|Scientific Name:||Himantura uarnak|
|Species Authority:||(Gmelin, 1789)|
Himantura punctata Günther, 1870
Himantura variegatus (McClelland, 1841)
Raja sephen var. uarnak Forsskål, 1775
Raja uarnak Gmelin, 1789
|Taxonomic Source(s):||Gemlin, J. F. 1789. Caroli a Linné ... Systema Naturae per regna tria naturae, secundum classes, ordines, genera, species; cum characteribus, differentiis, synonymis, locis. Lipsiae.|
|Taxonomic Notes:||Himantura uarnak possibly forms a species complex (B.M. Manjaji pers. obs. 2007). It is often confused with H. undulata and H. fava. Colour pattern in H. uarnak varies throughout its range; fine spot and reticulated forms need to be compared in detail (W. White pers. obs. 2007).|
|Red List Category & Criteria:||Vulnerable A2bd ver 3.1|
|Assessor(s):||Manjaji Matsumoto, B.M., White, W.T. & Gutteridge, A.N.|
|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 Reticulate Whipray (Himantura uarnak) is a large-bodied stingray (to 160 cm disc width) that has a wide distribution in the Indian and Western Pacific Oceans. This species has also entered the Mediterranean Sea from the Red Sea through the Suez Canal.
It is taken as a utilised bycatch of tangle/gill net, trawl net, and dropline fisheries throughout Southeast Asia and parts of the Indian Ocean where inshore fishing pressure is intense. The Reticulate Whipray faces many of the same threats as other Himantura species within its range, however, its large size at maturity and maximum size, low fecundity and preference for shallow waters (which are being heavily utilised and degraded in many parts of its range), suggest that it may be more vulnerable than some of its congeners. It is caught in particularly high numbers in the target fishery for rhynchobatids operating in the Arafura Sea.
Although no species-specific data are available, overall catches of stingrays are reported to be declining, with fishermen having to travel further and further to sustain catch levels. Aggregated time series data for rays also shows a steady decline from 1973-1994 in the Gulf of Thailand. This species’ preference for inshore coastal waters means it is also threatened by extensive habitat degradation and destructive fishing practices throughout a large part of its range. Given the species’ high levels of exploitation, extensive habitat degradation and its large size, significant population declines are inferred to have occurred and are likely to be ongoing in Southeast Asia and more widely in the Indian Ocean. Conversely, this species has refuge from fishing pressure in northern Australia, where fishing pressure is light, bycatch mitigation measures are in place and it is not commercially utilised and consequently is considered at low risk.
Given the continuation of high levels of exploitation throughout most its range 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. The Leopard 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:|
|Range Description:||The Reticulate Whipray is widespread in the Indo-West Pacific, from South Africa to northern Australia, including the Red Sea, the Persian/Arabian Gulf, India, and Southeast Asia (north to at least the Philippines) (White et al. 2006; W. White and B.M. Manjaji-Matsumoto, pers. obs. 2007; Last and Stevens 2009). The species is thought to be a Lessepsian immigrant, having entered the Mediterranean Sea from the Red Sea through the Suez Canal (Serena 2005). In northern Australia, it occurs widely from Shark Bay in Western Australia to Brisbane in Queensland (Last and Stevens 2009).|
Native:Australia (Northern Territory, Queensland, Western Australia); Bangladesh; Brunei Darussalam; Cambodia; Egypt; Eritrea; India; Indonesia; Iran, Islamic Republic of; Israel; Japan (Nansei-shoto); Kenya; Kuwait; Lebanon; Madagascar; Malaysia; Mozambique; Myanmar; Oman; Pakistan; Papua New Guinea (Papua New Guinea (main island group)); Philippines; Saudi Arabia; Somalia; South Africa; Sri Lanka; Sudan; Taiwan, Province of China; Tanzania, United Republic of; Thailand; United Arab Emirates; Yemen
|FAO Marine Fishing Areas:|
Indian Ocean – eastern; Indian Ocean – western; Mediterranean and Black Sea; Pacific – western central; Pacific – northwest
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||The Reticulate Whipray is uncommon throughout much of its range (B.M. Manjaji-Matsumoto, pers. obs. 2007), but appears to be common in parts of northern Australia (W. White., pers. obs. 2007).|
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 Reticulate Whipray in Southeast Asia and elsewhere in the Indo-West Pacific (including East Africa, Middle East, India) 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 Reticulate Whipray is often found off sandy beaches, in sandy areas of coral reefs, in shallow estuaries and lagoons, and may even enter freshwater (Vaudo and Heithaus 2009, Gutteridge 2012). This species also occurs offshore to depths of at least 50 m (White et al. 2006). Tracking data for the Reticulate Whipray suggests that within sandy, shallow water areas, the species is a highly resident mesopredator, though the home range for individuals can be relatively restricted (Vaudo and Heithaus 2012). Reproduction is viviparous, with histotrophy. This species reaches 160 cm disc width (DW) (Last and Stevens 2009) (up to 450 cm total length in Compagno and Last 1998). Males mature at 82-84 cm DW and size at birth is 21-28 cm DW (Manjaji 2004, White et al. 2006, White and Dharmadi 2007). Fecundity is assumed to be low as a single pregnant female observed possessed two embryos (B.M. Manjaji-Matsumoto, pers. obs.).|
As there is no information on this species’ maximum age and age at maturity, generation length was inferred as 20 years based on data for the congener, the Blackspotted Whipray (Himantura astra). Female Blackspotted Whiprays are reported to have a maximum age of 29 years and an age at maturity of nine years (Jacobsen and Bennett 2011). These were used to calculate a generation length of 19 years based on the equation: generation length = (((29-9)/2)+9). The maximum size of the Reticulate Whipray is considerably larger (~160 cm DW) than that of the Blackspotted Whipray (80 cm DW) so it is possible the generation length of the Leopard Whipray could be greater than 20 years.
