Swimming with an elegant, undulating motion of their broad front fins, New Zealand’s 26 species of rays and skates move like large birds in flight.
Rays and skates are wide, flattened fish belonging to the same family as sharks, and sharing some of the same features: they have skeletons of cartilage, not bone, and open gill slits.
Rays and skates also differ from sharks. They have blunt rather than sharp teeth, and their gill slits are on the belly rather than along the sides.
Although skates and rays have similar, kite-shaped bodies, skates are usually not as large or as venomous. Rays are not aggressive animals, but if attacked or accidentally stood on they can inflict painful and serious wounds.
Skates lay leathery eggs, known as mermaid’s or sailor’s purses, on the sea floor.
Other rays carry their offspring inside them and give birth to live young.
These rays generate electric charges from muscle tissues in two kidney-shaped glands on either side of their heads – the currents can be strong enough to knock down an adult person. Electric rays stun fish and crabs, which they prey on at night. Ancient Romans and Greeks called electric rays numbfish because of their effect on people who touch them.
A species of electric ray, the New Zealand torpedo (Torpedo fairchildi), is endemic to the country. They are 1 metre long, grey-brown above and white underneath. They are found on or near the ocean floor, at depths from 5 metres to more than 1,150 metres. Māori know them as mātā and whai repo.
The most common skate around New Zealand, where it is endemic, is the rough skate (Dipturus nasutus). This species was first described scientifically by the naturalists who accompanied James Cook on his first visit to the country in 1769–70. Growing to 1.1 metres, rough skates are mottled brown with white and black spots and white undersides. Like other skates, they have thorny tails, but are essentially harmless. They inhabit the ocean floor at depths from 10 to 1,500 metres.
Rough skates are commercially harvested. In 2001–2 reported landings were 1,566 tonnes. The wings of skates are usually eaten grilled, fried or baked. Although they are not to everyone’s taste, some people consider them a delicacy.
Rough skates are also known by the Māori names uku, whai, waewae and pākaurua.
The longtail stingray (Dasyatis thetidis) grows to 4 metres, including the tail which is twice the length of its disc-shaped body. They are dark olive green, grey or black, and white underneath. They are also called whiptail stingrays, or whai in Māori. They can be found in New Zealand, southern Australia and south-eastern Africa, in the shallows and down to about 400 metres.
Longtail stingrays are feared because of the serrated, poisonous spines at the base of their tails, which they thrust into anything that tries to catch them. If a person accidentally stands on them they will be injured, but these stingrays do not seek out victims. Growing to a maximum of 214 kilograms, they feed on crabs, mantis shrimps, molluscs, worms and conger eels.
The eagle ray (Myliobatis tenuicaudatus) lives on the sea floor around New Zealand and Norfolk Island, in shallow waters and to depths of 160 metres. Growing to 2 metres, they are olive green or yellow brown, with pale blue or grey markings. Eagle rays are known in Māori as whai keo.
Their pointed fins make them excellent swimmers. Their teeth work like nutcrackers to crush their prey, which include crabs and other crustaceans from the sea floor. Eagle rays have a poisonous spine on their tails, but, unlike stingrays, they cannot swing their spine around and can be safely handled from the front.
Spinetail devil rays
Although not as large as some manta rays, the spinetail devil ray (Mobula japonica), which visits New Zealand waters during summer, is nevertheless a sizeable 3 metres long. They are dark blue to black above, with a white underbelly. In common with other members of the manta ray family, they cruise the open oceans straining the water for plankton. Found worldwide in tropical and subtropical seas, spinetail devil rays are harmless unless harassed.
Acknowledgements to Malcolm Francis (National Institute of Water and Atmospheric Research)