Determination of growth spurts in Hawaiian green sea turtles using skeletochronology and histological analysis of gonads

Abstract

The population of Hawaiian green sea turtles (Chelonia mydas) has steadily increased since its protection under the Endangered Species Act of 1978. However, a more complete understanding of the state of recovery of Hawaiian green turtles is stymied by lack of certainty regarding age structure of the population. Based on the observed slow growth rates of juveniles, current assessments place age to maturity in Hawaiian green sea turtles at 35-40 years. However, it is possible that dynamics such as growth spurts associated with the maturation process have been missed. Studies such as skeletochronology and histological analysis of the gonads provide data on growth rates and maturity of marine turtles, but comparative analysis using both techniques has never been completed. Finding maturing spermatozoa in the juvenile and sub-adult sized turtles suggests that using carapace length may not be an accurate indicator of sexual maturity. Combining data from both techniques have revealed that growth spurts occur throughout the life span of Hawaiian green turtles, but peak lower for males between 50-60 cm than at 70-80 cm in the females, and it indicates that relying on mean annual growth rates may overestimate age to maturity.