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Unveiling loggerhead turtles size decline at a major Brazilian nesting ground

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Abstract

Brazil’s second-largest reproductive colony of loggerhead turtles (Caretta caretta) has a long history of overexploitation, with its temporal ecological dynamics still unknown. This study investigates changes in the average size of females and post-maturity somatic growth rates in marked and recaptured loggerhead turtles at a breeding site over a 33-year period (1982–2014). Loggerhead curved carapace length (CCL) was evaluated over the course of the study using a generalized additive model (GAM) with a Gaussian family distribution and time smoothed. Includes the nesting year and the CCL for a total of 2.359 female loggerhead turtles. The overall average length of females was 99.4 cm ± 5.8 (mean ± SD). The results suggest that the CCL of females in the nesting area is decreasing. From 1982 to 1998, the mean CCL was 102.6 cm; from 1999 to 2014, the average length was 98.7 cm. There were no statistically significant differences in post-maturity growth rates among recaptured females, supporting the hypothesis of increased recruitment. The GAM results showed significant differences in the size structure changes of reproductive site females over time. The study highlights how a population parameter can be influenced by long-term conservation of feeding and nesting areas for sea turtles, resulting in a higher number of recruits. The curved carapace length serves as an important metric to describe population changes and raise awareness about future conservation challenges.

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Data availability

The dataset analyzed during the current study is not publicly. However, the data are available from Projeto TAMAR upon reasonable request. For more information contact Gustavo Stahelin (Advisor to the National Directorate of Research and Conservation; gustavo@tamar.org.br).

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Acknowledgements

We would like to thank the TAMAR Project Foundation and TAMAR/ICMbio Center for their support throughout the project and for providing the database. ASM anda JAP was partially supported by a scholarship from the National Council for Scientific and Technological Development (CNPq) and for the Coordination for the Improvement of Higher Education Personnel – Brazil (CAPES).

Funding

Data collection was funded essentially from Visitor Center and Stores that are part of the circular economy program of Fundação Projeto TAMAR, a private nonproft organization. The authors declare that no funds, grants, or other support were received during the preparation of this manuscript.

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Contributions

All authors contributed to the conception and design of the study. Conceptualization, methodology, formal analysis, investigation, data curation, writing, and visualization were conducted by JAP, ASM, and WVS participated in conceptualization, process, writing, and supervision. Resources, writing, and methodology were carried out by ASS and ACM. The initial manuscript draft was written by JAP, and all authors provided comments on previous versions of the manuscript. All authors have read and approved the final manuscript.

Corresponding author

Correspondence to Josiele Alves Pereira.

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The authors declare that they have no confict of interest.

Ethical approval

All procedures performed in studies involving animals were in accordance with the ethical standards of the Centro TAMARICMBio and conducted under SISBIO permit 28938–3 from the Brazilian Ministry of the Environment.

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Responsible Editor: P. Casale.

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Pereira, J.A., Martins, A.S., dos Santos, A.S. et al. Unveiling loggerhead turtles size decline at a major Brazilian nesting ground. Mar Biol 171, 92 (2024). https://doi.org/10.1007/s00227-024-04408-3

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  • DOI: https://doi.org/10.1007/s00227-024-04408-3

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