Reptilian species have a fast growth rate during earlier stages of their life cycle. Growth rates of an individual animal reflect the correlation between the biotic and abiotic factors of its surrounding environment. The green sea turtle (Chelonia mydas) is found in tropical and subtropical marine habitats, including the Dry Tortugas (DRTO) and the U.S. Virgin Islands (USVI) where marine protected areas are established. To assess survival of juvenile C. mydas populations over the long-term, we established mark-recapture studies in both locations. Methods of capture consisted of dip netting and in-water diving. We collected standard body measurements of both curved and straight carapace length (CCL and SCL, respectively) and inserted PIT tags and Inconel flipper tags for identification purposes. We conducted mark-recapture activities either seasonally (DRTO) or biannually (USVI) since 2008 (DRTO) and 2012 (USVI). We calculated individual growth rates by subtracting the initial from last SCL measurement and averaged across individuals.
The mean annual growth rate for juvenile green turtles in DRTO was 5.67 + 1.34 SD cm year -1 (n=32); juveniles were 27.3 to 52.0 cm SCL upon initial capture. The subpopulation in the USVI had a lower mean annual growth rate of 3.63 + 1.14 SD cm year-1 (n=55); juveniles were 24.8 to 58.2 cm SCL upon initial capture. An earlier study provided growth rates of juvenile C. mydas in USVI waters that were comparatively similar or higher, ranging from 3.48 to 6.93 cm year -1 SCL. The DRTO growth rate is among the highest in the region with the exception of Indian River Lagoon, Florida where over two decades, 132 juveniles had an average growth rate of 4.55 + 1.22 SD cm year -1. Subpopulations of DRTO and USVI have comparatively high growth rates of juvenile C. mydas. Over time, a consistent and high growth rate could indicate high quality foraging resources for resident sea turtles in USVI and DRTO. Protected environments in both of these locations could be contributing to the high growth rate and the recent increase in C. mydas numbers globally.