a Breaching Great White shark — Breaching Great White Shark | Via Getty Images

It’s hard to imagine the ocean without great white sharks. These sleek, powerful apex predators have long ruled the coastal waters of South Africa—especially in False Bay, one of the world’s former hotspots for white shark activity. But something dramatic has happened: between 2015 and 2019, great white sharks vanished from False Bay entirely. And their absence is rippling through the ecosystem in unexpected—and deeply concerning—ways.

A new scientific study has revealed what marine ecologists have long suspected but rarely captured so clearly in the wild: the disappearance of an apex predator can unravel the stability of an entire ecosystem. This isn't just about sharks—it’s about what happens when the top of the food web collapses, and the species below begin to scramble for balance.

Before we dive deeper, let’s unpack what an apex predator really is. These are the species at the top of the food chain, with no natural predators of their own. They play a critical role in controlling prey populations and shaping the behavior of entire ecosystems. And when they disappear, the effects are rarely subtle.

This unfolding story is more than just a scientific curiosity—it’s a wake-up call. South Africa’s coastlines are home to some of the richest biodiversity on the planet. From the endangered African penguin to iconic land giants like rhinos supported through South Africa’s rhino conservation tourism, this is a region that thrives when wildlife thrives.

Let’s explore what happened in False Bay—and what it reveals about the fragility of ocean ecosystems when apex predators disappear.

What Happened to the White Sharks?

Between 2015 and 2019, great white sharks (Carcharodon carcharias) virtually disappeared from False Bay. Once regularly seen near Seal Island and other parts of the bay, these apex predators became rare sightings, eventually vanishing altogether.

Long-term data collected between 2000 and 2020 revealed a sharp and sudden decline in great white numbers after 2015. By mid-2018, they were entirely absent from the study area. The reasons for this disappearance are still debated, with some pointing to increasing orca predation, while others blame shark nets and drum lines off the coast of KwaZulu-Natal—designed to protect beachgoers but deadly for sharks.

aerial view over false bay in cape town — False Bay Cape Town | Photo by Nat Trass

What Is a Trophic Cascade?

This isn’t just a story about missing sharks. It’s about what happens when the top of the food web collapses. A trophic cascade occurs when changes at the top of the food chain trickle down, causing imbalances all the way through the ecosystem.

In False Bay, researchers documented just that.

Cape fur seals and sevengill sharks—both common prey for great whites—increased significantly in number once the sharks disappeared.
These animals, in turn, fed more heavily on small fish and sharks, including species like pyjama catsharks and smooth-hound sharks, whose populations started to decline.
Seals, no longer afraid of predation, were observed in deeper waters where they previously avoided venturing. One study even found lowered cortisol levels in seal feces, indicating reduced stress since the sharks disappeared.

It’s a textbook case of how apex predators keep ecosystems in check—not just by eating prey, but by shaping the behavior of the entire food web.

What the Data Shows

Lead researcher Neil Hammerschlag and his team drew from an impressive array of sources: boat-based surveys, baited remote underwater video systems (BRUVS), and even citizen science data from seal watchers. The result was a clear pattern of cascading ecological shifts.

A 522% increase in seal sightings was recorded.
Sevengill sharks, which previously stayed hidden in kelp forests far from great white territory, began appearing around Seal Island.
Small fish populations like horse mackerel and anchovies began to decline, likely due to increased pressure from seals.

This isn’t just theoretical, it’s happening now, in one of the most studied marine environments on the planet.

Why This Matters

The loss of white sharks from False Bay offers a cautionary tale. Apex predators, especially in marine environments, are disappearing at an alarming rate around the world. When they go, the systems they helped stabilize start to fall apart.

Marine ecosystems are delicate. When one species booms unnaturally because its predator is gone, other species can crash. And these shifts are not always easy, or even possible, to reverse.

You might enjoy reading Bull Shark Species: 12 Interesting Facts to see another predator’s role in coastal waters, or How Ocean Pollution Affects Sea Animals to understand broader stressors compounding these declines.

great white shark breaching with a bird on its mouth — Great White Shark on False Bay

Why Are the Sharks Really Gone?

While orca predation has received a lot of media attention, some experts believe it’s only part of the story. Researchers like Hammerschlag and Enrico Gennari point to human impact, specifically the use of shark nets and drum lines—as a key contributor to the decline.

These systems, intended to keep swimmers safe, can entangle and kill sharks, especially migratory species like great whites. And when those numbers dwindle at one end of their migratory range, the effects are felt across the map.

This aligns with declines recorded in other former great white hotspots across South Africa, including Mossel Bay, Gansbaai, and Plettenberg Bay.

What Comes Next?

The most urgent task is understanding how long-lasting and far-reaching these ecosystem changes will be. Are we seeing a permanent shift in the structure of False Bay’s marine community, or could great whites return and restore balance?

Here’s what scientists are hoping to study next:

How smaller predator populations (like sevengill sharks) continue to respond to the loss of competition.
Whether altered prey behaviors (like those of seals) will remain in the long term.
How these shifts affect other species down the chain, including seabirds, invertebrates, and reef fish.

Researchers stress that while their study is based in False Bay, similar scenarios may be unfolding globally. As apex predators decline across oceans, we may be overlooking many more of these slow-motion collapses.

It’s easy to fear sharks—they’re big, fast, and powerful. But this study reminds us that they’re also essential. Great whites are architects of the ocean’s balance. Without them, systems unravel in ways we’re only beginning to measure.

So next time someone says sharks are scary, consider this: it’s their absence that should really concern us.

Want to explore more about marine giants? Don’t miss on The Top 12 World’s Biggest Animals or Best Places to Swim with Sharks!

The Disappearance of White Sharks: A Cascade of Consequences in False Bay, South Africa