Table of Contents
Overview
Brief Summary
Biology
Despite its enormous size, rivalling the Mekong giant catfish as largest freshwater fish in the world, the giant freshwater stingray is elusive and understudied. It is thought to mature at around 110 cm across and gives birth to live young of 30 cm across (4). It is venomous but uses its sting in self-defence as it preys upon invertebrates and relatively small fish (2).
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Comprehensive Description
Description
Awe-inspiringly large, the giant freshwater stingray lives up to its name, possessing a venomous sting and a large whip-like tail (2). It is brown on the upper surface of its broad, thin, disc-shaped body, and paler beneath with a ring of black around the edge. It has a large snout but small eyes (3).
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Biology
Inhabits sandy bottoms in estuaries and large rivers (Ref. 12693). Feeds on benthic invertebrates (Ref. 12693) and fishes (Ref. 32457). Ovoviviparous (Ref. 50449). Caught occasionally by demersal gillnet and longline fisheries operating in riverine and estuarine areas. Utilized for its meat and possibly its cartilage (Ref.58048). Marketed fresh, with large individuals being sold in cut pieces by the kilogram (Ref. 12693). Size reaches to about 500 cm TL. Threatened due to over harvesting and pollution (Ref. 58490).
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Rainboth, W.J. 1996 Fishes of the Cambodian Mekong. FAO Species Identification Field Guide for Fishery Purposes. FAO, Rome, 265 p. (Ref. 12693)
http://www.fishbase.org/references/FBRefSummary.php?id=12693&speccode=26747
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Distribution
Range Description
The species is known from several disjunct freshwater localities in south and southeast Asia, from India to eastern Indonesia (Last et al. 2010), although the presence and taxonomic status of some of the reported populations requires confirmation.
In Thailand it is known from the Chao Phraya, Nan, Mekong, Bangpakong (Bang Pakong), Tachin and Tapi (Tapee) rivers. It is recorded from the mainstream of the Mekong in Lao PDR, Viet Nam and Cambodia. It is possibly present as far upstream on the Mekong as Chiang Khong in northern Thailand, where unidentified stingrays have been seen (Z. Hogan, pers. comm.).
In Indonesia it is recorded from the Mahakam basin in Kalimantan (Monkolprasit and Roberts 1990), and from Java (the holotype locality; given as "Jakarta [Batavia]", most likely from the Ciliwung River drainage). C. Leh (pers. comm.) reported anecdotal records of the species being collected by locals in the Kapuas River at Pontianak, Kalimantan, and the Kapuas was connected to the Lupar River in Sarawak in geological times, however extensive survey along the length of the Kapuas River in 1997 (C. Lim. pers. comm.) did not record the species. There are no recent records of the species from Java and recent surveys of both the Ciliwung and Cisidane drainages (R.K. Hadiaty, pers. comm.) have reported a very high level of decline in fish diversity; further survey in coastal areas is required to confirm the species presence.
While this species was reported from Sarawak by Kottelat et. al. (1993) and by Roberts (1989), it is largely unknown in Sarawak, and the species has not been recorded there in the last 25 years (C. Leh pers. comm. 2011). Extensive recent survey in the Rajang River in Sarawak by Parenti and Lim (2005) did not report the species. Specimens have been collected from the Kinabatangan (Fyler and Caira 2006) and Buket (in 1997; Yano et al. 2005) rivers in Sabah. Last et al. (2010) consider it to be probably common in the Kinabatangan River, but rarely caught, and found in coastal and marine and brackish habitats in other parts of Indonesia. No specimens of the species are held by the Sarawak Museum, and the conclusion by C. Leh (pers. comm.) is that the status of the species in Sabah and Sarawak is largely unknown and that there is insufficient data the species. There do not appear to be records from Brunei Darussalam (a survey in the Belalong River in the early 1990's in the Temburong National Park by the Earl of Cranbrook did not report the species) or from Singapore (Chong Ving Ching, pers. comm.).
It was reported to be present in Myanmar, but there is no information is available on its distribution there; its presence in Myanmar rivers requires confirmation, and R. Britz (pers. comm.) has not seen nor is aware of any records from Myanmar. It is also recorded as present in India (as Trygon fluviatilis Annandale, 1909) but there appear to be no recent records. The identification of the records from the Ganges and the Bay of Bengal require confirmation (Last and Manjaji-Matsumoto 2008). Sezaki et al. (1999) compared specimens from India and Thailand and found significant molecular differences.
