South Africa has long been celebrated as one of the world’s prime destinations for encountering great white sharks. These magnificent predators have captured the imagination of scientists, tourists and thrill-seekers, drawing them to the country’s coastline, particularly in the Western Cape.
However, recent years have seen a worrying trend: substantial declines in the numbers of great white sharks frequenting their traditional gathering sites along the Western Cape coast. These sites, such as Seal Island in False Bay, have historically served as essential locations where these sharks congregate to feed, interact socially and even rest.
This decline in shark numbers has raised significant concerns about the overall conservation status of great white sharks in South Africa. Why is this cause for concern? The answer lies in understanding the pivotal role they play in marine ecosystems.
Great white sharks are often referred to as the ‘keystone predators’ of the ocean. As top predators, they occupy the highest position in the marine food web, regulating the populations of prey species below them.
Their presence significantly influences the behaviour and distribution of other marine animals, which in turn affects the entire structure and stability of the ecosystem.
In essence, the health and balance of marine food webs depend, to a significant extent, on the presence of great white sharks. Any significant disturbance in their populations can have far-reaching consequences for the marine environment.
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Therefore, the recent declines in shark numbers along the Western Cape coast have prompted marine biologists and conservationists to investigate the reasons behind this shift.
To understand the extent of this issue, marine biologists undertook an extensive study, utilising data collected by scientists, tour operators and shore anglers. The goal was to examine the trends in shark abundance over time and to determine if there had been shifts in their distribution within South Africa.
The study yielded intriguing results. While some primary gathering sites witnessed declines in shark numbers, others showed increases or remained stable.
On the whole, there appears to be a consistent trend, suggesting that white shark numbers have remained relatively constant since receiving protection in 1991. This stability is encouraging for the species’ overall conservation.
However, it’s not just about numbers; it’s also about where these sharks are now being spotted. There has been a noticeable shift in human-shark interactions from the Western Cape to the Eastern Cape.
This phenomenon has sparked further questions about whether the sharks that vanished from the Western Cape have indeed migrated to the Eastern Cape or if these are distinct populations.
Understanding the reasons behind these shifts in shark abundance and distribution is a complex task. Several factors come into play, making it challenging to pinpoint a single cause.
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One key factor is the environmental conditions, including water temperature, lunar phases, seasons and food availability. Great white sharks are highly adaptable predators that target a wide range of prey.
They can thrive in various temperature ranges, with a preference for waters between 14 and 24°C. When unfavourable conditions arise, their migratory nature allows them to seek more suitable environments.
Climate change and long-term changes in ocean conditions might also be influencing their movements. Great whites can live for over 70 years and their behaviour varies across different life stages. Juveniles, especially males, tend to stay close to the coastline, while sub-adults and adults, particularly females, venture further offshore.
Another fascinating and concerning development is the predation of great whites by killer whales. These specialist killer whales have developed a taste for shark livers and have been observed preying on white, sevengill and bronze whaler sharks.
The first documented cases of such predation were reported in 2015 along the South African coast, coinciding with significant behavioural shifts in white sharks within areas like Gansbaai and False Bay.
While a direct cause-and-effect link is not definitively established, observations and tracking data support the idea of a distinct flight response among white sharks following confirmed predation incidents.
In one notable incident in Mossel Bay, a pod of killer whales killed at least three white sharks, prompting the remaining sharks to vacate the area.
One critical aspect of conserving great white sharks is understanding the risks they encounter in their environments. A study conducted in 2022 revealed a notable overlap between white shark habitats and commercial fishing activities.
Approximately 25% of South Africa’s Exclusive Economic Zone showed this overlap, with sharks spending 15% of their time exposed to these fisheries.
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KwaZulu-Natal reported the highest white shark catches, averaging around 32 per year. This emphasises the need for a comprehensive approach that combines shark movement data with reliable catch records to assess the risks to shark populations.
As shark movement patterns shift eastward, the potential change in risk must be considered. Increased overlap between white sharks, shark nets, drumlines (baited hooks) and gillnets could heighten the likelihood of shark captures.
While shark bites remain a relatively low-risk occurrence, the changing patterns in shark movements do pose potential challenges for beach safety and management. The presence of sharks can significantly influence human activities, particularly in popular swimming and water sports areas.
As shark distributions change, beach safety and management strategies may need to be adjusted. This could involve increased signage, temporary beach closures when sharks are present in the area, or improved education about shark behaviour.
The goal is to strike a balance between ensuring the safety of beachgoers and conserving these magnificent marine creatures.
In Cape Town, for instance, shark spotters have adapted their efforts to specific beaches. Following two fatal shark incidents in 2022, their programme expanded to Plettenberg Bay. Anecdotal evidence also points to additional locations in the Eastern Cape where surfers and divers encounter more white sharks than in previous years.
The conservation of great white sharks is a complex and evolving challenge. While the stable population of the predators is reassuring, the shift in their distribution introduces new complexities and considerations. Researchers and conservationists must continue their efforts to monitor and understand these creatures’ movements.
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Picture: Gerald Schömbs / Unsplash