Overview

Comprehensive Description

Biology

A freshwater species; may be found in estuaries (Ref. 9840). Poorly known (Ref. 32457). Ovoviviparous (Ref. 50449).
  • 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)
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Distribution

Range Description

This species occurs in feshwater habitats. It is known from Grand Lac and Phnom Penh, Cambodia (Mekong River), and also from Thailand in the lower Mae Nam Nan and Chao Phraya river system (Compagno and Roberts 1982, Kottelat 1985, Cook and Compagno 1994, Compagno and Cook 1995a). Photographic evidence of a specimen landed from the Mahakam River, Kalimantan (Indonesia) (P. Last pers. comm.). It may be present but unrecorded in other rivers because of its rarity. Subpopulation details are unknown. If, as seems likely, this ray is unable to transit marine habitats, each riverine population will be completely isolated.
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Cambodia, Thailand and Borneo.
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Asia: Cambodia, Thailand, and Borneo.
  • 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)
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Physical Description

Size

Maximum size: 360 mm WD
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Max. size

36.0 cm WD (male/unsexed; (Ref. 9840))
  • 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)
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Ecology

Habitat

Habitat and Ecology

Habitat and Ecology
This rarely recorded freshwater species is known from only five specimens in museum collections. No information is available on any of its life history parameters.

Systems
  • Freshwater
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Environment

demersal; freshwater; brackish
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Life History and Behavior

Life Cycle

Ovoviviparous (Ref. 205). Distinct pairing with embrace (Ref. 205).
  • 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)
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Conservation

Conservation Status

IUCN Red List Assessment


Red List Category
EN
Endangered

Red List Criteria
B1ab(iii)

Version
3.1

Year Assessed
2005

Assessor/s
Compagno, L.J.V.

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

Contributor/s

Justification
This assessment is based on the information published in the 2005 shark status survey (Fowler et al. 2005).

The Longnose Marbled Whipray (Himantura oxyrhyncha)) is a very rare species, known from only five specimens in museum collections worldwide,with three being the syntypes from Phnom Penh, Cambodia. It is known to occur from only three or four riverine systems. It is confined to tropical freshwater habitats that are under intensive threat from fisheries, pollution, logging in the catchment areas and river engineering projects and is a desirable aquarium species.

History
  • 2000
    Endangered
  • 2000
    Endangered
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Population

Population
Rare.

Population Trend
Unknown
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Threats

Major Threats
This rare ray is taken very infrequently as bycatch in freshwater teleost fisheries, which are intensive through much of its range. It is possibly also sought after for the aquarium trade, as the young of this ray are small and particularly attractive. Two of the five known museum specimens were from aquarium suppliers. Its habitat is seriously threatened by riverine pollution from agricultural chemicals, sewage and industrial waste in the river catchments, logging activities and river engineering projects (e.g. dam construction on the Chao Phraya River). Continued habitat loss and degradation are likely a major impact on the species.
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Endangered (EN) (B1ab(iii))
  • IUCN 2006 2006 IUCN red list of threatened species. www.iucnredlist.org. Downloaded July 2006.
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Management

Conservation Actions

Conservation Actions
The Thai government started a project in the 1990s to breed this and other freshwater stingrays in captivity at Chai Nat above the dam on the Chao Phraya River to counter declines of freshwater rays in the river. A single specimen of this ray was seen in captivity there in 1993 (but this was moribund and died during our visit). We later (1996) learned that the project had been put on hold, at least temporarily.
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Wikipedia

Marbled whipray

The marbled whipray (Himantura oxyrhyncha) is a little-known species of stingray in the family Dasyatidae, native to several freshwater rivers in Southeast Asia. This species has an oval pectoral fin disc with an elongated, pointed snout and a very long, whip-like tail without fin folds. It is characterized by numerous heart-shaped dermal denticles and tubercles on its upper surface, as well as a reticulated pattern of brown blotches on a light background. The maximum recorded disc width is 36 cm (14 in). The marbled whipray has been assessed as Endangered by the International Union for Conservation of Nature (IUCN); it is heavily threatened by fishing and habitat loss, degradation, and fragmentation.