Records from Australia pertain to H. dalyensis (Last and Manjaji-Matsumoto 2008), which may also occur in most of the large rivers of tropical Australia; records from New Guinea (Fly River) most likely also refer to dalyensis, but this requires study of material to confirm. Records of the species from Papua New Guinea also require taxonomic confirmation, and are probably also dalyensis (P. Last pers. comm. 2011).
The species has also been recorded in estuarine waters. Despite records of this species from estuarine waters, there is only a possibility that it may be able to transit marine waters between riverine systems, most of its populations are thought likely to be geographically isolated.
In Thailand it is known from the Chao Phraya, Nan, Mekong, Bangpakong (Bang Pakong), Tachin and Tapi (Tapee) rivers. It is recorded from the mainstream of the Mekong in Lao PDR, Viet Nam and Cambodia. It is possibly present as far upstream on the Mekong as Chiang Khong in northern Thailand, where unidentified stingrays have been seen (Z. Hogan, pers. comm.).
In Indonesia it is recorded from the Mahakam basin in Kalimantan (Monkolprasit and Roberts 1990), and from Java (the holotype locality; given as "Jakarta [Batavia]", most likely from the Ciliwung River drainage). C. Leh (pers. comm.) reported anecdotal records of the species being collected by locals in the Kapuas River at Pontianak, Kalimantan, and the Kapuas was connected to the Lupar River in Sarawak in geological times, however extensive survey along the length of the Kapuas River in 1997 (C. Lim. pers. comm.) did not record the species. There are no recent records of the species from Java and recent surveys of both the Ciliwung and Cisidane drainages (R.K. Hadiaty, pers. comm.) have reported a very high level of decline in fish diversity; further survey in coastal areas is required to confirm the species presence.
While this species was reported from Sarawak by Kottelat et. al. (1993) and by Roberts (1989), it is largely unknown in Sarawak, and the species has not been recorded there in the last 25 years (C. Leh pers. comm. 2011). Extensive recent survey in the Rajang River in Sarawak by Parenti and Lim (2005) did not report the species. Specimens have been collected from the Kinabatangan (Fyler and Caira 2006) and Buket (in 1997; Yano et al. 2005) rivers in Sabah. Last et al. (2010) consider it to be probably common in the Kinabatangan River, but rarely caught, and found in coastal and marine and brackish habitats in other parts of Indonesia. No specimens of the species are held by the Sarawak Museum, and the conclusion by C. Leh (pers. comm.) is that the status of the species in Sabah and Sarawak is largely unknown and that there is insufficient data the species. There do not appear to be records from Brunei Darussalam (a survey in the Belalong River in the early 1990's in the Temburong National Park by the Earl of Cranbrook did not report the species) or from Singapore (Chong Ving Ching, pers. comm.).
It was reported to be present in Myanmar, but there is no information is available on its distribution there; its presence in Myanmar rivers requires confirmation, and R. Britz (pers. comm.) has not seen nor is aware of any records from Myanmar. It is also recorded as present in India (as Trygon fluviatilis Annandale, 1909) but there appear to be no recent records. The identification of the records from the Ganges and the Bay of Bengal require confirmation (Last and Manjaji-Matsumoto 2008). Sezaki et al. (1999) compared specimens from India and Thailand and found significant molecular differences.
Records from Australia pertain to H. dalyensis (Last and Manjaji-Matsumoto 2008), which may also occur in most of the large rivers of tropical Australia; records from New Guinea (Fly River) most likely also refer to dalyensis, but this requires study of material to confirm. Records of the species from Papua New Guinea also require taxonomic confirmation, and are probably also dalyensis (P. Last pers. comm. 2011).
The species has also been recorded in estuarine waters. Despite records of this species from estuarine waters, there is only a possibility that it may be able to transit marine waters between riverine systems, most of its populations are thought likely to be geographically isolated.
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Range
Thought to occur in most large rivers of tropical Australia, as well as the Fly River basin, New Guinea, the Mahakam River basin, Borneo and several rivers in Thailand (4).
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Asia and Oceania: Mekong and Chao Phraya basins; also from eastern Borneo, New Guinea and northern Australia.
