Fisheries interaction is one of the most significant threats to sea turtles in their marine habitats. Sea turtles are reptiles and therefore need to surface intermittently to breathe. This dependence on the surface means they inhabit much of the vertical space in coastal and neritic habitats, exposing them to encounter fisheries in a wide range of depths. Turtle dive profiles may vary greatly depending on their species, behaviour and the ambient water temperature, for example they may undertake longer dives in the winter, exhibiting a type of dormancy. The dive behaviour of Loggerhead sea turtles (Caretta caretta) in the Mediterranean is relatively well known, at least for females where nesting allows for easy access, but knowledge is lacking for adult males of the species. To address this lack, we tracked three adult male turtles from their breeding area in Kyparissia Bay, Greece to their foraging areas in the eastern Mediterranean using devices that transmitted depth and temperature time series data. Tracking duration ranged from 98 to 547 d. The turtles demonstrated different behaviours that were influenced by time and ambient temperature. The turtles showed diel changes in dive behaviour, split-level dives in the presence of thermoclines, and extended dive durations when waters approached 15 °C. All turtles spent over 50% of the time in depths shallower than 10 m and even the deepest diving turtle spent 95% of its time shallower than 70 m. These data can be used to support fisheries management, such as depth and soak-time limits for setting gear that evolve based on seasonal sea temperatures.
Rees et al. (Sun,) studied this question.