United states department of interior bureau of ocean energy management

3.7Leatherback Sea Turtle

3.7.1Description of the Species

The leatherback sea turtle (Dermochelys coriacea) is the largest living sea turtle; adults range in length from 4½ to 5½ feet and weigh from 650 to 2,000 pounds (Dundee and Rossman1989). The leatherback lacks a hard, bony shell and has a leathery thick connective tissue that sits upon dermal bones (NOAA Fisheries 2017c). This species also lacks chewing plates, used by a wide variety of sea turtles to crush hard-shelled prey. The leatherback esophagus contains numerous backwards pointing spines that trap prey and prevent escape (NOAA Fisheries 2011c).

3.7.2Species Habitat and Distribution

The leatherback is found throughout the tropical waters of the Atlantic, Pacific, and Indian Oceans (Ernst and Barbour 1972), the GOM, and the Caribbean (Carr 1952). Critical habitat for the leatherback includes the waters adjacent to Sandy Point, St. Croix, U.S. Virgin Islands, up to and inclusive of the waters from the hundred fathom curve shoreward to the level of mean high tide with boundaries at 17°42'12" N and 64°50'00" W. This turtle exhibits seasonal fluctuations in distribution in response to the Gulf Stream and other warm water features (Pritchard 1971; Fritts et al. 1983). During the summer, leatherbacks tend to be found along the east coast of the U.S. from the Gulf of Maine south to mid-Florida.

Leatherback turtles are omnivorous but feed primarily on jellyfish and other cnidarians, and have been associated with large schools of cabbage head jellyfish (Stomolophus meleagris). Fritts et al. (1983) reported that these turtles also ingest plastic, apparently mistaking it for food.

Nesting occurs from February through July at sites located from Georgia to the U.S. Virgin Islands. Nesting leatherbacks occur along beaches in Florida, Nicaragua, and islands in the West Indies; however, no nesting has been reported in Louisiana (Gunter 1981; Dundee and Rossman 1989). In Louisiana, leatherbacks are believed to occur offshore in deep waters; however, they have been collected from or sighted in Cameron Parish, Atchafalaya Bay, Timbalier Bay, and Chandeleur Sound (Dundee and Rossman 1989).

3.7.3Status and Cause of Decline

The leatherback sea turtle was listed as an endangered species throughout its range on June 2, 1970 (35 FR 8491). Critical habitat was designated on September 26, 1978 (43 FR 43688), March 23, 1979 (44 FR 17710), and March 23, 1999 (64 FR 14051). Critical habitat has been designated for shoreline and adjacent waters of the U.S. Virgin Islands (50 CFR 17.95; 50 CFR 226.207).

Because adult female leatherbacks frequently nest on different beaches, nesting population estimates and trends are especially difficult to monitor. However, it is estimated that the global population has declined an estimated 40% over the past three generations (Wallace et al. 2015).

In the Caribbean, Atlantic and GOM, leatherback populations are generally increasing (NOAA Fisheries 2017c). In the United States, the Atlantic coast of Florida is one of the main nesting areas in the continental United States. NOAA Fisheries data from this area reveals a general upward trend of, though with some fluctuation. Florida index nesting beach data from 1989-2014, indicate that number of nests at core index nesting beach ranged from 27 to 641 in 2014 (NOAA Fisheries 2017c). In the U.S. Caribbean, nesting in Puerto Rico, St. Croix, and the U.S. Virgin Islands continues to increase as well, with some shift in the nesting between these two islands, according to NOAA Fisheries.

3.8Green Sea Turtle

3.8.1Description of the Species

The green sea turtle (Chelonian mydas) is one of the largest marine turtles; adults weigh between 250 and 450 pounds (Dundee and Rossman 1989). This species usually reaches sexual maturity between 20 to 50 years and can live longer than 50 years. Yearling turtles live in and around offshore areas and are primarily carnivorous (NOAA Fisheries 2011d), feeding mainly on invertebrates. Green turtles are the only sea turtles that eat large amounts of plants, feeding in shallow water areas with abundant seagrasses or algae (Fritts et al. 1983; Spotila 2004). These turtles also feed on invertebrates and carrion (Dundee and Rossman 1989).

3.8.2Species Habitat and Distribution

Although green sea turtles are found worldwide in oceans and gulfs with water temperatures greater than 68°F (20°C), their distribution can be correlated to grass bed distribution, location of nesting beaches, and associated ocean currents (Perrine 2003; Spotila 2004). Long migrations are often made between feeding and nesting grounds (Carr and Hirth 1962). Within Louisiana waters, these turtles probably occur all along the coast and may nest on the Chandeleur Islands (Dundee and Rossman 1989). Population decline has been attributed to heavy fishing pressure and human nest predation (Dundee and Rossman 1989; Perrine 2003; Spotila 2004). Historically, green sea turtles were fished off the Louisiana coast, especially the Chandeleur Islands (Rebel 1974). Exploitation and incidental drowning in shrimp trawls has contributed to the decline of this species and its eventual listing (King 1981). During their first year of life, green sea turtles are primarily carnivorous, feeding mainly on invertebrates. Green turtles are the only sea turtles that eat large amounts of plants, feeding in shallow water areas with abundant seagrasses or algae (Fritts et al. 1983; Spotila 2004). Green sea turtles also feed on invertebrates and carrion (Dundee and Rossman 1989). The green sea turtle grows to the second largest size of any sea turtle, with a maximum shell length of 55 in (140 cm) and a maximum weight of 517 lbs (235 kg), but most are considerably smaller (Perrine 2003).

