TRANSATLANTIC DEVELOPMENTAL MIGRATIONS OF LOGGERHEAD SEA-TURTLES DEMONSTRATED BY MTDNA SEQUENCE-ANALYSIS

Molecular markers based on mitochondrial (mt) DNA control region seque nces were used to test the hypothesis that juvenile loggerhead sea tur tles (Caretta caretta) in pelagic habitats of the eastern Atlantic are derived from nesting populations in the western Atlantic. We compared mtDNA haplotypes from 131 pelagic juvenile turtles (79 from the Azore s and 52 from Madeira) to mtDNA haplotypes observed in major nesting c olonies of the Atlantic Ocean and Mediterranean Sea. A subset of 121 p elagic samples (92%) contained haplotypes that match mtDNA sequences o bserved in nesting colonies. Maximum likelihood analyses (UCON, SHADRA CQ) estimate that 100% of these pelagic juveniles are from the nesting populations in the southeastern United States and adjacent Yucatan Pe ninsula, Mexico. Estimated contributions from nesting populations in s outh Florida (0.71, 0.72), northern Florida to North Carolina (0.19, 0 .17), and Quintana Roo, Mexico (0.11, 0.10) are consistent with the re lative size of these nesting aggregates. No contribution was detected from nesting colonies in the Mediterranean (Greece) or South Atlantic (Brazil), although samples sizes are insufficient to exclude these loc ations with finality. The link between west Atlantic nesting colonies and east Atlantic feeding grounds provides a more complete scientific basis for assessing the impact of subadult mortality in oceanic fisher ies. Demographic models for loggerhead turtles in the western Atlantic can now be improved by incorporating growth and mortality data from j uvenile turtles in pelagic habitats. These data demonstrate that the a ppropriate scale for loggerhead turtle conservation efforts is vastly larger than the current scale of management plans based on political b oundaries.