|Scientific Name:||Rhynchobatus australiae|
|Species Authority:||Whitley, 1939|
|Taxonomic Notes:||The species previously referred to as the wide-ranging Rhynchobatus djiddensis is a species complex of at least four species (L.J.V. Compagno pers. comm. in: Cavanagh et al. 2003). The current known range of R. djiddensis is in the Western Indian from the Eastern Cape Province, South Africa, to the Red Sea.
Several different colour morphs of Rhynchobatus australiae are present in Indonesia which may be different species (W. White, pers. obs., P. Last, pers. comm.). Further investigation into the taxonomy of this species in this region is required to be able to make a more accurate assessment.
|Red List Category & Criteria:||Vulnerable A2bd+3bd+4bd ver 3.1|
|Assessor(s):||White, W.T. & McAuley, R. (SSG Australia & Oceania Regional Workshop, March 2003)|
|Reviewer(s):||Kyne, P.M. & Cavanagh, R.D. (Shark Red List Authority)|
Rhynchobatus australiae is taken by multiple artisanal and commercial fisheries throughout its range both as a target species and as bycatch. Flesh is sold for human consumption in Asia and the fins from large animals fetch exceptionally high prices, creating a significant incentive for bycatch to be retained. Very little is known about the biology or population status of this species. Given its susceptibility to capture by multiple fishing gear types, including trawl nets, gillnets and hooks and its high value fins, it is probable that numbers have been locally reduced by fishing throughout its range. Local population depletion can be inferred from Indonesia where the target gillnet fishery fleet for rhinids and rhynchobatids has declined significantly, reportedly due to declining catch rates. Therefore, globally this species meets the criteria of Vulnerable A2bd+3bd+4bd due to the apparent population decline outlined above and the remaining very high level of exploitation in South East Asia. Habitat destruction may also pose a significant threat to this species throughout much of its range.
There are no target fisheries for R. australiae in Australia but it is a known bycatch of demersal trawl fisheries in the region. The introduction of Turtle Exclusion Devices (TEDs) in some Australian trawl fisheries in 2000 and the implementation of various elasmobranch-finning prohibitions, has probably led to a recent reduction in captures by this sector. However, given the population declines throughout South East Asia and the high value placed on fins (even in Australia), the Australian population may meet the criteria of Vulnerable A2d, but more detailed catch data is required and it is thus assessed as Near Threatened in these waters.
|Range Description:||Rhynchobatus australiae is a locally common species found in the Indo-West Pacific from the Gulf of Thailand in Thailand, Macassar, East Indies, Java, Bali, Lombok and Papau in Indonesia, Philippines and Queensland in Australia (Compagno and Last 1999, W. White, pers. obs.). However, records of R. djiddensis from this region cannot be identified to species and may actually be R. australiae, thus the range cannot be accurately determined.|
Native:Australia (Queensland); Indonesia; Philippines; Thailand
|FAO Marine Fishing Areas:||
Indian Ocean – eastern; Pacific – western central
|Range Map:||Click here to open the map viewer and explore range.|
|Current Population Trend:||Decreasing|
|Habitat and Ecology:||
Rhynchobatus australiae inhabits inshore waters on the continental shelves (Compagno and Last 1999). This species has a maximum total length (TL) of 223 cm (female), and probably up to 300 cm TL (from Thailand), with males mature at 131 cm TL (Compagno and Last 1999, W. White, unpubl. data). Very little is known about the biology and ecology of this species. Grant (1978) reports that in Queensland, this species feeds predominantly on crabs and other shellfish.
There is no published information on the age and growth and natural mortality of Rhynchobatus australiae.
Rhynchobatus australiae is one of the most sought after elasmobranchs in southeast Asia (particularly Indonesia), with the dorsal fins and upper caudal fin considered to be of premium quality and fetch the highest prices (Chen 1996). A set of fins from a single individual have been reported to have fetched up to Rp 900 000 or US$396/kg (Chen 1996). The skins and flesh are also of good quality.
