Tracking a Great White Shark
by Halle Gray Carlson, International Marine Volunteer
A few of us from the International Marine Volunteer team were recently given the opportunity to join the Dyer Island Conservation Trust team on Lwazi to tag and track a Great White Shark! We launched early in the morning and began looking for a good shark to tag. After about an hour at sea a large male was tagged as it calmly swam past the boat. Once the tag was on, the tracking portion of the trip began.
To track a shark using acoustic tags, you stick a hydrophone (underwater microphone) in the water and listen for a “ping” sound from a connected transmitter. If you are close to the shark, the ping is loud and very clear. However, if the shark begins to swim away, it’s harder to hear the ping.
Alison Towner, the biologist on board, let us all take a turn at using the hydrophone to track our shark (which was later named Brian, after one of my co-volunteers). I was kind of nervous to try it at first because I didn’t want to be the one to lose the shark, but Alison was super helpful and told us exactly what to do. Basically, you want to point the hydrophone in the direction of the shark while following the sound of the pings. Every 60 seconds, another person records GPS coordinates, water temperature and depth of the animal.
Over the course of 2 hours, we found that Brian made a tour of the shallows and stopped at a couple of cage diving boats. It was cool to be able to see what a great white shark does during a typical day, and hopefully we’ll get to go out on Lwazi again soon so that we can see what he’s up to now!
Further Comment by Alison Towner, Dyer Island Conservation Trust marine biologist:
This aspect of white shark research for me in the most fascinating. Many may find active tracking tedious as it involves extensive hours at sea, essentially puttering around after a ping…however ultimately that ping represents an acoustic signal on one of the oceans top predators. It never gets old homing in on our shark and then tracking its movements. It is almost as if we are in the mind of the shark as it goes about its daily thing which is fascinating to me. Whether the shark we track is foraging for a seal for breakfast at Dyer Island or cruising the beautiful stretch of beach inshore near Kleinbaai, we are literally entering the sharks’ world every time we track. Each individual has its own personality and hunting behaviour. That sort of research experience really allows you to get an understanding of this species and beats any day stuck behind a computer crunching numbers!
I particularly enjoy it when the volunteers, after training with me, start to get confident on the tracking machine. Every time we take new volunteers out there, at first they are a little nervous of losing the shark but after some hours we are able to teach them how to ‘listen’ to where the shark is. It involves real team work, co-ordination and focus. While one person takes data another watches the time and scribes data. At the end of a track, with hours of data having been collected, heading back into the sunset while leaving the shark to carry on in its world, I often turn and look at the vols faces. I don’t need to say a thing, their expressions are of sheer accomplishment and satisfaction – because we just spend hours in the natural daily life of the great white shark and what an exclusive privilege that is!