Himantura chaophraya

Taxonomy

Assessment Information

Geographic Range

Population

Habitat and Ecology

Threats

Conservation Actions

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Taxonomy [top]

Kingdom	Phylum	Class	Order	Family
ANIMALIA	CHORDATA	CHONDRICHTHYES	RAJIFORMES	DASYATIDAE

Scientific Name:

Himantura chaophraya

Species Authority:

Monkolprasit & Roberts, 1990

Infra-specific Taxa Assessed:

See Himantura chaophraya (Thailand subpopulation)

Common Name/s:

English

–

Giant Freshwater Stingray, Giant Freshwater Stingray, Whipray

Assessment Information [top]

Red List Category & Criteria:

Vulnerable A2bcde+3ce ver 3.1

Year Assessed:

2005

Assessor/s

Compagno, L.J.V. & Cook, S.F.

Evaluator/s:

Musick, J.A. & Fowler, S.L. (Shark Red List Authority)

Justification:
This freshwater species is recorded from several rivers in Southeast Asia and northern Australia and is probably unrecorded in others. The potential for exchange between these subpopulations is presumably very limited. The Giant Freshwater Stingray (Himantura chaophraya)) has been and will continue to be adversely affected in much of its range by a complex of factors including directed and bycatch fisheries and habitat alteration or destruction. The possibility of extinction in the wild for some subpopulations is considered extremely high, but the status of those in Australia is probably favourable.

History:

2000	–	Vulnerable
1996	–	Endangered (Baillie and Groombridge 1996)

Geographic Range [top]

Range Description:	The Giant Freshwater Stingray was only formally described in 1990, though its existence has been known for some years (Compagno and Roberts 1982, Monkolprasit and Roberts 1990). It is known from highly disjunct localities including: fresh waters in Thailand in the Chao Phraya (the type locality), Nan, Mekong, Bongpakong, Tachin and Tapi Rivers. It is also recorded from Mahakam Basin in Kalimantan (Borneo) (Monkolprasit and Roberts 1990), the Kinabatangan River, Sabah (Borneo), the Fly River Basin (New Guinea) and from Australia in the Gilbert River (Queensland), the Daly and South Alligator Rivers (Northern Territory), Pentecost and Ord Rivers (Western Australia) (Taniuchi and Shimizu 1991, Taniuchi et al. 1991, Last and Stevens 1994, Compagno and Cook 2000). It may occur in most of the large rivers of tropical Australia. It has also been recorded in estuarine waters. The specimen collected in Sabah differs greatly in disk shape from the two Australian specimens. This suggests that these specimens, at least, represent two distinct subpopulations. Despite records of this species from estuarine waters, and the possibility that it may be able to transit marine waters between riverine systems, most of its populations could be geographically isolated. The species has been previously misidentified in Australia as the Estuary Stingray (Dasyatis fluviorum, Ogilby 1908) (Merrick and Schmida 1984, Last and Stevens 1994, Compagno and Cook 1995a) and may have been listed under the old name of Himantura polylepis (Bleeker) in Indonesia (Last and Stevens 1994).
Countries:	Native: Australia; Cambodia; China; Indonesia; Lao People's Democratic Republic; Myanmar; Papua New Guinea; Thailand; Viet Nam

Range Description:

The Giant Freshwater Stingray was only formally described in 1990, though its existence has been known for some years (Compagno and Roberts 1982, Monkolprasit and Roberts 1990). It is known from highly disjunct localities including: fresh waters in Thailand in the Chao Phraya (the type locality), Nan, Mekong, Bongpakong, Tachin and Tapi Rivers. It is also recorded from Mahakam Basin in Kalimantan (Borneo) (Monkolprasit and Roberts 1990), the Kinabatangan River, Sabah (Borneo), the Fly River Basin (New Guinea) and from Australia in the Gilbert River (Queensland), the Daly and South Alligator Rivers (Northern Territory), Pentecost and Ord Rivers (Western Australia) (Taniuchi and Shimizu 1991, Taniuchi et al. 1991, Last and Stevens 1994, Compagno and Cook 2000). It may occur in most of the large rivers of tropical Australia. It has also been recorded in estuarine waters. The specimen collected in Sabah differs greatly in disk shape from the two Australian specimens. This suggests that these specimens, at least, represent two distinct subpopulations. Despite records of this species from estuarine waters, and the possibility that it may be able to transit marine waters between riverine systems, most of its populations could be geographically isolated. The species has been previously misidentified in Australia as the Estuary Stingray (Dasyatis fluviorum, Ogilby 1908) (Merrick and Schmida 1984, Last and Stevens 1994, Compagno and Cook 1995a) and may have been listed under the old name of Himantura polylepis (Bleeker) in Indonesia (Last and Stevens 1994).

