Great white sharks no longer common in South Africa, leaving researchers puzzled

It’s a bumpy ride through the cool waters of Gansbaai, South Africa for famed shark expert Sara Andreotti. The region was once the shark capital of the world, but now the ultimate predator, which has survived over 400 million years, is in dire straits.

Four years ago you could see five to 20 great white sharks a day during peak season. Now you would be lucky to see so many in an entire year. Their numbers are dropping sharply, and sightings of the deadly predator off the country’s western cape have declined rapidly over the past five years.

There is silence and stillness in the oceans, and Andreotti said the lack of sharks is in fact a wake-up call.

“It’s sad too, the disappearance of such a big predator,” Andreotti told CBS News’s Debora Patta.

While at sea recently with a group of researchers who were urgently trying to figure out why the ocean is so calm, Andreotti spotted a great White shark. It was the first she had seen in two years. Andreotti and the researchers obtained a sample of the shark.

“The sample will give us an indication if there are new sharks entering the bay or a new shark in the bay,” she said.

So where have all the other sharks gone?

Scientists like Andreotti and his colleagues believe longline fishing is one of the main culprits. It legally targets small shark species exported to Australia for fish and chips. The problem, says marine biologist Mary Rowlinson, is that it’s also the shark’s food.

“And so we are depleting their food resources. And if you deplete the food resources, it creates more competition between individuals, which makes it harder for each white shark to survive,” Rowlinson said.

Then there is the problem of inadvertent fishermen catch sharks.

“You put down a big net and you try to catch hake, but instead you catch sharks, squid and rays. So that’s kind of collateral damage,” Andreotti said.

Some researchers attribute the disappearance of great whites to another predator: killer whales. They say they have driven out the shark population.

But Andreotti doesn’t buy it. Orcas and great white sharks have lived in the immediate vicinity of the area without any problems.

“My biggest fear is that while we argue over whether they have moved or if they are killed, we will lose the few that are left,” she said.

More than 100 miles away in False Bay, another hot spot, the shark population has also declined dramatically. Seferino Gelderbloem has been a shark watcher for twelve years. His job has been to watch out for the great whites, issuing a warning when they swim dangerously close to surfers. But this siren has been silent for a long time now.

“It concerns me because, I mean, they’re at the top of the food chain, so they keep the seals intact. So they feed on the sick and the injured, so they just keep it in balance,” Gelderbloem said.

Without the sharks circling the bay, there has been a proliferation of seals. More seals mean more fish are eaten, affecting the delicate ocean ecosystem – an ocean we depend on for oxygen.

“If you don’t have these big predators out there, keeping everything in balance and in control, unfortunately our oceans will die eventually. So protecting the oceans is protecting us,” Rowlinson said.

Great whites are often mistakenly portrayed as bloodthirsty killers preying on humans. But it turns out that humans may be their biggest threat.

About Mitchel McMillan

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