Abstract
Exchange of immature loggerhead sea turtles (Caretta caretta) between the northern and southern regions of the western Mediterranean was investigated using data obtained from several Spanish tagging programmes. Tagged turtles ranged in straight carapace length from 23.0 to 74.0 cm. Thirty-six turtles were recaptured after an average interval of 390.5±462.6 days (SD). As the mean dispersal distance (MDD) of a turtle population that spreads over the western Mediterranean would stabilize after 117 days (CI 95%: 98 to 149), two analyses were conducted that included data from turtles recaptured after 98 and 149 days respectively. In both analyses, turtles were recaptured more often than expected in the same region where they had been tagged. No difference was found in either of the two regions between the average distance between the capture and recapture locations and the expected MDD if the turtles were to remain in the region where they were first captured. Turtles recaptured after 15 and 25 days respectively were excluded from the analysis to ensure data independence. The overall evidence indicates that immature turtles exhibit strong site fidelity to certain areas and that there is a strong barrier to dispersal between the northern and southern parts of the western Mediterranean. Therefore, loggerhead turtles in the western Mediterranean should be split into at least two management units.
Highlights
The loggerhead sea turtle (Caretta caretta (Linnaeus, 1758)) is the most common sea turtle in the Mediterranean
Genetic analyses have revealed that turtles from North American rookeries prevail along the southern coast of the western Mediterranean while those from the eastern Mediterranean prevail along the European shore north of Cape La Nao (Carreras et al, 2006; Revelles et al, 2007a)
Further insight into the dispersal pattern of the immature loggerhead sea turtles found along the European shore of the western Mediterranean north of Cape La Nao is essential in order to determine whether the genetic structuring observed in the western Mediterranean is the consequence of the homing behaviour of North American loggerhead sea turtles that have been trapped by currents within the Mediterranean (Revelles et al, 2007a) or due to the existence of a powerful, symmetrical barrier between the northern and southern regions of the western Mediterranean
Summary
The loggerhead sea turtle (Caretta caretta (Linnaeus, 1758)) is the most common sea turtle in the Mediterranean. Genetic analyses have revealed that turtles from North American rookeries prevail along the southern coast of the western Mediterranean while those from the eastern Mediterranean prevail along the European shore north of Cape La Nao (Carreras et al, 2006; Revelles et al, 2007a). Further insight into the dispersal pattern of the immature loggerhead sea turtles found along the European shore of the western Mediterranean north of Cape La Nao is essential in order to determine whether the genetic structuring observed in the western Mediterranean is the consequence of the homing behaviour of North American loggerhead sea turtles that have been trapped by currents within the Mediterranean (Revelles et al, 2007a) or due to the existence of a powerful, symmetrical barrier between the northern and southern regions of the western Mediterranean
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