Countries:

Native:

Australia; Cambodia; China; Indonesia; Lao People's Democratic Republic; Myanmar; Papua New Guinea; Thailand; Viet Nam

Population [top]

Population Trend:	Unknown

Population Trend:

Unknown

Habitat and Ecology [top]

Habitat and Ecology:	This is mainly a freshwater species, but there have also been records of the species from estuarine waters. It is possible that it may be able to transit marine waters between riverine systems. It reaches a size up to 200 cm disc width (DW) and 600 kg in weight (Thailand and most other locales in range). However, Australian specimens are reported as only reaching slightly more than 100 cm DW. Males mature by 110 cm DW. Young (a single pup) are born at about 30 cm DW (Last and Stevens 1994). Other life history parameters (age at maturity, average generation period and maximum lifespan in the wild) are unknown.
Systems:	Freshwater

Habitat and Ecology:

This is mainly a freshwater species, but there have also been records of the species from estuarine waters. It is possible that it may be able to transit marine waters between riverine systems. It reaches a size up to 200 cm disc width (DW) and 600 kg in weight (Thailand and most other locales in range). However, Australian specimens are reported as only reaching slightly more than 100 cm DW. Males mature by 110 cm DW. Young (a single pup) are born at about 30 cm DW (Last and Stevens 1994). Other life history parameters (age at maturity, average generation period and maximum lifespan in the wild) are unknown.

Systems:

Freshwater

Threats [top]

Major Threat(s):	The Giant Freshwater Stingray has been taken by fishermen on the rivers in Central Thailand, as a small portion of larger fisheries for bony fishes, including notably Giant Gouramy (Osphrenemeus gouramy) and giant river catfishes (Pangasius spp). In 1992 Thai fishermen reported 25 individuals of this species in their catch, but by 1993 the reported landings had dropped to three specimens, a decline of 88% in one year (Cook and Compagno 1994). The species is similarly occasionally caught incidentally in artisanal fisheries on the Kinabatangan River and presumably elsewhere over much of its range. Although the large adults are not taken for food, they may be killed, or at least maimed (tails removed) before being distangled from fishing gear and returned to the river. Due to a complex series of factors causing degradation or habitat alteration in riverine habitats in the region, only about 30–31 of the 190 species of indigenous Thai freshwater fishes are thought to reproduce in the wild in the Chao Phyra River (S. Pimbolboot pers. Comm.). It is likely that a somewhat higher biodiversity exists in backwater habitats where small, isolated pockets of endemism undoubtedly occur (T. Roberts pers. Comm.). Factors causing degradation of riverine environments in Thailand and elsewhere in Southeast Asia include: over-harvesting of forest leading to drought upstream and flooding downstream during monsoon conditions, which further leads to excess silt deposition; dam building to control flooding which again leads to silt build-up and retention of agrochemicals behind impoundments; and development of lands adjoining river habitats, which facilitates degradation and destruction of ray habitats with deposition of broad-spectrum wastes. The dams effectively isolate portions of the reproductive populations of all riverine stingrays (Giant Freshwater Stingray (H. chaophraya), Longnose Marbled Stingray (H. oxyrhyncha), White-edge Freshwater Stingray (H.signifer) and Mekong Freshwater Stingray (Dasyatis laoensis)) from intermixing during mating, cutting the diversity of the gene pool for any given species dramatically. In the case of some very low density riverine elasmobranch species, like the sawfishes, a combination of fisheries and habitat changes have effectively eliminated them from the Chao Phraya and adjoining freshwater habitats, where they have not been reported for some 40 years (Cook and Compagno 1994, also unpubl.data).

