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Pacific 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, 5]. It migrates enormous distances between foraging and nesting areas [5]. Typical near-shore habitats are shallow waters inside bays, reefs, and inlets. Most nesting occurs on minimally disturbed open beaches. Females generally reproduce every two or more years, with an average of 3-4 nests during a breeding year.

United States populations occur in the Atlantic from Massachusetts to Texas and the Caribbean, and in the Pacific from the mainland coast to Hawaii, Guam and the Mariana Islands [1, 5]. Nesting populations within the U.S have increased in size since the species was placed on the endangered list in 1978.

The Pacific green sea turtle is variously considered a population and a subspecies (Chelonia mydas agassizii); the East Pacific population is sometimes considered a distinct species [2, 3]. In Hawaii, greater than 90% of nesting occurs at French Frigate Shoals [2, 6]. Nesting females increased there from 75 in 1973 to 470 in 2003 due to cessation of hunting and habitat degradation. The relatively recent increase in fibropapillomatosis (a tumerous disease) is a concern [2]. Other U.S.-associated Pacific Islands that support green sea turtle populations include American Samoa (25-35 nesting females), the Federated States of Micronesia (three atolls, >100 nesting females), and Guam (little but regular nesting) [2]. In general, the major threat on urbanized Pacific islands is habitat loss and problems associated with rapidly expanding tourism. In particular, human development is having an increasingly serious impact on green sea turtle nesting beaches. On rural and developing islands, including American Samoa and some islands of the Northern Mariana Islands and Micronesia, human consumption remains a problem.

The population status and migratory habits of East Pacific green turtles frequenting waters off the U.S. west coast are unknown and there are no known nesting sites in the United States [3]. Severe population declines in this population over the past 30 years were due largely to massive over-harvesting of wintering turtles in the Sea of Cortez from 1950-1970 and intense collection of eggs between 1960 and early 1980 on mainland beaches of Mexico. The population was thought to be declining as of 1998. A small group (30-50) of resident East Pacific green sea turtles is found in San Diego Bay. Although they do not nest in the U.S., this group appears to remain in the area for much of the year because of the warm water effluent from a power generating station [2]. There is a ban on high-speed boat traffic in the south portion of the bay, but it is rarely enforced and boat strikes may pose a threat [2].

[1] 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. National Marine Fisheries Service, Silver Spring, Maryland.
[2] NMFS and USFWS. 1998. Recovery Plan for U.S. Pacific Populations of the Green Turtle (Chelonia mydas). National Marine Fisheries Service, Silver Spring, MD.
[3] NMFS and USFWS. 1998. Recovery Plan for U.S. Pacific Populations of the East Pacific Green Turtle (Chelonia mydas). National Marine Fisheries Service, Silver Spring, MD.
[5] USFWS. 1991. Recovery Plan for U.S. Populations of Atlantic Green Turtle. National Marine Fisheries Service, Washington, DC.
[6] Balazs, G.H. and M. Chaloupka. 2004. Thirty-year recovery trend in the once depleted Hawaiian green sea turtle stock. Biological Conservation 117:491-498.

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