Common name(s)
Broad Cowtail Stingray.
Identification
A very large stingray with a kite-shaped disc that is slightly wider than long; disc width approximately 1.2-1.3 x length. Snout fairly short and rounded or obtusely angular. Small protruding lobe at tip. Anterior margins of disc straight. Pectoral fin apices somewhat angular. Pelvic fins large with narrowly rounded apices.
Eyes small and somewhat protruding. Snout length 1.7-2.3 x combined eye and spiracle length.
Mouth small and arched, with 5 oral papillae. Jaws bulbous. Nasal curtain skirt-shaped with a central crease (bi-lobed). Nostrils thin, positioned obliquely.
Wide band of flattened denticles on central disc in adults. Usually 4 small heart-shaped thorns on midline at shoulder. No other enlarged denticles or thorns present on midline. Tail fairly short, tapering gently to tail sting, then filamentous to tip. Tail length (when intact) approximately 2x disc width. Dorsal finfold absent. Ventral finfold long and very deep; depth beyond caudal sting 3.6-5.7 x tail height. Ventral fold base length 0.74-0.92 x disc width. One caudal sting usually present; set well back on tail.
Colour
Dorsum greyish-brown or almost black. Ventrum white, often with a thin dark margin. Tail beyond caudal sting usually dark. Ventral finfold dark.
Size
Maximum disc width 200cm. Disc width at birth 18cm.
Habitat
Tropical seas. On sand and mud, sometimes adjacent to reefs. From shallow estuaries to at least 60m. Occasionally enters freshwater.
Distribution
Indian Ocean and equatorial western Pacific. Madagascar, East Africa, Arabian Peninsula (including the Persian Gulf), India, Southeast Asia, northern Australia, and New Caledonia.
Conservation Status
LEAST CONCERN
Assessment based on a limited range in Australia and PNG that has since been extended to include all of the Indian Ocean.
The broad cowtail stingray is caught regularly in demersal tangle net, bottom trawl, longline, Danish seine and beach seine fisheries throughout its range. In the Arafura Sea, the Indonesian rhynchobatid fishery is very intensive and the level of exploitation is extremely high. Catches in inshore waters of the Arafura Sea have declined, and as a result these vessels have had to travel farther distances to sustain catches. This declining trend is likely to continue in future in the absence of management and because of continued, if not increasing, fishing effort. However, heavy fishing pressure in the Arafura Sea represents only a portion of this species’ total range. It is considered common and the population appears to be healthy in northern Australia where fisheries are well-managed and effective gear modifications exclude large stingrays in prawn trawl fisheries. Furthermore, it occurs in some significant marine protected areas in Australian waters, including the Great Barrier Reef Marine Park. On account of its status in Australian waters, which represents a large portion of its range, it is assessed as Least Concern.
Citation
Morgan, D.L., White, W.T. & Manjaji Matsumoto, B.M. 2016. Pastinachus ater. The IUCN Red List of Threatened Species 2016: e.T70682232A70708697. https://dx.doi.org/10.2305/IUCN.UK.2016-1.RLTS.T70682232A70708697.en. Downloaded on 22 February 2021.
Reproduction
Matrotrophic aplacental viviparity. Two pups per litter.
Diet
Diet unknown.
Behavior
Sedentary. Behavior poorly known.
Reaction to divers
Shy but approachable if accustomed to divers.
Diving logistics
The broad cowtail stingray is widespread in the Indian Ocean but probably easiest to observe in Australia. I have seen this ray in Exmouth at the navy pier but it is seen from Shark Bay on the west coast, north and east to the Clarence River in New South Wales.
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Similar species
Cowtail Stingray Distinguishable by 3 midline thorns (rather than 4), somewhat paler ventral finfold, and longer tail filament.