Dermochelys coriacea (Northwest Atlantic Ocean subpopulation)
|Scientific Name:||Dermochelys coriacea (Northwest Atlantic Ocean subpopulation)|
|Red List Category & Criteria:||Least Concern 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):||Meylan, A., Patino-Martinez, J., Turny, A., Tomas, J., Stewart, K., Chacon, D., DeFreitas, R., Diez, C., Eckert, S., Entraygues, M., Felix, M., Garner, J., Guada, H., Harrison, E., Kalamandeen, M., Livingstone, S. & Lloyd, C.|
The Northwest Atlantic Leatherback subpopulation nests in the southeastern U.S.A., throughout the mainland and insular Caribbean, and the Guiana Shield, and marine habitats extend throughout the North Atlantic, including the Gulf of Mexico, north beyond 50N, into the Mediterranean, and across the equator to northwestern Africa (Figure 1 in Supplementary Material). Several genetic nesting stocks have been identified within this subpopulation, but metapopulation dynamics support its designation as a single subpopulation, or regional management unit (Wallace et al. 2013, Dutton et al. 2013). Based on long-term time series datasets of abundance—i.e. annual counts of nesting females and nests—this Northwest Atlantic subpopulation is large (>50,000 nests yr-1, ~10,000 females yr-1; Table 1 in Supplementary Material) and has increased by 20.6% over the past three generations, and is projected to increase to >180,000 nests yr-1 in the next generation (by 2040) (Table 2 in Supplementary Material). Therefore, the Northwest Atlantic subpopulation is considered Least Concern under current IUCN Red List Criteria. However, future population increases depend on the success of current conservation efforts to protect Leatherbacks, their offspring, and their habitats being maintained—or augmented, wherever possible—throughout their enormous geographic distribution, but particularly in breeding and foraging areas, to ensure that current and future threats do not reach levels capable of causing population decreases. Thus, this “Least Concern” status should be considered as entirely conservation-dependent.
Comprehensive analyses of 17 existing datasets—including 14 time series datasets with ≥10 years of data—of abundance of nesting females or their nesting activities on beaches revealed different rookery trends within the Northwest Atlantic Leatherback subpopulation, but an overall subpopulation increase based on rookery trends weighted by rookery size relative to subpopulation size three generations ago (see Table 1 in Supplementary Material for all datasets used). Presently, the Northwest Atlantic subpopulation—i.e. from Florida, USA, throughout the Wider Caribbean—is large and increasing (Table 1 in Supplementary Material). To explore future projections of Northwest Atlantic Leatherback subpopulation abundance and trends, we also applied Criterion A4, which analyses the subpopulation trend within time intervals from the past, present, and future (Table 2 in Supplementary Material). According to our assessment of the data under Criterion A4, the Northwest Atlantic subpopulation will continue to increase over the next generation (Table 3 in Supplementary Material).
However, the precedent of the collapse of the historically large Pacific subpopulations (Santidrián Tomillo et al. 2007, Sarti Martínez et al. 2007, Tapilatu et al. 2013), is cause for concern for the Northwest Atlantic subpopulation. Significant threats persist in the Northwest Atlantic in nesting and foraging areas (see Wallace et al. 2011 and Eckert et al. 2012 for review), and this subpopulation’s enormous geographic distribution spans dozens of national and international jurisdictions, making effective conservation extremely challenging. Current efforts to protect Leatherback and their offspring, particularly in critical habitats already identified (e.g. Nova Scotia, Canada, nesting beaches in and adjacent waters off Trinidad, the Guiana Shield, etc.) must be maintained and even increased to sustain population growth in the Northwest Atlantic and prevent similar population declines observed for other Leatherback subpopulations.
Given the widespread, long-lived nature of Leatherbacks, and the Northwest Atlantic subpopulation in particular, Criterion A (i.e., decline in population of mature individuals over time) was the only appropriate criterion that could be used for this assessment; the restricted geographic range and small population size criteria (Criteria B, C and D) did not apply, and no population viability analysis was available (Criterion E).
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.
|Range Description:||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). The Northwest Atlantic Leatherback subpopulation range extends throughout the North Atlantic Ocean, from the equator to beyond 50°N, and from the Gulf of Mexico into the Mediterranean (Wallace et al. 2010) (Figure 1 in Supplementary Material).|
Native:Albania; Anguilla; Antigua and Barbuda; Aruba; Bahamas; Barbados; Belize; Benin; Bermuda; Bonaire, Sint Eustatius and Saba (Saba, Sint Eustatius); Bosnia and Herzegovina; Brazil; Canada; Colombia; Costa Rica; Côte d'Ivoire; Croatia; Cuba; Curaçao; Cyprus; Dominica; Dominican Republic; Egypt; France (France (mainland)); French Guiana; Gambia; Ghana; Greece; Grenada; Guadeloupe; Guatemala; Guinea; Guinea-Bissau; Haiti; Honduras; Ireland; Israel; Italy; Jamaica; Lebanon; Liberia; Libya; Martinique; Mauritania; Mexico; Montenegro; Montserrat; Morocco; Nicaragua; Nigeria; Panama; Portugal; Puerto Rico; Saint Kitts and Nevis; Saint Lucia; Saint Martin (French part); Saint Vincent and the Grenadines; Senegal; Sierra Leone; Sint Maarten (Dutch part); Slovenia; Spain; Suriname; Syrian Arab Republic; Togo; Trinidad and Tobago; Tunisia; Turkey; Turks and Caicos Islands; United Kingdom; United States; Venezuela, Bolivarian Republic of; Virgin Islands, British; Virgin Islands, U.S.
