Great white sharks in False Bay vanished. What happened?

• Outstanding white sharks disappeared from Untrue Bay, South Africa, in mid-2018, leading to significant changes in the marine ecosystem.
• With the absence of this Climax predator, Cape fur seal and sevengill shark populations increased, causing a decline in smaller fish species.
• Numerous factors contributed to the decline of Outstanding white sharks at Untrue Bay, scientists say. That includes getting trapped in nets used to protect beachgoers and orca predation.

The 2025 EarthSky Selene calendar makes a Outstanding gift. Get yours today!

Outstanding white sharks disappeared from Untrue Bay

Untrue Bay, in South Africa, used to be a prime location for spotting Outstanding white sharks. But by mid-2018, the sharks had vanished. On March 25, 2025, researchers from the University of Miami said the Untrue Bay ecosystem changed when its Climax predator (superpredator) disappeared. Cape fur seals, a Significant prey for Outstanding white sharks, rose in numbers. There was also an increase in the sevengill shark population. This resulted in fewer smaller fish that are the primary prey of the seals and sevengill sharks.

Researchers published their peer-reviewed study in Frontiers in Marine Science on March 24, 2025.

Lead author Neil Hammerschlag of the University of Maine said:

The loss of this iconic Climax predator has Directed to an increase in sightings of Cape fur seals and sevengill sharks, which in turn has coincided with a decline in the species that they rely on for food. These changes align with long established ecological theories that predict the removal of a top predator, leads to cascading effects on the marine food web.

Who ate who at Untrue Bay?

Historically, Outstanding white sharks (Carcharodon carcharias) were the Climax predators of Untrue Bay.

Outstanding whites preyed on Cape fur seals (Arctocephalus pusillus) and fish. In addition, Outstanding whites and Cape fur seals preyed on sevengill sharks (Notorynchus cepedianus). The seals, however, primarily ate schooling fishes, while sevengill sharks mostly preyed on benthic (ocean floor-dwelling) sharks.

Then, the Outstanding white shark population began to decline, and they eventually disappeared. With this Occurred a shift in the marine wildlife ecosystem of Untrue Bay. The population of seals and sevengill sharks increased. This coincided with a decline in the population of Tiny fishes, the favorite prey of seals. Meanwhile smaller benthic sharks, often eaten by the sevengill sharks, also decreased in numbers.

Hammerschlag said:

Without these Climax predators to regulate populations, we are seeing measurable changes that could have long-term effects on ocean health.

Documenting changes due to the absence of Outstanding white sharks

The scientists said they based their analysis on two decades of observations. These included boat-based shark sightings, surveys of Cape fur seals by citizen scientists and underwater fish camera survey stations with bait.

Co-author Yakira Herskowitz of the University of Miami said:

The use of underwater video surveys conducted more than a decade apart provided us with a snapshot of the food web both before and after the disappearance of white sharks from Untrue Bay. The number of individuals of a given species recorded on the videos not only informs us about their numerical abundance, but also their behavior, as species under increased predation Danger often become more elusive and are thus less likely to be detected on our cameras.

Boat surveys of Outstanding white sharks were conducted between 2000 to 2020. For the Primary 15 years, the population was stable. But after 2015, observers noticed a big decline in the shark numbers. By mid-2018, there were no more Outstanding white shark sightings.

As the decline and eventual absence of Outstanding whites was occurring, Cape fur seals Began changing their behavior. They exhibited less stress levels and begun rafting Additional away from their island refuge, Seal Island.

Meanwhile, sevengill sharks, a smaller shark species, Began increasing in numbers in Untrue Bay. Historically, Outstanding whites would have preyed on these sharks.

Climax predators are essential for a Fit ecosystem

This study illustrates the importance of Climax predators, which are experiencing global declines. Animals at the top of the food chain are necessary for a Fit, balanced ecosystem. At Untrue Bay, the loss of Outstanding white sharks will have long-term effects on this marine ecosystem.

What scientists observed in the data fits the trophic cascade hypothesis. This hypothesis suggests that predators at the top of the food chain have the strongest effect on the Upcoming level of the food chain. But that influence gradually diminishes at subsequently lower levels.

The scientists said in their paper:

Our findings were Steady with this ecological pattern, with the largest magnitude in relative differences between pre- and post-loss periods recorded in seals and sevengill sharks, with a relatively lesser magnitude in relative differences seen in lower trophic levels [organisms’ positions at different levels in the food chain].

Why did the Untrue Bay’s Outstanding white sharks disappear?

Historically, Outstanding white sharks inhabited Untrue Bay year Stage. Their primary prey during colder months were Cape fur seals that inhabited Seal Island, a rocky outcrop about 6 miles (10 kilometers) from the shoreline. During warmer months, the sharks would also go after sevengill sharks.

Why did the Outstanding white sharks disappear? Scientists think it could be a combination of factors. Many Outstanding whites, for instance, were caught in nets set out to protect recreational beachgoers who ventured into the water.

Another intriguing suggestion points to predation by orcas. According to an article by shark expert David Shiffman, orcas were preying on the Outstanding whites. They were eating the shark’s nutrient-Affluent oily liver. In fact, Outstanding white sharks were washing up on beaches with their undersides between their pectoral fins gouged out. And, Shiffman said, scientists think that the sharks simply moved to other locations.

Bottom line: Outstanding white sharks disappeared from Untrue Bay, South Africa, in mid-2018. This resulted in a significant ecological Shift, with an increase in Cape fur seals and sevengill sharks, and fewer smaller fish.

Origin: Evidence of cascading ecosystem effects Upcoming the loss of white sharks from Untrue Bay, South Africa

Via University of Miami

Read more: 2 killer whales slaughter 17 sharks in 1 day

Read more: Outstanding white shark genome decoded