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Kottelat, M. 1998 Fishes of the Nam Theun and Xe Bangfai basins, Laos, with diagnoses of twenty-two new species (Teleostei: Cyprinidae, Balitoridae, Cobitidae, Coiidae and Odontobutidae). Ichthyol. Explor. Freshwat. 9(1):1-128. (Ref. 27732)
http://www.fishbase.org/references/FBRefSummary.php?id=27732&speccode=26858
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Physical Description
Morphology
Dorsal spines (total): 0; Dorsal soft rays (total): 0
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Kottelat, M. 1998 Fishes of the Nam Theun and Xe Bangfai basins, Laos, with diagnoses of twenty-two new species (Teleostei: Cyprinidae, Balitoridae, Cobitidae, Coiidae and Odontobutidae). Ichthyol. Explor. Freshwat. 9(1):1-128. (Ref. 27732)
http://www.fishbase.org/references/FBRefSummary.php?id=27732&speccode=26858
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Size
Max. size
240 cm WD (male/unsexed; (Ref. 27732)); max. published weight: 600.0 kg (Ref. 6871)
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Last, P.R. and J.D. Stevens 1994 Sharks and rays of Australia. CSIRO, Australia. 513 p. (Ref. 6871)
http://www.fishbase.org/references/FBRefSummary.php?id=6871&speccode=5891
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Kottelat, M. 1998 Fishes of the Nam Theun and Xe Bangfai basins, Laos, with diagnoses of twenty-two new species (Teleostei: Cyprinidae, Balitoridae, Cobitidae, Coiidae and Odontobutidae). Ichthyol. Explor. Freshwat. 9(1):1-128. (Ref. 27732)
http://www.fishbase.org/references/FBRefSummary.php?id=27732&speccode=26858
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Diagnostic Description
Absence of ventral and dorsal skin folds on the tail, and the broad greyish to blackish marginal band on the ventral surface of the disc. The dorsal surface of the disc is brown (Ref. 27732). Spiral valve with 21 turns; dorsal surface with uniform brown or grey coloration (Ref. 12693). Lacking caudal fin; with long whip-like tail (Ref. 43281).
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Kottelat, M. 1998 Fishes of the Nam Theun and Xe Bangfai basins, Laos, with diagnoses of twenty-two new species (Teleostei: Cyprinidae, Balitoridae, Cobitidae, Coiidae and Odontobutidae). Ichthyol. Explor. Freshwat. 9(1):1-128. (Ref. 27732)
http://www.fishbase.org/references/FBRefSummary.php?id=27732&speccode=26858
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Ecology
Habitat
Habitat and Ecology
Systems
- Freshwater
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Habitat and Ecology
Habitat and Ecology
Systems
This is mainly a freshwater species found in large rivers with a muddy or sandy bottom. There have been records of the species from estuarine waters. Martin (2005) considered it an obligate freshwater species, though Last et al. (2010) report records from coastal and marine and brackish habitats in parts of Indonesia. Based on catch data and tagging work, the species does appear to occur in both brackish and freshwater, but it is considered unlikely that that the species needs to move between brackish and freshwater to complete its life cycle (Z. Hogan pers. comm. 2011), however large numbers of pregnant females are seen in brackish waters, so estuaries could be a pupping ground at least for some populations.
It is possible that it may be able to transit marine waters between riverine systems. The movement pattern of the species within and between river systems is not known and requires further research.
It reaches a size of up to 200 cm disc width (DW) and 600 kg in weight (Thailand). Males mature by 110 cm DW. Young (a single pup) are born at about 30 cm DW (Last and Stevens 1994); recruitment is likely to be limited. Other life history parameters (age at maturity, average generation period and maximum lifespan in the wild) are unknown. Ovoviviparous, the fish gives birth to live young measuring 30 cm wide.
It is often observed at the water margin where it is thought to be feeding on earthworms (I. Baird, pers comm.; C. Vidthayanon, pers. comm.).
It is possible that it may be able to transit marine waters between riverine systems. The movement pattern of the species within and between river systems is not known and requires further research.
It reaches a size of up to 200 cm disc width (DW) and 600 kg in weight (Thailand). Males mature by 110 cm DW. Young (a single pup) are born at about 30 cm DW (Last and Stevens 1994); recruitment is likely to be limited. Other life history parameters (age at maturity, average generation period and maximum lifespan in the wild) are unknown. Ovoviviparous, the fish gives birth to live young measuring 30 cm wide.
It is often observed at the water margin where it is thought to be feeding on earthworms (I. Baird, pers comm.; C. Vidthayanon, pers. comm.).
Systems
- Freshwater
- Marine
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Habitat
Inhabits the sandy bottoms of large rivers and estuaries (1).
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Environment
demersal; potamodromous (Ref. 51243); freshwater; brackish
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Riede, K. 2004 Global register of migratory species - from global to regional scales. Final Report of the R&D-Projekt 808 05 081. Federal Agency for Nature Conservation, Bonn, Germany. 329 p. (Ref. 51243)
http://www.fishbase.org/references/FBRefSummary.php?id=51243&speccode=4683
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Migration
Potamodromous. Migrating within streams, migratory in rivers, e.g. Saliminus, Moxostoma, Labeo. Migrations should be cyclical and predictable and cover more than 100 km.