The Aru Islands rhinid and rhynchobatid gill net fishery first began in the mid 1970s and rapidly expanded to reach its peak in 1987 with more than 500 boats involved. In future years the catches declined very rapidly with only 100 boats fishing in this area in 1996 (Chen 1996). The demersal gill net fishery for batoids in Merauke still land large quantities of rhynchobatids. A similar fishery also exists in Merauke (south Papua) with gillnet boats operating in the Arafura Sea, close to Australian waters, and the frozen catch sent by boat to processing areas in Jakarta. One observed catch weighed close to eight tonnes with Rhynchobatus spp. constituting more than 30% of the total mass (W. White, unpubl. data). Catches from these boats include a variety of large dasyatids, but the rhynchobatids constitute the largest proportion of the catch (W. White, unpubl. data). There is also evidence that fisherman in these regions occasionally fish in Australian waters (Chen 1996; W. White, unpubl. data).
Rhynchobatus djiddensis (probably R. australiae) was found to be one of the four most commonly caught elasmobranchs in the bycatch of the trawl fisheries (prawn and fish) in northern Australia, with approximately 10% of these dying in the trawl net (Stobutzki et al. 2002, Stephenson and Chidlow in prep). However, since the introduction of Turtle Exclusion Devices (TEDS) in some northern Australian trawl fisheries, catches of large elasmobranchs have been reduced (Brewer et al. 1998) and thus R. australiae are probably caught in lower numbers. Rhynchobatids are also a common target of recreational anglers in some parts of their range, including northern Australia (Last and Stevens 1994). There is also evidence of such finning of large shovelnose rays and guitarfish in northern Australia (R. McAuley, unpubl. data).
The introduction of TEDs in other Australian trawl fisheries is highly recommended for mitigating bycatch of this and similar species. Finning of rhynchobatids is also prohibited in some parts of Australia but there is thought be a continuing black market trade in their fins (Rose and McLoughlin 2000, McAuley unpubl. data).
Further investigation into the taxonomy, population and range, biology and ecology of Rhynchobatus australiae is required. Recent catch data for this species in eastern Indonesia and northern Australia, as well as elsewhere in its range, are required to assess to what extent the population decline is occurring. Improved species composition data from all fisheries that take shovelnose rays and guitarfish is necessary.
Bentley, N. 1996. A Preliminary Survey of Shark Fisheries in Indonesia. Unpublished TRAFFIC Southeast Asia Field Report.
Brewer, D.T., Rawlinson, N., Eayrs, S. and Burrige, C. 1998. An assessment of bycatch reduction devices in a tropical Australian prawn trawl fishery. Fish Research 36: 195-215
Chen, H.K. (ed.) 1996. Shark Fisheries and the Trade in Sharks and Shark Products in Southeast Asia. TRAFFIC Southeast Asia Report, Petaling Jaya, Selangor, Malaysia
Compagno, L.J.V. and Last, P.R. 1999. Rhinidae. In: K.E. Carpenter and V.H.Niem (eds) FAO species identification guide for fishery purposes. The living marine resources of the Western Central Pacific. Volume 3. Batoid fishes, chimaeras and bony fishes part 1 (Elopidae to Linophyrnidae), pp. 1418-1422. FAO, Rome.
IUCN. 2003. 2003 IUCN Red List of Threatened Species. www.iucnredlist.org. Downloaded on 18 November 2003.
IUCN SSC Shark Specialist Group. Specialist Group website. Available at: http://www.iucnssg.org/.
Last, P.R. and Stevens, J.D. 2009. Sharks and Rays of Australia. Second Edition. CSIRO Publishing, Collingwood.
Stephenson, P. and Chidlow, J.A. 2003. Bycatch in the Pilbara Trawl Fishery. Final Report to Natural Heritage Trust, Report.
Stobutzki, I.C., Miller, M.J., Heales, D.S. and Brewer, D.T. 2002. Sustainability of elasmobranches caught as bycatch in a tropical prawn (shrimp) trawl fishery. Fishery Bulletin 100: 800-821.
|Citation:||White, W.T. & McAuley, R. (SSG Australia & Oceania Regional Workshop, March 2003). 2003. Rhynchobatus australiae. The IUCN Red List of Threatened Species 2003: e.T41853A10580429. . Downloaded on 06 May 2016.|
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