ESR 18:35-45 (2012)  -  DOI: https://doi.org/10.3354/esr00428

ABSTRACT: Understanding the dispersal pattern and mechanisms affecting the mixing of Endangered loggerhead sea turtles Caretta caretta is a key issue for establishing sound conservation strategies. Loggerhead turtles are commonly encountered all along the Tunisian coast and particularly in the Gulf of Gabès, which is one of the most important foraging habitats for this species in the Mediterranean Sea. We conducted extensive sampling of 175 juvenile and adult loggerhead turtles that were stranded or incidentally captured in the areas along the northern (NTC), eastern (Gulf of Hammamet, GHAM) and southern (Gulf of Gabès, GGAB) Tunisian coast over a 6 yr period (2004 to 2009). A 380 bp fragment of the mitochondrial DNA control region was sequenced and analysed. Seven haplotypes were revealed, and a gradual variation in haplotype frequencies was observed among the studied areas. The extreme samples (NTC and GGAB) differed genetically from each other, while both were similar to the central sample (GHAM). This finding was confirmed by mixed stock analysis estimates, which suggested that the proportions of Atlantic turtles were very high in the NTC and decreased southward, while the proportions of Mediterranean contributions were higher in the GGAB and decreased in the opposite direction. The observed pattern of genetic variation and turtle distribution, which is probably related to differences in geomorphology and sea surface currents among these coastal areas, should be considered in future management plans.

KEY WORDS: Loggerhead sea turtle · Mitochondrial DNA · Foraging · Dispersal · Mixed stock analysis