Green Island lies approximately 11 km off the north Queensland coast of Australia. The associated 710-ha reef flat supports a Chelonia mydas foraging population, which has been monitored by the Queensland Government's Threatened Species Program since 1988. Population census data for this area show a significant adult age-class-specific population decline for C. mydas. Preliminary evaluation indicates the decline in adult age-classed turtles is unlikely to be caused by incidental capture, habitat degradation, pollution, change of foraging sites or climate change. Traditional take (locally or during reproductive migrations) provides a plausible explanation. A continuation of this trend may threaten the existence of C. mydas in this part of the Great Barrier Reef World Heritage Area.