Glyphis siamensis

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Taxonomy [top]

Kingdom Phylum Class Order Family
ANIMALIA CHORDATA CHONDRICHTHYES CARCHARHINIFORMES CARCHARHINIDAE

Scientific Name: Glyphis siamensis
Species Authority: (Steindachner, 1896)
Common Name(s):
English Irrawaddy River Shark
Synonym(s):
Carcharias siamensis Steindachner, 1896
Taxonomic Notes: Until recently (Compagno et al. 2005), the species was classified as a species dubium in the genus Carcharhinus (Compagno 1988). Some have considered it to be a synonym of G. gangeticus but this is incorrect and it is a clearly distinct Glyphis species (L.J.V. Compagno pers. comm. 2007).

Assessment Information [top]

Red List Category & Criteria: Critically Endangered B1ab(iii,v) ver 3.1
Year Published: 2009
Date Assessed: 2008-12-01
Assessor(s): Barnett, L.A.K., Quaranta, K.L., Ebert, D.A., White, W.T. & Compagno, L.J.V.
Reviewer(s): Stevens, J.D., Valenti, S.V. & Fowler, S.L. (Shark Red List Authority)
Justification:
The Irrawaddy River Shark (Glyphis siamensis) is known only from a single 19th century museum specimen. Artisanal fisheries do operate within the geographic range of the Irrawaddy River Shark, but their presence in the catch is unconfirmed. Mangrove forests, potentially important habitat for the species, are being depleted for fuel, construction materials, and non-timber forest products. Pollution in this river system is also a major concern. If present, this species would be captured in the artisanal fisheries operating in the Irrawaddy River, since Glyphis species elsewhere are susceptible to net and line fisheries, but there are no specific records of their presence or abundance in the catch. The lack of records of this species is highly likely a result of overexploitation on a species which was possibly of a naturally low abundance and, potentially, has a very restricted range. The Irrawaddy River Shark is known only from the type locality and has not been recorded again since its description more than 100 years ago. Although no specific surveys have been conducted, efforts have been made to locate further specimens and none have been found. It is reasonable to assume a decline in the number of mature individuals given continued fishing pressure across its known range. A decline in habitat quality is also highly likely from pollution in this river. The species is assessed as Critically Endangered on the basis of these factors.

Geographic Range [top]

Range Description:The full extent of this species' range is unknown. The Irrawaddy River Shark is known from only a single specimen collected in the Irrawaddy River delta, near the city of Yangon, Myanmar (Steindachner 1896).
Countries:
Native:
Myanmar (Myanmar (mainland))
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: Known only from one specimen recorded in the original species description (Steindachner 1896).
Population Trend: Unknown

Habitat and Ecology [top]

Habitat and Ecology: The Irrawaddy River where  G. siamensis occurs is a very large tropical waterway, lined with mangrove forests in its lower reaches. One of the most heavily silted rivers in the world (Scott 1989), visibility is extremely limited, which potentially is a factor in the evolution of the Irrawaddy River Shark's notably small eyes (Compagno 1989). The species is assumed to be euryhaline, having been recorded from brackish water, and with congeners recorded from inshore marine waters.
Systems: Freshwater; Marine

Threats [top]

Major Threat(s): Mangrove forests, which potentially is important habitat for the Irrawaddy River Shark, are being depleted for fuel, construction materials, and non-timber forest products (Scott 1989, Rao et al. 2002). Pollution in this river system is also a major concern.

This species would be captured in the artisanal fisheries operating in the Irrawaddy River since Glyphis species elsewhere are susceptible to net and line fisheries, but there are no specific records of their presence or abundance in the catch. Fishing pressure is intense in the Irrawaddy River. During surveys for the Irrawaddy Dolphin Orcaella brevirostris, a total of 5,701 fishing gears were recorded in the main channel of the Irrawaddy River (November to December 2002) (Smith 2003). Gillnets accounted for the majority of gear (excluding sticks with multiple hooks). Electric fishing was also reported during the survey (Smith 2003).

Conservation Actions [top]

Conservation Actions: Some small protected areas do exist within the Irrawaddy River Shark's range, but they are lacking proper personnel for effective management (Rao et al. 2001).

Bibliography [top]

Compagno, L.J.V. 1988. Sharks of the order Carcharhiniformes. Princeton University Press, Princeton, New Jersey.

IUCN. 2009. IUCN Red List of Threatened Species (ver. 2009.2). Available at: www.iucnredlist.org. (Accessed: 3 November 2009).


Citation: Barnett, L.A.K., Quaranta, K.L., Ebert, D.A., White, W.T. & Compagno, L.J.V. 2009. Glyphis siamensis. In: The IUCN Red List of Threatened Species. Version 2014.2. <www.iucnredlist.org>. Downloaded on 01 October 2014.
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