Age and growth of olive ridley sea turtles Lepidochelys olivacea in the main Brazilian nesting ground

Olive ridleys Lepidochelys olivacea are the most abundant sea turtles in the world, and their early life and adulthood offshore distributions make them less prone to anthropogenic coastal threats. However, primary use of oceanic habitat also results in olive ridley life history being the least studied of all sea turtle species. Here, age at maturation and growth rates of 68 olive ridleys washed ashore dead in northeastern Brazil were estimated through skeleto chronological analysis of humerus bones. Turtles ranged from 58.0 to 77.0 cm in curved carapace length (CCL), with estimated ages between 14 and 26 yr old. As the sample comprised mostly adults, it was necessary to apply a correction factor from skeletochronological analysis of northcentral Pacific olive ridley sea turtles to estimate the number of skeletal growth marks potentially lost at the bone’s core. Mean age at sexual maturation was estimated to be 16 yr for a mean size at sexual maturation of 66.0 cm CCL. Growth models fit to the data showed a clear plateau of growth at 15 yr old, which likely coincides with the time when turtles begin directing energy toward reproduction instead of somatic growth. The olive ridley population in the study area is threatened in oceanic and neritic waters by longline and trawl fisheries, respectively. Despite this current threat, the number of nests has increased sharply for the past 16 yr, a time frame co incident with initiation of conservation actions on the beaches in 1982 and which corresponds with the mean age at maturity found in the current study.