Unveiling loggerhead turtles size decline at a major Brazilian nesting ground

Abstract

Brazil’s second-largest reproductive colony of loggerhead turtles (Caretta caretta) has a long history of overexploitation, with its temporal ecological dynamics still unknown. This study investigates changes in the average size of females and post-maturity somatic growth rates in marked and recaptured loggerhead turtles at a breeding site over a 33-year period (1982–2014). Loggerhead curved carapace length (CCL) was evaluated over the course of the study using a generalized additive model (GAM) with a Gaussian family distribution and time smoothed. Includes the nesting year and the CCL for a total of 2.359 female loggerhead turtles. The overall average length of females was 99.4 cm ± 5.8 (mean ± SD). The results suggest that the CCL of females in the nesting area is decreasing. From 1982 to 1998, the mean CCL was 102.6 cm; from 1999 to 2014, the average length was 98.7 cm. There were no statistically significant differences in post-maturity growth rates among recaptured females, supporting the hypothesis of increased recruitment. The GAM results showed significant differences in the size structure changes of reproductive site females over time. The study highlights how a population parameter can be influenced by long-term conservation of feeding and nesting areas for sea turtles, resulting in a higher number of recruits. The curved carapace length serves as an important metric to describe population changes and raise awareness about future conservation challenges.