The Save Our Seas Foundation (SOSF) White Shark Research Team together with the Shark Spotters tracked a 3-metre great white shark for 24 hours straight. This was the first successful overnight continuous track of a white shark in False Bay.
Following reports from the Shark Spotters of shark sightings close to shore within the last two weeks in False Bay, the Save Our Seas Foundation white shark research team headed out to survey the coast for sharks and attempt to tag one of them. They found a white shark at 12h42 on Tuesday 8th December swimming along the surface between Seal Island and Strandfontein. After monitoring the shark’s behaviour for a few minutes the research boat slowly approached the shark to get a photographic identification of its dorsal fin, assign a catalogue number and determine the shark’s size and sex. After closer inspection it was determined that the shark was a 3-meter female, subsequently named Deepblue.
Alison Kock, the white shark project leader with the SOSF and Shark Spotters, then tagged the animal at the base of her dorsal fin. The tag allowed the researchers to follow the shark in real time using specialized equipment mounted on the boat. “It is important to asses the shark’s behaviour while doing a track such as this in order to maintain the correct tracking distance; too far and the shark could swim out of range, too close and the boat disturbs her behaviour,” said Alison.
Although the research team was prepared to track her across False Bay, Deepblue remained in the general area between Strandfontein and Seal Island. She was in no hurry to swim anywhere and her swimming speed varied between 2 – 4 km / hour. Deepblue spent a considerable amount of time at the surface and sometimes it appeared as though she was just drifting in the current and not actively swimming at all. Occasionally she swam within 200 meters from the coast before swimming as far as 4 kilometers offshore again.
During the daylight track the team observed Deepblue approach another white shark of similar size at the surface. She slowly followed the second shark within 5 meters for a few seconds before breaking off the encounter and swimming in the opposite direction. Deepblue’s night behaviour was similar to her daytime behaviour, except that she went further offshore and also made some excursions in the direction of Gordon’s Bay and then towards Muizenberg, but always returning to Strandfontein.
“We did, however get an unforgettable surprise during the night, when bioluminescent plankton lit up both the ocean and the shark in a sparkling green glow,” said Alison.
The research has previously documented the inshore behaviour of white sharks during summer. However, it is still unclear why exactly the sharks are present close to shore. Three predominant theories exist, namely 1) the sharks are predating on summer fish and smaller species of shark prevalent in the bay during summer time 2) environmental conditions such as warmer water or oxygen rich water may be what’s attracting them and 3) the inshore behaviour may be related to reproduction. Tracking the sharks in this way is a step towards determining the factors involved in inshore white shark activity.
The team would like to thank Dave Hurwitz of Simonstown Boat Company for assisting with the logistics of the track. Keep track of the team yourself when the next weather gap lets them track white sharks again at staging.saveourseas.com.
The Save Our Seas Foundation White Shark Project was initiated in 2003 and is a dedicated research programme focusing on the ecology and behaviour of white sharks in False Bay, Cape Town, South Africa. It is collaboration between the Save Our Seas Shark Center, University of Cape Town, Department of Environmental Affairs and Tourism Marine and Coastal Management Branch and Shark Spotters.
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White Shark Project Leader
Save Our Seas Foundation and Shark Spotters
Website: staging.saveourseas.com & www.sharkspotters.org.za