WOBBY STILL RULES!
With the flat seas last week, out came the cray pots for many keen boaties, with divers also making the most of another good crayfish season. I managed to get underwater last week and learnt a valuable experience which I have since researched a little more and thought worth sharing with readers.
Shark stories are highly sensitive in the capes region and for good reason. I am one of many who have surfed and dived for years with never a thought about the risks associated with sharks. So under pressure from my good lady I decided last year to invest in a shark shield which I now wear while diving, but on the rare occasions I am surfing, I do not use. I have always been sceptical of devices that prove to do wonderful things, so did a bit of research beforehand and although there probably is nothing on the market that will prevent a large predator in attack mode, this seemed the best of what was available at the time. Researchers from University of WA were able to conduct a series of quite robust tests, largely due to a $220,000 grant from the WA Govt, on the effectiveness of shark shields repelling white pointer sharks. These tests were conducted in Mossel Bay, South Africa in 2014 with the final results not released until 2016. For these tests, in these waters, at this time, “the study concluded that the Shark ShieldTM produced an effective deterrent field an average of 1.3 metres from the device’s electrodes. It was found to prevent white sharks (Carcharodon carcharias) from interacting with a static bait 10 out of 10 times on their first approach. It was only after subsequent approaches that the rate dropped slightly to 9 out of 10 times, showing signs of habituation to the Shark ShieldTM, which decreased the effectiveness of the deterrent field by an average of 12 centimetres per approach by the same shark. However, despite an increase in tolerance, white sharks continued to be deterred from biting or interacting with the bait if an active Shark ShieldTM was present.” The down side is that the shark shield is a 2m long device, whereas other products like anklets, that are much better suited for surfers, are not proven to be as effective.
So while diving the other day, I had an experience with a curious two metre wobbegong, otherwise known as carpet shark. They can be very protective of crayfish, highly territorial, in past experiences I have had them attack a cray bag attached to my weight belt and on one occasion one snatched a snare out of my hand and receded to the dark corners of a cave, never to be seen again. So when this one came nosing out of a ledge that was crawling with feelers, I decided to detach my shark shield, wave it right under his nose and I actually think he smiled back at me as though he knew something I didn’t. He was right. Further research later that night revealed something I probably should have known. Apparently shark shields don’t affect Wobbegongs or Port Jacksons, because they don’t have ampullae of lorenzini which are the sensing organs called electroreceptors found on sharks snouts. So after all that cost, another piece of kit trailing behind me while diving with cray bag, torch, fins, snares, etc and not to mention getting zapped myself every now again when I turn in a tight circle, the wobby still rules!
