ESR 11:35-45 (2010)  -  DOI: https://doi.org/10.3354/esr00264

Long-term monitoring of black turtles Chelonia mydas at coastal foraging areas off the Baja California Peninsula

Melania C. López-Castro1,2, Volker Koch3,4,*, Antonio Mariscal-Loza3, Wallace J. Nichols5,6

1Grupo Tortuguero de Las Californias, C.P. 23060 La Paz, Baja California Sur, Mexico
2Centro de Investigaciones Biológicas del Noroeste, C.P. 23090 La Paz, Baja California Sur, Mexico
3Departamento de Biología Marina, Universidad Autónoma de Baja California Sur, C.P. 23080 La Paz, Baja California Sur, Mexico
4Investigación para la Conservación y el Desarrollo A.C. (INCODE A.C.), La Paz, Baja California Sur, Mexico
5The Ocean Conservancy, Davenport, California 95017, USA
6Department of Herpetology, California Academy of Sciences, San Francisco, California 94118, USA
*Corresponding author. Email:

ABSTRACT: Monthly in-water monitoring was conducted at 5 foraging areas off the Baja California Peninsula, Mexico, from 2001 to 2006 to assess black turtle population status. Turtles were captured with entanglement nets, size (straight carapace length, SCL) and weight of each individual were recorded and turtles were tagged on both rear flippers. A total of 1238 turtles were captured, involving 6309 h of effort. Of this total, 937 ind. were marked and 155 were recaptured. SCL ranged from 30 to 95.5 cm; immature turtles accounted for >94% of the total catch and were dominant at all sites. However, size class distribution varied among sites, and turtles from the Gulf of California were significantly larger than those caught in the Pacific. Catch per unit of effort (defined as the number of turtles caught per 100 m of net soaking for 24 h) varied from 1.79 at Bahía Magdalena to 17.35 at Punta Abreojos. Mean (±SD) annual growth rate for black turtles was 2.27 ± 0.71 cm yr–1, with the lowest and highest growth rates in Bahía Magdalena (1.37 ± 0.71 cm yr–1) and Laguna Ojo de Liebre (3.05 ± 2.23 cm yr–1), respectively. Lack of recaptures from adjacent sites and multiple recaptures of specimens at the site of origin over several years indicate a low connectivity among foraging areas and a high site fidelity. Hence, strengthening local protection is imperative to the recovery of black sea turtle populations.


KEY WORDS: Black turtle · East Pacific green turtle · Chelonia mydas · Population ecology · Northwest Mexico · Growth · Size distribution · CPUE · Population status


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Cite this article as: López-Castro MC, Koch V, Mariscal-Loza A, Nichols WJ (2010) Long-term monitoring of black turtles Chelonia mydas at coastal foraging areas off the Baja California Peninsula. Endang Species Res 11:35-45. https://doi.org/10.3354/esr00264

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