|Scientific Name:||Aipysurus apraefrontalis Smith, 1926|
|Red List Category & Criteria:||Critically Endangered A2ac; B2ab(iii,v) ver 3.1|
|Assessor(s):||Lukoschek, V., Guinea, M. & Milton, D.|
|Reviewer(s):||Livingstone, S.R., Elfes, C.T., Polidoro, B.A. & Carpenter, K.E. (Global Marine Species Assessment Coordinating Team)|
This species is only known from the Ashmore and Hibernia Reefs and it has a very restricted distribution and shallow depth range, with an area of occupancy estimated to be less than 10 km². This species has gone from being the third most commonly recorded sea snake in the 1990s to no individuals being recorded in intensive surveys since 2000, indicating a decline of at least 90% in the past 15 years (three generation lengths). Threats are largely unknown, however, declines are possibly due to habitat degradation from coral bleaching and decline of ecosystem health. It is listed as Critically Endangered.
|Range Description:||This is an endemic species with a small range. This species is found on Ashmore Reef and Hibernia Reefs in Australia (Smith 1926, Minton and Heatwole 1975, Cogger 2000). It has never been seen from Scott Reef or other reefs in the Ashmore Reef region. This species also has very occasionally been recorded from other locations in northwest Australian waters (Shuntov 1972, Cogger 2000); however, these rare records from outside Ashmore and Hibernia Reefs are thought to be of vagrant individuals and not part of the range of breeding populations of this species (M. Guinea pers. comm. 2009). This species range has approximately 70 km of shoreline, and given its very shallow depth range of 10 m, it has an area of occupancy estimated to be less than 10 km².|
|FAO Marine Fishing Areas:|
Indian Ocean – eastern
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||A. apraefrontalis occurs as two subpopulations – Ashmore Reef and Hibernia Reef. Current population sizes are unknown. It is likely that there is very little movement between these subpopulations. Genetic studies of a far more widely distributed congener, Aipysurus laevis, indicates restricted gene flow between Ashmore, Hibernia and Cartier Reefs (Lukoschek et al. 2007, 2008). A. laevis occurs in a much wider range of habitat types (including deeper water) than A. apraefrontalis, thus it is likely that dispersal is more restricted for A. apraefrontalis than for A. laevis.|
There have been serious declines in A. apraefrontalis since surveys in 1998.
There are no specific current or previous abundance estimates; however, A. apraefrontalis comprised 6.02% of sea snakes seen on the reef flat high tide at Ashmore Reef in 1994 (Guinea and Whiting 2005). The mean density of all sea snakes on the reef flat at high tide was 228 individuals km² giving a total abundance estimate of sea snakes on the reef flat of ~39,675 (95% CI 26,451 – 53,073) (Guinea and Whiting 2005). Given that 6.02% were A. apraefrontalis, this suggests that this species abundance was 2,388 individuals (95% CI 1592 – 3195). The total abundance estimate and percent contribution of A. apraefrontalis was derived from boat transects of the reef flat at high tide. Seven transects were conducted and a total of 83 sea snakes were sighted, of which five were A. apraefrontalis (Guinea and Whiting 2005). The estimate is, therefore, provisional; nonetheless, it suggests that population size on Ashmore Reef in the 1990s was substantial, potentially in the vicinity of 1,600 to 3,200 individuals. In addition, A. apraefrontalis was the third most commonly seen sea snake on the reef flat at low tide in the 1990s and comprised ~14% of individuals (Guinea and Whiting 2005).
In 1926, Malcolm Smith obtained ~100 sea snakes from Ashmore Reef, which were collected for him by Malay fishers, presumably at random. Of these 100 sea snakes, seven were A. apraefrontalis, suggesting that this species comprised ~7% of the population. These were the first records of A. apraefrontalis (Smith 1926). A. apraefrontalis comprised 2% of 367 sea snakes (seven individuals) caught at Ashmore Reef between Dec 31st 1972 and January 13th 1973 but was not seen or captured at Hibernia, Cartier or Scott Reef during these surveys (Minton and Heatwole 1975).
Despite extensive surveys by Michael Guinea (Guinea 2006, 2007) and Vimoksalehi Lukoschek (pers. comm. 2009) no individual of this species has been recorded on either Ashmore or Hibernia reef since 2000. Therefore, there appears to have been a decline of at least 90% since 1998.
The reasons for the local extinctions of these populations are unknown. This species has not been sighted at any other location. A possible threat could be unusually high water temperatures leading to severe coral bleaching and coral reef habitat degradation throughout the area (Francis 2006).
|Current Population Trend:||Decreasing|
|Habitat and Ecology:||This species is found on the reef flat and the reef edge. It is usually found associated with coral reefs and prefers sandy substrata with sparse coral (Minton and Heatwole 1975). It is found during the daylight hours resting beneath small coral overhangs or coral heads in 1-2 m water (McCosker 1975). This species eats fish, especially eels (Smith 1926). |
Dispersal for this species is very restricted by deep water barriers. Based on similar species, this species has a generation length of approximately five years, based on a longevity of approximately 8-10 years, and age of first maturity of 4-5 years.
|Generation Length (years):||5|
There are no specific, clearly identified or quantified past, current or future threats to A. apreafrontalis or any other reef-associated sea snake species, and it is unclear why populations at both Ashmore and Hibernia Reefs have declined so severely. A. apreafrontalis is not targeted by fisheries; there is no evidence that it is being illegally harvested; and is it not subject to incidental bycatch (some sea snake species are routinely captured as by-catch in trawls, but this is not the case for strongly reef-associated species such as A. apreafrontalis; Lukoschek et al. 2007a).
Nonetheless, something is clearly impacting this species and it is most likely that current and future threats relate to degradation or modification of shallow-water coral reef habitats from bleaching events due to increased sea surface temperatures. However, compared to other areas, the Ashmore Reef was not badly affected by the 1998 bleaching event (V. Lukoschek pers. comm. 2009), although it suffered severe bleaching in 2003 (Kaspartov et al. 2006). Thus, climate change may be a threat to some sea snake species (Francis 2006). In addition, increased water temperatures on the reef flat may exceed the upper lethal limit for A. apraefrontalis, which has been reported to be 36°C for the sea snake Pelamis platurus (Graham et al. 1971).
|Conservation Actions:||Ashmore Reef has been a nature reserve since 1983 and has had various levels of monitoring against illegal fishing since that time. Management plans that focused on protection of marine life did not come into effect until 1990 (Australian National Parks and Wildlife Service 1989), with a second management plan coming into effect in 2002 (Commonwealth of Australia 2002), and since 1998 protection has actively been enforced. However, these management plans have not specifically addressed threat abatement or recovery of any sea snake species. Nonetheless, these management plans are designed to protect marine biodiversity and habitat quality; however, there are no data to indicate how, or to what extent, these measures are providing threat abatement to A. apraefrontalis.|
|Citation:||Lukoschek, V., Guinea, M. & Milton, D. 2010. Aipysurus apraefrontalis. The IUCN Red List of Threatened Species 2010: e.T176770A7301138.Downloaded on 20 March 2018.|
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