|Scientific Name:||Dermochelys coriacea (Northeast Indian Ocean subpopulation)|
|Species Authority:||(Vandelli, 1761)|
|Red List Category & Criteria:||Data Deficient ver 3.1|
|Assessor/s:||Tiwari, M., Wallace, B.P. & Girondot, M.|
|Reviewer/s:||Bolten, A.B., Casale, P., Chaloupka, M.Y., Dobbs, K., Dutton, P.H., Eckert, K.L., Mortimer, J.A., Musick, J.A., Nel, R., Pritchard, P.C.H., van Dijk, P.P. & Miller, J. & Limpus, C.|
|Contributor/s:||Shanker, K., Hamann, M. & Kapurusinghe, T.|
The Northeast Indian Leatherback subpopulation nests primarily in the Andaman and Nicobar Islands, India, Sri Lanka, and to a lesser extent in Thailand and Sumatra, Indonesia (Nel 2012). A significant gap persists in our knowledge of the genetic structure of Leatherback rookeries in the Northeast Indian subpopulation, although it is hypothesized that the nesting beaches in Sri Lanka and the Nicobar islands might belong to a distinct Indian Ocean subpopulation (P. Dutton pers. comm.). Tissue samples have been collected in the Andaman Islands and Thailand, but no results are currently available (Nel 2012). The marine habitat for this subpopulation is thought to extend throughout the Bay of Bengal and south of Sri Lanka and along the west coast of Sumatra, Indonesia (Figure 1 in attached PDF), but the geographic boundaries lack resolution. Continuous long-term data sets are unavailable for this subpopulation; existing estimates of nesting activities are incomplete and historical data are unavailable. Therefore this subpopulation is classified as Data Deficient for all applicable criteria A2, A4, B, C, and D.
Application of Criterion A2 is usually most appropriate for sea turtle populations, as population reduction has been observed in the past where the causes of reduction may not have ceased OR may not be understood OR may not be reversible. Furthermore, applicable subcriteria under Criterion A2 include (b) an index of abundance appropriate to the taxon, and d) actual or potential levels of exploitation. However, A2 could not be evaluated for this subpopulation because population monitoring was insufficient to derive reliable abundance and trend data (Table 1 in attached PDF).
We also applied Criterion B, C, and D to the Northeast Indian subpopulation, but the extent of occurrence exceeded the threshold, and the area of occupancy has not been determined. Because population abundance data are not available, Criteria C and D could not be evaluated.
Our limited knowledge of this subpopulation is summarized by Nel (2012): based on one year of data, the nesting population in Sri Lanka is estimated to be 100 to 200 females per year; in the Andaman and Nicobar Islands it is estimated at approximately 400 to 600 females per year and in Thailand fewer than 10 nests (<3 females per year). Intensity and extent of threats such as egg harvest and consumption of meat, bycatch, and predation have not been sufficiently quantified.
We assessed the status of the Northeast Indian Leatherback subpopulation by Criteria A-D; as no population viability analysis has been performed, Criterion E could not be applied.
Criterion A: We were able to compile some data on abundance of nesting females or their nesting activities from only the Andaman and Nicobar Islands (Table 1 in attached PDF). For marine turtles, annual counts of nesting females and their nesting activities (more often the latter) are the most frequently recorded and reported abundance metric across index monitoring sites, species, and geographic regions (NRC 2010). We presented and analysed all abundance data in numbers of nests yr-1, as this metric was the most commonly available (Table 1 in attached PDF). However, population monitoring has been sporadic and incomplete, and historical data are not available, and so reliable abundance and trend data could not be derived, despite some basic information on abundance (Table 1 in attached PDF). This subpopulation was classified as Data Deficient.
Criterion B: We defined extent of occurrence (EOO) as the total area included within the geo-referenced boundaries of the Northeast Indian Leatherback subpopulation (Figure 1 in attached PDF), which we calculated to be >8million km2. We defined area of occupancy (AOO) as the linear distribution of nesting sites within the EOO, multiplied by 2 km to account for the IUCN Guidelines for calculating linear AOOs using minimum grid cell size of 2 km x 2 km. The AOO for this subpopulation could not be determined because the distribution of all the nesting beaches is not known. We defined “locations” as biological rookeries, i.e. genetic stocks, within the EOO, but genetic information is unavailable for this population and the number of locations could not be determined. Therefore, this subpopulation classified as Data Deficient for Criterion B.
Criterion C: Abundance data and life history data (e.g., clutch frequency per female, re-migration intervals, sex ratios) are not available for this subpopulation to estimate the mature adult population and it is therefore classified as Data Deficient under Criterion C.
Criterion D: The number of mature individuals and the number of locations are not known for the Northeast Indian subpopulation and therefore it is classified as Data Deficient under Criterion D.
Sources of Uncertainty
This is a relatively data poor subpopulation. Nesting beach monitoring is limited because of the remoteness of nesting beaches and unavailability of sufficient infrastructure and resources. Therefore, continuous long-term datasets are not available. Additionally, since the 2004 tsunami, access to many key nesting sites has become more logistically challenging. For further reading on sources of uncertainty in marine turtle Red List assessments, see Seminoff and Shanker (2008).
Leatherbacks are distributed circumglobally, with nesting sites on tropical sandy beaches and migratory and foraging ranges that extend into temperate and sub-polar latitudes. The Northeast Indian Leatherback subpopulation nests primarily in the Andaman and Nicobar Islands, Sri Lanka, and to a lesser extent in Thailand and Sumatra, Indonesia (Nel 2012). See Eckert et al. (2012) for review of Leatherback geographic range.
