Population dynamics of marine turtles under harvest

Most assessments of sea turtle population trends are based on adult females at the nesting beach and there is a paucity of information available on the status and dynamics of foraging populations. Where legal marine turtle fisheries operate, these data are critical to assess the impact on stocks and to regulate harvest. In the Turks and Caicos Island's (TCI) there is a legal marine turtle harvest. There is no closed season, there are no quotas and the fishery is not monitored. A recent survey estimated that 400-2,000 green and hawksbill turtles (listed as endangered and critically endangered by the IUCN) are legally harvested in TCI each year; one of the largest legal marine turtle harvests in the world. It is not known whether this harvest is sustainable and therefore there is a need for quantitative data to be gathered on both the harvested animals and foraging stocks of marine turtles in the TCI. Understanding the dynamics of the marine turtle populations of TCI and collecting baseline data on the harvest, are crucial first steps towards assessing the sustainability of this fishery and will help underpin sea turtle conservation practices in many nations. The student will establish an in-water capture/mark/recapture study to monitor the species, and size classes of turtles in TCIs waters and collect tissue samples for mtDNA, sex hormones and stable isotope analysis in order to address the following questions: 1) What are the origins of marine turtles within the foraging grounds of the TCI? 2) At what size do turtles recruit to the foraging grounds? 3) Do primary sex ratios persist through to later life-stages? 4) How do origin and sex affect growth rates? This project is a direct request from the TCI Government to the CASE partner (Marine Conservation Society) for help in assessing the status of marine turtle populations in their waters. Data will be provided to the TCI government for use in policy making and to direct legislation amendments. This project will also assist TCI government in their commitments to biodiversity and to meet TCI's current obligations under the Convention on Migratory Species (CMS).