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South Africa is well known for having one of the world’s biggest populations of great white sharks, but in recent months researchers have noticed a decline of these ancient predators in the places where they usually congregate.

These declines have sparked concerns about the overall conservation status of the species, but with new information it appears the sharks are moving to different locations from their usual hang-out spot, particularly along the West Coast.

Cape Town ‘shark spotters’ documented a peak of over 300 great white shark sightings across eight beaches in 2011, but have recorded no sightings since 2019.

As the top predator in the region, sharks play a vital role in maintaining the sustainability of the ocean eco-system in our waters.  It’s therefore important for marine biologists to know whether the decline in shark numbers in the Western Cape indicated changes in the whole South African population, or whether the sharks had moved to a different location.

The latter seems to be the case with our ‘local’ sharks.

An extensive study has been undertaken to examine data collected by scientists, tour operators and shore anglers, tracking the trends over time of the distribution of sharks across South Africa’s oceans. The data has so far revealed significant differences in the abundance at primary gathering sites, along with declines at some locations.

It’s not a crisis situation, thankfully, and overall, there appears to be a stable trend, suggesting that white shark numbers have remained constant since they were given protection in 1991. But a definite shift in human-shark interactions from the Western Cape to the Eastern Cape is notable.

Researchers note that more research is required to be sure whether the sharks that vanished from the Western Cape are the same sharks documented along the Eastern Cape.

For example, at Seal Island, False Bay (Western Cape), shark sightings declined from 2.5 sightings per hour in 2005 to 0.6 in 2017. Shifting eastward to Algoa Bay, in 2013, shore anglers caught only six individual sharks. By 2019, this figure had risen to 59.

The changes at each site are complex. Understanding the patterns remains challenging due to environmental factors like water temperature, lunar phase, season and food availability.

Changes in the climate and ocean over extended periods might also come into play – as adaptable predators, great white sharks target a wide range of prey and thrive in a broad range of temperatures, with a preference for 14–24°C. Their migratory nature allows them to seek optimal conditions when faced with unfavourable environments.

Although shark bites remain a low risk, changing shark movements could also influence beach safety. The presence of sharks, particularly in popular swimming and water sports areas will require adjustments to existing shark management strategies as distributions change.

In Cape Town, for example, shark spotters have adjusted their efforts on specific beaches. Following two fatal shark incidents in 2022, their programme expanded to Plettenberg Bay.

Anecdotal evidence highlights additional Eastern Cape locations where surfers and divers encounter more white sharks than before.

South Africa is not alone in dealing with migrating sharks, and various countries across the world have seen movements similar to ours.

Sharks have been getting a lot of bad press ever since Peter Benchley freaked everyone out with Jaws, but the truth is that they are rather amazing creatures that have managed to survive for millions of years by adapting to the environment they rule, so the movement is not ‘a problem’ for them.

Perhaps their movement is another clue that climate change is not just a fear-mongering myth, but an actual thing. When the meanest guy in your hood moves somewhere else, something’s definitely up.

[source:theconversation]