Marine turtles are wide-ranging, long-lived, iteroparous species of conservation concern. From indirect threats, such as development at their breeding grounds and negative fisheries interactions, to direct take of eggs meat and shells, they are impacted at all stages of their life-cycle by the activities of Man. A better understanding of their reproductive and spatial ecology together with knowledge of population status can inform conservation and management actions for their protection. This thesis presents a collection of chapters covering three species of marine turtle, from four countries in two regions where major knowledge gaps existed on marine turtle biology and ecology. In Oman we identify plasticity in adult loggerhead turtle (Caretta caretta) internesting behaviour combined with globally-atypical, predominantly oceanic habitat use and we raise concerns over potential bias derived from temporally-restricted tracking studies. Conversely, we show that adult female individuals of the principally oceanic olive ridley turtle (Lepidochelys olivacea) remain in neritic waters outside of the breeding season, with some local turtles unusually utilising the same location both during and after the breeding period. We also show that green turtles (Chelonia mydas) nesting on Masirah Island are long distance migrators, travelling 2000 km or more into the Red Sea. Together with our tracking data for the other species in Oman we highlight the threat that fisheries interaction, in a region with poor fisheries regulation, is likely to have on these populations.

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