Fig. 2

Path taken by the platform terminal transmitter (PTT) detached from a tiger shark (Galeocerdo cuvier) as it drifted across the North Atlantic Ocean, permitting the comparison of geomagnetic-based (red circles) and irradiance-based (yellow circles) to Doppler-based ARGOS positions (white triangles). The solar cell became fouled with sessile organisms as it drifted past 40°W depriving the transmitter with sufficient power to communicate with the ARGOS satellite. Note the less accurate irradiance-based estimates at the equinoxes, when day length is similar at latitudes and more accurate at the solstice when day length differs with latitude