Movement Patterns of Juvenile Loggerhead Turtles (Caretta caretta L. 1758) and Green Turtles (Chelonia mydas L. 1758) Hatched in Captivity and Released in the Korean Waters.

Abstract

Simple SummaryDespite the continuous observation and drift of globally endangered sea turtles in Korean waters, relevant research and protection policies are deficient. To restore sea turtle populations near Korea, the Ministry of Oceans and Fisheries, Republic of Korea, has been hatching and rearing sea turtles in captivity and releasing juveniles into the sea. We satellite-tracked juvenile loggerhead and green turtles to confirm their movement patterns and adaptability in the wild. The tracked sea turtles used sea currents for movement, and the tracking duration and movement patterns differed according to their body size. In addition, while the loggerhead turtles moved to the Northeast East Sea, the green turtles tended to move west or southwest from the release point. By considering the release time and location, according to the growth level and species, the adaptability of artificially hatched and reared turtles to natural habitats is expected to be high.With most sea turtle populations declining, activities to conserve their habitat and nesting grounds and restore their populations are being implemented worldwide. To preserve the Northwestern Pacific populations, the National Marine Biodiversity Institute of Korea has been releasing artificially propagated sea turtles, but whether these individuals join the wild population remains unknown. The present study aimed to determine the movement patterns of artificially propagated juvenile loggerhead (Caretta caretta) and green (Chelonia mydas) turtles fitted with satellite transmitters on their carapaces and released in the waters of Jeju or Yeosu, Republic of Korea, between August 2018 and April 2022. Loggerheads traveled northward to the East Sea, whereas green turtles moved west or southwest. Two 36-month-old and two 48-month-old loggerheads moved toward their potential nursery grounds and toward their feeding grounds, respectively. Three green turtles with a curved carapace length (CCL) of <40 cm moved toward their nursery or feeding grounds, while three individuals (CCL > 45 cm) moved toward their inshore foraging areas. The travel paths were closely related to the direction of local sea currents. Our results implied that releasing artificially propagated sea turtles, considering their age and CCL, can positively contribute to the conservation of Northwestern Pacific populations.