|Scientific Name:||Himantura granulata|
|Species Authority:||(Macleay, 1883)|
Himantura ponapensis (Günther 1910)
Trygon granulata Macleay, 1883
|Taxonomic Source(s):||Eschmeyer, W.N., Fricke, R. and Van der Laan, R. (eds). 2016. Catalog of Fishes: genera, species, references. Updated 31 March 2016. Available at: http://researcharchive.calacademy.org/research/ichthyology/catalog/fishcatmain.asp. (Accessed: 31 March 2016).|
|Red List Category & Criteria:||Vulnerable A2bd ver 3.1|
|Assessor(s):||Manjaji Matsumoto, B.M., White, W.T., Fahmi, Ishihara, H. & Morgan, D.L.|
|Reviewer(s):||Dulvy, N.K., Bigman, J.S. & Kyne, P.M.|
|Facilitator/Compiler(s):||Kyne, P.M., Walls, R.H.L., Simpfendorfer, C. & Chin, A.|
The Mangrove Whipray (Himantura granulata) 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).
n 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.
|Previously published Red List assessments:|
The Mangrove Whipray is likely widespread in the Indo-West Pacific, around the Red Sea, Maldives, New Guinea, Micronesia, Gulf of Thailand, the Philippines, eastern Indonesia, and off the Andaman, Santa Cruz, and Solomon Islands (Last and Stevens 2009). In Australia, it is reported inshore from Western Australia (Ningaloo Reef) to Queensland (Whitsunday Passage) (Last and Stevens 2009). There have been records from southern Queensland, but these are likely erroneous (Last and Stevens 2009). Records from the western Indian Ocean are documented by Moore (2012) and include a specimen from a fish market in Bir Ali, Gulf of Aden, Yemen in July 2009, as well as a further specimen captured on video being landed in the Gulf of Aqaba (Red Sea) near Aqaba, Jordan in April 2010.
Native:Australia (Northern Territory, Queensland, Western Australia); Bangladesh; Fiji; Guam; India (Andaman Is., Nicobar Is.); Indonesia (Bali, Jawa, Kalimantan, Lesser Sunda Is., Maluku, Papua, Sulawesi); Jordan; Malaysia (Peninsular Malaysia, Sabah, Sarawak); Micronesia, Federated States of ; Myanmar (Coco Is., Myanmar (mainland)); Papua New Guinea (Papua New Guinea (main island group)); Philippines; Solomon Islands; Sri Lanka; Thailand; Yemen
|FAO Marine Fishing Areas:|
Indian Ocean – eastern; Indian Ocean – western; Pacific – western central
|Range Map:||Click here to open the map viewer and explore range.|
Globally, shark and ray landings have declined by at least 20% since 2003, but the Indo-Pacific is amongst the regions where this decline has been more severe (Dulvy et al. 2014). Catches of sharks and rays in Southeast Asia are very high but are declining and fishers are travelling much further from port in order to increase catches (Chen 1996). Net and trawl fisheries in Indonesia (especially the Java Sea) and elsewhere are very extensive and as a result, many shark and ray species are highly exploited and stocks of most species have declined by at least an order of magnitude (Blaber et al. 2009). Batoids are heavily exploited (White and Dharmadi 2007) and datasets from as early as 1963–1972 show the considerable decline in batoids in the Gulf of Thailand (Pauly 1979). Trawl and gill net fisheries are also moving further afield. For example, in Jakarta the gillnet fishery at Muara Baru travels to waters around Kalimantan due to the decline in local populations (W.T. White, unpubl. data). While species-specific data on long-term declines in elasmobranchs in the Southeast Asian region are lacking, declines of the Mangrove Whipray in Southeast Asia and elsewhere in the Indo-West Pacific are inferred given the widespread historical and continuing declines of demersal fisheries in this region (Stobutzki et al. 2006). Furthermore, the extensive loss and degradation of habitats such as coastal mangroves are another key threat to coastal and inshore species; Southeast Asia has seen an estimated 30% reduction in mangrove area since 1980 (FAO 2007, Polidoro et al. 2010).
|Current Population Trend:||Decreasing|
|Habitat and Ecology:||The Mangrove Whipray appears to prefer shallow inshore waters, including mangroves, estuaries, sand flats, and broken rocky-sandy substrate, although adults may move offshore and it has been recorded to a depth of at least 85 m (White et al. 2006; B.M. Manjaji-Matsumoto and W. White, pers. obs. 2007). This species also appears to be solitary rather than forming aggregations, like some other stingrays (B.M. Manjaji-Matsumoto, pers. obs. 2007). Reproduction is viviparous with histotrophy (White et al. 2006). The species reaches a maximum reported size of 141 cm disc width (DW), >275 cm total length (TL) (White and Dharmadi 2007, W. White, pers. obs. 2007) and size at birth is reported at 14-28 cm DW (Manjaji 2004, White et al. 2006). Manjaji (2004) reports that males mature at 55-65 cm DW, but the biology and life-history characteristics of this species are generally poorly known. A generation length of 20 years can be estimated based on the Blackspotted Whipray (Himantura astra) (Jacobsen and Bennett 2011), but noting that the Blackspotted Whipray grows to a much smaller maximum size (80 cm disc width) than the Mangrove Whipray (141 cm DW).|
Davy et al. (2015) examined the movement patterns of juveniles (29.5-44.0 cm DW) at Orpheus Island, Australia between March and December 2012, with the majority of individuals showing high site fidelity, and were found to seek refuge within mangrove roots; presumed to be to reduce predation risk. The preference for nearshore habitats may increase its susceptibility to habitat loss (mangroves) and fisheries interactions (Davy et al. 2015).
