Post-nesting migrations of Galápagos green turtles Chelonia mydas in relation to oceanographic conditions: integrating satellite telemetry with remotely sensed ocean data

Post-nesting movements of 12 green turtles from the Galapagos Islands (Ecuador) were tracked with satellite telemetry during the 2003 and 2005 nesting seasons. To illuminate potential environmental influences on turtle movements we compared tracks with a variety of remotely sensed oceanographic variables including sea surface temperature (SST), SST front probability, surface height anomaly, surface current, and surface chlorophyll a concentration. Three distinct post-nesting migratory strategies were observed, including oceanic migration to Central America (Type A1 movements, n = 3), residency within the Galapagos (Type A2 movements, n = 2), and movement into oceanic waters southwest of the Galapagos (Type B movements, n = 7). Two turtles migrating to Central America reached neritic foraging areas in Nicaragua and Panama that were 1500 and 1542 km, respectively, from their nesting sites, and one resident turtle established a foraging home range 75 km from its final nesting site. Oceanic movements occurred in waters with a mean SST of 26.5C and mean surface chlorophyll a concentration of 0.18 mg m super(-3), whereas neritic movements were in waters with a mean SST of 24.3C and mean surface chlorophyll a concentration of 0.47 mg m super(-3). All turtles accessed SST frontal zones at a greater rate than their availability, and at least 2 turtles conducted movements in the oceanic zone that were indicative of foraging activity. This is the first report of migratory corridors for Galapagos green turtles, confirming prior flipper tagging data that show that the Galapagos is a source rookery for green turtles in coastal areas of Central America. The high proportion of green turtles departing the Galapagos (83%) indicates that marine fisheries bycatch and directed hunting on this stock outside the Galapagos may impact this population more than previously believed, and underscores the need for multi-national conservation efforts that combat these threats.