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About the Authors:
Donald R. Kobayashi
* E-mail: [email protected]
Affiliation: Pacific Islands Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, Honolulu, Hawaii, United States of America
Richard Farman
Affiliation: Aquarium des Lagons, Nouvelle-Calédonie
Jeffrey J. Polovina
Affiliation: Pacific Islands Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, Honolulu, Hawaii, United States of America
Denise M. Parker
Affiliation: Joint Institute for Marine and Atmospheric Research, University of Hawaii, Newport, Oregon, United States of America
Marc Rice
Affiliation: Hawaii Preparatory Academy, Kamuela, Hawaii, United States of America
George H. Balazs
Affiliation: Pacific Islands Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, Honolulu, Hawaii, United States of America
Introduction
Loggerhead turtles (Caretta caretta) are a circumglobal species of sea turtle found throughout temperate and tropical oceans and seas [1]. Loggerhead turtle nesting is restricted to a few locations in major ocean basins such as the Southeastern USA, the Mediterranean, Oman, Western Australia, and Southern Japan, where females lay their eggs on sandy beaches [2], [3]. After hatchlings leave the nesting beaches, they are thought to remain oceanic for 7–12 years before migrating to coastal habitats [4]. Despite good swimming abilities, juvenile loggerhead turtles are thought to drift passively for a significant portion of their existence on the high seas [5]. In contrast, Polovina et al. [6] found that active swimming seemed to be a large component of overall movement for oceanic juveniles. It is likely that a behavioral response cued by current flow orientation (i.e., rheotaxis) is involved. With passive drifting, active swimming, and rheotactic responses, it is important to know the magnitude and direction of ocean currents the oceanic juveniles have to contend with, as it is clear that the response of an organism to a moving flow field can be highly complex [7]. For oceanic juvenile loggerhead turtles, a key issue is their placement in the vertical portion of the water column, which will be closely linked to their diving behavior.
Oceanic juvenile diving behavior is not well studied, with scant data from only a small number of tagged individuals. Studies in the Atlantic have shown that oceanic juveniles spend ∼75% of their time in the upper 5 m of the water...