Native:Bangladesh; India; Indonesia; Malaysia; Myanmar; Sri Lanka; Thailand
|FAO Marine Fishing Areas:||
Indian Ocean – eastern; Indian Ocean – western
|Range Map:||Click here to open the map viewer and explore range.|
Leatherbacks are a single species globally comprised of biologically described regional management units (RMUs; Wallace et al. 2010), which describe biologically and geographically explicit population segments by integrating information from nesting sites, mitochondrial and nuclear DNA studies, movements and habitat use by all life stages. RMUs are functionally equivalent to IUCN subpopulations, thus providing the appropriate demographic unit for Red List assessments. There are seven Leatherback subpopulations, including the Northeast Indian Ocean, Southwest Indian Ocean, East Pacific Ocean, West Pacific Ocean, Northwest Atlantic Ocean, Southeast Atlantic Ocean, and Southwest Atlantic Ocean. Multiple genetic stocks have been defined according to geographically disparate nesting areas around the world (Dutton et al. 1999, 2013), and are included within RMU delineations (Wallace et al. 2010; shapefiles can be viewed and downloaded at: http://seamap.env.duke.edu/swot).
|Habitat and Ecology:||
See species account for details. For a thorough review of Leatherback biology, please see Eckert et al. (2012).
Threats to Leatherbacks (and other marine turtle species), vary in time and space, and in relative impact to populations. Threat categories were defined by Wallace et al. (2011) as the following:
1) Fisheries bycatch: incidental capture of marine turtles in fishing gear targeting other species;
2) Take: direct utilization of turtles or eggs for human use (i.e. consumption, commercial products);
3) Coastal Development: human-induced alteration of coastal environments due to construction, dredging, beach modification, etc.;
4) Pollution and Pathogens: marine pollution and debris that affect marine turtles (i.e. through ingestion or entanglement, disorientation caused by artificial lights), as well as impacts of pervasive pathogens (e.g. fibropapilloma virus) on turtle health;
5) Climate change: current and future impacts from climate change on marine turtles and their habitats (e.g. increasing sand temperatures on nesting beaches affecting hatchling sex ratios, sea level rise, storm frequency and intensity affecting nesting habitats, etc.).
The relative impacts of individual threats to all Leatherback subpopulations were assessed by Wallace et al. (2011). At a global scale, fisheries bycatch was classified as the highest threat to Leatherbacks globally, followed by human consumption of Leatherback eggs, meat, or other products and coastal development. Due to lack of information, pollution and pathogens was only scored in three subpopulations and climate change was only scored in two subpopulations. Enhanced efforts to assess the impacts of these threats on Leatherbacks—and other marine turtle species—should be a high priority for future research monitoring efforts.
For this Northeast Indian subpopulation, Wallace et al. (2011) found that insufficient information was available to assess impacts of fisheries bycatch, pollution and pathogens, and climate change. Human consumption of turtles and eggs was identified as a high threat to this subpopulation. According to Nel (2012), intensity and extent of threats for the Northeast Indian subpopulation include egg harvest and consumption of meat, fisheries bycatch, and predation of turtles and eggs, but have not been sufficiently quantified.
Leatherbacks are protected under various national and international laws, treaties, agreements, and memoranda of understanding. A partial list of international conservation instruments that provide legislative protection for Leatherbacks are: Annex II of the SPAW Protocol to the Cartagena Convention (a protocol concerning specially protected areas and wildlife); Appendix I of CITES (Convention on International Trade in Endangered Species of Wild Fauna and Flora); and Appendices I and II of the Convention on Migratory Species (CMS); the Inter-American Convention for the Protection and Conservation of Sea Turtles (IAC), the Memorandum of Understanding on the Conservation and Management of Marine Turtles and their Habitats of the Indian Ocean and South-East Asia (IOSEA), the Memorandum of Understanding on ASEAN Sea Turtle Conservation and Protection, and the Memorandum of Understanding Concerning Conservation Measures for Marine Turtles of the Atlantic Coast of Africa.
Long-term efforts to reduce or eliminate threats to Leatherbacks on nesting beaches have been successful (e.g. Dutton et al. 2005, Chacón-Chaverri and Eckert 2007, Sarti Martínez et al. 2007). Reducing Leatherback bycatch has become a primary focus for many conservation projects around the world, and some mitigation efforts are showing promise (Watson et al. 2005; Gilman et al. 2006, 2011). However, threats to Leatherbacks—bycatch and egg consumption and female exploitation, in particular, persist, and in some places, continue to hinder population recovery (Bellagio report 2007, Fretey et al. 2007,Alfaro-Shigueto et al. 2011, Wallace et al. 2013). For depleted Leatherback populations to recover, the most prevalent and impactful threats must be reduced wherever they occur, whether on nesting beaches or in feeding, migratory, or other habitats (Bellagio report 2007; Wallace et al. 2011, 2013); a holistic approach that addresses threats at all life history stages needs to be implemented (Dutton and Squires 2011).
|Citation:||Tiwari, M., Wallace, B.P. & Girondot, M. 2013. Dermochelys coriacea (Northeast Indian Ocean subpopulation). In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.2. <www.iucnredlist.org>. Downloaded on 20 April 2014.|
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