ISTS: What can sea surface temperatures and bathymetry tell us about the travel patterns of three green turtles migrating from Baja California to Michoacan, Mexico?

The advent of satellite tracking of sea turtles coupled with parallel information on oceanographic conditions has facilitated the testing of hypotheses on how environmental conditions affect their migration patterns. Two deterministic factors that are often proposed are Sea Surface Temperature (SST) and bathymetry. Satellite tracks obtained for three eastern Pacific green turtles (Chelonia mydas) migrating from their foraging grounds in Baja California to their nesting beaches in Michoacan, Mexico were compared against SST maps derived from AVHRR daytime imagery and bathymetric charts of the Gulf of California and Mexican Pacific regions. Signal transmission of turtles’ position started on January, August 1997 and November 1998, respectively. Migrations lasted between 51 and 90 days. The information gathered so far shows they follow very similar routes, travel through different patterns and ranges in ambient temperature, and take different paths while crossing deep waters. The observed paths taken after reaching the vicinity of continental Mexico, because they are consistent for all turtles, remain close to the shore and mostly on the continental platform, which is relatively narrow on that coast, indicate that these habits render the species particularly vulnerable to incidental and direct take as they pass through areas of intense fishing activities in frontal and upwelling zones.