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Description |
Geographic Range [top]
Range Description: Widespread in the eastern Indian Ocean and Western Pacific, but distribution is poorly defined.
Eastern Indian Ocean: occurs from India, Sri Lanka (De Bruin et al. 1995; Morón et al. 1998), and east to Myanmar. Records from elsewhere in the Indian Ocean (west of India) (e.g., Compagno 1986, Compagno et al. 1989) may represent a separate species, identified as Himantura sp. B (Manjaji 2004).
Northwest Pacific: Taiwan, Province of China.
Western central Pacific: South and East China Seas (e.g., Annandale 1909, 1910; Shen 1993; Last and Compagno 1999), Samoa (Fowler 1956), South China Sea and Sulu Sea off Sabah (Fowler et al. 1999).
FAO Fishing Area: 51, 57, 61 and 71.
Countries occurrence:
Native:
India; Malaysia (Sabah); Myanmar (Myanmar (mainland)); Samoa; Sri Lanka; Taiwan, Province of China (Taiwan, Province of China (main island))
FAO Marine Fishing Areas:
Native:
Indian Ocean – western; Indian Ocean – eastern; Pacific – northwest; Pacific – western central
Range Map: Click here to open the map viewer and explore range.
Population [top]
Population: Appears to be a naturally common species. For example it is caught in very large amounts in Borneo and Indonesia (W. White pers. obs. 2007, Compagno et al. 2005). Population size in Indonesia (and throughout much of its range) is still unknown, market observations were conducted at several landing sites in Java and Kalimantan from 2005 to present, showed that the species is quite common and they were recorded at almost all landing sites (fishing areas including the Java Sea, off southern Java (Indian Ocean), Sunda Strait, Karimata Strait, Makassar Strait, West Kalimantan, southern Natuna Islands).
Current Population Trend: Unknown
Additional data:
?Population severely fragmented: No
Habitat and Ecology [top]
Habitat and Ecology: This species is demersal, found on the inner continental shelf, from inshore waters to depths of at least 60 m (White et al. 2006). Presumably occurs on soft substrates (White et al. 2006). It appears to occur more frequently in shallow trawls (20-33 m depth) in warmer months on the Tugela Bank, Natal, South Africa and this may be a nursery ground (Fennessy 1994). Reproduction is viviparous, with histotrophy, and gives birth to litters of 1-4 pups after an unknown gestation period (White et al. 2006). Small individuals are present in trawl catches all year round, suggesting that this species is able to reproduce all year round with no reproductive season (White et al. 2006). Diet presumably consists of bivalve molluscs, crustaceans and small fishes (White et al. 2006). Males reach maturity at ~48 cm disc width (DW) (White and Dharmardi 2007). Size at maturity in females is >54 cm DW (Manjaji 2004, White et al. 2006). The species attains at least 100 cm DW (White et al. 2006) and size at birth is 18-21 cm (Manjaji 2004, White et al. 2006).
Systems: Marine
Use and Trade [top]
Use and Trade: Flesh is used fresh or salted or smoked and dried for human consumption. In some areas, vertebrae is dried and exported; skins are dried and used for manufacturing items such as wallets, belts, shoes, handbags etc. most of which are exported e.g., Thailand. Cartilage also utilised
Threats [top]
Major Threat(s): This species is captured in very large quantities in demersal tangle net, bottom trawl, trammel net and Danish seine fisheries (White et al. 2006, Famhi pers. obs.). Inshore fishing pressure is high throughout much of this species known range in the Indian Ocean and Southeast Asia. In Southeast Asia (and presumably in other parts of its range, such as India), most specimens caught as bycatch by commercial fisheries (especially trawlers) are usually retained and marketed for human consumption (B.M. Manjaji, W. White, Famhi and Vidthayanon pers. obs.). In Sabah (Malaysia), this species constitutes an important component of inshore trawl and longline fisheries (20-50 landed per day). This species is taken in commercial gillnet fisheries off Indonesia, particularly in the fishery that targets rhynchobatid rays in the Arafura Sea (Last and Compagno 1999, W. White pers. obs. 2007). It is thought to be heavily impacted in this area, where more than 600 trawl vessels operate (W. White pers. obs. 2007). The Rhynchobatus species gillnet fishery catches large numbers of stingrays and Himantura gerrardi is important in this fishery. Catches in inshore waters have declined and these vessels are having to travel longer and longer distances to sustain catches. The Rhynchobatid fisheries are very intensive in this region, thus the level of exploitation is extremely high.
It is also commonly caught in large numbers by trawl and Danish seine boats operating in the Java Sea. This species is the most important elasmobranch caught by the Danish seine fishery according to the total catch (biomass) (contributing ~ 1950 kg/boat average and also contributed to about 10-40% of the total catch according to the biomass) (Fahmi pers. obs.). Fishermen are having to travel further to maintain catches of the same level as previously throughout Southeast Asia , indicating that numbers have most likely declined in shallower water (W. White pers. obs. 2007).
Artisanal and industrial fishing pressure is intensive off India (Flewwelling and Hosch 2006, Morgan 2006). Fisheries throughout India operate on an open access basis. Inshore marine species are thought to be fully or overexploited, with extensive use of illegal mesh sizes reported, and ever-increasing bottom trawl effort (Flewwelling and Hosch 2006, Morgan 2006). Demersal species, such as this, suffer more fishing mortality than pelagic species on the eastern coast of India and declines in demersal shrimp and fish stocks have led to fishery closures in areas of the western coast (Morgan 2006). Indias inshore fisheries are generally characterised by declining catch rates, recruitment and biomass and a shift from regular landing patterns (Flewwelling and Hosch 2006). Although no species-specific data are available on catches, this species produces only 1-4 pups per litter and likely shares the limiting life-history characteristics similar to many elasmobranchs, making it vulnerable to depletion.
Marine pollution and coastal degradation has also impacted the coastal habitat of this species (including estuaries) (Morgan 2006). Extensive trawl and gillnet fisheries also operate off Pakistan (Khan 2006) and in other areas of this species range in the Indian Ocean.
Conservation Actions [top]
Conservation Actions: In Malaysia, the Shark Specialist Group together with various government departments in Sabah and Sarawak States have initiated elasmobranch biodiversity studies since 1996 (Fowler et al. 2002). While the monitoring surveys should continue to ascertain the status and possible threats to this species here, as well as in other portions of its range (New Guinea and Indonesia), efforts in further research should be directed to also obtain the population, habitat and ecology and life history parameters. The fishery is largely unregulated (licenses being issued, but catches/ landings are not properly monitored), and presently there is no specific conservation actions in place to help address this problem.
Citation: Manjaji, B.M., Fahmi & White, W.T. 2009. Himantura gerrardi. The IUCN Red List of Threatened Species 2009: e.T161566A5453080. http://dx.doi.org/10.2305/IUCN.UK.2009-2.RLTS.T161566A5453080.en. Downloaded on 14 June 2016.
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Indo-Pacific: India to New Guinea, north to Japan. Reported from the Red Sea and east African coast but these western records need to be confirmed. Collected from the estuary and freshwater of the River Ganges (Ref. 33178). Probably a species complex |
