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Kemp’s Ridley Turtle (Lepidochelys kempii)

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Adult Kemp’s ridleys are considered the smallest marine turtle in the world. Their top shell (carapace) is often as wide as it is long and contains 5 pairs of costal “scutes”. Each of the front flippers has one claw while the back flippers may have one or two.

Similar to olive ridleys, Kemp’s ridleys display one of the most unique synchronized nesting habits in the natural world. Large groups of Kemp’s ridleys gather off a particular nesting beach near Rancho Nuevo, Mexico, in the state of Tamaulipas. Then, wave upon wave of females come ashore and nest in what is known as an “arribada,” which means “arrival” in Spanish.

There are many theories on what triggers an arribada, including offshore winds, lunar cycles, and the release of pheromones by females. Scientists have yet to conclusively determine the cues for ridley arribadas. Arribada nesting is a behavior found only in the genus Lepidochelys.

Female Kemp’s ridleys nest from May to July, laying two to three clutches of approximately 100 eggs, which incubate for 50-60 days.

Taxonomy

Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Testudines
Family: Cheloniidae
Genus: Lepidochelys
Species: kempii

Species Description

Weight: Adult: 100 pounds (45 kg)
Hatchling: 0.5 ounces (14 g)
Length: Adult: 24-28 inches (60-70 cm)
Hatchling: 1.5 inches (3.8 cm)
Appearance:  grayish-green, nearly circular, top shell with a pale yellowish bottom shell
Lifespan: unknown
Diet: crabs, fish, jellyfish, and mollusks
Behavior: “arribada” nesting, where large groups gather and come ashore and nest all at once

Habitat

Adult Kemp’s primarily occupy “neritic” habitats. Neritic zones typically contain muddy or sandy bottoms where prey can be found. Their diet consists mainly of swimming crabs, but may also include fish, jellyfish, and an array of mollusks.

Depending on their breeding strategy, male Kemp’s ridleys appear to occupy many different areas within the Gulf of Mexico. Some males migrate annually between feeding and breeding grounds, yet others may not migrate at all, mating with females opportunistically encountered.

Female Kemp’s have been tracked migrating to and from nesting beaches in Mexico. Females leave breeding and nesting areas and continue on to foraging zones ranging from the Yucatán Peninsula to southern Florida. Some females take up residence in specific foraging grounds for months at a time, leading scientists to suggest that females have a goal-oriented migration, opposed to the suggested wandering strategy employed by olive ridleys. Kemp’s ridleys rarely venture into waters deeper than 160 ft (50 m) (Byles and Plotkin, 1994).

Newly emerged hatchlings inhabit a much different environment than adult turtles. After emerging from the nest, hatchlings enter the water and must swim quickly to escape near shore predators. There is strong evidence that many sea turtle species employ an open ocean developmental stage because encounters with healthy, neonate sea turtles are extremely rare in near shore waters. Some hatchlings remain in currents within the Gulf of Mexico while others may be swept out of the Gulf, around Florida, and into the Atlantic Ocean by the Gulf Stream.

Juveniles of many species of sea turtles have been known to associate with floating sargassum seaweed, utilizing the sargassum as an area of refuge, rest, and/or food. This developmental drifting period is hypothesized to last about two years or until the turtle reaches a carapace length of about 8 inches (20 cm). Subsequently, these sub-adult turtles return to neritic zones of the Gulf of Mexico or northwestern Atlantic Ocean to feed and develop until they reach adulthood.

Critical Habitat
On February 17, 2010, NOAA Fisheries and USFWS were jointly petitioned to designate critical habitat [pdf] for Kemp’s ridley sea turtles for nesting beaches along the Texas coast and marine habitats in the Gulf of Mexico and Atlantic Ocean.

Distribution

Kemp’s ridleys are distributed throughout the Gulf of Mexico and U.S. Atlantic seaboard, from Florida to New England. A few records exist for Kemp’s ridleys near the Azores, waters off Morocco, and within the Mediterranean Sea.

There is only one confirmed Kemp’s ridley arribada in the state of Tamaulipas, Mexico, where nearly 95% of worldwide Kemp’s ridley nesting occurs.

The three main nesting beaches in Tamaulipas, Mexico are

  • Rancho Nuevo
  • Tepehuajes
  • Barra del Tordo

Nesting also occurs in Veracruz, Mexico, and in Texas, but on a much smaller scale. Occasional nesting has been documented in North Carolina, South Carolina, and Florida.

Population Trends

The Kemp’s ridley has experienced a historical, dramatic decrease in arribada size. An amateur video from 1947 documented an extraordinary Kemp’s ridley arribada near Rancho Nuevo. It has been estimated that approximately 42,000 Kemp’s ridleys nested during that single day! The video also provided evidence of Kemp’s ridley egg collection. Dozens of villagers are seen on the beach excavating the nests and subsequent interviews have suggested that 80% of the nests, about 33,000, were collected and transported to local villages (Hildebrand, 1963).

