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

Effective management of threatened and endangered sea turtle species requires not only knowledge of mean values for demographic and life history parameters, but also temporal and spatial trends, the variance surrounding the means, and the underlying drivers. The importance of age and growth data has been highlighted during efforts to characterize sea turtle population dynamics, as models have been found to be sensitive to variations in stage duration and age at maturation values, with minor parameter changes resulting in diverging predictions. For Kemp’s ridley sea turtles, the need for baseline information of this type has been emphasized during efforts to characterize population impacts of the 2010 Deepwater Horizon oil spill in the Gulf of Mexico (GOM) and during subsequent attempts to understand causes underlying the recent, abrupt truncation in the recovery trajectory for numbers of nesting females. Due to increased anthropogenic impacts and uncertainty regarding nesting trends, NMFS has elevated the species Recovery Priority Number to the highest level and emphasized the need for increased data collection for the population, including juvenile growth rate and habitat use data. This study integrates analysis of skeletal growth marks and skeletal increment-specific stable isotopes and trace elements for humerus bones collected from dead, stranded Kemp's ridley sea turtles along the US Atlantic coast. Data yielded by this approach will allow characterization of cohorts affected by mortality events, as well as regional somatic growth patterns and factors underlying potential spatial and temporal trends.

The objectives of the proposed study are to:

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 Atlantic Kemp's ridleys with results from the Gulf of Mexico, to characterize regional differences.

3) Characterize trophic ecology and habitat use (including movements between the Atlantic and Gulf of Mexico) 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.

Data Expected Soon in note from PI Dated 08/28/2018

NOAA Beaufort Laboratory, Beaufort, North Carolina