Alison Kock is SANParks’ shark expert. Her recently published research highlights how sharks really need safe marine areas on the high seas – and how great whites bullet through water from depths of 20 metres to breach. To see what happens under the waves before they burst into the air to snatch seal prey, Alison’s team attached biologgers to 23 sharks. How?
The latest research shows that great whites are a lot more agile than previously thought. Image credit: Morné Hardenberg/ Shark Explorers
By dangling a piece of tuna over the side of the research boat and when the sharks came within range – one metre – attaching a ‘crittercam’ around the dorsal fin with a special pole and clamp. It was ‘unbelievably hard’, said Kock. ‘It took numerous days at sea and many attempts before a success. Then, we had to wait till the next day to see if the device released and floated to the surface, and had to find it again using a VHF receiver. Once found, we downloaded the footage and data, and only then could we watch what was recorded.’ The biologgers have a small camera as well as sensors to measure depth and acceleration. The results showed that breaching sharks increased their speed 6,5-fold and beat their tails far more rapidly, plus changed direction with ease. Hard-won data indeed: those 23 successful records were collected over two long years – and only three breaches were recorded.
Take Action
Mako sharks and shark-like rays called guitarfish and wedgefish are finally on the Cites Appendix II lists – more than 73 million sharks lost their fins (for soup) and lives last year. Back home, there were no confirmed reports of great whites in False Bay in 2019 and there were only 50 confirmed sightings by shark spotters over the 2018 spring and summer season (down from an average of 205 annual sightings).
In January 2020, Dr Alison Kock did an aerial survey and she photographed a great white from the air, which was the second reported sighting within a week. Sightings increase from spring, so let’s hope Shark Spotters claps eyes on more big guys soon.
Donate via sharkspotters.org.za
Also read: Second great white shark sighting in False Bay
Field Notes by Janine Stephen
Image credit: Morné Hardenberg/ Shark Explorers
