Fine-scale behaviour of whale sharks off Mafia Island, Tanzania

Background Mafia Island off the Tanzanian coast features a year-round resident whale shark population. Many of the sharks are seen regularly, making this a great natural laboratory to study their behaviour in detail. At the same time, whale sharks here also face threats locally from net entanglement and boat strike. We therefore set out to determine their fine-scale behaviour using novel telemetry methods in order to establish a profound baseline. Approach We conducted field work at Mafia Island from November–December 2015 and used 3D tags (Open Tags) and satellite tags (Desert Star SeaTagMODs) to examine whale shark behaviour. 3D tags recorded depth, temperature, acceleration as well as gyrometer and magnetometer readings at 200 data points per second. Satellite tags recorded depth, temperature, acceleration and geolocation. We attached 3D behavioural tags to the first dorsal fin using a padded clamp, and double-tagged some of the sharks with satellite tags attached with a titanium dart anchor and short ...