Twenty-year changes in the composition of a mixed stock of foraging green turtles in the Yaeyama Islands of Japan

A recent study reveals a significant increase in the proportion of Japanese green turtles (Chelonia mydas) within the foraging aggregation around the Yaeyama Islands, Japan, over the past two decades. This shift is linked to an observed trend of increasing mean straight carapace length (SCL), suggesting reduced juvenile mortality due to declining sea turtle fisheries. Researchers compared natal origin compositions from 1997-1999 and 2016-2018, using single nucleotide polymorphisms to analyze size categories (<55 cm and >55 cm SCL). The findings indicate a stable proportion of Japanese turtles across size classes in recent years, while populations from lower latitudes showed substantial declines. This study provides detailed insights into the composition of the Yaeyama foraging aggregation, including size distributions and sex ratios, offering valuable data for conservation efforts.

Hamabata, T., Kawata, M., Kondo, S., Matsuo, A., Suyama, Y., Suzuki, K., & Kameda, K. (2023). Twenty-year changes in the composition of a mixed stock of foraging green turtles in the Yaeyama Islands of Japan. Marine Ecology Progress Series, 716, 93–105. https://doi.org/10.3354/meps14367