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Riede, K. 2004 Global register of migratory species - from global to regional scales. Final Report of the R&D-Projekt 808 05 081. Federal Agency for Nature Conservation, Bonn, Germany. 329 p. (Ref. 51243)
http://www.fishbase.org/references/FBRefSummary.php?id=51243&speccode=4683
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Life History and Behavior
Life Cycle
Exhibit ovoviparity (aplacental viviparity), with embryos feeding initially on yolk, then receiving additional nourishment from the mother by indirect absorption of uterine fluid enriched with mucus, fat or protein through specialised structures (Ref. 50449). Distinct pairing with embrace (Ref. 205). Young are born at about 30 cm disc width (Ref. 6871).
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Breder, C.M. and D.E. Rosen 1966 Modes of reproduction in fishes. T.F.H. Publications, Neptune City, New Jersey. 941 p. (Ref. 205)
http://www.fishbase.org/references/FBRefSummary.php?id=205&speccode=1256
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Conservation
Conservation Status
IUCN Red List Assessment
Red List Category
CR
Critically Endangered
Red List Criteria
A1bcde+2ce
Version
2.3
Year Assessed
2000
Assessor/s
Compagno, L.J.V. & Cook, S.F.
Reviewer/s
Musick, J.A. & Fowler, S. (Shark Red List Authority)
Contributor/s
Justification
This possibly obligate freshwater species is recorded from several rivers in South East Asia and northern Australia and is probably unrecorded in others. The potential for exchange between these subpopulations is presumably very limited. The species 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.
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IUCN Red List Assessment
Red List Category
EN
Endangered
Red List Criteria
A2bcd
Version
3.1
Year Assessed
2011
Assessor/s
Vidthayanon, C., Baird, I. & Hogan, Z.
Reviewer/s
Ng, H.H., Rainboth, W. & Allen, D.
Contributor/s
Hadiaty, R.K., Musick, J.A., Compagno, L.J.V., Fowler, S.L., Britz, R., Vishwanath, W., Cook, S.F. & Kyne, P.M.
Justification
This species is recorded from several rivers in Southeast Asia and is probably unrecorded in others, however the potential for exchange between these subpopulations is thought to be very limited, and the continued presence and taxonomic status of other sub-populations requires confirmation. There appear to be no recent records from the Ganges/Brahmaputra, Ayeyarwaddy or Salween basins, and there are few recent known records from Sabah and none from Sarawak.
The species has been and continues to be adversely affected in much of its range by a number of factors including fisheries, and habitat degradation or destruction. The species is taken by fishermen on the rivers in Central Thailand and the Mekong. In Thailand, Thai fishermen reported 25 individuals of this species in their catch in 1992, but by 1993 the reported landings had dropped to three specimens, a decline of 88% in one year (Cook and Compagno 1994). In the Maeklong and Bangpakong rivers in central Thailand, fishing pressure is increasing due to capture for aquariums and sportfishing. Anecdotal information from fishermen suggest that catches have gone from a catch of 2-3 fish per day to one fish every 2-3 days, a significant decline (N. Chansue pers. comm.). In Cambodia, fishers ( reported a 62% decline in the catch of this species since 1980 (Z. Hogan, unpublished data). The average size of an individual fish has also fallen from 23.2kg in 1980 to 6.9kg in 2006. At the same time, the maximum size of a fish reported in an average season dropped from 175kg in the 1980’s to 60kg in recent times. Seven fishers in central Thailand reported that they can no longer catch the species in their area (Z. Hogan, unpublished data).
Populations appear to be healthier in the upper Cambodia Mekong (where fishers regularly catch the species and report population declines of 30-50%) and less healthy in the Tonle Sap Lake/Kampong Cham/Prey Veng areas where fishermen report declines of 50-95%. C. Vidthayanon (pers. comm.) observed numerous specimens in markets in Stung Treng (Cambodia) in 2006. Although the species is still harvested in significant numbers in many areas where it occurs, catch data and local knowledge indicates a significant decline over the past 20-30 years. Past and future harvest, habitat degradation, and future habitat modification due to dam building are likely to continue to negatively impact this large-bodied, long-lived species. Population trends in other parts of the species range (e.g., India, Malaysia and Indonesia) are not known, but there are very few recent records from Malaysia and Indonesia.
A population decline of at least 30-50% can be inferred from data from the rivers of central Thailand and catch rates in Cambodia, therefore the species is assessed as Endangered A2bcd. Recruitment rates (at one pup per season) are low, and the capacity for populations to recover in the face of continuing threats is limited.
