04/05/2025
Vanishing Great white shark impacts South African marine health
Over the last two decades and at the hands of ill-informed overfishing and more recently orca predation, the Great white shark has been slowly disappearing from South Africa's False Bay. As a result, the local marine life has shifted and its health suffered.
A two-decade study into the gradual disappearance of Great white sharks from False Bay in South Africa has gone to new lengths to underscore the crucial role that apex predators play in maintaining ocean health as well as the consequences of ecosystem disruption.
Historically abundant in False Bay, Great white sharks have experienced a dramatic decline and subsequent disappearance over the last 20 years, with the finger of blame being directed at a combination of factors, including decades of unsustainable capture in nets and some more recent instances of predation by orcas.
With the loss of the Great white shark (Carcharodon carcharias) from the region, room has been given for a notable increase in Cape fur seals (Arctocephalus pusillus) and sevengill sharks (Notorynchus cepedianus) which – in-turn – has been linked, by researchers, to a decline in fish that seals feed on and smaller shark species that the sevengills prey on.
It all illustrates, scientists have said, the ripple effect of losing a top ocean predator.
This piece of research has been conducted by scientists at the University of Miami Rosenstiel School of Marine, Atmospheric, and Earth Science, spanning the course of two decades to document the cascading ecological disruptions and the vital role that an apex predator such as the Great white shark plays in maintaining ocean health.
Consistent with ecological theory and the kind of experiments that – until now – have only been documented in the laboratory, the study provides the real-world evidence of such food web cascades driven by the loss of top-down predation pressure from Great white sharks.
“The loss of this iconic apex predator has led 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,” said Neil Hammerschlag, Ph.D – the study’s lead author.
“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.”
