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MEPS prepress abstract   -  DOI: https://doi.org/10.3354/meps13507

Regional differences in Kemp’s ridley sea turtle growth trajectories and expected age at maturation

Larisa Avens*, Matthew D. Ramirez, April G. Hall, Melissa L. Snover, Heather L. Haas, Matthew H. Godfrey, Lisa R. Goshe, Melissa Cook, Selina S. Heppell

*Corresponding author:

ABSTRACT: For species of conservation concern, somatic growth and age at maturation are key parameters in models used to evaluate population dynamics, as spatial and temporal variability in growth rates may be particularly important for predicting population recovery. Following an oceanic juvenile developmental stage, endangered Kemp’s ridley sea turtles (Lepidochelys kempii) occupy neritic habitats in two primary regions, the Gulf of Mexico (GoM) and along the US Atlantic coast. Results of prior studies suggest that somatic growth rates differ between these groups, which has the potential to influence maturation trajectories and relative reproductive contributions. To determine the nature and extent of potential regional differences, we conducted skeletal growth mark analysis (skeletochronology) with complementary annual bone growth increment-specific stable nitrogen isotope (ẟ15N) analysis that allowed delineation of oceanic-to-neritic habitat shifts for turtles stranded 1993 to 2016. Results demonstrate that in the GoM, the oceanic-to-neritic habitat transition is associated with younger ages and faster somatic growth rates than in US Atlantic waters. Overall, US Atlantic somatic growth response was depressed relative to that in the GoM throughout all juvenile life stages and this disparity persisted for more than 20 years. This discrepancy translated into regional divergence in size-at-age relationships and maturation trajectories, with the prediction that US Atlantic Kemp’s ridleys would mature on average 2 to 3 years later than their GoM counterparts. These analyses provide important baseline information on somatic growth rates and predicted age at maturation that can facilitate evaluation of factors contributing to recent fluctuations in reproductive output for this endangered population.