Major Threat(s):

The Giant Freshwater Stingray has been taken by fishermen on the rivers in Central Thailand, as a small portion of larger fisheries for bony fishes, including notably Giant Gouramy (Osphrenemeus gouramy) and giant river catfishes (Pangasius spp). In 1992 Thai fishermen reported 25 individuals of this species in their catch, but by 1993 the reported landings had dropped to three specimens, a decline of 88% in one year (Cook and Compagno 1994). The species is similarly occasionally caught incidentally in artisanal fisheries on the Kinabatangan River and presumably elsewhere over much of its range. Although the large adults are not taken for food, they may be killed, or at least maimed (tails removed) before being distangled from fishing gear and returned to the river. Due to a complex series of factors causing degradation or habitat alteration in riverine habitats in the region, only about 30–31 of the 190 species of indigenous Thai freshwater fishes are thought to reproduce in the wild in the Chao Phyra River (S. Pimbolboot pers. Comm.). It is likely that a somewhat higher biodiversity exists in backwater habitats where small, isolated pockets of endemism undoubtedly occur (T. Roberts pers. Comm.). Factors causing degradation of riverine environments in Thailand and elsewhere in Southeast Asia include: over-harvesting of forest leading to drought upstream and flooding downstream during monsoon conditions, which further leads to excess silt deposition; dam building to control flooding which again leads to silt build-up and retention of agrochemicals behind impoundments; and development of lands adjoining river habitats, which facilitates degradation and destruction of ray habitats with deposition of broad-spectrum wastes. The dams effectively isolate portions of the reproductive populations of all riverine stingrays (Giant Freshwater Stingray (H. chaophraya), Longnose Marbled Stingray (H. oxyrhyncha), White-edge Freshwater Stingray (H.signifer) and Mekong Freshwater Stingray (Dasyatis laoensis)) from intermixing during mating, cutting the diversity of the gene pool for any given species dramatically. In the case of some very low density riverine elasmobranch species, like the sawfishes, a combination of fisheries and habitat changes have effectively eliminated them from the Chao Phraya and adjoining freshwater habitats, where they have not been reported for some 40 years (Cook and Compagno 1994, also unpubl.data).

Conservation Actions [top]

Conservation Actions:	The precipitous decline of riverine stingrays in Thai fresh waters led the Thai government to implement an experimental programme for captive propagation to try to stabilise levels of biodiversity while they attempt to solve problems with degradation of river habitats. The authors observed the operations at Chai Nat, Suppraya Province, Central Thailand in December 1993, where healthy individuals of H. chaophraya ranging in size from 0.45–1.6 m DW and ranging from an estimated 50–500kg were observed. In the South Alligator (and possibly East Alligator) River which runs through the Kakadu National Park, Australia, concern has arisen for both the Giant Freshwater Stingray and riverine populations of the Bull Shark (Carcharhinus leucas). These are related to possible adverse effects of silt carrying heavy metals and radio¬isotopes from experimental mines (operated by international conglomerates) that are gearing up to extract and process an estimated A$100 billion (US$80 billion) in uranium ore believed to be in the area around Coronation Hill and along the Alligator Rivers in the Park (Compagno and Cook 1995a,b). Further research is very much needed to ascertain the status and possible threats to this species in other portions of its range (New Guinea and Indonesia).

Conservation Actions:

The precipitous decline of riverine stingrays in Thai fresh waters led the Thai government to implement an experimental programme for captive propagation to try to stabilise levels of biodiversity while they attempt to solve problems with degradation of river habitats. The authors observed the operations at Chai Nat, Suppraya Province, Central Thailand in December 1993, where healthy individuals of H. chaophraya ranging in size from 0.45–1.6 m DW and ranging from an estimated 50–500kg were observed. In the South Alligator (and possibly East Alligator) River which runs through the Kakadu National Park, Australia, concern has arisen for both the Giant Freshwater Stingray and riverine populations of the Bull Shark (Carcharhinus leucas). These are related to possible adverse effects of silt carrying heavy metals and radio¬isotopes from experimental mines (operated by international conglomerates) that are gearing up to extract and process an estimated A$100 billion (US$80 billion) in uranium ore believed to be in the area around Coronation Hill and along the Alligator Rivers in the Park (Compagno and Cook 1995a,b). Further research is very much needed to ascertain the status and possible threats to this species in other portions of its range (New Guinea and Indonesia).

Citation:	Compagno, L.J.V. & Cook, S.F. 2005. Himantura chaophraya. In: IUCN 2009. IUCN Red List of Threatened Species. Version 2009.2. <www.iucnredlist.org>. Downloaded on 10 February 2010.
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