Long-term trends of hawksbill turtle nest numbers and female abundance across key Brazilian nesting areas

Hawksbill turtles are globally distributed along tropical waters and are recognized as Critically Endangered by the IUCN, with unique populations facing different challenges. While nesting populations in the Pacific are experiencing marked declines in nesting numbers, Atlantic populations show some increase, highlighting the need for regional assessments. This study assesses the nesting trends of the hawksbill turtle in two important Brazilian nesting regions: Bahia/Sergipe (BA/SE) and Rio Grande do Norte (RN), covering 29 seasons in BA/SE (1991-2019) and 17 in RN (2003-2019). An overall 7.8-fold increase in nest numbers was found in BA/SE, with pronounced increase during the first two decades, transitioning into a possible stabilization in the last decade. The inflection curve in BA/SE around 1996-1997 aligns with the maturation time required for hawksbill turtles in the Atlantic and might reflect protection measurements started in 1980. RN experienced a 1.5-fold increase during the study period, with a stabilization since 2015. However, estimates of annual nesting females (ANF) and total female population (TF) showed no clear trends during 2003–2019 in either region, highlighting the importance of including these estimates to interpret population status accurately. To enhance conservation strategies, future research should focus on refining population estimates, improving methodologies for nest counts, estimating nesting female abundance, and including in-water assessments and genetic studies for a more comprehensive understanding of hawksbill turtle population status. These steps are vital in a rapidly changing world where marine turtle populations face complex, cumulative, and dynamic threats.