|FAO Marine Fishing Areas:|
Atlantic – western central; Atlantic – southwest; Atlantic – northwest; Atlantic – northeast; Atlantic – eastern central; Mediterranean and Black Sea
|Range Map:||Click here to open the map viewer and explore range.|
Leatherbacks are a single species globally comprising 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 (RMU shapefiles can be viewed and downloaded at: http://seamap.env.duke.edu/swot). RMUs are functionally equivalent to IUCN subpopulations, thus providing the appropriate demographic unit for Red List assessments. There are seven Leatherback subpopulations: Northwest Atlantic Ocean, Southeast Atlantic Ocean, Southwest Atlantic Ocean, Northeast Indian Ocean, Southwest Indian Ocean, East Pacific Ocean, and West Pacific Ocean. Multiple genetic stocks have been defined within the Northwest Atlantic subpopulation—Florida (U.S.A.), the northern Caribbean (St. Croix, US Virgin Islands; British Virgin Islands, Puerto Rico), Costa Rica (and likely including Panama and Colombia), the Guianas (Guyana, Suriname, French Guiana), and Trinidad (Dutton et al. 2013)—that overlap significantly in migratory and feeding areas throughout the North Atlantic (TEWG 2007, Wallace et al. 2010, Eckert et al. 2012).
|Current Population Trend:||Increasing|
|Habitat and Ecology:||See the species-level account for 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:||Leatherback eggs and animals are taken for human use (i.e. consumption and commercial products).|
Threats to Leatherbacks—and other marine turtle species—vary in time and space, and in relative impact to populations. Threat categories were described by Wallace et al. (2011) as:
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 and for the Northwest Atlantic subpopulation (Wallace et al. 2011, 2013), 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 and reduce the impacts of these threats on Leatherbacks—and other marine turtle species—should be a high priority for future conservation efforts.
Although threats to Leatherbacks persist globally (see Wallace et al. 2011 and Eckert et al. 2012 for review), conservation efforts in the Northwest Atlantic appear to have contributed to stable or increasing population trends for most rookeries (Dutton et al. 2005, Girondot et al. 2007, Hilterman and Goverse 2007, TEWG 2007, Stewart et al. 2011). However, continued threats from fisheries bycatch in small- and large-scale fishing operations (Wallace et al. 2011, 2013), particularly those near nesting beaches (e.g. Lee Lum 2006) and in distant foraging areas (e.g. James et al. 2006, Stewart et al. 2013), could jeopardize the future state of this subpopulation’s abundance and trend. Thus, continued, effective efforts to mitigate bycatch impacts are absolutely necessary to ensure future population stability or increases for Northwest Atlantic Leatherbacks.
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, in particular—persist, and in some places, continue to hinder population recovery (Alfaro-Shigueto et al. 2011, 2012; Tapilatu et al. 2013; Wallace et al. 2013).
Fortunately, conservation efforts in the Northwest Atlantic appear to have contributed to stable or increasing population trends for most rookeries (Dutton et al. 2005, Girondot et al. 2007, Hilterman and Goverse 2007, TEWG 2007, Stewart et al. 2011). However, continued threats from fisheries bycatch in small- and large-scale fishing operations and egg harvest for human consumption (Revuelta et al. 2012) could jeopardize the future state of this subpopulation’s abundance and trend (James et al. 2005; Lee Lum 2006; Wallace et al. 2011, 2013). To ensure successful Leatherback conservation, 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). Therefore, current conservation efforts, legal protections, and resources supporting those mechanisms must be maintained—and augmented, wherever possible—to sustain current population trends for the Northwest Atlantic Leatherback subpopulation. Regional and local efforts to protect Leatherbacks, their offspring, and their habitats should be designed to address threats at appropriate scales, and implemented with participation of appropriate stakeholders.
|Citation:||Tiwari, M., Wallace, B.P. & Girondot, M. 2013. Dermochelys coriacea (Northwest Atlantic Ocean subpopulation). The IUCN Red List of Threatened Species 2013: e.T46967827A46967830.Downloaded on 25 April 2018.|
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