During the mid-20th century, the Kemp’s ridley was abundant in the Gulf of Mexico.  Historic information indicates that tens of thousands of ridleys nested near Rancho Nuevo, Mexico, during the late 1940s.  The population experienced a devastating decline between the late 1940s and the mid-1980s.  The number of nests at Rancho Nuevo was at a record low of 702 in 1985, representing fewer than 250 nesting females.  Due to intensive conservation actions, the Kemp’s ridley began to slowly rebound during the 1990s.  The number of nests increased about 15% each year through 2009.  However, since 2010 the number of nests  has decreased causing concern that the positive growth in the population seen over the last decades may have stalled or reversed.

Threats

  • incidental capture in fishing gear
    • primarily in shrimp and other trawls, but also in gill nets, longlines, traps/ pots, and dredges
  • egg collection (historically)
  • general threats to marine turtles

Kemp’s ridleys face threats on both nesting beaches and in the marine environment. The greatest cause of decline and the continuing primary threat to Kemp’s ridleys is incidental capture in fishing gear, primarily in shrimp trawls, but also in gill nets, longlines, traps and pots, and dredges in the Gulf of Mexico and North Atlantic.

Egg collection was an extreme threat to the population, but since nesting beaches were afforded official protection in 1966, this threat no longer poses a major concern.

Conservation Efforts

The highly migratory behavior of sea turtles makes them shared resources among many nations. Thus, conservation efforts for sea turtle populations in one country may be jeopardized by activities in another. Protecting sea turtles on U.S. nesting beaches and in U.S. waters alone, therefore, is not sufficient to ensure the continued existence of the species.

Sea turtles are protected by various international treaties and agreements as well as national laws:

  • CITES: listed in Appendix I of the Convention on International Trade in Endangered Species of Wild Flora and Fauna, which prohibits international trade
  • CMS: listed in Appendices I and II of the Convention on Migratory Species and are protected under the following auspices of CMS:
  • SPAW: protected under Annex II of the Specially Protected Areas and Wildlife Protocol of the Cartagena Convention
  • IAC: The U.S. is a party of the Inter-American Convention for the Protection and Conservation of Sea Turtles, which is the only international treaty dedicated exclusively to marine turtles

In the U.S., NOAA Fisheries(NMFS) and the U.S. Fish and Wildlife Service (USFWS) have joint jurisdiction for sea turtles, with NOAA having the lead in the marine environment and USFWS having the lead on the nesting beaches. Both federal agencies, along with many state agencies and international partners, have issued regulations to eliminate or reduce threats to sea turtles, while working together to recover them.

In the Atlantic and Gulf of Mexico, we have required measures to reduce sea turtle bycatch in pelagic longline, mid-Atlantic gillnet, Chesapeake Bay pound net, and southeast shrimp and flounder trawl fisheries, such as

  • gear modifications
  • changes to fishing practices
  • time/ area closures

NOAA Fisheries have worked closely with the shrimp trawl fishing industry to develop turtle excluder devices (TEDs) to reduce the mortality of sea turtles incidentally captured in shrimp trawl gear. TEDs that are large enough to exclude even the largest sea turtles are now required in shrimp trawl nets. Since 1989, the U.S. has prohibited the importation of shrimp harvested in a manner that adversely affects sea turtles. The import ban does not apply to nations that have adopted sea turtle protection programs comparable to that of the U.S. (i.e., require and enforce the use of TEDs) or to nations where incidental capture in shrimp fisheries does not present a threat to sea turtles (for example, nations that fish for shrimp in areas where sea turtles do not occur). The U.S. Department of State is the principal implementing agency of this law, while we serve as technical advisor. We provide extensive TED training throughout the world.

We are also involved in cooperative gear research projects designed to reduce sea turtle bycatch in the Gulf of Mexico and Atlantic pelagic longline fisheries, the Hawaii-based deep set longline fishery, the Atlantic sea scallop dredge fishery, the Chesapeake Bay pound net fishery, and non-shrimp trawl fisheries in the Atlantic and Gulf.

In 1991, NOAA Fisheries and USFWS finalized the recovery plan for Kemp’s ridleys in the U.S. Caribbean, Atlantic, and Gulf of Mexico. Since that time, a wealth of new information has been gained regarding Kemp’s biology, distribution, and population status as well as threats to the species. Therefore, NOAA Fisheries and USFWS have initiated a revision of the Kemp’s ridley recovery plan for the U.S. Caribbean, Atlantic, and Gulf of Mexico. The joint Final Recovery Plan published in September 2011.

The Mexican government has played a vital role in the conservation of the Kemp’s ridley. The Kemp’s ridley has benefited from legal protection by Mexico since the 1960s. In 1977, a refuge was established at the only known nesting beach and included the Rancho Nuevo nesting beach as part of a system of reserves for sea turtles. On May 28, 1990, a complete ban on taking any species of sea turtle was implemented by the Mexican government. In 2002, the beach at Rancho Nuevo was designated as a Natural Protected Area under the category of Sanctuary; and in February 2004, it was included on the list of RAMSAR  sites.

SOURCE: NOAA

-TSF-

#turtles #terrapins #tortoises #TSF

 
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