Latitudinal cline in the foraging dichotomy of loggerhead sea turtles reveals the importance of East China Sea for priority conservation

Aim: Quantifying the importance of habitat areas for conservation of highly migratory marine species with complex life histories can be challenging. For example, loggerhead turtles (Caretta caretta) nesting in Japan forage both oceanically and neritically after their reproductive period. Here, we aimed to quantify the proportions of turtles using these two contrasting habitats (foraging dichotomy) to suggest priority conservation areas.
Methods: We examined the occurrence of foraging dichotomy at three nesting sites (Ishigaki, Okinoerabu Islands, and Ichinomiya) based on stable isotope analysis of the egg yolks for 82 turtles and satellite tracking of post-nesting migration for 12 turtles. Moreover, we used the data of three other sites from previous studies (Yakushima Island, Minabe, and Omaezaki).
Results: Two neritic foraging grounds (East China Sea and the coastal area of the Japanese archipelago), and an oceanic ground (North Pacific Ocean) were identified. We found a latitudinal c...