Principal Investigator: Larisa Avens (SEFSC)
Co-Principal Investigator: Heather Haas (NEFSC)
External Partners: Selina Heppell and Matthew Ramirez (Oregon State University)


Project title

Atlantic Kemp’s ridley age, growth dynamics, habitat use, and trophic ecology, with comparison to the Gulf of Mexico

Background

A recent truncation in the recovery trajectory for numbers of nesting Atlantic Kemp’s ridley females has highlighted the need for more information on the population, including juvenile growth rate and habitat use data. There is also limited understanding still of how much the Atlantic foraging populations contribute to the reproductive population, and better characterizing juvenile movements between the Gulf of Mexico and the Atlantic could provide insight into how discrete mortality events (e.g., cold stuns) impact contributions to the reproductive population. Further exploration is also warranted of regional differences in somatic growth that could be associated with foraging ecology and environmental conditions. Use of skeletochronology in tandem with sequential isotopic and elemental analysis of inert tissues can provide information about age, growth rate, cumulative prey consumption, and habitat occupation over time.

Kemp's ridley sea turtle

Research Objectives

1) Obtain size-at-age, ontogenetic stage duration, and age at sexual maturation data, as well as the variation associated with these parameters, for Kemp’s ridley sea turtles along the Atlantic US coast through skeletochronological analysis.
2) Quantitatively compare age and growth parameters derived for the Atlantic Kemp’s ridleys with results from the Gulf of Mexicoa to characterize regional differences.
3) Characterize trophic ecology and habitat use (including movements between the Atlantic and GOM) relative to size and age through integration of skeletochronology and growth increment-specific stable isotope and trace element analyses.
4) Assess the influence of trophic ecology, sex, location, and year on growth patterns.

Bone cross-section

Project significance, impacts, and applications

The proposed study is designed to address NMFS Sea Turtle Assessment Theme B, Life History and Vital Rates. Recent age and growth data for Kemp’s ridley sea turtles along the US Atlantic coast are not available to assess potential differences between the Atlantic and GOM and how these might influence maturation trajectories and observed fluctuations in nesting numbers, characterize the population demographic affected by mass cold stunning events, investigate the influence of habitat use and trophic ecology on somatic growth, and assess movement between Atlantic and GOM habitats. As a result, this study will yield data to fill a significant data gap for modeling population dynamics, informing management efforts and increasing understanding of species ecology. This study also addresses specific recommendations put forward by the recent NRC review of sea turtle stock assessments (NRC 2010), which called for increased data collection to assess age at maturation for the different sea turtle species.

National Research Council (2010) Assessment of Sea-Turtle Status and Trends: Integrating Demography and Abundance. The National Academies Press, Washington D.C.

Southeast Fisheries Science Center (SEFSC) (2009) An assessment of loggerhead sea turtles to estimate impacts of mortality reductions on population dynamics. NMFS SEFSC Contribution PRD-08/09-14, July 2009, 46 p

National Marine Fisheries Service & US Fish and Wildlife Service (2015) Kemp’s ridley sea turtle (Lepidochelys kempii) 5-year review: summary and evaluation