Horizontal and vertical movements

Acoustic telemetry has been the cornerstone of Ryan Johnson’s white shark research since 2000. Acoustic telemetry is a technology that enables the continuous monitoring and tracking of great whites using transmitters and receivers that emit ultra high frequency sound.

In 2000, an array of eight listening stations (acoustic receivers) was placed around Mossel Bay at known shark hotspots. White sharks encountered around Mossel Bay were then tagged with acoustic transmitters. Tagged shark swimming within 500 meters of one of the listening stations are automatically detected and electronically logged by the station. Over 1 million data points have been logged over the last five years, which has provided unprecedented information on the movement, residency and habitat use of white sharks in Mossel Bay.

Tagged sharks were also tracked manually using a boat with an onboard acoustic receiver. In 2005, the SAMPLA team tracked white sharks for over 600 hours, including a record breaking of 103 hours continuous tracking of a 4.3 meter female white shark.

  • © Andy Brandy Casagrande IV - Whilst manually tracking white sharks in Mossel Bay they occasionally surface enabling visual tracking. Surface swimming appears more common when they move between aggregation sites.
  • © Russell Smith - SAMPLA scientist Ryan Johnson is circled by a great white while maintaining an acoustic listening stations. Encounters are frequent as receivers are placed in the midst of aggregation sites.
  • © Russell Smith - A white shark cruises past a listening station. The transmitter it carries emits a unique acoustic pulse that enables the receiver to archive the shark’s presence