|
|
|
Smooth Stingray

Smooth Stingray

Dasyatis brevicaudata

The smooth ray is the largest stingray in the world, growing up to 4.3 metres in length, with a 2 metre disc length and weighing up to 350 kilograms.  They are one of several rays referred to as “bull rays”.  They have a rounded, fleshy body, lacking both a dorsal and tail fin, which is covered in soft, velvety skin.  Their tail is thick close to the body, before it tapers to a point.   Midway along the tail is a slender thorn in front of two venomous barbs (one considerably smaller than the other).  The smooth stingray is black to grey on top, lighter underneath and has a distinctive pattern of numerous white spots on either side of the head and across the base of the fins.

The smooth ray has flattened, plate-like teeth.  They cruise along the sea bed in search for invertebrate prey such as fish, bivalves, polychaetes, crustaceans and squid.  They are strong swimmers and have the ability to move quickly.

Smooth stingrays are inquisitive, approaching swimmers and divers, even entering shallow water less than a metre in depth to be hand-fed.  While they appear harmless caution should be taken. When threatened as a defense against predators they can curl up their tail, like a scorpion, displaying their venomous barb which can cause severe or potentially fatal wounds.  They are considered to be more curious than aggressive.

Smooth rays are aplacental viviporous species (young hatch from an egg before leaving the mother’s body), whereby the embryos are nourished by yolk initially before absorbing a thick, fatty “milk” in utero.  At birth the young are approximately 36 centimetres across the disc.  Litter size and gestation period are unknown as are pupping grounds and nursery areas.

Smooth rays are a bottom-dwelling species inhabiting sand, reef habitats on the continental shelf.  They occur at a range of depths from 0 to 470 metres and common throughout Australian coastal waters from Shark Bay, WA and around southern Australia to Maroochydore, QLD.  They are also found in the temperate waters of New Zealand and South Africa.

A group of stingrays is known as a fever or a squadron.

Other common names include: short-tail stingray, bull ray, giant stingray, short-tail black stingray, smooth short-tail stingray.

 

Occurrence at the Busselton Jetty: 

The smooth ray is commonly observed from the Busselton Jetty, particularly in the summer months when the water clarity is at its best, as they cruise above the sand surface.  They can be seen in very shallow water close to the shore and below nine metres of water out at the underwater observatory.  Unfortunately increasing numbers of these gentle giants are seen with their tails amputated, often by anglers and commercial trawlers to prevent potential injuries to themselves from the barb before throwing the ray back.