Mixed‐stock aging analysis reveals variable sea turtle maturity rates in a recovering population. Issue 4 (24th March 2022)

• Record Type: Journal Article
• Authors: Turner Tomaszewicz, Calandra N.; Avens, Larisa; LaCasella, Erin L.; Eguchi, Tomoharu; Dutton, Peter H.; LeRoux, Robin A.; Seminoff, Jeffrey A.
• Is Part Of: Journal of wildlife management. Volume 86:Issue 4(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-03-24
• Subjects: age at sexual maturity -- Chelonia mydas -- demography -- endangered species management -- green sea turtle -- growth -- life history; Wildlife management -- Periodicals; Zoology -- Periodicals; 333.954
• DOI: 10.1002/jwmg.22217
• Languages: English
• ISSNs: 0022-541X

Abstract

Abstract: Quantifying demographic parameters and variable vital rates, such as somatic growth rates, time to maturity, and reproductive longevity, is important for effective management of threatened and endangered populations such as sea turtles (Cheloniidae). To address these knowledge gaps, we applied skeletochronology to analyze and compare somatic growth rates and variation in life‐history traits such as age and size at sexual maturity for 65 green turtles ( Chelonia mydas ) in the eastern Pacific Ocean (EP), along the west coast of the United States; turtles belonged to ≥2 nesting subpopulations that differed in body size (mean nesting size). Green turtles in the EP spend approximately 5 years in the oceanic stage before recruiting to nearshore habitats, males may be smaller and younger than females at maturation (x̅ = 17.7 ± 5.5 yr vs. 28.0 ± 8.2 yr), and younger age at sexual maturity was associated with smaller size at sexual maturity, suggesting that mean nesting body size may be reflective of maturation timing for subpopulations. Smaller body sizes for females nesting at Michoacán, Mexico (continental) rookeries, yielded a younger predicted age at sexual maturity (x̅ = ~17 yr) compared to females from Revillagigedo Islands, Mexico rookeries, which displayed larger body sizes and older age at sexual maturity (x̅ = ~30 yr). We consider possible mechanisms driving the observed divergence in life‐history traits, including the possibility that earlier maturation (reduced generation length) for turtles in the Michoacán nesting subpopulation may be a response to intense harvesting in the past 50 years, and consideration of such anthropogenic impacts is warranted by population managers. Finally, our results indicate green turtles moved into nearshore neritic habitats at a young age (4–6 yr), emphasize the importance of protecting neritic habitats along the southwestern United States and northwestern Mexican coasts, and encourage the incorporation of variable maturation time in population recovery assessments. Abstract : Differences in body size of female sea turtles arriving at different nesting beaches within the same geographic region prompt questions about variation in life‐history traits such as age‐ and size‐at‐sexual‐maturity. We applied skeletochronology to analyze and compare somatic growth rates and maturation age and size for green turtles in the eastern Pacific Ocean along the United States west coast and belonging to ≥2 nesting subpopulations that differ in mean nesting body size. Time to maturity varied by 25 years across the entire population; such life‐history information needs to be incorporated into population recovery planning and management.