Great white sharks flee in terror

04 June 2017 - 02:00 By CLAIRE KEETON
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The great white shark.
The great white shark.

Who's the king of the ocean: Free Willy or Jaws?

What's clear is that South Africa's apex marine predator, the great white shark, has been swimming scared after orcas killed three of them around Gansbaai in the Western Cape about a month ago.

South African National Parks marine biologist Alison Kock said: "The evidence so far supports the notion that the predation on the three white sharks by the orcas has also resulted in other white sharks leaving the area."

Autopsies on the trio found that their livers, weighing as much as an average person, had been ripped out with almost surgical precision.

White shark expert Chris Fallows said False Bay and Gansbaai had arguably had the worst season yet for white shark sightings, and orcas could be influencing this.

Over the past few months in Mossel Bay, one of South Africa's top three white shark zones, sightings have been consistently high, with up to 18 individuals spotted in a single day.

Marine biologist Enrico Gennari, who is based at Oceans Research in Mossel Bay, thinks white sharks from other parts of the coast could be taking refuge there.

Over the past two years in Mossel Bay the white sharks disappeared every time orcas were seen, he said. Two Decembers ago they were gone for about six weeks.

But the human threat to white sharks is far greater than any natural predation. Last week, scientists did an autopsy in Mossel Bay on a white shark that seemed to have been killed by fishing lines and hooks.

Gennari said: "It was a very healthy animal, not missing any parts. In its stomach was a seal and two sets of fishing lines and hooks, and another one behind the jaws."

More than 25 years after white sharks were given possibly endangered status, fishermen seemed to be targeting them with thick steel lines, he said.

At sea Gennari saw another protected species, a southern right whale, being throttled with fishing rope and then being eaten by a white shark.

Fallows said he had seen fewer and fewer white sharks in False Bay. "Regulars are not coming back and we are finding a huge inconsistency in their arrivals and departures, which were like clockwork over more than 15 years."

He blamed the decline on poaching, entanglement and trawlers that swept them up as by-catch.

Only about one in 10 of white sharks were more than 4m long and losing one or two of those mature females could have a big effect, Fallows said.

He has seen a 6m shark and, in 2000, watched 28 white sharks feeding on a whale carcass.

White sharks take 30 years or more to mature and breed slowly. Their mating and breeding patterns have not been observed but scientists who have studied them say individual sharks have distinct personalities.

Gansbaai marine biologist Alison Towner said: "Nemo was only 2.5m when we tagged her. She had a missing pectoral fin and was a bit clumsy.

"She would return year after year and now she is more than 4m and relaxed. Despite her disability we have seen her move far away to the coast of Madagascar.

"Rosie is another magnificent tagged female, now over 4m, who likes to circle with deliberation."

Fallows described a shark named Rasta, "an incredibly relaxed animal which would cruise gently around the boat, poke his head up and look at what was going on".

"But another shark we called Shy Guy only came to the boat once even though we watched him for 11 years. We saw him make in excess of 60 kills," Fallows said.

Scientists agree that tourists benefit shark conservation and research.

"Without cage diving nobody would be policing the sharks, there would not be monitoring and data collected every day, and perceptions would not change," said Towner.

• The white shark population off South Africa is estimated at between 350 and 1,000;

• One tagged shark swam 11,000km from South Africa to Australia in 99 days — and was back six months later;

• One autopsied shark had three seals bitten in half in its stomach;

• White sharks are solitary animals without favourite companions, but similar sizes and sexes tend to group more;

• They are one of few species of fish or sharks to keep their body temperature warmer than the ocean;

• Orcas are the only natural predator of the white sharks;

• 785 orcas have been documented along the coastline from the Western Cape to KwaZulu-Natal.

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