Principal Investigator: Peter Dutton (SWFSC)
Co-Principal Investigators: Kelly Stewart, Phillip Morin (SWFSC)


Project title

Comparing Pacific and Atlantic leatherback population vital rates using genetic approaches

Background

Limited demographic information for leatherbacks sea turtles (particularly males) has limited the ability to conduct more rigorous population and risk assessments. Vital rate information is difficult to observe directly, but previous research using genetic analysis has allowed for the examination vital rates by genetically “tagging” hatchlings for Capture-Mark-Recapture (CMR) application. Genetic analysis has also provided means to sample males without seeing them or catching them by using hatchling genotyping and kinship analysis to examine genotypes and quantify the number of breeding males in the population. The nesting population on St. Croix, US Virgin Islands offers unique opportunities for research and development of tools and approaches for getting at vital rate parameters that are needed to improve stock assessments for sea turtles globally. This proposal will initiate the second (“recapture”) phase of the CMR experiment to determine whether any of the “tagged” hatchlings from the cohorts sampled 6-7 years ago have nested. Furthermore, a comparative study using the same approach to examine vital rates could provide some insight into the decline of Pacific leatherback populations.

Research Objectives

1) Analyze stockpiled CMR samples collected from the first cohorts of leatherback hatchlings to determine first age of reproduction and juvenile survival rates for the Caribbean index population.

2) Initiate mass-tagging of leatherback hatchlings for a CMR study to determine age at first reproduction and age-specific survival rates for eastern Pacific index populations.

3) Apply kinship approaches to census males to determine operational sex ratios of the eastern Pacific breeding populations, along with reproductive success of males and to assess the mating system.

4) Determine fine scale stock structure of eastern Pacific leatherback turtles using both nuclear (microsatellite, SNP) and mtDNA markers to provide a comprehensive assessment of demographic history as well as male and female connectivity between populations.

These objectives have all been identified as priorities in the Marine Turtle Recovery Plans (Recovery Goal 1.1.5.3 Pacific Sea Turtle Recovery Plans, & 2211-2213 in the Atlantic Recovery Plan and are identified as the highest priority in the Research Plan for Marine Turtle Stock Assessments (see NMFS 2004, 2013; NRC 2010). The objectives also link directly to Theme B (Estimation of Vital Rates) and Theme C (Determination of Population Structure) of the four research priorities in the NOAA-NMFS Sea Turtle Assessment Status and Research Plan (2013). Results from this proposed project will elevate the SAIP status for Pacific leatherbacks from the current Tier 1 (inadequate) levels to Tier 2 (adequate).

Finally, this proposal responds to the directive in NOAA’s Species in the Spotlight Initiative (NMFS 2015) to prioritize research on Pacific leatherbacks.

Project significance, impacts, and applications

Our results will address gaps in life history information for sea turtles that have been long-standing and critical needs for building accurate population models. We will develop and implement tools to enable long-term CMR studies of hatchlings in order to establish age at first reproduction and survivorship at different life history stages. These genetic approaches may be used in conjunction with traditional tagging studies and satellite telemetry to improve stock assessments by incorporating missing life history and demographic parameters that allow estimation of vital rates of populations, including age at first reproduction, survivorship at different life history stages, dispersal and migration at different life history stages, census of breeding male populations to determine demographic connectivity of males vs. females, determination of mating systems, operational sex ratios (sex ratios of the breeding population) and spatial ecology.