|Scientific Name:||Enhydrina schistosa|
|Species Authority:||(Daudin, 1803)|
Disteira schistosa (Daudin, 1803)
Hydrophis schistosus Daudin, 1803
Hydrus valakadyn Boie, 1827
|Red List Category & Criteria:||Least Concern ver 3.1|
|Assessor/s:||Rasmussen, A., Sanders, K., Lobo, A. & Courtney, T.|
|Reviewer/s:||Livingstone, S.R., Elfes, C.T., Polidoro, B.A. & Carpenter, K.E. (Global Marine Species Assessment Coordinating Team)|
This is a widespread common species and can live in a variety of habitats, including disturbed areas. There are no major threats, although it is captured as bycatch in trawl fisheries. This species is therefore listed as Least Concern.
|Range Description:||This species is found from the Arabian Gulf of Pakistan, India, and Sri Lanka, east to Australia and Papua New Guinea and north to Viet Nam (Heatwole 1999).|
Native:Australia; Bahrain; Bangladesh; Cambodia; China; India (Andaman Is., Nicobar Is.); Indonesia; Iran, Islamic Republic of; Iraq; Kuwait; Malaysia; Myanmar; Oman; Pakistan; Papua New Guinea; Philippines; Qatar; Saudi Arabia; Singapore; Sri Lanka; Thailand; United Arab Emirates; Viet Nam
|FAO Marine Fishing Areas:||
Indian Ocean – eastern; Indian Ocean – western; Pacific – northwest; Pacific – western central
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||This species is common throughout its range. It is very common along the coasts of the Malay Peninsula and less common in Australian waters. A mark-recapture study estimated between 600 and 2,000 juveniles of this species in the Muar River estuary in Malaysia in 1983. There were also estimates of 900-2,500 adults in the population of that area (Voris 1985).|
|Habitat and Ecology:||
This species occurs in shallow open sea, river mouths, estuaries, coastal lagoons, and mangrove forests (Limpus 1975, Lim and Sawai 1975, Murthy 1977, Murthy and Rama Rao 1988, Venkateswarlu et al. 1995). It is found from 3.7-22.2 m (Redfield et al. 1978). It occurs over soft substrates such as mud and sand (Limpus 1975). It is also found in freshwater lakes in Cambodia and India, and can travel up rivers. It has been found at least 7 km upriver in Goa, India (A. Lobo pers. comm. 2009).
Common in near shore shallow waters and estuaries, especially in the soft bottom marine environments, where its preffered prey, catfish, occur in high abundances (A. Lobo pers. comm. 2009). Animals are active during the night and day and prefers water depth from less than 5 m to a maximum of 30 m (Leviton et al. 2003).
This species has displayed tightly synchronized annual reproductive cycles. It produces relatively large numbers of offspring with low effort per embryo (2%) (Lemen and Voris 1981). Clutch size increases with the size of the female and can reach 30 or more. The snakes are born with a snout-vent length of 21-24 cm, and grow at a rate of 0.1 cm per day for the first year. Females mature at around 18 months and produce a first clutch at around 24 months (Marsh et al. 1993, Voris and Jayne 1979). Between 10-20% of the species survive the first year and about 6% of females survive to reproduce. Snakes four years old or more make up a very small percentage of the population (Voris and Jayne 1979).
This species is commonly encountered as bycatch in trawler as well as other fishing operations, for example along the Goa coast (Lobo et al. 2004). It appears to have a low trawl-related mortality rate (A. Lobo pers. comm. 2009). It is captured in trawl fisheries in Australia in more shallow waters where the trawl time is very short (15-20 minutes) and therefore the mortality is low (Courtney et al. 2010). There is evidence to suggest that post-release mortality may be high (A. Rasmussen and M. Guinea pers. comms. 2009).
Due to the nature of its habitat, this species is also likely to be impacted by coastal pollution.
Collection is thought to occur in high numbers in Thailand for the venom industry (A. Lobo pers. comm. 2009), but it is not known how this affects the population or if it is a major threat.
