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Himantura imbricata

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Taxonomy [top]

Kingdom Phylum Class Order Family
ANIMALIA CHORDATA CHONDRICHTHYES RAJIFORMES DASYATIDAE

Scientific Name: Himantura imbricata
Species Authority: (Bloch & Schneider, 1801)
Common Name(s):
English Scaly Whipray
Synonym(s):
Himantura dadong (Bleeker 1877)
Raja imbricata Bloch & Schneider, 1801
Taxonomic Notes: A limited number of specimens are presently available for taxonomic description. Nevertheless, Himantura imbricata is very similar to H. walga (it is often confused with H. walga), particularly in general disc shape, however their geographical distributions appear limited and almost non-overlapping (P. Last pers. obs.). The former is apparently found only in the Indian Ocean, the latter in the South China Sea. Two forms of H. imbricata are herein recognized, also based on the morphology of the tail.

Assessment Information [top]

Red List Category & Criteria: Data Deficient ver 3.1
Year Published: 2009
Date Assessed: 2004-09-06
Assessor(s): Manjaji, B.M., Last, P.R. & White, W.T.
Reviewer(s): Valenti, S.V. & Notarbartolo di Sciara, G. (Shark Red List Authority)
Justification:
This relatively small (to 22 cm DW), coastal stingray's geographic range is poorly defined due to regular confusion with the Dwarf Whipray (Himantura walga). The Scaly Whipray (Himantura imbricata) has a patchy distribution from the Red Sea to Thailand. Its distribution south of Thailand is uncertain, but includes Java and Borneo. No specific depth range information is avialable. The species is a utilised bycatch of demersal fisheries, and is taken in large numbers by trawlers operating in the Andaman and Java Seas. Levels of exploitation on the habitat that this species occurs in are generally very high and unregulated throughout large areas of its range. As it is caught in large numbers (in all size ranges), it is considered under a severe level of threat, although no data are available. Habitat destruction, including the removal of mangrove also threatens its coastal habitat. Further information is required on the impact of fisheries and habitat degredation on this species throughout its range. At present it is not possible to assess it beyond Data Deficient as a result of taxonomic confusion with Dwarf Whipray. Further study is needed to accurately define this species' range, catch levels and trends. The species may prove to qualify for a threatened category with further information and should be reassessed in the near term.

Geographic Range [top]

Range Description: The range of this species is not well defined due to regular confusion with H. walga (Compagno 1998). Its distribution appears limited and may prove to be restricted to the Indian Ocean (P. Last pers. obs.). Western Indian Ocean: Red Sea, India (shore area, Coromandel coast; lower Bengal).

Eastern Indian Ocean and western central Pacific: Vietnam, Cambodia and Thailand. The species' range south of Thailand is uncertain, but includes Indonesia (Java and possibly southern Borneo) (M. Majaji pers. obs. 2007).

FAO fishing area: 51, 57.
Countries:
Native:
Cambodia; India; Thailand; Viet Nam
FAO Marine Fishing Areas:
Native:
Indian Ocean – eastern; Indian Ocean – western
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: Caught in considerable numbers by trawlers operating in the Andaman Sea (P. Last pers. comm.).
Population Trend: Unknown

Habitat and Ecology [top]

Habitat and Ecology: Very little is known of the biology and ecology of this coastal, demersal stingray at present. Maximum size is reported at 65 cm total length (TL) and 22 cm disc width (DW) (Compagno 1998). The largest female examined by Manjaji (2004) (20.7 cm DW) was maturing. Size at birth is about 10 cm DW, and males mature ar 20.5-21 cm DW (Manjaji 2004).
Systems: Marine

Use and Trade [top]

Use and Trade: Flesh is utilized fresh or salted and dried for human consumption where it is caught. Typically all retained.

Threats [top]

Major Threat(s): This species is a utilised bycatch of demersal fisheries, and is taken in considerable numbers by trawlers operating in the Andaman and Java Seas (P. Last pers. obs.). Levels of exploitation on the habitat in which this species occurs are generally very high and unregulated throughout large areas of its range. As it is caught in large numbers (in all size ranges), it is considered to be under a severe level of threat. Flesh is utilized fresh or salted and dried for human consumption where it is caught.

The alteration of marine habitats by mining and mangrove deforestation poses a threat to many coastal species, such as this. In adjacent areas of Cambodia and Viet Nam, deforestation, residues of warfare chemicals and silting are the one of the main threats to coastal elasmobranch species such as Himantura imbricata (Vidthayanon 1997). Significant areas of mangrove forest have been lost from countries within this species' range (FAO 2007).

Conservation Actions [top]

Conservation Actions: This species needs to be monitored in the future due to the very high quantities taken by the large number of prawn and/or fish trawlers that operate in Thailand,Indonesia and other areas of its range.

Citation: Manjaji, B.M., Last, P.R. & White, W.T. 2009. Himantura imbricata. The IUCN Red List of Threatened Species. Version 2014.2. <www.iucnredlist.org>. Downloaded on 22 September 2014.
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