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Allometric models for sex ratio determination in all stages of ontogeny of Chelonia mydas from Bahía de los Ángeles, México

Published online by Cambridge University Press:  26 August 2020

Elena Solana-Arellano Open the ORCID record for Elena Solana-Arellano [Opens in a new window] ,
David Ramírez-Delgado  and
Erika Santacruz-López
Elena Solana-Arellano*
Affiliation:
Departamento de Ecología Marina, Centro de Investigación Científica y Educación Superior de Ensenada, Ensenada, Baja California, 22860, México
David Ramírez-Delgado
Affiliation:
Departamento de Ecología Marina, Centro de Investigación Científica y Educación Superior de Ensenada, Ensenada, Baja California, 22860, México
Erika Santacruz-López
Affiliation:
Bahía de los Ángeles, Ensenada, Baja California, CP 22980, México.
*
Author for correspondence: Elena Solana-Arellano, E-mail: esolana@cicese.mx
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Abstract

In order to determine the sex of Chelonia mydas individuals found within one of the principal foraging areas of the Gulf of California during any given stage of ontogeny, 529 individuals were sampled in Bahía de los Ángeles from 1995–2012, and their morphometric data were collected. A principal component analysis (PCA) was performed for the morphometric variables, and two principal components were obtained that unambiguously separated sexes and ontogenetic stages. The first component was defined by straight carapace length (SCL), curve carapace length (CCL), plastron length (PL) and carapace depth (CD), while the second factor was represented by total tail length (TTL). Allometric models were fitted with the most important variables determined by the PCA. The model PL = αSCLβ was able to distinguish between adults and immature individuals. For adult organisms, the model that best separated males from females was TTL = αSCLβ. Adult females had SCL values of 66–96.7 cm and TTL values of 16.3–25 cm, while adult males had SCL values of 66.4–12.5 cm and TTL values > 25 cm. As the organisms were considered immature only if SCL < 77.3, we were able to determine the TTL values for immature individuals by using elemental mathematics and solving for SCL in the equation TTL = αSCLβ for each group (i.e. adult females, adult males and immatures). So, considering the mathematical approach and acknowledging the lack of background information, immature individuals may be considered potential females if the TTL value is between 7.04–17.8 cm and potential males if the TTL value > 17.8 cm.

Keywords

Gulf of Californiamathematical modelsontogenysea turtles
Type
Research Article
Information
Journal of the Marine Biological Association of the United Kingdom , Volume 100 , Issue 5 , August 2020 , pp. 825 - 830
Copyright
Copyright © Marine Biological Association of the United Kingdom 2020

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Footnotes

*

Present address: Centro de Investigación Científica y Educación Superior de Ensenada. 3918 Carretera Tijuana-Ensenada, Zona Playitas, Ensenada 22860, Mex.

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