It is very abundant in shallow lagoons of Sri Lanka's west coast, where they are frequently caught as bycatch and are a major cause of snake bite mortality among fishermen; for this reason they are usually deliberately killed before being removed from nets (K. Sanders and de Silva pers. comms. 2010).
No sea snake species is currently listed by CITES (the Convention on International Trade in Endangered Species of Wild Fauna and Flora).
Sea snakes are protected in Australia since their addition to the ‘Listed Marine Species’ by the Department of Environment and Water Resources in 2000. They are protected in Australia under the Environment Protection Biodiversity and Conservation Act 1999. This requires that all Australian industries interacting with protected species, directly or indirectly, demonstrate sustainability for the species impacted by their activities (Milton et al. 2008).
Courtney, A. J., Schemel, B.C., Wallace, R., Campbell, M.J., Mayer D.G. and Young, B. 2010. Reducing the impact of Queensland's trawl fisheries on protected sea snakes. Fisheries Research and Development Coorporation (FRDC) Project #2005/053 Final Report.
Guinea, M.L. 2007. Marine Snakes: Species Profile for the North-western Planning Area. Report for the Department of the Environment, Water, Heritage and the Arts. Charles Darwin University, Darwin, NT.
Heatwole, H. 1999. Sea Snakes. Krieger Publishing Company, Malabar, Florida.
IUCN. 2010. IUCN Red List of Threatened Species (ver. 2010.4). Available at: http://www.iucnredlist.org. (Accessed: 27 October 2010).
Lemen, C.A. and Voris, H.K. 1981. A comparison of reproductive strategies among marine snakes. The Journal of Animal Ecology 50(1): 89-101.
Leviton, A.E., Wogan, G.O.U., Koo, M.S., Zug, G.R., Lucas, R.S. and Vindum, J.V. 2003. The dangerously venomous snakes of Myanmar: illustrated checklist with keys. Procedings of the California Academy of Sciences 54(24): 407-462.
Lim, B.-L. and Sawai, Y. 1975. Ecology and distribution of some seasnakes in Malay Peninsula. The Snake 7(1): 28-31.
Limpus, C.J. 1975. Coastal sea snakes of subtropical Queensland waters (23° to 28° south latitude). In: W.A. Dunson (ed.), The Biology of Sea Snakes, pp. 173-182. University Park Press, Baltimore, Maryland.
Lobo, A.S., Vasudevan, K. and Pandav, B. 2005. Trophic Ecology of Lapemis curtus (Hydrophiinae) along the Western Coast of India. Copeia 3(2005): 637-641.
Marsh, H., Corkeron, P.J., Limpus, C.J., Shaughnessy, P.D. and Ward, T.M. 1993. Conserving marine mammals and reptiles in Australia and Oceania. In: C. Moritz and J. Kikkawa (eds), Conservation Biology in Australia and Oceania, pp. 225-244. Surrey, Beatty & Sons, Chipping Norton.
Murthy, T.S.N. 1977. On sea snakes occurring in Madras waters. Journal of the Marine Biological Association of India 19(1): 68-72.
Murthy, T.S.N and Rama Rao, K.V. 1988. Snakes of the Chilka Lake, Orissa, India. The Snake 20(1): 67-73.
Redfield, J.A., Holmes, J.C. and Holmes, R.D. 1978. Sea snakes of the eastern Gulf of Carpentatria. Australian Journal of Marine and Freshwater Research 29(3): 325-334.
Venkateswarlu, T., Pattanayak, J.G., Nahar, S.C. and Mohapatra, A. 1995. On the collection of snakes from Mahanadi Estuary (Orissa, India). The Snake 27(1): 49-52.
Voris, H.K. 1985. Population Size Estimates for a Marine Snake (Enhydra shistosa) in Malaysia. Copeia 4(1985): 955-961.
Voris, H.K. and Jayne, B.C. 1979. Growth, reproduction and population size of a marine snake (Hydrophiidae). Copeia 1979(2): 307-318.
|Citation:||Rasmussen, A., Sanders, K., Lobo, A. & Courtney, T. 2010. Enhydrina schistosa. In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.2. <www.iucnredlist.org>. Downloaded on 21 December 2013.|
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