Regional scale horizontal and local scale vertical movements of whale sharks in the Indian Ocean off Seychelles

Little information on the movements and use of habitat by whale sharks is available. We present data on regional horizontal and local vertical movement of juvenile whale shark from waters off Seychelles into the Indian Ocean, as recorded by satellite telemetry. Tracking data show that the direction of travel in three sharks was influenced by the prevailing geo-strophic currents. The temperature distribution frequencies recorded show that the sharks spent the majority of time in waters of 25–35 °C. However, short exposures to very cold waters, below 10 °C were recorded and these are consistent with dives to deeper depths. Depth recordings show that up to 53% of the time was spent in water shallower than 10 m, but dives to depths of 750–1000 m were also recorded. These results are discussed in relation to diel patterns and diving behaviour in a similar planktivore, the basking shark. The marked preference of the whale sharks for swimming in relatively shallow water may indicate the importance of this range with respect to their foraging activities and has implications for their management and conservation.