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Hawksbill sea turtle life stage durations, somatic growth patterns, and age at maturation

Larisa Avens*, Matthew D. Ramirez, Lisa R. Goshe, Jamie M. Clark, Anne B. Meylan, Wendy Teas, Donna J. Shaver, Matthew H. Godfrey, Lyndsey Howell

*Corresponding author:

ABSTRACT: Sea turtles exhibit complex life histories, encompassing intermittent use of multiple spatially separated habitats throughout long lifespans. This broad scope presents challenges for collecting comprehensive biological and ecological data, yet absence of such information complicates evaluation of management strategies for populations at risk of extinction. For example, hawksbill sea turtles are endangered worldwide, primarily due to long-term, directed harvest. However, available information regarding life stage durations, somatic growth patterns, and maturation attributes to enhance understanding of anthropogenic impacts and recovery potential remains constrained. To address data gaps for the species in the western North Atlantic, we conducted skeletochronological analysis for hawksbills stranded along US coastlines to generate straightline carapace length (SCL)-at-age and somatic growth data. Generalized additive mixed models (GAMMs) and bootstrapped von Bertalanffy growth curves were used to characterize age at maturation and covariate influence on somatic growth. For a subset of turtles, annual bone growth increment-specific stable isotope and trace element analyses were incorporated to evaluate habitat use relative to age. Integration of these multiple data sources indicated that juveniles transitioned from oceanic to neritic habitat at ages ranging from 1–3 yr and mean SCLs of 23–24 cm (total range 15.7–35.0 cm). Initial ages at maturation for this population at minimum nesting female SCLs were estimated at 15–25 yr. Somatic growth varied significantly relative to size, age, and stranding location, while no association with sex or calendar year was observed. Taken together, these results demonstrate the utility of these complementary analytical approaches for generating baseline data fundamental to characterizing hawksbill sea turtle population attributes.