeth are very small and blunt or prickly for grinding up small fish, shellfish, worms, and other bottom-dwellers. Like sharks, most rays have light undersides and colour-camouflaged backs to conceal them in their environment.

Rays of the Great Barrier Reef

Blue-spotted fantail ray, Taeniura lymma. This ray is the most commonly seen stingray on the Great Barrier Reef. It moves in schools into shallow, sandy areas during the high tide to feed, and leaves on the low tide to find shelter in caves and under ledges. Divers and swimmers have to be careful not to accidentally kneel or stand on a well-camouflaged blue-spotted fantail ray as it has one or two needle-sharp tail spines coated with poisonous mucus which can cause extreme pain. (About 70 cm in total length)

Reticulated whip ray, Himantura uarnak. (Up to 131 cm in total length) This ray is named for its very long, slender, whip-like tail, which is banded. Like other stingrays, it has a poisonous barb on its tail used for defence.

Manta ray, Manta birostris. This ray is distinguishable from other rays by the pair of large protruding flaps in front of the mouth. It feeds on plankton, using the flaps to direct food into its mouth. It has no spines on its whip-like tail. Manta rays are common in Reef waters and, at times, will leap out of the water and fall back with a great splash. Doing this might be to remove parasites from their skin, or it might be a display of territoriality - no one knows for sure. (Grows to at least 7 metres wide and can weigh more than 1300 kg)

Porcupine ray, Urogymnus asperrimus. The central part of this ray is raised and covered with bony nodules and sharp thorns. Like the manta ray, its tail lacks stinging spines. (Body up to at least 100 cm wide)

Coffin ray, Hypnos monopterygium. These rays are able to generate an electric charge, which they use to stun fish and other small reef creatures. When dead, the body swells in thickness and looks like a coffin, which gives this ray its common name. (Up to 40 cm in length)

Blue-spotted maskray, Dasyatis kuhlii. This is a common inshore species over coral reefs. Like the blue-spotted fantail ray, it is covered in bluish spots, however its body is not as rounded and its tail is more slender. (Reaches about 67 cm in total length)

Shovelnose ray, Rhinobatos batillum. This shark-like ray has many small, blunt teeth used for crushing molluscs and crustaceans. All Australian shovelnose rays live mainly on soft sand or mud bottoms, often close to shore. They are also known as guitarfish. (Up to 3 m in total length)

Beautiful but painful

Buried in the mud or sand on the seafloor, rays can be difficult to see. Always shuffle your feet when walking in lagoons in order to avoid stepping on a ray. Many species have a poisonous barb in their tail, which they use to defend themselves, and which can inflict an extremely painful wound. Always seek medical advice if wounded by a ray.