The turtles migrate from nesting areas to feeding grounds, which are sometimes several thousand miles away. Most turtles migrate along the coasts, but some populations are known to migrate across the ocean from nesting area to feeding grounds. The major nesting beaches are always found in places where the seawater temperature is greater than 77°F (25°C). As a species that migrates long distances, these turtles face special problems associated with differing attitudes toward conservation in different countries. Green sea turtles are the only sea turtles known to come ashore for purposes other than nesting. Both immature and adult green sea turtles are known to bask (Perrine 2003).

In the southeastern United States, green sea turtles are found around the U.S. Virgin Islands, Puerto Rico, and the continental U.S. from Texas to Massachusetts. The primary nesting sites in U.S. Atlantic waters are along the east coast of Florida, with additional sites in the U.S. Virgin Islands and Puerto Rico.

Green sea turtles are also found throughout the North Pacific, ranging as far north as Eliza Harbor, Admiralty Island, Alaska, and Ucluelet, British Columbia. In the eastern North Pacific, green sea turtles have been sighted from Baja California to southern Alaska. In the central Pacific, green sea turtles can be found at most tropical islands. In U.S. Hawaiian waters, green sea turtles are found around most of the islands in the Hawaiian Archipelago. The primary nesting site is at French Frigate Shoals.

Female green sea turtles lay one to seven clutches of eggs in a single nesting season with each clutch containing an average of 110 eggs (Spotila 2004). The number of nests has been estimated to be between 350 to 2,300 nests annually. Green sea turtles nest at two, three, or four-year intervals. This nesting activity indicates a population of less than 1,000 females in the breeding population of Florida and Mexico. It takes longer for a green turtle to reach maturity than any other sea turtle, typically living 45-59 years (Spotila 2004).

During the construction of the Caminada Headlands Beach and Dune Restoration Project (BA-45), turtle trawling and relocation was conducted in conjunction with hopper dredging activities in the South Pelto Borrow Area. Of the total 154 sea turtle relocations, 2 green turtles were relocated as a part of the project activities (Coastwise Consulting, 2014). There were no turtle mortalities or injuries associated with relocation trawling on this Project.

During the construction of the Caminada Headlands Beach and Dune Restoration Increment II Project (BA-143), turtle trawling and relocation was conducted in conjunction with hopper dredging activities in the South Pelto Borrow Area. Zero Green Sea Turtles were relocated as a part of the project activities on BA-143. There were no turtle mortalities or injuries associated with relocation trawling on this project (East Coast Observers, 2014). There were zero incidental takes during the hopper dredge operation of the BA-143 Project (REMSA, 2016).

The BA-45 Project clearly established the presence of Green Sea Turtles in the South Pelto portion of Ship Shoal.

3.8.3Status and Cause of Decline

The green turtle was listed as threatened in U.S. waters, except for the Florida breeding population that was listed as endangered, on July 28, 1978 (43 FR 32800). Green turtles are listed as endangered in all U.S. waters away from the nesting beaches because these populations are difficult to distinguish. Critical habitat for the green sea turtle was designated on September 2, 1998 (63 FR 46701); critical habitat was redesignated and amended on March 23, 1999 (64 FR 14067). Critical habitat has also been designated for waters surrounding Culebra Island, Puerto Rico (50 CFR 226.208).

In the U.S., green turtles nest primarily along the central and southeast coast of Florida where an estimated 200-1,100 females nest annually. The two largest nesting populations are found at: Tortuguero, on the Caribbean coast of Costa Rica, where 22,500 females nest per season on average and Raine Island, on the Great Barrier Reef in Australia, where 18,000 females nest per season on average

The principal cause of the historical, worldwide decline of the green turtle is long-term harvest of eggs and adults on nesting beaches and juveniles and adults on feeding grounds. These harvests continue in some areas of the world and compromise efforts to recover this species. Incidental capture in fishing gear, primarily in gillnets, but also in trawls, traps and pots, longlines, and dredges is a serious ongoing source of mortality that also adversely affects the species' recovery. Green turtles are also threatened, in some areas of the world, by a disease known as fibropapillomatosis (FP), which causes tumors on turtles (NOAA Fisheries 2017d). The USFWS and NMFS have funded research on FP to expand knowledge of the disease to develop an approach for remedying the problem. Additional threats to this species in the U.S. include coastline and barrier island erosion, which result in the loss of suitable habitat (LDWF 2004).