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Himantura astra

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Taxonomy [top]

Kingdom Phylum Class Order Family
ANIMALIA CHORDATA CHONDRICHTHYES RAJIFORMES DASYATIDAE

Scientific Name: Himantura astra
Species Authority: Last, Manjaji-Matsumoto & Pogonoski, 2008
Common Name/s:
English Blackspotted Whipray, Tosh's Longtail Ray, Coachwhip Ray, Tosh's Whipray, Wulura
Taxonomic Notes:

There have been recent taxonomic name changes within the genus Himantura due to access to more specimens (Last et al. 2008). Himantura astra had previously been confused with H. toshi and the two forms had been considered to be a single species, however they are now known to be two morphologically distinct species. Himantura toshi (sensu Last & Stevens, 1994) has been renamed H. astra Last, Manjaji-Matsumoto & Pogonoski, 2008 (Last et al. 2008, Last and Stevens 2009) and Himantura sp. A (sensu Last & Stevens, 1994) is considered to be H. toshi Whitley, 1939 (Last et al. 2008, Last and Stevens 2009).

The presence of black spots on juveniles of H. astra and their absence in H. toshi distinguishes juveniles of these two species. Adult colouration of the dorsal disc and post-sting tail is also different: Himantura astra have dark spots often surrounded by a rosette of white spots with the post-sting tail black and white banded dorsally and pale ventrally while H. toshi often have fine whitish spots and flecks with the post-sting tail blackish both dorsally and ventrally (Last et al. 2008, Last and Stevens 2009).

In addition, H. astra has been frequently misidentified as a colour variant of H. uarnak and H. gerrardi. Newborns and small juveniles of H. astra are similar in disc shape and sometimes colour to other species of the uarnak complex (a subgroup of mainly reticulated, ocellated or spotted whiprays); in particular to H. uarnak and H. gerrardi, however the snout angle of H. astra is the narrowest of the three species. Adults of H. astra have a spotted pattern rather than the reticulate pattern of adult H. uarnak and black spots rather than the small white spots of adult H. gerrardi (Last et al. 2008, Last and Stevens 2009).

Assessment Information [top]

Red List Category & Criteria: Least Concern ver 3.1
Year Published: 2011
Date Assessed: 2010-11-28
Assessor/s: Rigby, C.
Reviewer/s: Ebert, D.A. & Kyne, P.M.
Justification:

The Blackspotted Whipray (Himantura astra) is a medium-sized whipray that occurs from inshore to depths of 140 m and is widely distributed throughout tropical Australia and off southern New Guinea and West Papua. This species attains a maximum size of at least 80 cm disc width (DW). It is utilized bycatch of trawl and beach seine fisheries operating in the Arafura Sea, outside the Australian Fishing Zone (AFZ). Trawl fishing pressure in this area is intensive; previously more than 600 trawlers operated and although the numbers of currently active trawlers is unclear, there are still high levels of Indonesian trawl fishing in the area. This level of exploitation is of concern to the sustainability of the Blackspotted Whipray populations in the Arafura Sea outside the AFZ. In Australian waters, this species was shown to have a high capacity to recover after depletion from trawling, however the level of trawling activity in Australian waters is not as intensive as that outside the AFZ and an assessment of catches and monitoring of population trends is required in the Arafura Sea outside the AFZ. Fisheries in northern Australia are relatively well managed and the introduction of Turtle Exclusion Devices (TEDs) and other bycatch reduction devices significantly reduced the bycatch of this species, particularly those individuals >1 m DW. As the majority of the Blackspotted Whipray distributional range is in tropical Australia where mortality in fisheries is low, and where it is common and abundant, it is assessed as Least Concern globally at present.

Geographic Range [top]

Range Description:

The Blackspotted Whipray (Himantura astra) occurs across northern Australia, southern West Papua (Indonesia) and southern Papua New Guinea. Throughout tropical Australia it is widely distributed and occurs between Shark Bay (Western Australia) and Moreton Bay (Queensland) including the Arafura Sea and near the Timor Sea (Last et al. 2008, Last and Stevens 2009).

