Oceanic migration of post-nesting loggerhead sea turtles (Caretta caretta) in the northwestern North Pacific tracked by satellite telemetry

Abstract

Two post-nesting loggerhead turtles which nested at Omaezaki beach, Japan were tracked during 2002 and 2003 in the northwestern North Pacific by satellite telemetry. The first loggerhead was tracked for 265 days from 29 July 2002 to 19 April 2003 with total distance of approximately 9, 800 km. The turtle traveled eastward from the Pacific coast of Honshu to offshore after staying near its nesting site for a week. Then it remained in the offshore area around 36-37°N and 155-158°E from the end of September to the middle of November. In late November, the turtle moved eastward again, and turned to the south when it reached 170°E in the middle of December. Finally, it turned westward in February. Tracking of the second loggerhead tagged in 2003 is still in progress, although this loggerhead was released in a subsequent year, its tracks were similar to the first turtle. The relationship between movements of the turtles and oceanographic conditions (sea surface temperature and sea surface currents) were examined. Movement tracks of these turtles correlated with the Kuroshio Extension Current and seasonal changes of temperature in the Transition Region. The Transition Region is known as a highly productive area and may provide an important feeding ground for post-nesting loggerhead turtles.