Global marine turtle population assessments highlight the importance of the south-west Indian Ocean region, despite data gaps for the Chagos Archipelago. The archipelago hosts nesting hawksbill Eretmochelys imbricata and green turtles Chelonia mydas, both heavily exploited for 2 centuries until protection in 1968–1970. We assessed available nesting habitat and spatial distribution of nesting activity during rapid surveys of 90% of the archipelago's coastline in 1996, 1999, 2006 and 2016. We quantified seasonality and mean annual egg clutch production from monthly track counts during 2006–2018 along a 2.8 km index beach on Diego Garcia island. An estimated 56% (132 km) of coastline provided suitable nesting habitat. Diego Garcia and Peros Banhos atolls accounted for 90.4% of hawksbill and 70.4% of green turtle nesting. Hawksbill turtles showed distinct nesting peaks during October–February, and green turtles nested year-round with elevated activity during June–October. Estimates of 6,300 hawksbill and 20,500 green turtle clutches laid annually during 2011–2018 indicate that nesting on the Chagos Archipelago has increased 2–5 times for hawksbill turtles and 4–9 times for green turtles since 1996. Regional estimates indicate green turtles produce 10 times more egg clutches than hawksbill turtles, and the Chagos Archipelago accounts for 39–51% of an estimated 12,500–16,000 hawksbill and 14–20% of an estimated 104,000–143,500 green turtle clutches laid in the south-west Indian Ocean. The improved status may reflect > 40 years without significant exploitation. Long-term monitoring is needed to captureinterannual variation in nesting numbers and minimize uncertainty in population estimates.

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印度洋西南部海龟筑巢种群的估计表明查戈斯群岛的重要性

尽管查戈斯群岛存在数据缺口，但全球海龟种群评估强调了西南印度洋地区的重要性。群岛拥有筑巢玳瑁红毛茛和绿海龟Chelonia mydas,两者都被大量开采了 2 个世纪，直到 1968 年至 1970 年得到保护。我们在 1996 年、1999 年、2006 年和 2016 年对群岛 90% 的海岸线进行快速调查期间评估了可用的筑巢栖息地和筑巢活动的空间分布。我们从 2006 年至 2018 年的每月轨道计数中量化了季节性和平均年产蛋量，沿着 2.8公里索引海滩迭戈加西亚岛上。估计有 56%（132 公里）的海岸线提供了合适的筑巢栖息地。Diego Garcia 和 Peros Banhos 环礁占玳瑁的 90.4% 和绿海龟筑巢的 70.4%。玳瑁在 10 月至 2 月期间出现明显的筑巢高峰，绿海龟在 6 月至 10 月期间全年筑巢，活动量增加。估计有 6,300 只玳瑁和 20 只，2011-2018 年间每年产下 500 只绿海龟巢表明，自 1996 年以来，在查戈斯群岛筑巢的玳瑁增加了 2-5 倍，绿海龟增加了 4-9 倍。区域估计表明，绿海龟的产蛋量是玳瑁的 10 倍海龟，查戈斯群岛占印度洋西南部约 12,500-16,000 只玳瑁的 39-51% 和约 104,000-143,500 只绿海龟的 14-20%。改善的状态可能反映 > 40 年没有显着开发。需要进行长期监测以捕捉筑巢数量的年际变化并最大限度地减少种群估计的不确定性。区域估计表明，绿海龟的产卵量是玳瑁的 10 倍，查戈斯群岛占估计的 12,500-16,000 只玳瑁的 39-51% 和估计在南部铺设的 104,000-143,500 只绿海龟窝的 14-20% -西印度洋。改善的状态可能反映 > 40 年没有显着开发。需要进行长期监测以捕捉筑巢数量的年际变化并最大限度地减少种群估计的不确定性。区域估计表明，绿海龟的产卵量是玳瑁的 10 倍，查戈斯群岛占估计的 12,500-16,000 只玳瑁的 39-51% 和估计在南部铺设的 104,000-143,500 只绿海龟窝的 14-20% -西印度洋。改善的状态可能反映 > 40 年没有显着开发。需要进行长期监测以捕捉筑巢数量的年际变化并最大限度地减少种群估计的不确定性。