Future threats to the species include the development of mainstream dams on the Mekong River. The species habitat and reproductive success would be greatly impacted if these dams were to be developed.
Further research and survey is required to confirm the presence, population trend, and taxonomic status of populations of the species from all parts of its range, especially India, Bangladesh, Myanmar, Viet Nam, parts of Indonesia and Malaysia, and Papua New Guinea.
The species has been and continues to be adversely affected in much of its range by a number of factors including fisheries, and habitat degradation or destruction. The species is taken by fishermen on the rivers in Central Thailand and the Mekong. In Thailand, Thai fishermen reported 25 individuals of this species in their catch in 1992, but by 1993 the reported landings had dropped to three specimens, a decline of 88% in one year (Cook and Compagno 1994). In the Maeklong and Bangpakong rivers in central Thailand, fishing pressure is increasing due to capture for aquariums and sportfishing. Anecdotal information from fishermen suggest that catches have gone from a catch of 2-3 fish per day to one fish every 2-3 days, a significant decline (N. Chansue pers. comm.). In Cambodia, fishers ( reported a 62% decline in the catch of this species since 1980 (Z. Hogan, unpublished data). The average size of an individual fish has also fallen from 23.2kg in 1980 to 6.9kg in 2006. At the same time, the maximum size of a fish reported in an average season dropped from 175kg in the 1980’s to 60kg in recent times. Seven fishers in central Thailand reported that they can no longer catch the species in their area (Z. Hogan, unpublished data).
Populations appear to be healthier in the upper Cambodia Mekong (where fishers regularly catch the species and report population declines of 30-50%) and less healthy in the Tonle Sap Lake/Kampong Cham/Prey Veng areas where fishermen report declines of 50-95%. C. Vidthayanon (pers. comm.) observed numerous specimens in markets in Stung Treng (Cambodia) in 2006. Although the species is still harvested in significant numbers in many areas where it occurs, catch data and local knowledge indicates a significant decline over the past 20-30 years. Past and future harvest, habitat degradation, and future habitat modification due to dam building are likely to continue to negatively impact this large-bodied, long-lived species. Population trends in other parts of the species range (e.g., India, Malaysia and Indonesia) are not known, but there are very few recent records from Malaysia and Indonesia.
A population decline of at least 30-50% can be inferred from data from the rivers of central Thailand and catch rates in Cambodia, therefore the species is assessed as Endangered A2bcd. Recruitment rates (at one pup per season) are low, and the capacity for populations to recover in the face of continuing threats is limited.
Future threats to the species include the development of mainstream dams on the Mekong River. The species habitat and reproductive success would be greatly impacted if these dams were to be developed.
Further research and survey is required to confirm the presence, population trend, and taxonomic status of populations of the species from all parts of its range, especially India, Bangladesh, Myanmar, Viet Nam, parts of Indonesia and Malaysia, and Papua New Guinea.
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Status
The giant freshwater stingray is classified as Vulnerable (VU A1bcde + 2ce) on the IUCN Red List (1).
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Trends
Population
Population
Population Trend
The population has generally declined as a result of pollution and fishing pressure, and is locally uncommon. In some parts of the range (e.g., Mae Khlong in Thailand, Stung Treng in Cambodia (C. Vidthayanon, pers. comm.) the species occurs in fish markets occasionally. WWF (2010) report that populations of the species are suffering less than other very large fish in the Mekong from overfishing and pollution, possibly because of the depth of the river these species inhabit as well as the fact that they are difficult to catch.
The species is taken by fishermen on the rivers in Central Thailand and the Mekong. 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). However C. Vidthayanon (pers. comm.) observed numerous specimens in markets in Stung Treng (Cambodia) in 2006. Population trends in other parts of the species range (e.g., India, Malaysia and Indonesia) are not known, but there are very few recent records from Malaysia and Indonesia.
In the Maeklong and Bangpakong rivers in central Thailand, fishing pressure is increasing due to capture for aquariums and sportfishing. Anecdotal information from fishermen suggest that catches have gone from a catch of 2-3 fish per day to one fish every 2-3 days, a significant decline (N. Chansue pers. comm.). In Cambodia, fishers (age 40 years an older, n = 36) report a 62% decline in the catch of this species since 1980 (Z. Hogan, unpublished data). The average size of an individual fish has dropped from 23.2kg in 1980 to 6.9kg in 2006. At the same time, the maximum size of a fish reported in an average season dropped from 175kg in the 1980’s to 60kg in recent times. Average catch per fish has dropped from 306.2kg per season to 27.6kg per season in 2006. Seven fishers report that they can no longer catch stingray in their area (Z. Hogan, unpublished data).
