Black-spotted whipray

Lore & Background

The black-spotted whipray was traditionally thought to be the same species as the brown whipray (H. toshi). In 1994, CSIRO researchers Peter Last and John Stevens tentatively identified a spotted variant as 'Himantura sp. A', but it was not until the mid-2000s that more specimens confirmed it as a distinct species. Last, Mabel Manjaji-Matsumoto, and John Pogonoski formally described it in a 2008 CSIRO publication, giving the specific epithet astra from the Latin for 'constellation'. The type specimen is an adult male 59 cm across, collected from the Gulf of Carpentaria. This species belongs to the 'uarnak' species complex, which also includes H. fai, H. gerrardi, H. jenkinsii, H. leoparda, H. uarnak, and H. undulata. Other common names include coachwhip ray, Tosh's longtail ray, and wulura.

The black-spotted whipray has a diamond-shaped, relatively thin pectoral fin disc about 1.1–1.2 times wider than long, with angular outer corners and nearly straight leading margins. The snout is triangular with a barely protruding pointed tip. The upper surface is densely covered by tiny heart-shaped dermal denticles in a wide central band, with those at the disc center slightly larger and spear-shaped. Newborns lack denticles. The tail is whip-like, 2.1–2.7 times as long as the disc is wide, and lacks fin folds. One or two slender stinging spines are present atop the tail, though many individuals have the sting missing. The species is grayish brown above with many small dark spots covering all or part of the disc and tail base; sometimes there are subtle to prominent white spots that may form rosettes or indistinct rings. The tail past the sting bears alternating light and dark saddles, which form complete bands in juveniles under 50 cm across. The disc and tail are plain white beneath.

Reader's Guide

The black-spotted whipray is found widely off northern Australia from Shark Bay in Western Australia to Moreton Bay in Queensland, including the Timor Sea, and is particularly abundant in the Gulf of Carpentaria. It has also been reported from off southern New Guinea. This bottom-dwelling species inhabits coastal waters 1–141 m deep, favoring sandy habitats, and tends to be found farther from shore than the brown whipray. In Shark Bay, it is found in greater numbers during the warm season than the cold.

Over 90% of its diet consists of crustaceans; in the Gulf of Carpentaria, it is a major predator of penaeid prawns, which constitute over half its diet. Shrimp are the predominant prey of young rays under 23 cm across, while stomatopods and crabs become more important with age. For rays off Queensland and in the Torres Strait, polychaete worms are an important secondary food source. This species has also been known to take bony fishes. It is aplacental viviparous, with females nourishing their young with histotroph ('uterine milk'). Females have a single functional ovary and uterus (on the left) and produce litters of 1–3 pups. Newborns measure 17–19 cm across; both sexes mature at about 46–50 cm across. The growth rate is relatively low, with females growing much more slowly than males.

Most of its range lies within Australian waters, where it faces minimal conservation threats due to the widespread deployment of bycatch-reducing measures on commercial trawlers, such as Turtle Exclusion Devices (TEDs). It is caught in small numbers for meat, skin, and cartilage by Indonesian fishers, and by prawn seine fishers off Papua New Guinea. A 2004 IUCN assessment of the brown whipray, which also included data on the black-spotted whipray, listed them under Least Concern.

Did You Know?

• The black-spotted whipray was formally described in 2008 by Last, Manjaji-Matsumoto, and Pogonoski.
• Its specific epithet 'astra' comes from the Latin word for 'constellation'.
• Over 90% of its diet consists of crustaceans, with penaeid prawns making up over half in the Gulf of Carpentaria.
• Females produce litters of only 1–3 pups, and newborns measure 17–19 cm across.