Résumé
Loggerhead turtle Caretta carretta is the main species of sea turtle accidentally hooked by longliner vessels off the coast of Reunion Island. Since 2007, in collaboration with local fishermen, captured individuals are brought to Kelonia, our sea turtle center, to be cured and released. Our study aims at improving the knowledge on loggerhead migrating and diving behavior in order to reduce interactions with fisheries. Between May 2008 and March 2011, 14 captured individuals were equipped with satellite tags including depth sensors. These tags not only allowed us to study turtle movement but also permitted to compute animal diving profile during daylight and nighttime. After a short veterinary treatment in Kelonia, turtles would be released few miles away from Reunion island coast. Deployment period lasted between 2 and 6 months with individual surprisingly migrating from latitude 40 degree S to latitude 20 degree N, sometimes swimming more than 4000km away from the release point. Individuals exhibited various migrating behaviors either remaining oceanic or heading rather to semi-oceanic and coastal waters near countries such as Madagascar, Somalia, Yemen or Oman. Regarding diving behavior, two types of dives have been identified: subsurface <10m) and deep dives (30-60m). Occasionally, depth of dive could exceed 200m. Data analyses also showed a dichotomy between daylight and nighttime dives with turtles diving significantly longer at night and spending more time near the surface during the day. Future work should include spatial analysis in relation to oceanographic variables to determine loggerhead turtle habitat. Despite the great attention given to loggerhead turtles worldwide, our study is the first intensive tracking program on this species in Reunion Island. In addition to ongoing conservation actions with fishermen, such study is also required for appropriate regional conservation planning.