Dermochelys coriacea (West Pacific Ocean subpopulation)
|Scientific Name:||Dermochelys coriacea (West Pacific Ocean subpopulation)|
|Red List Category & Criteria:||Critically Endangered A2bd+4bd ver 3.1|
|Assessor(s):||Tiwari, M., Wallace, B.P. & Girondot, M.|
|Reviewer(s):||Chaloupka, M.Y., Dobbs, K., Dutton, P.H., Eckert, K.L., Hughes, G., Limpus, C., Miller, J., Mortimer, J.A., Musick, J.A., Nel, R., Pritchard, P.C.H. & van Dijk, P.P.|
|Contributor(s):||Pilcher, N.J., Tapilatu, R. & Tiwari, M.|
The West Pacific Leatherback subpopulation nests primarily in Papua Barat, Indonesia, Papua New Guinea, and the Solomon Islands, and to a lesser extent in Vanuatu, all of which belong to a single regional genetic stock (Dutton et al. 2007). The marine habitat for this subpopulation extends north into the Sea of Japan, northeast and east into the North Pacific to the west coast of North America, west to the South China Sea and Indonesian Seas, and south into the high latitude waters of the western South Pacific Ocean and Tasman Sea (Benson et al. 2011; Figure 1 in Supplementary Material). The once large nesting population in Terrengannu, Malaysia, is now functionally extinct (Chan and Liew 1996; Malaysian Fisheries Department unpubl. data). Despite some areas of overlap in distribution with the east Pacific subpopulation, the West Pacific subpopulation is genetically distinct from all other Leatherback subpopulations (Dutton et al. 1999), and it occupies broad foraging and migratory habitats (Benson et al. 2011, Bailey et al. 2012). Based on analysis of long-term time series datasets of abundance—i.e. annual counts of nesting females and nests—this West Pacific Leatherback subpopulation has declined 83.0% during the past three generations. Because the threats to this subpopulation (e.g. human exploitation of females and eggs, low hatching success, fisheries bycatch) have not ceased, the West Pacific Leatherback subpopulation is considered Critically Endangered according to IUCN Red List Criterion A2, subcriteria (b) and (d). Likewise, applying Criterion A4 reveals a population decline of 96% by the year 2040, or one generation from now, which meets the requirements of Critically Endangered under A4, subcriteria (b) and (d).
Application of Criterion A2 is appropriate, 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 (i.e., annual counts of nesting females, nests), and d) actual or potential levels of exploitation. Based on Criterion A4, this subpopulation will be greatly diminished—population decline of 96%—in another generation (i.e., by 2040), with a remaining abundance of approximately 572 nests (~104 females) per year, or approximately 260 adult females total.
We assessed the status of the West Pacific Leatherback subpopulation by Criteria A-D; as no population viability analysis has been performed, Criterion E could not be applied.
Leatherback age at maturity is uncertain, and estimates range widely (see Jones et al. 2011 for review). Reported estimates fall between 9-15 yr, based on skeletochronology (Zug and Parham 1996), and inferences from mark-recapture studies (Dutton et al. 2005). Furthermore, updated skeletochronological analyses estimated Leatherback age at maturity to be between 26-32 yr (mean 29 yr) (Avens et al. 2009). Extrapolations of captive growth curves under controlled thermal and trophic conditions suggested that size at maturity could be reached in 7-16 yr (Jones et al. 2011). Thus, a high degree of variance and uncertainty remains about Leatherback age at maturity in the wild. Likewise, Leatherback lifespan is unknown. Long-term monitoring studies of Leatherback nesting populations have tracked individual adult females over multiple decades (e.g. Santidrián Tomillo et al. unpublished data, Nel and Hughes unpublished data), but precise estimates of reproductive lifespan and longevity for Leatherbacks are currently unavailable.
Leatherbacks are distributed circumglobally, with nesting sites on tropical sandy beaches and foraging ranges that extend into temperate and sub-polar latitudes. See Eckert et al. (2012) for review of Leatherback geographic range. The West Pacific Leatherback subpopulation nests primarily in Papua Barat, Indonesia, Papua New Guinea, and the Solomon Islands, and to a lesser extent in Vanuatu. The marine habitat for this subpopulation extends north into the Sea of Japan, northeast and east into the North Pacific to the west coast of North America, west to the South China Sea and Indonesian Seas, and south into the high latitude waters of the western South Pacific Ocean and Tasman Sea (Benson et al. 2011; see Figure 1 in Supplementary Material).
Native:American Samoa; Australia; Brunei Darussalam; Cambodia; Canada; China; Fiji; French Polynesia; Guam; Indonesia; Japan; Kiribati; Korea, Democratic People's Republic of; Korea, Republic of; Malaysia; Marshall Islands; Micronesia, Federated States of ; New Caledonia; New Zealand; Northern Mariana Islands; Palau; Papua New Guinea; Philippines; Russian Federation; Samoa; Solomon Islands; Taiwan, Province of China; Thailand; Tonga; Tuvalu; United States
|FAO Marine Fishing Areas:|
Pacific – western central; Pacific – southwest; Pacific – southeast; Pacific – northwest; Pacific – northeast; Pacific – eastern central
|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 West Pacific Ocean, East Pacific Ocean, Northwest Atlantic Ocean, Southeast Atlantic Ocean, Southwest Atlantic Ocean, Northeast Indian Ocean, and Southwest Indian 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).
|Current Population Trend:||Decreasing|
|Habitat and Ecology:|
See the species account for a summary of the details. For a thorough review of Leatherback biology, please see Eckert et al. (2012).
|Generation Length (years):||30|
|Movement patterns:||Full Migrant|
|Congregatory:||Congregatory (and dispersive)|
|Use and Trade:||Egg and females are collected for human consumption and eggs are also eaten by feral pigs and dogs.|
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). 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.
The greatest threats to the recovery of Leatherbacks in the Western Pacific are bycatch, egg collection and exploitation of females, and low hatching success due to high sand temperatures, erosion, feral pig and dog predation (Bellagio Report 2007, Tapilatu et al. 2013). The multi-directional and long distance migratory trajectories of the western Pacific Leatherbacks increases the probability of fisheries bycatch as they encounter multiple fishing zones and fishing gear (Benson et al. 2011, Bailey et al. 2012, Wallace et al. 2013). Rigorous estimates of Leatherback bycatch in fishing gear throughout the region are necessary to adequately quantify the relative impacts on this subpopulation. Most importantly, Leatherback bycatch in fishing gears throughout the region, especially those with the largest population-level impacts, must be reduced as soon as possible to avoid extinction of this subpopulation.
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, Santidrián Tomillo et al. 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 (Fretey et al. 2007, Bellagio report 2007, Alfaro-Shigueto et al. 2011, Tapilatu et al. 2013, 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 (Steering Committee, Bellagio Conference on Sea Turtles 2004; 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 (West Pacific Ocean subpopulation). The IUCN Red List of Threatened Species 2013: e.T46967817A46967821.Downloaded on 24 May 2018.|
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