Taxonomy[edit]

French zoologist Henri-Emilé Sauvage originally described the marbled whipray as Trygon oxyrhynchus based on a female specimen caught near Saigon, Vietnam, in an 1878 volume of the scientific journal Bulletin de la Société philomathique de Paris. In 1913, Samuel Garman synonymized this species with Himantura uarnak, a judgment that remained unquestioned in subsequent literature until Maurice Kottelat referenced the name in his 1984 review of Indochinese fishes.[2] This species may also be referred to as the longnose marbled whipray or the marbled freshwater stingray.[3]

Distribution and habitat[edit]

Among the few members of its family restricted to fresh water, the marbled whipray has been reported from Saigon in Vietnam, the Mekong River near Tonle Sap and Phnom Penh in Cambodia, the lower Nan and Chao Phraya Rivers in Thailand, and the Mahakam River in Kalimantan, Indonesia. The subpopulations inhabiting these rivers are likely isolated from one another.[1][2] This bottom-dwelling species favors a sandy substrate in which it can bury itself.[4]

Description[edit]

The marbled stingray has a thin, oval-shaped pectoral fin disc longer than wide. The snout is long and triangular, with the pointed tip projecting from the disc. The eyes are small, and immediately followed by spiracles over twice their diameter. There is a curtain of skin between the nares with a fringed trailing margin. The mouth is gently arched and contains an anterior row of four and posterior row of two papillae across the floor, which are followed by a seventh papilla in larger individuals. There are 40–42 tooth rows in the upper jaw and 42–46 tooth rows in the lower jaw; the teeth are arranged with a quincunx pattern into pavement-like surfaces. The tail measures three times as long as the disc and bears two long stinging spines on top; after the spine the tail becomes thin and whip-like, without any fin folds.[2][5]

There are numerous flattened, heart-shaped dermal denticles on the back, arranged in a dense central band reaching the base of the tail, and becoming smaller and sparser on the outer portions of the disc. Larger, heart-shaped denticles are scattered over the disc, especially around the "shoulders" and the middle of the back. Two pearl spines are present. There is a line of 40–41 flat tubercles running down the dorsal midline, from between the eyes to the tail spines; adult individuals also have two lines of spiny denticles running along the sides of the tail from the spine to the tip. The dorsal coloration is white to light gray, with brownish hexagonal blotches forming a reticulated pattern that fades towards the disc margin. Smaller individuals are covered by many irregular dark spots. The underside is entirely light-colored.[2] This ray attains a disc width of 36 cm (14 in).[3]

Biology and ecology[edit]

The natural history of the marbled whipray is poorly understood. It likely feeds on benthic organisms such as small crustaceans and molluscs. Reproduction is aplacental viviparous with females supplying their unborn young with histotroph ("uterine milk"), as in other stingrays.[4][6]

Human interactions[edit]

Only five specimens of the marbled whipray have been deposited in museums. However, it is reportedly locally common in some rivers and streams. It is an infrequent incidental catch of intense fishery activities taking place across much of its range, using demersal tangle nets, fish traps, and hook-and-line. These attractively colored rays, especially the young, are valued by the aquarium trade. Another major threat to the marbled whipray is habitat loss and degradation, from pollution, logging, and dam construction. In Thailand, dams on the Chao Phraya have prevented stingrays in different stretches of the river from intermingling, with a negative effect on genetic diversity. Citing these threats, the International Union for Conservation of Nature (IUCN) has assessed this species as Endangered. During the 1990s, the Thai government initiated a captive breeding program for this and other endangered freshwater stingrays at Chai Nat, but by 1996 the program had been placed on hold.[1][6]

References[edit]

  1. ^ a b c Compagno, L.J.V. (2005). Himantura oxyrhyncha. In: IUCN 2008. IUCN Red List of Threatened Species. Retrieved January 11, 2010.
  2. ^ a b c d Deynat, P.P. and Y. Fermon (2001). "Resurrection of Himantura oxyrhyncha (Sauvage, 1878) from the synonymy of H. uarnak, a senior synonym of H. krempfi (Chabanaud, 1923) (Myliobatiformes: Dasyatidae)". Cybium 25 (2): 161–176. 
  3. ^ a b Froese, Rainer and Pauly, Daniel, eds. (2010). "Himantura oxyrhyncha" in FishBase. January 2010 version.
  4. ^ a b Baensch, H.A. and R. Riehl. Aquarium Atlas (Volume 4). Steven Simpson Books. pp. 14–15. ISBN 3-88244-058-9. 
  5. ^ Fowler, S.L., R.D. Cavanagh, M. Camhi, G.H. Burgess, G.M. Cailliet, S.V. Fordham, C.A. Simpfendorfer, and J.A. Musick (2005). Sharks, Rays and Chimaeras: The Status of the Chondrichthyan Fishes. International Union for Conservation of Nature and Natural Resources. pp. 350–351. ISBN 2-8317-0700-5. 
  6. ^ a b Sharks and Rays of Borneo. CSIRO Publishing. 2010. pp. 204–205. ISBN 978-1-921605-59-8. 
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