Ten years ago, we tracked some great white sharks

Tracking in progress

Tracking great white sharks

Equipment and general process

Just so there’s no confusion, ‘tracking’ involves tagging a device to a shark and following it around the sea. Its movements and our observations there of, are essentially ‘tracked’ over a period of time.

The specific method of tracking we used is called manual acoustic tracking, wherein said device emits a ‘ping’ to a receiver on the boat. We used two types of hydrophone to receive that ping. I’ve completely forgotten what they’re called. Such intellectual shortcomings may be somewhat contributory to me not being as involved with shark research as I once was.

Basically, one can receive pings from all directions but at a relatively low distance. This was very useful in instances where we just wanted to confirm the shark was nearby. Most often this would be at the start of a tracking session after we’d been kept off sea for a couple of days. We’d take the boat to a few spots where we expected the shark to be in. The hydrophone would get dropped into the water and fingers crossed – we’d get a ping.

The right tool for a particular job

Once successful, we’d switch over to the other hydrophone. This receives pings from a greater distance, but in a straight line. I (once again) forget wether this is a completely straight line or more of a ‘cone’. I therefore ask that nerds please forgive me if the following illustration isn’t entirely accurate.

Anyway, we used this one pretty much exclusively once the shark had been found. This is because it allowed us to maintain sufficient distance as to not interfere with the shark’s behaviour. However, because this one didn’t receive pings from all directions, it wasn’t not particularly helpful at finding a shark once they’d been lost. So let’s say the shark just darted off in a different direction or had moved behind some unseen underwater obstructions. On these occasions we’d move over to where they were last sending pings from and go back to the previous solution. On days particularly poor in weather, dancing between the two in this fashion was pretty much constant.

What’s a ping?

You might be wondering how this ping manifests itself… well, as a ping. It’s literally a pinging noise on the receiver. The louder the ping, the closer the shark, therefore the stronger the signal. We’d basically be at sea for hour upon hour, intensely focusing in on this noise much like a (good) drummer would practice to a metronome. Team’s would typically comprise four people: one skippering the boat, one controlling the direction of the hydrophone, one collecting data and then another for rotation.

My favourite role was always being sat at the hydrophone. I quite enjoyed the challenge of endurance and focus, of keeping the shark ‘in our sights’. This was especially demanding when the shark was at distance and/or there was a lot of noise coming through the receiver. After a while, you find yourself subconsciously trying to get into the animal’s head. You start letting that guide your intuition when feedback from the technology is less than perfect.

What data is sent by said ping?

The tag itself collects some data, such as the shark’s depth and our distance from it. Every team does things slightly differently, but in Gansbaai we kept a constant log of this data. We would supplement it with further observations such as whether seals were in the area. Said data was collected for as long as possible, often for consecutive days and nights at a time. I believe the team I was part of in Mossel Bay from 2009 to 2012 (Oceans Research) broke the record for longest continuous track of a great white shark.

Tracking during the night is an absolute treat. Sure, it can be cold and moody, being sat on a boat at 4am with the rain coming down and you’re tracking a shark which is being particularly stealthy. But sharing in it’s hourly routines, seeing the bioluminescence of seals and dolphins as they swim by the boat, it’s not a feeling or experience I’ve had any luck in since replicating.

Because nothing says ‘growing up’ quiet like riding the inevitable decline in diversity and enrichment quality of life experiences.