Where are the Great Whites? Bronzies and cow sharks taking over False Bay

2018-10-04 12:00 - Gabi Zietsman
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Something fishy is happening in False Bay. 

Last summer, Cape Town-based, non-profit safety and research organisation Shark Spotters recorded a new low for great white sightings along the beaches of Cape Town, reports Save our Oceans Foundation. At the same time, however,  the number of bronze whaler sharks, or bronzies, have increased in False Bay and sevengill cow sharks have taken over Seal Island, and now 'cow shark cage diving' has become the new push from tour operators in the area.

SEE: Ensuring 20/20 vision for the Shark Spotters of Cape Town's shores

How did it use to be?

Great white sharks used to be the top of the food chain in the area (before orcas moved in) and could hunt without competition from other predators. In winter they gathered around Seal Island to hunt the inexperienced pups, but when their prey has learned the knack for not getting eaten by the summer months, the great whites move inshore to feast on shoals of fish and getting a little too close for comfort to human swimmers. 

Cow sharks and bronzies tended to avoid these alphas and the former stuck to shelter during the day and hunted at night, while the latter only used to venture in small numbers to False Bay during summer.

What has changed?

This however has changed over the last year.

"If you have a look at Figure 1 below, you will notice that the last six years have yielded a downward trend in the number of white sharks recorded by Shark Spotters in the inshore zone of False Bay. This trend has also been observed at Seal Island, where the famous 'Flying sharks' of False Bay have been increasingly scarce, leaving their worldwide fan base disappointed for multiple seasons," writes Tamlyn Engelbrecht from Save our Oceans.

There have been dips in the white shark populations before, followed by a surge afterwards, but today that dip has been going on for much longer than usual, with a surge in bronze whaler sightings, says Save our Ocean.

WATCH: Greater protection for sharks around the world

Number of shark sightings per day of spotting effort across all Shark Spotters beaches in Cape Town over the period from 2007 - 2018. (Graph: Tamlyn Engelbrecht, Save our Oceans)

With the top predators gone, cow sharks have taken over the Seal Island territory, and the bronzies are more prevalent in the inshore zones. This has resulted in shark cage diving operators in the area starting to advertise 'cow shark cage diving' instead of the now more scarce great whites, which has become more a bonus sighting rather than a guaranteed one.

Why is this happening?

Save our Oceans note that the reason for the decrease is still up for debate. Some believe the cause of the decline could be attributed to the May 2017 attack of three great white sharks by orcas, their carcasses washing up on the shore.

The Department of Environmental Affairs has labelled the decline a natural phenomenon - due to a change in temperatures and the food chain of the animal kingdom. The Atlantic Ocean waters are being affected all across the globe and the reasons remain unclear.

Gansbaai is also feeling the decline. According to the Marine Dynamics blog post on 5 October 2017 - great white sightings in Gansbaai have dramatically decreased but there is still hope that this will improve.

Save our Oceans however see that "the observed decrease in white shark presence in False Bay does not appear to be mirrored all along the South African coast, with certain areas on the south and east coast actually experiencing increased white shark activity lately. This is promising as it points to a regional distribution shift, rather than a country-wide population decline, which would have far worse repercussions for our coastal ecosystems."

SEE: Why are Great Whites leaving US shores? 

What does the future hold?

But what does this mean for the future of sharks in False Bay and the tourism dependant on them? Save our Oceans just doesn't know enough to say for sure, but research is being conducted to get a better understanding of the decline and behaviour of the different shark species. Tagging is being done when possible around Seal Island, and they are looking to get hold of a bronzie to tag so they can learn more about their elusive nature. 

Shark Spotters have also started a volunteer programme, where you can get involved with the organisation and help them continue their research through fundraising, logistical and awareness raising support.

"It is hoped that through ongoing research, environmental monitoring and collaboration with other researchers, we can gain a better understanding of what is driving these current changes, and what the future holds for the sharks of False Bay."

As we approach summer though, beachgoers still need to be on the lookout and make careful note of the shark flags that are installed across Cape Town's beaches - great whites can return when you least expect it.

WATCH: Spectacular slow motion footage of great white sharks in Gansbaai

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