Abstract
Long-term monitoring programs of species at risk are efficacious tools to assess population changes, evaluate conservation strategies, and improve management practices to ensure populations reach levels at which they can fulfill their ecological roles. For sea turtles, annual nesting beach surveys are the most accessible method to estimating the population abundance and reproductive output, especially when these are done in primary nesting sites. However, little data exist on the long-term assessment of these parameters. Here, we present the trends of the nest abundance, female size, hatching, and emergence success of hawksbill (Eretmochelys imbricata) and green (Chelonia mydas) turtles at key nesting beaches in the southern Gulf of Mexico over 31 years (from 1990 to 2021). The nest abundance showed an increasing trend in both species as a result of the sustained protection and conservation effort, but there was no significant temporal trend in the annual female size, clutch size, hatching, and emergence success. However, these indicators showed decreasing mean values over the last decade and should be closely monitored. We suggest these decreases link to the combined effects of ocean warming and anthropogenic pressures affecting the sea turtle foraging grounds. Aside from protecting key nesting sites, protecting and restoring crucial foraging habitats should be an immediate priority requiring international cooperation.
Keywords:
green turtle; hawksbill turtle; long-term monitoring; population trends; reproductive parameters.
Grants and funding
Different funding sources have supported the monitoring efforts at Celestún, El Cuyo and Holbox including SAC-TUN (CALICA), the US Fish and Wildlife Service, Industria Salinera de Yucatán, S. A. Fondo Mexicano para la Conservación de la Naturaleza, Alianza WWF-Fundación Carlos Slim, The Nature Conservancy, SEE Turtles Billion Baby Turtles Program, National Fish and Wildlife Foundation, Programa de Especies en Riesgo—CONANP, Programa de Monitoreo Biológico- CONANP, Sea Turtle Inc., Coastal Wildlife Club, Fomento Social Banamex, Familia Andrews, IdeaWild, Casa Tortuga, Telefónica Movistar, and many individual donors. Protection and conservation activities in Lechuguillas were initially funded by the Secretaría de Desarrollo Social (SEDESOL), and later with funds from the Secretaría del Medio Ambiente, Recursos Naturales y Pesca (SEMARNAP) through the Instituto Nacional de PESCA (INP)—Centro Regional de Investigación Pesquera (CRIP) Veracruz, the Secretaría de Medio Ambiente y Recursos Naturales (SEMARNAT), and now by the Comisión Nacional de Áreas Naturales Protegidas (CONANP)—Parque Nacional Sistema Arrecifal Veracruzano, the Universidad Veracruzana, the Gladys Porter Zoo, Fundación Tony A. C., Ayuntamiento de Vega de Alatorre, Veracruz, and many community subsidies programs operated by CONANP. At Isla Aguada, funding was provided by CRIP–Carmen-INAPESCA, DGVS-SEMARNAT, and APFFLT CONANP. At Cayos Arcas, the VIII Zona Naval Militar, and EIO-Carmen supported the monitoring efforts. San Lorenzo was funded by SEMARNYD, SMAAS, SEMARNATCAM, and SEMABICCE.