It’s an uneven journey through the cool waters of Hansbay, South Africa, for renowned shark expert Sarah Andreotti. The region was once the capital of sharks in the world, but now the top predator, which has survived for over 400 million years, is in deep trouble.
Four years ago, you would have seen five to 20 great white sharks a day during the peak season. Now you will be lucky to see so much for a whole year. Their numbers are declining sharply, and sightings of the deadly predator off the country’s western tip have been declining rapidly over the past five years.
There is silence and stillness in the oceans, and Andreotti said the lack of sharks is actually an alarm.
While recently at sea with a group of researchers urgently trying to understand why the ocean is so quiet, Andreotti noticed. It was the first thing she’d seen in two years. Andreotti and the researchers took a sample of the shark.
“The test will give us an indication of whether there are new sharks in the bay or a new shark in the bay,” she said.
So where did all the other sharks go?
Scientists like Andreotti and her colleagues believe that longline fishing is one of the main culprits. It is legally targeted at smaller shark species exported to Australia for fish and chips. The problem, explains marine biologist Mary Rawlinson, is that this is also the shark’s food.
“And so we deplete their food resources. And if you run out of food resources, it creates more competition between individuals, which makes it difficult for each white shark to survive,” Rawlinson said.
Then there is the problem of inadvertent fishermen.
“You put on a big net and try to catch hake, but instead you catch sharks, squid and ray. So that’s some additional damage,” Andreotti said.
Some researchers blame the extinction of the great whites for another predator: killer whales. They are said to have driven away the shark population.
But Andreotti doesn’t buy it. Killer whales and great white sharks have lived in the immediate vicinity of the area before without problems.
“My biggest fear is that while we are arguing about whether they have moved or are being killed, we are losing the few that are still left,” she said.
More than 100 miles away in False Bay, another hot spot, the shark population has also declined dramatically. Seferino Gelderblom has been a shark observer for twelve years. His job was to keep track of great whites by issuing a warning when swimming dangerously close to surfers. But this siren has long been silent.
“It worries 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 wounded, so they just keep them balanced,” Gelderblom said.
Without the sharks that roam the bay, there is a spread of seals. More seals mean eating more fish, which affects the delicate ecosystem of the ocean – an ocean on which we depend on oxygen.
“If you don’t have the best predators there, keeping everything in balance and under control, unfortunately our oceans will eventually die. So protecting the oceans means protecting ourselves,” Rawlinson said.
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