seaturtle.org : MTN : ARCHIVES : Sign In

Marine Turtle Newsletter 73:2-5, © 1996

Good News! Rising Numbers of Kemp's Ridleys Nest at Rancho Nuevo, Tamaulipas, México

René Marquez-M.,¹ Ma. Miguel A. Carrasco-A.,¹ Carmen Jimenez-O,¹ Richard A. Byles,² Patrick Burchfield,³ Manuel Sanchez-P.,⁴ Juan Diaz-F.,⁴ and Alma S. Leo-P.^5
1Inst. Nacional de la Pesca, CRIP-Manzanillo, A.P. 591, Manzanillo, Colima, México 28200
²S Fish and Wildlife Service, P. O. Box 1306, Albuquerque, New México 87103 USA
³Gladys Porter Zoo, 500 Ringgold St., Brownsville, Texas 78520 USA
⁴Inst. Nacional de la Pesca, Chilpancingo 73, Col. Hipodromo Condesa, México D.F. 06170
⁵INP-CRIP-Tampico, A.P. 197, Tampico, Tamaulipas, México 89000

It is natural for the number of gravid sea turtles arriving at the nesting beach to fluctuate widely from year to year. When these fluctuations indicate a persistent positive trend, however, there is a justified hope that the population at large is experiencing an increase in size. This Marine Turtle Newsletter, 1996, No. 73 - appears to be the case with the highly endangered Kemp's ridley turtle (Lepidochelys kempii), which has shown steadily rising numbers of females arriving at the primary nesting beach at Rancho Nuevo, Tamaulipas (located on the northeast coast of México) for the past eight years.

Each year between March and July, gravid females come ashore to lay hundreds of eggs in multiple clutches. Later, mainly between May and September, thousands of hatchlings enter the waters of the Gulf of México and disappear for at least a decade (Márquez-M., 1994). Those that survive will someday return to Rancho Nuevo to lay their own eggs. To study and protect this population, a conservation program was undertaken by the Méxican government in 1966. In 1978, the United States joined forces with México to collaborate on species recovery initiatives. This successful binational program is ongoing.

The historical decline of Kemp's ridley is well documented. Film footage taken in 1947 shows more than 40,000 nesting females on the beach at Rancho Nuevo (Carr, 1963; Hildebrand, 1963). Population monitoring began in 1966, and an estimated 2,000 females arrived to nest in a single day in May 1968 (Márquez et al., 1994). Since then, the least number of females was reported in 1987 with an estimated 748 nests laid at Rancho Nuevo throughout the entire breeding season [N.B. 748 nests represents ca. 374 females]. From then onward, however, a steadily increasing number of gravid females (judged by the number of nests laid) has been documented. In 1995, a record 1429 nests were recorded on the beach at Rancho Nuevo (Figure 1).

To enhance conservation and data collection over a larger area, a second field camp (in addition to the one at Rancho Nuevo) was established in 1989 at Barra del Tordo, 13.4 km south of Rancho Nuevo. That year, 12 nests were protected. In 1990, a third camp was established 25.2 km to the north of Rancho Nuevo at Barra de Ostionales. With three camps now operational we have been able, since 1991, to monitor nesting along nearly 120 km of beach. Despite a relatively few years of data, these secondary nesting beaches, specially Ostionales, are showing modest positive trends in the annual number of nests laid (Figure 2).

The slow but steady recovery of this population may yet be compromised by high numbers of stranded turtles reported in 1994 (Steiner, 1994; Teas, 1994, 1995). While 'cold stunning' and hu~man factors have played causal roles in the population's historical decline, the most important threat to the species, especially in recent years, has been incidental capture by shrimp trawlers in the Gulf of México, principally in the coastal waters of Texas and Louisiana (USA) (U.S. National Research Council, 1990). Many of these turtles drown and wash ashore to be logged as strandings. We expect that future nesting seasons will indicate the degree to which record numbers of strandings in recent years will stifle recovery trends.

In the years to come we are hopeful that the steadily increasing numbers of hatchlings released from Rancho Nuevo will translate into ever-rising levels of recruitment into the adult population. Increasingly frequent nestings reported outside the wider Rancho Nuevo area, such as in Veracruz and Campeche in México, as well as along the southeastern coast of the USA (i.e., Florida, South Carolina, North Carolina), could indicate an already expanding population ... but if fisheries-induced mortality continues, no amount of effort will be sufficient to recover this endangered species.

Acknowledgements: We would like to thank the Méxican and U.S. governments (particularly Instituto Nacional de la Pesca, the U.S. Fish and Wildlife Service, and the U.S. National Marine Fisheries Service) for their assistance and support. We are also indebted to enthusiastic people in the community of Rancho Nuevo (including Sres. Antonio and Juán González), several Directors of CRIP-Manzanillo and Tampico, students and teachers from the CET del Mar (in Barra del Tordo), Universidad del Noreste, Universidad de Tamaulipas, Delegación and Dirección de Pesca from the Tamaulipas State (in Barra Ostionales), Gladys Porter Zoo, HEART of Texas, the Secretar¡a de Marina, Scouts de México, and volunteers (including Javier Alvarado, Alfredo Figueroa, Carlos Delgado from the Universidad de Morelia, Vicente Mongrel from the Cd. Victoria Zoo and many others) who played a part during the last 30 years helping us to save this species.

Carr, A. 1963. Panspecific reproductive convergence in Lepidochelys kempi. Ergebnisse der Biologie 26:298-303.

Hildebrand, H. 1963. Hallazgo del rea de anidación de la tortuga "lora" Lepidochelys kempii (Garman), en la costa occidental del Golfo de México (Rept., Chel.). Ciencia, Mex. 22(4):105-112.

Márquez-M.,R. 1990. Sea Turtles of the World. An annotated and illustrated catalog of sea turtle species known to date. FAO Fisheries Synopsis No. 125(11):1-81.

Márquez-M.,R. 1994. Sinopsis de datos biólogicos sobre la tortuga lora, Lepidochelys kempi (Garman, 1880). Instituto Nacional de la Pesca, México/FAO Sinopsis. SAST-Tortuga Lora 5.31(07)016.02, INP/S152. 141 pp.

Steiner, T. 1994. Shrimpers implicated as strandings soar in the USA. Marine Turtle Newsletter 67:2-5.

Teas, W. G. 1994. 1993 Annual report of the Sea Turtle and Salvage Network. Atlantic and Gulf coasts of the United States. January - December 1993. NOAA-NMFS-SEFSC Miami Lab. Contrib. No. MIA-94/95-12. 46 pp.

Teas, W. G. 1995. 1994 Semi-Annual report of the Sea Turtle and Salvage Network. Atlantic and Gulf coasts of the United States. January - December 1993. NOAA-NMFS-SEFSC Miami Lab. Contrib. No. MIA-94/95-23. 12 pp. (manuscript)

U.S. National Research Council. 1990. Decline of the Sea Turtles: Causes and Prevention. Committee on Sea Turtle Conservation (J. J. Magnuson, Chair), Commission on Life Sciences, U.S. Natl. Research Council. Natl. Academy Press, Washington D.C. 259 pp.