We successfully completed a twenty four hour tracking session of Sampla, our first tagged shark. It was a gruelling tracking session, not least because it involved only me (Enrico), Andrea and Antonin (our two first students).
We worked rotating shifts: one hour off (sleep), one hour skippering the boat and one hour doing receiver work (listening for the acoustic signal, thereby tracking the shark). Every 10 minutes, we recorded the shark’s GPS coordinates and swimming direction, the surface water temperature and the bottom depth. Every hour we noted the environmental conditions including: wind speed and direction, swell height and direction, water visibility, and water column temperature (specifically, we needed to establish the depth of the thermocline).
The ping of the receiver gave you an umbilical-like connection to the swimming shark, and a certain comfort that it was there and desperation to keep it there – evoking the scene of the old man and his fish in Hemingway’s famous story. We were alone, between the expanse of the night sky and the Indian Ocean, keeping an acoustic rein on our shark. The cold, dark and lack of sleep made keeping in touch with the shark difficult, a couple of times Sampla managed to escape the 500m range of our receiver. With calm and perseverance, acoustic connection was soon re-established.
Once back in
We will track Sampla again. Soon we hope to tag new sharks with acoustic tags, but the acoustic tags will be enhanced. The tags will feature sophisticated devices designed to provide us with more information about the biology and ecology of the white shark.
ENRICO & TOBY