|Generation Length (years):||20|
|Use and Trade:||The flesh of the Reticulate Whipray is used fresh or salted and dried for human consumption (Last et al. 2010). In some areas, vertebrae are dried and exported, and the skin is dried and used for wallets, belts, shoes, handbags (high value) etc. most of which are exported (White et al. 2006).|
The Reticulate Whipray faces many of the same threats as other Himantura species within its range, however, its large size at maturity, maximum size, and preference for shallow waters (which are being heavily utilised and degraded in many parts of its range), suggest that it may be more sensitive than some of its congeners (B.M. Manjaji-Matsumoto, Fahmi, W. White, pers. obs. 2007).
The inshore fishing pressure for the Reticulate Whipray is high throughout much of its range in Southeast Asia, and in this area, most bycatch by commercial fisheries (especially trawlers) are landed and sold as food fish (White et al. 2006, Last et al. 2010, Krajangdara 2014). In Indonesia, and probably throughout other areas of its range, this species is captured by demersal tangle net, bottom trawl, commercial gillnet and, to a lesser extent, longline fisheries (White et al. 2006). The Reticulate 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. Within Borneo, the species is an occasional capture in the demersal tangle net and bottom trawl fisheries (Last et al. 2010), and it has been observed from fish market surveys within Thailand (Krajangdara 2014). Its inshore distribution also overlaps with coastal artisanal and commercial fisheries throughout large areas of the Indian and western Pacific oceans. There is also evidence that fisherman in these regions increasingly illegally fish in Australian waters (Chen 1996, W. White, unpubl. data). In Sabah (Malaysia) and Indonesia, Himantura species are often caught and landed in the inshore fisheries (trawls and longlines) and are also taken by Danish seine fishing gear (M. Manjaji-Matsumoto and Fahmi, pers. obs. 2007). Within the artisanal gillnet fishery of the Daru region within Papua New Guinea, the Reticulate Whipray forms a component of the non-target catch within a fishery that predominantly targets barramundi (L. Baje, National Fisheries Authority PNG. pers. comm. 2015).
Demersal fishing pressure has increased in both effort and capacity in many areas of this species' inshore range during recent decades. For example, demersal resources in the Gulf of Thailand went from being lightly exploited to severely overexploited between 1973 and 1994 (Pauly et al. 2005). Available time series data for grouped biomass of 'rays' for this area and period applied to an ecosystem model for the area, suggested that this group was one of the most severely affected by the initial increase in fishing pressure, showing a steady declining trend (Pauly et al. 2005). Species-specific catch data are not collected, but aggregated landings data for 'Rays, stingrays, mantas, nei' are reported to FAO by some countries. Indonesian landings increased from ~10,000 t in 1975 to almost 60,000 t in 2003. Data are not available for India, but data for Pakistan show that landings increased to a peak of 53,000 t as early as 1982, after which landings dropped to ~10,000 t in 1983 and have not risen above 21,000 t since (FAO 2008).
This species' preference for inshore waters, shallow estuaries and lagoons means it is also susceptible due to habitat degradation and loss of mangrove forest and seagrass areas. It may also be affected by destructive fishing practices and pollution. Extensive areas of mangrove forest have been lost in Indonesia and Malaysia through conversion of land for shrimp farms, excessive logging, urban development and, to a lesser extent, conversion of land to agriculture or salt pans (FAO 2007). Between 1980 and 2005 combined overall mangrove area in Indonesia and Malaysia was reduced by >30% (FAO 2007).
Within Australia, catch data for this species is relatively limited, though it is taken as bycatch in the Australian Northern Prawn Fishery. However, with the introduction of turtle exclusion devices (TEDs) and other exclusion devices in the fishery, the ray bycatch has declined by 36.6% and there has been significant reductions in the catch and associated mortality of large rays (Brewer et al. 2006).
There is no species-specific conservation measures in place. Further research is required on the species biology, as is assessment of catches throughout its range.
In Australia, the use of turtle exclusion devices (TEDs) in the Northern Prawn Fishery (NPF) 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 waters, such as Great Barrier Reef Marine Park and Shark Bay Marine Reserve, has reduced the potential for this species to be captured.
|Citation:||Manjaji Matsumoto, B.M., White, W.T. & Gutteridge, A.N. 2016. Himantura uarnak. The IUCN Red List of Threatened Species 2016: e.T161692A68629130.Downloaded on 24 June 2017.|
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