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Himantura granulata

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Taxonomy [top]

Kingdom Phylum Class Order Family
ANIMALIA CHORDATA CHONDRICHTHYES RAJIFORMES DASYATIDAE

Scientific Name: Himantura granulata
Species Authority: (Macleay, 1883)
Common Name(s):
English Whitetail Whipray, Mangrove Whipray, Mangrove Ray, Whitetail Stingray, MacLeay's Coachwhip Ray
Synonym(s):
Himantura ponapensis (Günther 1910)
Trygon granulata Macleay, 1883

Assessment Information [top]

Red List Category & Criteria: Near Threatened ver 3.1
Year Published: 2009
Date Assessed: 2004-09-06
Assessor(s): Manjaji, B.M., White, W.T., Fahmi & Ishihara, H.
Reviewer(s): Valenti, S.V. & Notarbartolo di Sciara, G. (Shark Red List Authority)
Justification:
The Whitetail Whipray (Himantura granulata) is a large (to 141 cm disc width), uncommon stingray, with a widespread distribution in the eastern Indian and western Pacific oceans, from Sri Lanka and eastern India, through to Indonesia. It also occurs along the northern coast of Australia and throughout some of the Pacific Islands. The species appears to prefer shallow inshore waters, including mangroves, estuaries, sand flats and broken rocky-sandy substrate, although adults may move offshore to at least 85 m depth. The species' preference for inshore habitats and the fact that it is apparently uncommon compared to other Himantura species, makes it particularly vulnerable to widespread and intensive artisanal and industrial fisheries operating throughout large areas of its range, as well as habitat destruction and pollution. Significant destruction and degradation of mangrove areas and targeting of juveniles in shallow waters are thought to have significantly affected this species. It is caught irregularly by tangle net, bottom trawl (including large numbers of trawlers targeting Rhynchobatids in the Arafura Sea) and longline fisheries and retained for human consumption. Levels of exploitation are very high throughout its range in Southeast Asia and in many parts of the Indian Ocean, hence it is under a severe level of threat within most of this range. Although no species-specific data are available, overall catches of stingrays are reported to be declining in areas of Southeast Asia for which information is available, with fishermen having to travel further and further to sustain catch levels. Species that inhabit a similar range to this species (such as the Sharptooth Lemon Shark (Negaprion acutidens)) are now rarely observed in Indonesia due to high levels of exploitation, and significant declines are also inferred to have occurred in this species in Indonesia and other areas. This species is assessed as Endangered in Southeast Asia on the basis of inferred declines (>50%) due to continuing high levels of exploitation. Fisheries in northern Australia are generally well managed and the introduction of Turtle Exclusion Devices (TEDs) and other exclusion devices will have greatly reduced bycatch of this species. The species is considered at minimal threat throughout its wide range off northern Australia, where it is assessed as Least Concern. Globally the species is assessed as Near Threatened, considered close to meeting the criteria for Vulnerable A2d+A3d+A4d. Further research is required on life-history characteristics and to assess catch levels throughout the species range. It will require careful monitoring and may well qualify for a threat category in the future.

Geographic Range [top]

Range Description: Eastern Indian Ocean: from the Gulf of Mannar, Sri Lanka along the eastern Indian coast, Bangladesh and Myanmar, Andaman Islands, Thailand and Malaysia.

Western Central Pacific: throughout Indonesia (except southern Sumatra), Malasia (Borneo and Sabah), Papua New Guinea, Vanikoro, Pohnpei, Melanesia, and the Philippines. The range also extends through some Pacific Islands, including Guam and Fiji and along the entire northern coast of Australia.

FAO fishing area: 57, 71
Countries:
Native:
Australia (Northern Territory, Queensland, Western Australia); Bangladesh; Fiji; Guam; India (Andaman Is., Nicobar Is.); Indonesia (Bali, Jawa, Kalimantan, Lesser Sunda Is., Maluku, Papua, Sulawesi); Malaysia (Peninsular Malaysia, Sabah, Sarawak); Micronesia, Federated States of ; Myanmar (Coco Is., Myanmar (mainland)); Papua New Guinea (Papua New Guinea (main island group)); Philippines; Solomon Islands; Sri Lanka; Thailand
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: Not very commmon (W. White pers. obs. 2007).
Population Trend: Unknown

Habitat and Ecology [top]

Habitat and Ecology: The species appears to prefer shallow inshore waters, including mangroves, estuaries, sand flats and broken rocky-sandy substrate, although adults may move offshore and it has been recorded to a depth of at least 85 m (White et al. 2006, B.M. Manjaji and W. White pers. obs 2007). The species also appears to be solitary rather than forming aggregations, like some other stingrays (B.M. Manjaji pers. obs. 2007). Reproduction is viviparous, with histotrophy (White et al. 2006). The species reaches a maximum reported size of 141 cm disc width (DW), >275 cm total length (TL) (White and Dharmadi 2007, W. White pers. obs.) and size at birth is reported at 14-28 cm DW (Manjaji 2004, White et al. 2006). Manjaji (2004) reports that males mature at 55-65 cm DW, but the biology and life-history characteristics of this species are generally poorly known.
Systems: Marine

Use and Trade [top]

Use and Trade: Flesh is utilized fresh or salted and dried for human consumption. Skin used for leather (high value) (White et al. 2006)

Threats [top]

Major Threat(s): This species is caught irregularly by tangle net, bottom trawl, and, to a lesser extent, longline fisheries in Indonesia (White et al. 2006, W. White pers. obs. 2007) and in other parts of its range. All specimens are typically retained and utilised.

