109 1. Abstract The Grand Lagon Sud of New Caledonia is a major nesting area for the critically endangered South Pacific loggerhead turtle subpopulation. It has been acknowledge to concentrate 4045% of all nesting activities at the scale of the archipelago’s scale, scattered over 35 remote coral-reef islets scattered over the area. A significant spatiotemporal heterogeneity in the distribution of nesting activities is observed within the rookery. This singular pattern raises questions as to why reproductive females tend to lay their eggs in selected nesting islets and/or habitats. Implications for management are important, as prioritized conservation measures may only be implemented if essential nesting sites are identified, and the level and nature of threats precisely quantified. To fill in this prevailing knowledge gap, we have investigated nesting activities’ intensity and variability based on an extensive monitoring effort operated over 28 islets and 6 nesting seasons. Nesting site selection was also characterized through the assessment of environmental and anthropogenic variables’ influence over the predicted number of nests, both at the inter- and intra-islet scale. Our results have allowed the identification of nesting hotspots that may represent powerful conservation targets. Moreover, the negative impact of anthropogenic presence over nesting activities has been highlighted. Implementation of access restrictions on the most critical nesting islets of the area would ensure a well-balanced management trade off, guaranteeing maximized conservation benefits while maintaining a satisfying level of social and economic acceptability over the considered management strategies. Keywords Sea turtle, Caretta caretta, endangered species, coral-islets, nesting rookery, nesting site selection, conservation targets, science-based conservation. 2. Introduction Long-lived marine megafauna species face major conservation issues worldwide (Pimiento et al. 2020; Alves et al. 2022; Grémillet et al. 2022). Implementation of effective management measures requires not only long-term assessments of population demographic trends (Reynolds et al. 2011; Robinson et al. 2018; Ceriani et al. 2019), but also robust understanding of the variability of their fitness, including the spatial distribution of reproductive aggregations (Hays et al. 2019; Assersohn et al. 2021; Raposo et al. 2024). This is particularly important for populations of conservation concern (Allen and Singh 2016), for which targeted and prioritized management measures may only be implemented if breeding areas are identified and the level and nature of threats within these areas are precisely quantified (Taylor and Dizon 1999; Walker 2005; Wallace et al. 2011).
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