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NEWS NEWS The
9 May 2017
Cape Whale Coast
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Orcas behind spate of great white deaths De Waal Steyn
I
ndications are that orcas on the prowl for food are behind the recent deaths of three great white sharks in the area. The latest victim washed up on a beach in Struisbaai on Sunday. “We have never seen anything like this,” says Alison Towner, a biologist with Dyer Island Conservation Trust (DICT) in Gansbaai. “The third carcass is another large white shark, a 4,2 metre male with injuries that
seem to match those of the previous two dead specimens.” A 4,9 m female and a 3,4 m male that washed up last week in the Gansbaai area have been dissected and in both instances their liver was missing, which is indicative of an orca attack. “Orcas are apex predators and they seem to have a predilection for organ meat and shark livers in particular,” says Alison. Wilfred Chivell of DICT says sightings of orcas in the area are very rare. “We
witnessed a pod swimming past in 2012 and for the past few years we have seen a few orcas intermittently. There are two male orcas, nicknamed Port and Starboard, that have been regularly visiting the area. It is interesting to note that every time they are spotted the sharks seem to leave the area for a little while.” These findings indicate not only that orcas predate on sharks but also influence white shark behavior and movement patterns in our waters. This is clearly not good
news for the shark cage diving industry. “The first shark to wash ashore was a female of 4,9 m long and we estimate her weight at 1 110 kg. We have her recorded around Dyer Island last year in June but we hadn’t seen her since,” says Alison. “She has also been recorded in Mossel Bay between August and December 2016. At this size, she was nearing reproductive maturity and is the biggest white shark dissected in South Africa.”
any sharks for almost two weeks. It was the same last week when the dead sharks were discovered,” she says.
Alison was assisted by shark expert Dr Malcolm Smale from Bayworld in Port Elizabeth, Dr Alison Kock from Shark Spotters, members of the National White Shark Research Group and Meaghan McCord from the South African Shark Conservancy. The Department of Environmental Affairs permitted an onsite dissection.
The second shark was a 3,4 m long male and big pieces out of each flank were missing, including its heart and liver. Due to the extensive damage, its weight could not be calculated.
“It is very rare to see marine predator behavior such as this,” says Alison. “The last white shark washed up here on 8 February and the cage diving boats struggled to see
The Dyer Island Conservation Trusts says it is grateful for everyone's help and patience, especially the community of Gansbaai who assisted in finding the carcasses.