Populations appear to be healthier in the upper Cambodia Mekong (where fishers regularly catch the species and report population declines of 30-50%) and less healthy in the Tonle Sap Lake/Kampong Cham/Prey Veng areas where fishermen report declines of 50-95%. Although the species is still harvested in significant numbers in many areas where it occurs, catch data and local knowledge indicates a significant decline over the past 20-30 years. Past and future harvest, habitat degradation, and future habitat modification due to dam building are likely to continue to negatively impact this large-bodied, long-lived species.
The species is taken by fishermen on the rivers in Central Thailand and the Mekong. 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). However C. Vidthayanon (pers. comm.) observed numerous specimens in markets in Stung Treng (Cambodia) in 2006. Population trends in other parts of the species range (e.g., India, Malaysia and Indonesia) are not known, but there are very few recent records from Malaysia and Indonesia.
In the Maeklong and Bangpakong rivers in central Thailand, fishing pressure is increasing due to capture for aquariums and sportfishing. Anecdotal information from fishermen suggest that catches have gone from a catch of 2-3 fish per day to one fish every 2-3 days, a significant decline (N. Chansue pers. comm.). In Cambodia, fishers (age 40 years an older, n = 36) report a 62% decline in the catch of this species since 1980 (Z. Hogan, unpublished data). The average size of an individual fish has dropped from 23.2kg in 1980 to 6.9kg in 2006. At the same time, the maximum size of a fish reported in an average season dropped from 175kg in the 1980’s to 60kg in recent times. Average catch per fish has dropped from 306.2kg per season to 27.6kg per season in 2006. Seven fishers report that they can no longer catch stingray in their area (Z. Hogan, unpublished data).
Populations appear to be healthier in the upper Cambodia Mekong (where fishers regularly catch the species and report population declines of 30-50%) and less healthy in the Tonle Sap Lake/Kampong Cham/Prey Veng areas where fishermen report declines of 50-95%. Although the species is still harvested in significant numbers in many areas where it occurs, catch data and local knowledge indicates a significant decline over the past 20-30 years. Past and future harvest, habitat degradation, and future habitat modification due to dam building are likely to continue to negatively impact this large-bodied, long-lived species.
Population Trend
Decreasing
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Threats
Threats
Major Threats
The species is taken by fishermen on the rivers in Central Thailand and the Mekong. The species is similarly occasionally caught incidentally in artisanal fisheries on the Kinabatangan River (Sabah, Malaysia) and presumably elsewhere over much of its range. In the Maeklong and Bangpakong Rivers in central Thailand, fishing pressure is increasing due to capture for aquariums and sportfishing. Harvest for aquariums is a potential problem because survival in captivity is low (N. Chansue, pers. comm.). When a display animal dies, a new animal is harvested from the wild population. Sportfishing may also be a serious threat: sport anglers now have the equipment necessary to catch very large stingrays and sport anglers do not always practice catch and release (N. Chansue, pers. comm.). Moreover, mortality from catch-and-release angling is not known. Some catch and release anglers use very invasive techniques such as gaffing and hanging for display. Harvest for aquariums and sportfishing has lead to a decline in populations.
Factors causing degradation of riverine environments in Thailand and elsewhere in Southeast Asia include forest loss and degradation leading to drought upstream and flooding downstream during monsoon conditions; dam construction for hydropower and flood control (which again leads to siltation and retention of agrochemicals and other pollutants behind impoundments); and the development of land adjoining riverine habitats, which leads to the degradation of water quality through the the movement of sediment and pollution (domestic, agricultural, and industrial).
On Java, Indonesia, the Ciliwung River, the likely type locality, has been very heavily impacted by urban and industrial development (R.K. Hadiaty, pers. comm.).
In addition, dams effectively isolate portions of the reproductive populations of the species. Proposed mainstream dams on the Mekong in Lao PDR and in Cambodia would severely the impact the species, by further fragmenting their habitat and populations, however the time frame of the construction of these dams is uncertain.
Pollution impacts the species in the Thai parts of its range especially (C. Vidthayanon, pers. comm.); in the Bangpakong River, 30 specimens were found dead in one day in 2008-9 as a result of a pollution incident.
Factors causing degradation of riverine environments in Thailand and elsewhere in Southeast Asia include forest loss and degradation leading to drought upstream and flooding downstream during monsoon conditions; dam construction for hydropower and flood control (which again leads to siltation and retention of agrochemicals and other pollutants behind impoundments); and the development of land adjoining riverine habitats, which leads to the degradation of water quality through the the movement of sediment and pollution (domestic, agricultural, and industrial).