Countries:
Native:
Australia (Northern Territory, Queensland, Western Australia); Indonesia; Papua New Guinea (Papua New Guinea (main island group))
FAO Marine Fishing Areas:
Native:
Indian Ocean – eastern; Pacific – western central
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population:

The Blackspotted Whipray is very common and abundant in the Gulf of Carpentaria (Last and Stevens 1994, 2009). There is no information on population trends.

Population Trend: Unknown

Habitat and Ecology [top]

Habitat and Ecology:

The Blackspotted Whipray is demersal and occurs on soft substrates on the continental shelf from inshore to 140 m depth (White et al. 2006, Last et al. 2008, Last and Stevens 2009). It is more common offshore in the Gulf of Carpentaria, Australia than the closely related Brown Whipray (H. toshi) (Last et al. 2008). The Blackspotted Whipray attains at least 180 cm total length (TL) and 80 cm disc width (DW) with females generally larger than males; reports of individuals larger than 100 cm DW are probably incorrect. Both sexes mature at 40–47 cm DW and an estimated 8–10 years; birth size is about 17–21 cm DW (Jacobsen 2007, Last et al. 2008, Last and Stevens 2009). Maximum age estimates range from 19–24 years for males and 28–31 years for females (Jacobsen 2007).

Reproduction is viviparous with 1–3 pups. This species is a major predator of prawns in the Gulf of Carpentaria, Australia; its diet also includes fishes and polychaetes (White et al. 2006, Jacobsen 2007, Last and Stevens 2009). There are ontogenetic changes in diet; with increasing body size, similar prey items are consumed but the dominance of the prey items shifts and the diversity of the diet increases. Smaller animals rely heavily on carid shrimps while larger animals prey on a variety of crustaceans and polychaetes (Jacobsen 2007).

Systems: Marine

Threats [top]

Major Threat(s):

The threats previously reported for Himantura toshi in Indonesia and Papua New Guinea (PNG) (Manjaji and White 2004) are likely to be threats for H. astra as the recent taxonomic revision places H. astra not H. toshi in Indonesia and PNG. In the Arafura Sea, the Blackspotted Whipray is utilized bycatch of beach seine and bottom trawl fisheries (White et al. 2006, White and Dharmadi 2007). In 2004, it was reported that large numbers (~650) of trawlers operated in the Arafura Sea, from the port of Merauke in West Papua, and presumably took large quantities of the Blackspotted Whipray (Manjaji and White 2004). Although the numbers of trawlers currently operating is unclear, this intensive fishing pressure still continues; high levels of Indonesian trawl fishing in the Arafura Sea adjacent to the Australian Fishing Zone have recently been reported (Heazle and Butcher 2007, Northern Territory Government 2009). It was also previously stated that low numbers of juveniles were caught by beach seine fishermen targeting penaeid prawns in southern Papua (Manjaji and White 2004).

In Australia, the Blackspotted Whipray was one of the most commonly caught elasmobranchs in the Northern Prawn Fishery (NPF), however it was considered to be among the NPF bycatch species most likely to be able to sustain capture due partly to a high capacity to recover after depletion from trawling (Stobutzki et al. 2002). The introduction of Turtle Exclusion Devices (TEDs) in 2000 and other bycatch reduction devices has significantly reduced the bycatch of this species, particularly those individuals >1 m DW (Brewer et al. 2004). The Blackspotted Whipray has also been recorded in research surveys of the Queensland East Coast Trawl Fishery. It was a minor component of the bycatch in the banana prawn and scallop sectors (Stobutzki et al. 2001, Courtney et al. 2007). Although also a minor component of the tiger/Endeavour prawn sectors of this fishery, it was one of the most abundant elasmobranchs captured (Kyne 2008).

Conservation Actions [top]

Conservation Actions: In Queensland, Australia there is a recreational fishing limit per trip of one ray of 1.5 metres maximum total length; this limit is not species-specific and includes all rays. Otherwise there are no conservation actions currently in place for this species. It is a commonly captured bycatch species and research is required to improve knowledge of its life history characteristics and to assess catches and monitor population trends in the waters of the Arafura Sea outside the Australian Fishing Zone.
Citation: Rigby, C. 2011. Himantura astra. In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.2. <www.iucnredlist.org>. Downloaded on 21 April 2014.
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