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Marine Turtle Newsletter 58:15, © 2001
Rene Márquez M.1, Manuel Sanchez P.2, Juan Diaz F.2, Javier Vasconcelos,2
Ignacio Flores2, Israel Arguello1, Miguel A. Carrasco1, and Aristoteles Villanueva1
1Sepesca-INP/CRIP, A.P. 591, Manzanillo, Colima 28200 Mexico
2D.G. Pesca-Tamaulipas, Cd. Victoria, Tamaulipas Mexico
In order of abundance, the sea turtles arriving to nest at Rancho Nuevo in Tamaulipas, Mexico, in 1990 were the Kemp's ridley (Lepidochelys kempii), the green turtle (Chelonia mydas), and the loggerhead (Caretta caretta). Nesting began in April and ended in August, with Kemp's ridleys nesting mainly between April and July and green turtles mainly between June and August. The seasonality was clearly out of phase for both species. Most nesting took place along 75.8 km from La Barrita to the mouth of the Rio Soto Lamarina. Ridley nests were concentrated between La Coma and San Vincente. Since 1989 - and again this year - significant numbers of nests have been observed north of San Vincente. This is interesting behavior, since aerial surveys conducted in previous years did not detect high numbers of nests in this area. It is possible that recent hurricanes have somehow altered the nesting beaches. Perhaps the profile has changed, or sand grain characteristics are no longer suitable for nesting due to the large accumulation of coral rock between La Coma and Calabazas, historically the most important nesting area.
In 1990 there were two arribadas with more than 150 nests each. The first occurred on 28-29 April with 170 nests collected and the second on 24-26 May with 216 arriving turtles. Two hundred ninety-seven Kemp's ridley females were tagged with monel tags, 229 with PIT tags, and six with radio satellite transmitters. In total, 1,067 nests were protected; 106,991 eggs produced 78,412 hatchlings. For more than two decades the presence of 1-3 green turtles has been observed on these beaches. About five years ago, the numbers began to increase to 5-7 nestings. During 1988, there were 12 observations and seven nests collected; during 1989, the number of observations was 56. In 1990, 122 arrivals were registered and 82 nests were collected; 10,933 eggs produced 1,654 hatchlings (15.1% hatch success). Clearly the hatch success for the green turtles is quite low when compared to the 70% minimum success obtained for the Kemp's ridley. This may be because egg collection takes place the day after nesting, more than six hours after the eggs are laid.
Acknowledgements: As in past years, we have received support from the U. S. Fish and Wildlife Service (FWS), the Government of the State of Tamaulipas, Centro de Estudios Tecnologicos del Mar, and the Boy Scouts of Ciudad Madero. SEDUE commissioned a wildlife inspector to be present during nearly the entire season. Special thanks go to Jack Woody and Richard Byles (FWS) and to Patrick Burchfield of the Gladys Porter Zoo in Brownsville, Texas. As always, we also had excellent support from Ernesto Corripio C. (Director of Pesca) and Javier Llerena H. (Federal Pesca delegate in Tamaulipas). A special thanks to the community of Rancho Nuevo, particularly Antonio Gonzalez for his unselfish support and friendship, and to the personnel of CRIP of Tamaulipas for their collaboration.