Telemetry and Satellite Tracking of Whale Sharks, Rhincodon Typus, in the Sea of Cortez, Mexico, and the North Pacific Ocean

Abstract

We used satellite-linked radio telemetry to document the geographic and vertical movements and thermal habitats of whale sharks in the Sea of Cortez and as they migrated into the north Pacific Ocean. Of 17 sharks tagged between 1994 and 1996, six dispersed widely in the Sea of Cortez during 12–39 days of tracking. Four others left the Sea of Cortez and ranged extensively in the north Pacific Ocean. Indeed, one whale shark migrated to the western north Pacific Ocean, covering over 13 000 km in 37 months of tracking. The sharks generally occupied areas where sea surface water temperatures were between 28 and 32°C, though several ranged to depths of 240 m or deeper where water temperature reached 10°C or colder. Whale sharks may segregate by size and sex, and their movement patterns appear to be related to oceanographic features, such as sea mounts and boundary currents, where primary productivity may be enhanced. These results have important implications for the global conservation of the world's largest yet least known fish. We think that satellite telemetry is a exceptionally promising tool for learning more about the ecology of whale sharks, especially when combined with conventional methods of telemetry and molecular biology.