This species' preference for shallow inshore waters makes it particularly vulnerable to extensive and intensive artisanal and industrial fisheries operating throughout large areas of its range, as well as habitat destruction and pollution (B.M. Manjaji and W. White pers. obs, Vidthayanon 1997). Juveniles and sub-adults are known to be targeted in mangrove areas and destruction of mangrove forest is having a significant impact on this species (W. White pers. obs. 2007). Mangrove forests throughout Southeast Asia and large areas of the eastern Indian Ocean have been degraded (FAO 2007). In this region, ~1.9 million hectares of mangroves (or about 25% of the total 1980 area) have been lost during the last 25 years (FAO 2007). More than 90% of this loss has been caused by destruction of mangrove area in Indonesia, Pakistan, Vietnam, Malaysia and India (areas where this species occurs) through conversion of land for shrimp farms, excessive logging, conversion of land for agriculture or salt pans and degradation through oil spills and pollution (FAO 2007). Even in well-managed mangrove areas that are protected from destruction, for example, the UNESCO Biosphere Reserve in Ranong, Thailand (designated in 1997), this species may still face threats from local fisheries on which the people living in the reserve primarily depend (FAO 2007).

The Sicklefin Lemon Shark (Negaprion acutidens) occurs at similar depths to this species' preferred bathymetric range. N. acutidens is rarely observed in recent times in Indonesia due to the very high level of exploitation of inshore waters and its slow growth rate (White et al. 2006). This species is apparently uncommon compared to other large Himantura species in this region, making it particularly vulnerable. Given that H. granulata is a large stingray, probably with limiting life-history characteristics also, it is inferred that this species has also declined significantly in these areas.

The commercial gillnet fishery that targets rhynchobatid rays in the Arafura Sea, Indonesia, takes this species as retained bycatch, which is landed for human consumption (Last and Compagno 1999, W. White pers. obs. 2007). It is thought to be heavily impacted in this area, where more than 600 trawl vessels operate (W. White pers. obs. 2007). The Rhynchobatus species gillnet fishery catches large numbers of stingrays. Catches in inshore waters have declined and these vessels are having to travel longer and longer distances to sustain catches. The rhynchobatid fisheries are very intensive in this region, thus the level of exploitation is extremely high. There is also evidence that fisherman in these regions increasingly illegally fish in Australian waters (Chen 1996, W. White, unpubl. data).

Artisanal inshore fishing pressure is also very intensive off eastern India (Flewwelling and Hosch 2006). Fisheries throughout India operate on an open access basis and inshore marine species are thought to be fully or overexploited, with extensive use of illegal mesh sizes reported, and increasing ever-increasing bottom trawl effort (Flewwelling and Hosch 2006). Demersal species, such as this, suffer more fishing mortality than pelagic species on the eastern coast of India (Flewwelling and Hosch 2006). India's inshore fisheries are generally characterised by declining catch rates, declining recruitment and biomass, and a shift from regular landing patterns (Flewwelling and Hosch 2006). Although no species-specific data are available on catches, it is inferred that this species has also suffered declines as a result of high levels of inshore exploitation in these areas also.

No data or information is available on catches in the Pacific Islands, but this species may be taken as bycatch in inshore subsistence and artisanal fisheries there also.

In Australia, large specimens are caught as byatch in the Australian Northern Prawn Trawl Fishery, but the introduction of Turtle Exclusion Devices (TEDs) and other exclusion devices is thought to have greatly reduced bycatch of this species.

Conservation Actions [top]

Conservation Actions: No conservation and managment measures are in place, with the exception of Australian waters. Further research is required on the species' life-history, full range and capture in fisheries. Data need to be collected to allow accurate monitoring of population trends.

An elasmobranch biodiversity study in Borneo (Sabah, Malaysia) was initiated in 1996 (Fowler et al. 2002). While the monitoring surveys should continue to ascertain the status and possible threats to this species here, as well as in other portions of its range (New Guinea and Indonesia), further research should be directed at population, habitat and ecology and life history parameters due to the very high quantities taken by the large number of prawn and/or fish trawlers that operate in the region. The fishery is largely unregulated (licences being issued, but catches/ landings are not properly monitored), and presently there is no specific conservation actions in place to help address this problem.

In Australia, the use of Turtle Excluder Devices (TEDs) and Bycatch Reduction Devices (BRDs) in the Northern Prawn Fishery (NPF) has been compulsory since 2000 (Day 2000). The Northern Prawn Fishery Bycatch Action Plan (1998) also recommends that bycatch reduction targets be established and that bycatch levels be monitored (Day 2000).

Citation: Manjaji, B.M., White, W.T., Fahmi & Ishihara, H. 2009. Himantura granulata. The IUCN Red List of Threatened Species. Version 2014.2. <www.iucnredlist.org>. Downloaded on 20 August 2014.
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