71 al. 2023). To tackle this challenge, coherent population boundaries must be established (Wallace et al. 2011). Spatially explicit ’Management Units’ (MUs), defined as functionally independent population segments (Wallace et al. 2010b, 2023), are powerful tools to set appropriate short-term targets for conservation (Wallace et al. 2010b; Bourjea et al. 2015; Tolve et al. 2018). However, the delineation of population units is not always straightforward, and it requires a clear understanding of both conservation objectives and threats to the species of interest (Moritz 1994; Taylor and Dizon 1999). For the purpose of this paper, we will consider the MU at the resolution of the genetic stock as we aim to identify consistent management spatial frameworks at the functionally independent population scale (Fitzsimmons and Limpus 2014; Wallace et al. 2023). The loggerhead turtle Caretta caretta (Linnaeus, 1758) shows a cosmopolitan distribution in warm and temperate waters of the globe. It has been classified as ‘Vulnerable’ in the International Union for Conservation of Nature (IUCN) Red List on a global scale since 2015 (Casale and Tucker 2015, 2017). However, the South Pacific subpopulation, designated as a genetically distinct ‘Regional Management Unit’ (Boyle et al. 2009; Wallace et al. 2011; Fitzsimmons and Limpus 2014; Casale and Tucker 2015, 2017), suffered a strong demographic collapse and was therefore listed as ‘Critically Endangered’ in 2015 (Limpus and Casale 2015). Nesting aggregations of this subpopulation are restricted to the western part of the ocean basin. Eastern Australia is considered to aggregate a large majority of its nesting activities (Limpus and Limpus 2003), and the remaining of this subpopulation is essentially breeding and nesting in New Caledonia (Limpus and Casale 2015; Bourgogne et al. 2024c). In New Caledonia (Figure 18-A), two large nesting areas have been described (Limpus et al. 2005b; Barbier et al. 2023; Bourgogne et al. 2024c) (Figure 18-B): the ‘Roche Percée’ beach (RP), on the commune of Bourail (Limpus et al. 2005b; Barbier et al. 2023); and the ‘Grand Lagon Sud’ area (GLS), off the southern end of the main island (Bourgogne et al. 2024c). Both areas support several 10s of nesting females every year, combining for an 10-25% of all nesting activities reported in the South Pacific subpopulation (Limpus and Casale 2015; Barbier et al. 2023; Bourgogne et al. 2024c). They are roughly 150 km apart, yet show different habitat structures and threats of varying natures and intensities. As such, these nesting areas are currently rather managed as distinct conservation units with specific actions addressing specific local threats. However, the connectivity between these two nesting areas has never been evaluated. As a result, it is still unclear whether they should be considered as a single or two distinct MUs, which could have significant repercussions upon the definition and spatial framework of the management strategies to be implemented.
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