Himantura granulata, Mangrove Whipray. In: The IUCN Red List of Threatened Species 2016: e.T161431A68627924

Manjaji Matsumoto, B.M., White, W.T., Fahmi, , Ishihara, H. and Morgan, D.L. (2016) Himantura granulata, Mangrove Whipray. In: The IUCN Red List of Threatened Species 2016: e.T161431A68627924. International Union for Conservation of Nature and Natural Resources

Abstract

This is an amended version of the 2015 assessment to accommodate the change in genus from Himantura to Urogymnus.

The Mangrove Whipray (Urogymnus granulatus) is a large-bodied (to 141 cm disc width), uncommon stingray, with a widespread distribution in the eastern Indian and western Pacific oceans, from Sri Lanka and eastern India, through to Indonesia. It also occurs along the northern coast of Australia and throughout some of the Pacific Islands. The species appears to prefer shallow inshore waters, including mangroves, estuaries, sand flats and broken rocky-sandy substrate, although adults may move offshore to at least 85 m depth. The species' preference for inshore habitats and the fact that it is apparently uncommon compared to other Himantura species, makes it particularly vulnerable to widespread and intensive artisanal and industrial fisheries operating throughout large areas of its range, as well as habitat destruction and pollution. Significant destruction and degradation of mangrove areas and targeting of juveniles in shallow waters are thought to have significantly affected this species.

It is caught irregularly by tangle net, bottom trawl (including large numbers of trawlers targeting rhynchobatids in the Arafura Sea) and longline fisheries and retained for human consumption. Levels of exploitation are very high throughout its range in Southeast Asia and in many parts of the Indian Ocean, hence it is under a severe level of threat within most of this range. Although no species-specific data are available, overall catches of stingrays are reported to be declining in areas of Southeast Asia for which information is available, with fishermen having to travel further and further to sustain catch levels. Species that inhabit a similar habitat to this species (such as the Sicklefin Lemon Shark (Negaprion acutidens)) are now rarely observed in Indonesia due to high levels of exploitation, and significant declines are also inferred to have occurred in the Mangrove Whipray in Indonesia and other areas. Given the continuation of high levels of exploitation throughout its range in Southeast Asia where the species is caught in multiple types of fisheries, along with evidence for declines in catches of rays, the level of decline (>30% over the last three generations) and exploitation can be inferred from overall declines in fish catches in the region, as well as from habitat loss (in particular mangroves).

In Australia, the Mangrove Whipray is considered at minimal threat throughout its wide range as there is no information to suggest that this species has declined in this area. Fisheries in northern Australia are generally well managed and the introduction of turtle exclusion devices (TEDs) have significantly reduced the bycatch of large stingrays. There are also significant marine protected areas in this species' range. This large species may have limiting life history characteristics that would make it biologically susceptible to depletion in fisheries and therefore, efforts should be made to assess and monitor mortality in fisheries and population trends throughout its range. The Mangrove Whipray is assessed as Vulnerable globally based on inferred levels of decline and exploitation across a large part of its range, but is considered to be Least Concern in Australia.

Item Type:	Report
Murdoch Affiliation(s):	School of Veterinary and Life Sciences
Publisher:	International Union for Conservation of Nature and Natural Resources
Copyright:	© 2016 International Union for Conservation of Nature and Natural Resources
URI:	http://researchrepository.murdoch.edu.au/id/eprint/38247

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