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Atlantic green sea turtle

The green sea turtle (Chelonia mydas) occurs throughout the tropical and subtropical waters of the Mediterranean, Atlantic, Pacific, and Indian Oceans, and as far north as Massachusetts [1, 2]. It migrates enormous distances between foraging and nesting areas [2]. When not migrating, the green sea turtle’s typical near-shore habitat includes shallow waters inside bays, reefs, and inlets [1]. Most nesting occurs on minimally disturbed open beaches [3]. Females generally breed every two or more years, and nest an average of 3-4 times per breeding year [4].

Exploitation of the green sea turtle, their eggs, and their habitat resulted in population declines [1]. Although green sea turtle populations continue to decline throughout much of their range due to directed harvest (both illegal and legal), incidental capture in nearshore gillnets, and negative impacts on essential habitats [1], two populations that nest in the U.S. (Florida and Hawaii) have increased in size since the species was placed on the endangered list in 1978 [3].

Green sea turtle populations in the U.S. Atlantic occur from Massachusetts to Texas and the Caribbean [1, 2]. In the U.S. Pacific, green sea turtles occur from the mainland coast to Hawaii, Guam and the Mariana Islands [1, 2]. Atlantic green sea turtles are variously considered a population and a subspecies (Chelonia mydas mydas) [1]. In the U.S. Atlantic, nesting occurs primarily on beaches along Florida’s east coast, although smaller numbers of nests can be found in North Carolina, South Carolina, Georgia, the U.S. Virgin Islands and Puerto Rico [5]. Foraging occurs in the Gulf of Mexico to Texas and along the Atlantic Coast to Massachusetts [1].

Population estimates based on Florida nest counts have been conducted since the 1970s. In addition, standardized systematic surveys that control for survey effort have been conducted at Florida index beaches since 1988 [4]. Nest numbers tend to alternate between high and low years. Low year numbers remained relatively stable from 1989 to 2001, and then increased in 2003 [4]. Numbers during high years were stable to slightly increasing from 1990 to 1996, and since then, have increased steadily with the exception of an anomalous, hurricane-driven crash in 2004 [4]. The best indicator of population trends is produced by considering a combination of high and low years [4]. Total numbers of Florida nests counted increased from 2,100 in 1989-1990 (the equivalent of approximately 600 nesting females) to 9,609 (the equivalent of approximately nesting 2,745 females) in 2004-2005 [6].

Each winter green, Kemps Ridley and loggerhead sea turtles migrating southward from Northeastern waters are regularly stranded on shores of Cape Cod Bay between Brewster and Truro [7]. These turtles die of hypothermia if not rescued. The total number of strandings ranged between 49 and 281 turtles between 1995 and 2003. Green sea turtle strandings ranged from 0 to 7 each year [7]. A volunteer program has been established to rescue, rehabilitate, and release the turtles in Florida.

Reliable, long-term nesting data is unavailable for Puerto Rico and the Virgin Islands [8]. The number of green turtle nests has remained low for all the islands, but there appears to have been a gradual increase in the numbers of juveniles observed in foraging grounds since the mid-1970s [8]. The largest concentration of nests occurs on St. Croix, where an average of 100 nests were counted per year between 1980 and 1990. Waters surrounding the island of Culebra, Puerto Rico have been designated critical habitat [1].

In order for the green sea turtle to be delisted, the 1991 federal recovery plan requires that: 1) Florida supports an average of 5,000 nests over six consecutive years, 2) at least 105 km of nesting beach be in public ownership and support at least 50% of U.S. nests, and 3) a reduction in stage-class mortality results in an increase in individuals in foraging grounds [1].

[1] U.S. Fish and Wildlife Service. 1991. Recovery Plan for U.S. Populations of Atlantic Green Turtle. Washington, DC.
[2] Plotkin, P.T. (editor). 1995. National Marine Fisheries Service and U. S. Fish and Wildlife Service Status Reviews for Sea Turtles Listed under the Endangered Species Act of 1973. Silver Spring, Maryland.
[3] USFWS. 2004. Green Sea Turtle (Chelonia mydas). U.S. Fish and Wildlife Service, North Florida Office. Website (http://www.fws.gov/northflorida/SeaTurtles/Turtle%20Factsheets/Green-Sea-Turtle.htm) accessed January, 2006.
[4] Meylan, A., B. Schroeder, and A. Mosier. 1995. Sea Turtle Nesting Activity in the State of Florida 1979-1992. Florida Marine Research Publications no 52. State of Florida Department of Environmental Protection, Florida Marine Research Institute, St. Petersburg , FL.
[5] NMFS. Green Sea Turtle (Chelonia mydas). Threatened Species Account. Endangered Florida and Mexican Breeding Populations. NOAA Fisheries, Office of Protected Resources. Silver Spring, MD. Website (http://www.nmfs.noaa.gov/pr/species/turtles/green.html) accessed January, 2006.
[6] Fish and Wildlife Research Institute. 2006. Florida's index nesting beach survey data. Fish and Wildlife Research Institute, Florida Fish and Wildlife Conservation Commission,. Website (http://research.myfwc.com/features/view_article.asp?id=10690) accessed January, 2006.
[7] Lewis, D. Photo diary of a terrapin researcher. Website (http://terrapindiary.org/) accessed January 7, 2006.
[8] Hillis-Starr, Z.M., R. Boulon, M. Evans. Sea turtles in the Virgin Islands in Status and trends of the Nation's Biological Resources, USGS. Available at (http://biology.usgs.gov/s+t/SNT/noframe/cr136.htm, accessed January, 2006.)

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