On Java, Indonesia, the Ciliwung River, the likely type locality, has been very heavily impacted by urban and industrial development (R.K. Hadiaty, pers. comm.).
In addition, dams effectively isolate portions of the reproductive populations of the species. Proposed mainstream dams on the Mekong in Lao PDR and in Cambodia would severely the impact the species, by further fragmenting their habitat and populations, however the time frame of the construction of these dams is uncertain.
Pollution impacts the species in the Thai parts of its range especially (C. Vidthayanon, pers. comm.); in the Bangpakong River, 30 specimens were found dead in one day in 2008-9 as a result of a pollution incident.
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Vulnerable (VU) (A2bcde+3ce)
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IUCN 2006 2006 IUCN red list of threatened species. www.iucnredlist.org. Downloaded July 2006.
http://www.fishbase.org/references/FBRefSummary.php?id=57073
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FishBase
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Threats
In 1992, Thai fisherman reported having caught 25 individuals, but the following year this figure fell to just three, hinting at a rapid decline (4). Threats in Thailand are from poor habitat management, including the destruction of the forest canopy which leads to drought upstream and flooding downstream during the monsoon, as well as dam building which prevents migratory fish breeding successfully, and therefore reduces available prey. In Australia the main threat to this species is thought to be silt from uranium mines which contains heavy metals and radio-isotopes. However, it is not known how threatening this is to these fish (4). Throughout its range, the giant freshwater stingray is at risk from both direct and incidental fishing, habitat destruction and range fragmentation leading to inbreeding depression (2).
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ARKive
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Management
Conservation Actions
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 populations while they attempt to improve river habitats. The authors of the 2005 assessment observed the project 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 50-500 kg were observed. There is ongoing work in Thailand to tag individuals the Mekong and Bangpakong rivers (C. Vidthayanon, pers. comm.).
Further research and survey work is very much needed to ascertain the presence, taxonomic status, population trends, and possible threats to this species in other portions of its known and potential range (e.g., India, Myanmar, Bangladesh and Indonesia). Combining population assessments from known river basin populations would allow a more accurate global estimate of population size and trends to be made.
Movement patterns are unknown and require research. A significant gap in our knowledge of this species is its habitat use and requirements, movement patterns, and migrations or residency patterns (W. White, pers. comm., 2011).
Further research and survey work is very much needed to ascertain the presence, taxonomic status, population trends, and possible threats to this species in other portions of its known and potential range (e.g., India, Myanmar, Bangladesh and Indonesia). Combining population assessments from known river basin populations would allow a more accurate global estimate of population size and trends to be made.
Movement patterns are unknown and require research. A significant gap in our knowledge of this species is its habitat use and requirements, movement patterns, and migrations or residency patterns (W. White, pers. comm., 2011).
© International Union for Conservation of Nature and Natural Resources
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IUCN
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Conservation
Further research into this incredible fish's biology and status is necessary. The Australian government plan to form a national recovery team who will attempt to compile information on the distribution, abundance and ecology of the giant freshwater stingray (4).
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Relevance to Humans and Ecosystems
Benefits
Importance
fisheries: minor commercial; aquaculture: experimental; aquarium: potential
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Last, P.R. and L.J.V. Compagno 1999 Dasyatididae. Stingrays. p. 1479-1505. 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. Vol. 3. Batoid fishes, chimaeras and bony fishes part 1 (Elopidae to Linophrynidae). FAO, Rome. (Ref. 9840)
http://www.fishbase.org/references/FBRefSummary.php?id=9840&speccode=15387
© WorldFish Center - FishBase
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FishBase
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Wikipedia
Giant freshwater stingray
The giant freshwater stingray (Himantura chaophraya) is a species of stingray in the family Dasyatidae, native to large rivers and estuaries of Southeast Asia.[2] It is one of the largest freshwater fishes in the world, with reports from the Chao Phraya and Mekong Rivers of individuals weighing 500–600 kg (1,100–1,300 lbs).[3] Its numbers are dwindling due to overfishing and habitat loss, and it is in danger of extinction.[1] The smaller freshwater whipray of New Guinea and northern Australia was once considered to be conspecific with the giant freshwater stingray but is now recognised as a separate species. It is possible the correct scientific name for the giant freshwater stingray is Himantura polylepis.[1]
