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Atlantic leatherback sea turtle

The leatherback sea turtle (Dermochelys coriacea), the largest living turtle species, is a monotypic genus [1]. It is typically associated with continental shelf habitats and pelagic environments. Adult leatherbacks feed primarily on jellyfish in temperate and boreal latitudes, are highly migratory and have the most extensive range of any extant reptile [1]. Although their oceanic distribution is nearly worldwide, the number of nesting sites is few [3]. Gravid females emerge onto beaches to excavate nests and lay eggs. They prefer high-energy beaches with deep, unobstructed access, which occur most often along continental shorelines [2].

In the Western Atlantic, leatherbacks nest from North Carolina to southern Brazil [4]. In U.S. waters, leatherbacks can be found along the East Coast from Maine to Florida, and in the Greater and Lesser Antilles [6]. Critical habitat has been designated as the nesting beaches and adjacent waters of Sandy Point, St. Croix, U.S. Virgin Islands [2]. The Pacific population does not nest in the United States or its territories, but has important foraging areas on the West Coast and near Hawaii [1].

Although leatherback populations under U.S. jurisdiction have increased in size since 1970, worldwide their numbers are decreasing. Leatherback numbers have declined in Mexico, Costa Rica, Malaysia, India, Sri Lanka, Thailand, Trinidad, Tobago and Papua New Guinea [7]. In 1980 there were over 115,000 adult female leatherbacks worldwide. Now there are less than 25,000 [6]. The most precipitous declines have occurred in the Pacific Ocean [5]. One study estimated that the number of females in the eastern Pacific went from 91,000 in 1980 to 1,690 in 2000 [7]. The number of leatherback nests has also declined at all major nesting beaches throughout the Pacific [6]. Nesting along the Pacific coast of Mexico, which is estimated to represent about 50% of all nesting, declined at an annual rate of 22% over the last 12 years [6].

In the western Atlantic and Caribbean, the largest nesting assemblages are found in the U.S. Virgin Islands, Puerto Rico and Florida. Nesting data for these locations have been collected since the early 1980s [6]. Nest numbers in Florida as well as on St. Croix, USVI, and Culebra Island, Puerto Rico, increased over the past 20 years [8]. At St. Croix, the number of nests deposited annually on Sandy Point NWR, the largest nesting rookery in U.S. territory, ranged from 82 in 1986 to 260 in 1991 [2]. From 1979 on, the trend indicates a 7.5% increase per year (SE = 0.014). In Florida, several models estimated trends as indicating a 9.1% increase per year (SE = 0.049) to 11.5% per year (SE = 0.053) [2]. In Florida, the number of nests on beaches used as "index beaches" (beaches where standardized counts have been conducted, allowing for more accurate comparisons between years and between beaches) by the Index Nesting Beach Survey increased significantly between 1989 and 2004 [9]. Statewide, the number of nests in 1999 was 558, representing at least 100 individual female turtles. In the most recent statewide count in 2004, 473 nests were reported [9]. Information regarding the status of the entire leatherback population in the Atlantic is lacking, however [6], and the population still faces significant threats from incidental take in commercial fisheries and marine pollution [1].

Habitat destruction, incidental catch in commercial fisheries, and the harvest of eggs and flesh are the greatest threats to the survival of the leatherback [6]. In Indonesia there is nearly complete collection of eggs. Entanglement and ingestion of marine debris, including old abandoned nets, also pose a threat to leatherbacks [1]. Artificial lights on nesting beaches can result in mortality in hatchling turtles by causing newly emerged hatchlings to become disoriented [1]. Eggs can also be lost to beach erosion. At Sandy Point NWR, 40-60% of the eggs laid each year would be lost to erosion if not for human intervention [2]. Because leatherbacks nest in the tropics during hurricane season, there is also potential for storm-related loss of nests. In 1980, only four out of approximately 80 nests laid on Sandy Point NWR survived to hatch following the catastrophic effects of Hurricane Allen [2]. For the species as a whole, researchers believe egg collection is the most significant cause of population decline, followed by mortality associated with the fishing industry. One study estimates that halting egg collection and longlining (world-wide) would allow for the recovery of this species within the next 50 years [7].

[1] National Marine Fisheries Service and U.S. Fish and Wildlife Service. 1998. Recovery Plan for U.S. Pacific Populations of the Leatherback Turtle, (Dermochelys coriacea). Silver Spring, MD. 66pp.
[2] National Marine Fisheries Service and U.S. Fish and Wildlife Service. 1992. Recovery Plan for Leatherback Turtles, (Dermochelys coriacea) in the U.S. Caribbean, Atlantic and Gulf of Mexico. Washington, D.C.1992. 60 pp + appendices.
[3] NatureServe. 2005. NatureServe’s Central Databases. Arlington, VA. U.S.A.
[4] Rabon, D. R. Jr., S. A. Johnson, R. Boettcher, M. Dodd, M. Lyons, S. Murphy, S. Ramsey, S. Roff, and K. Stewart. 2003. Confirmed Leatherback Turtle (Dermochelys coriacea) Nests from North Carolina, with a Summary of Leatherback Nesting Activities North of Florida. Marine Turtle Newsletter 101:4-8.
[5] NOAA Fisheries. 2001. Stock Assessment of Leatherback Sea Turtles of the Western North Atlantic.
[6] NOAA Fisheries. 2005. Leatherback Sea Turtle {Dermochelys coriacea). Website (http://www.nmfs.noaa.gov/pr/species/turtles/leatherback.html) accessed December, 2005.
[7] Kaplan, I.C. 2005. A Risk Assessment for Pacific Leatherback Turtles (Dermochelys coriacea). Canadian Journal of Fisheries and Aquatic Sciences. 62(8):1710-1719.
[8] Endangered Species Technical Bulletin 22(3):25.
[9] Florida Fish and Wildlife Conservation Commission. Fish and Wildlife Research Institute. Florida's Index Nesting Beach Survey Data. Available at (http://research.myfwc.com/features/view_article.asp?id=10690)

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