Recovery of a green turtle Chelonia mydas rookery on Fernando de Noronha Island, Brazil: 35 years of conservation efforts

Understanding ecological parameters and population trends is critical for conserving species of concern. For marine turtles, annual nest counts are the most widely used metric for estimating population size and trends. However, detailed information on key reproductive parameters —such as clutch size, internesting intervals, clutch frequency, and remigration intervals—remains limited for many populations. This is particularly true for the green turtles Chelonia mydas nesting at the Fernando de Noronha Archipelago, Brazil. This study analyses 35 yr (1988-2022) of beach monitoring data to characterise the reproductive biology and population trends of green turtles on Fernando de Noronha Island. Annual nest counts increased significantly over the studied period, from an average of 39 nests yr -1 in the first 5 yr (1988-1992) to 313 nests yr -1 in the last 5 yr (2018-2022). Internesting intervals ranged from 9 to 17 d (mean ± SD: 11.7 ± 1.3 d; median: 12, n = 1236). Observed remigration intervals ranged from 1 to 16 yr, with the longest observed reproductive lifespan being 25 yr. Hatching success averaged 75.6 ± 24.8% (mean ± SD; range: 0-100, n = 2612 nests). The observed increase in nest counts suggests that conservation efforts initiated in the 1980s have likely contributed to the recovery of this green turtle population at the nesting beach level. However, the population remains vulnerable due to its small size, restricted nesting range, and ongoing threats from fishing and climate change.