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Distribution and habitat
Himantura chaophraya was originally described from Thailand (where it occurs in the Chao Phraya, Nan, Mekong, Bangpakong, Prachinburi and Tapi Rivers), the giant freshwater stingray is also found in Indonesia (the Mahakam River Basin in Kalimantan) and Malaysia (the Kinabatangan River in Sabah). There are also records from various other river systems in the region.[1] If all these populations are part of a single species, the name Himantura polylepis is a senior synonym and therefore the valid name.[1] However, the rays across these different regions are likely to be isolated from each other, and it is yet unclear whether they represent populations of the same species or a species complex.[4] It prefers a sandy habitat.[2]
Description
The giant freshwater stingray has a relatively thin, more or less oval-shaped pectoral fin disk and minute eyes. The snout is very broad with a projecting triangular tip. The mouth is small, with 4–7 papillae (2–4 large central and 1–4 small lateral) on the floor. The whip-like tail measures 1.8–2.5 times the length of the disk and lacks fin folds.[4] The serrated spine on the tail is the largest of any stingray, reaching 38 cm (15 in) long. It is covered with a sheath of toxic mucus and is capable of piercing bone.[5]
The upper surface of the body and tail are covered with small, rough tubercles, becoming sharp on the tail beyond the spine. The back is uniform brown to gray in color, sometimes becoming lighter towards the margins. The underside is white, with a distinctive broad, black band edged with small spots around the margins of the pectoral and pelvic fins.[3] The tail is black past the spine. This species reaches at least 4.6 meters (15 ft) long and 1.9 meters (6.2 ft) across.[4]
Biology and ecology
The diet of this species consists of benthic fishes and invertebrates, which it detects using electroreceptive ampullae of Lorenzini.[2] As in other stingrays, reproduction is ovoviviparous, with females giving birth to one offspring at a time.[6] A 4.3 meter (14 ft) captured female has been observed giving birth to a single newborn measuring 34 cm (13 in) across.[7] Males mature at 1.1 meters (3.6 ft) across.[4]
Relationship to humans
This species is threatened by overfishing and habitat loss; the World Conservation Union has assessed the giant freshwater stingray as endangered over most of its range,[1] except in Thailand where it is Critically Endangered.[8] It is occasionally caught as bycatch by longlines and gillnets in central Thailand and likely elsewhere. This species is sold for meat and possibly cartilage; adult fish are not usually used for food but may still be killed or maimed by fishers.[6] There is a growing sport fishery for this species. When caught on a line, it may bury itself under large quantities of mud, making it almost impossible to lift. It is also capable of pulling boats significant distances or underwater.[5]
In Thailand, the freshwater stingray is assessed as Critically Endangered with a high risk of extinction.[8] A combination of deforestation, dam construction, and development has degraded, altered, and fragmented river habitats such as that only a fraction of Thailand's native fish species still breed in the wild. In the 1990s, the Thai government initiated a captive breeding program to bolster the population of this and other freshwater stingray species until the habitat degradation can be remedied. However, the program was later put "on hold".[6]
References
- ^ a b c d e f Vidthayanon, C., Baird, I. & Hogan, Z. (2011). "Himantura polylepis". IUCN Red List of Threatened Species. Version 2011.2. International Union for Conservation of Nature. http://www.iucnredlist.org/apps/redlist/details/195320. Retrieved 3 February 2012.
- ^ a b c Froese, Rainer, and Daniel Pauly, eds. (2009). "Himantura chaophraya" in FishBase. March 2009 version.
- ^ a b Monkolprasit, S. and Roberts, T.R. (1990). "Himantura chaophraya, a new giant freshwater stingray from Thailand". Japanese Journal of Ichthyology 37 (3): 203–208. http://www.wdc-jp.biz/pdf_store/isj/publication/pdf/37/373/37301.pdf.
- ^ a b c d Last, P.R. and Compagno, L.J.V. (1999). "Myliobatiformes: Dasyatidae". In Carpenter, K.E. and Niem, V.H.. FAO identification guide for fishery purposes. The living marine resources of the Western Central Pacific. Rome: Food and Agricultural Organization of the United Nations. ISBN 92-5-104302-7.
- ^ a b Lovgren, S. (Apr. 23, 2008). "Giant River Stingrays Found Near Thai City". National Geographic News. National Geographic Society. Retrieved on March 23, 2009.
- ^ a b c Fowler, S.L. and Cavanagh, R.D. (2005). Sharks, Rays and Chimaeras: The Status of the Chondrichthyan Fishes. IUCN. ISBN 2-8317-0700-5.
- ^ Fishing in Thailand for Giant Freshwater Stingray. The Shark Trust. 2009. Retrieved on March 23, 2009.
- ^ a b Compagno, L.J.V. & Cook, S.F. (2000). Himantura polylepis (Thailand subpopulation)'. In: IUCN 2008. IUCN Red List of Threatened Species. Downloaded on 3 February 2012.
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