Shark Chronicles 054 – Tracking week
Posted by Niels D Ernst-Williams on July 21, 2009
The week began with an introduction to tracking from Oli for those of us who hadn't done it before.
We were introduced to a piece of kit called the 'Trackbox' but known to some as the VR100. This unit displays a reading indicating the strength a signal received from the radio tag and emits a beep each time a signal is detected. Readings of about 30-40 are normal if the shark is some distance away and around 80 is more normal when the boat is pretty much over the shark. The tag that we would be using also sends information about the depth and temperature of the tagged shark, and this is recorded along with the GPS coordinates of the shark each time a signal is received by the VR100. In order to follow the tagged shark we would use a uni-directional hydrophone to determine the direction from which signals were originating and allow us to move towards the shark as it goes through its sharky routine. We were also to record GPS coordinates manually every ten minutes during tracking as backup data, as well as bottom depth; and note environmental conditions every hour.
Monday morning dawned cold and rainy with large swell and a brisk wind. Those of us who were on the early chumming trip were not enthused by the conditions and our only glimmer of hope came from the possibility that Enrico would call the trip off or postpone it due to the weather. Predictably, our hopes were not realised and we just headed out regardless wrapped up in many layers of clothing. We chummed away stoically until lunchtime but despite seeing 5 sharks, we were unable to bring any within range of Enrico's tagging spear. This spear was a pole tipped with a spike onto which the barbed cone that would hold the tag in the flesh of the shark was threaded.
The weather on Tuesday was somewhat better but there was still a large swell running and the morning chum trip again failed to tag a shark. In the afternoon, an impromptu chum trip on Lamnidae was led by Oli with just 4 of us on the boat. Lamnidae did very well in the big seas and we surfed a few waves over to the island where we immediately picked up the sharks that had been around the departing cage-dive boat 'Shark Warrior'. The chum trip was great fun and our favourite shark of the day was a 3m female we called Wolfgang who managed to take bait off the line and then try to eat the buoy.
On Wednesday, good weather and 'Sharkville' celebrity skipper Ryan sent us on the morning chum trip in high spirits. Within 45 minutes of anchoring, a shark that we dubbed 'Warrior' was spending enough time around the boat for us to think about tagging it. We inspected its underside using the 'Sex-cam' (a pole-mounted waterproofed camera with viewing screen on the boat) and established, through intimate images of its nether bits, that Warrior was certainly female as she lacked the claspers of a male shark. Ryan then stepped up to the edge of the boat and stabbed her at the base of the dorsal fin with the tracking-spear and successfully attached the tag.
From 09:50 on Wednesday onwards, Warrior was tracked non-stop by a rotating crew on Cheetah with fresh trackers brought out on Lamnidae every 8 hours or so. At around 15:30, she was seen taking a seal right by seal island from close to the rocks, and after this successful predation, she headed of towards Hartenbos where she rested and then headed up towards Groot Brak. In their excitement, the crew at the time forgot to take the tracking pole out of the water when she was moving at speed and managed to shear it in half as the boat sped up. This left out shift with the task of cobbling a new pole together from duct tape, small metal tubes and a broom-handle.
On Friday at 13:00, tracking was ended and the crew of Lamnidae chummed to attract Warrior to the boat. Repeated and valiant efforts by Enrico and Tom to allow to remove the tag.
So ended the week of tracking and began the weekend of disturbing cave-camping and horseback Rhino-gazing…