|Generation Length (years):||20|
|Use and Trade:||The flesh is utilised fresh or salted and dried for human consumption (White et al. 2006, Moore 2012), and the skin is used for leather (high value) (White et al. 2006).|
The Mangrove Whipray is a rare species that is caught infrequently by tangle net, bottom trawl, and, to a lesser extent, longline fisheries in Indonesia (White et al. 2006; W. White, pers. obs. 2007) and in other parts of its range (Moore 2012). In these areas, most bycatch by commercial fisheries (especially trawlers) are landed and sold as food fish. The Mangrove Whipray and other stingrays are an important retained bycatch of the commercial gillnet fishery in Indonesia that targets rhynchobatid rays in the Arafura Sea (Last and Compagno 1999; W. White, pers. obs. 2007). Catches in inshore waters have declined and these vessels are having to travel farther to sustain catches; the rhynchobatid fisheries are very intensive in this region, thus the level of exploitation is extremely high. There is also evidence that fisherman in these regions increasingly illegally fish in Australian waters (Chen 1996; W. White, unpubl. data).
This species' preference for shallow inshore waters makes it particularly sensitive to extensive and intensive artisanal and industrial fisheries operating throughout large areas of its range, as well as habitat destruction and pollution (B.M. Manjaji-Matsumoto and W. White, pers. obs, Vidthayanon 1997, Davy et al. 2015). Juveniles and sub-adults are targeted in mangrove areas and destruction of mangrove forests are having a significant effect on this species (W. White, pers. obs. 2007). Mangrove forests throughout Southeast Asia and large areas of the Eastern Indian Ocean have been deforested and degraded (FAO 2007). In this region, ~1.9 million hectares of mangroves have been logged during the last 25 years (FAO 2007). More than 90% of this loss has been caused by destruction of mangrove area in Indonesia, Pakistan, Vietnam, Malaysia, and India (areas where this species occurs) through conversion of land for shrimp farms, excessive logging, conversion of land for agriculture or salt pans and degradation through oil spills and pollution (FAO 2007). Even in well-managed mangrove areas that are protected from destruction, for example, the UNESCO Biosphere Reserve in Ranong, Thailand (designated in 1997), this species may still face threats from local fisheries on which the people living in the reserve primarily depend (FAO 2007).
The Sicklefin Lemon Shark (Negaprion acutidens) occurs at similar depths to this species' preferred bathymetric range; the Sicklefin Lemon Shark is rarely observed in recent times in Indonesia due to the very high level of exploitation of inshore waters and its slow growth rate (White et al. 2006). The Mangrove Whipray is apparently uncommon compared to other large Himantura species in this region, making it particularly susceptible. Given that this is a large stingray, probably with 'slow' life-history characteristics also, by comparison it is inferred that this species has also declined significantly in these areas. Artisanal inshore fishing pressure is also very intensive off eastern India (Flewwelling and Hosch 2006). Fisheries throughout India operate on an open access basis and inshore marine species are thought to be fully or overexploited, with extensive use of illegal mesh sizes reported, and increasing bottom trawl effort (Flewwelling and Hosch 2006). Demersal species, such as this, suffer more fishing mortality than pelagic species on the eastern coast of India (Flewwelling and Hosch 2006). India's inshore fisheries are generally characterised by declining catch rates, declining recruitment and biomass, and a shift from regular landing patterns (Flewwelling and Hosch 2006). Although no species-specific data are available on catches, it is inferred that this species has also suffered declines as a result of high levels of inshore exploitation in these areas also.
In Australia, catch data for this species are relatively limited, though large specimens were previously reported as bycatch in the Australian Northern Prawn Fishery. However, with the introduction of turtle exclusion devices (TEDs) in the fishery, the ray bycatch has declined by 36.6% and there is likely to have been significant reductions in the catch and associated mortality of the Mangrove Whipray (Brewer et al. 2006).
No data or information is available on catches in the Pacific Islands, but this species may be taken as bycatch in inshore subsistence and artisanal fisheries there also.
|Conservation Actions:||The conservation measures in place for the Mangrove Whipray include both protected areas and gear modifications for fisheries. In Australia, the use of TEDs in the Northern Prawn Fishery has been compulsory since 2000 (Day 2000) and following their introduction, ray bycatch has reduced by 36.3% (Brewer et al. 2006). The presence of marine protected areas within Australian coastal waters, such as Great Barrier Reef Marine Park (GBRMP) and Shark Bay Marine Reserve, has reduced the potential for this species to be captured. There are little to no conservation measures in place for this species outside of Australia.|
|Citation:||Manjaji Matsumoto, B.M., White, W.T., Fahmi, Ishihara, H. & Morgan, D.L. 2016. Himantura granulata. The IUCN Red List of Threatened Species 2016: e.T161431A68627924.Downloaded on 26 September 2016.|
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