Surface detection probability of leatherback turtles at the Rio de La Plata and its Maritime Front: Implications for density estimates

The Río de la Plata and its Maritime Front (RLPMF) serve as a key, seasonal feeding area for leatherback sea turtles (Dermochelys coriacea) in the Southwestern Atlantic Ocean. While leatherback turtles can be frequently observed in these waters, there is little data on regional abundances and relative densities, which hinders threat assessments and the development of effective conservation strategies. Consequently, given that in this region parameters needed for in-water leatherback turtle density estimates have not been previously published, the objective of this study was to investigate the surface availability bias, g(0). This parameter requires region-specific considerations for factors like aggregation behaviour and environmental conditions. To address these gaps, our study assessed leatherback turtle aggregations in the RLPMF using satellite tag data and direct drone observations. Through satellite tracking, surfacing behaviour data of six leatherback turtles, g(0) was estimated to be 0.3183. This analysis represents the first of its kind in the region, providing an important contribution to sea turtle conservation studies. It enables substantial progress in characterising surface time, which is essential for understanding leatherback diving and surface behaviour in the region and for improving relative density estimates in the Southwestern Atlantic Ocean. Furthermore, this contribution represents a resource for planning more effective conservation strategies to mitigate threats and promote population recovery.