Orcas may be scaring off great whites in False Bay, but there’s still more to it

Orcas Source: Google Images

Marine biologist Leigh de-Necker says the mystery of False Bay’s disappearing great white sharks is a complex issue.

Scientists believe that hundreds of great white sharks have disappeared from False Bay in recent years.

De-Necker says there is no single or definitive answer for why the apex predators seem to have vanished.

Researchers have been studying shark activity in the area to investigate the factors contributing to a steep decline in sightings.

De-Necker says orcas, also known as a killer whales, could be frightening great whites away.

She has spotted orcas, which love to eat shark liver, preying on broadnose sevengill sharks within False Bay.

White shark carcasses – minus their livers – have also washed up on the shores of Gansbaai.

But De-Necker says orcas are not solely to blame. She says a combination of factors are likely influencing the presence of predatory sharks in the bay.

She’s written an opinion piece on the Daily Maverick about why False Bay’s apex predators fleeing from the area.

In it, she argues that offshore commercial long-line fishing and inshore shark fishing could be impacting the dietary needs of great whites, forcing them to migrate.

She adds that climate and other environmental issues could also be a factor.

We caught the orcas predating on the broadnose sevengill shark, also an apex predator… Later, they were found to have predated on great whites in Gaansbaai.

Leigh de-Necker, Marine biologist, aquarist and commercial diver – Two Oceans Aquarium

They [orcas] were definitely our prime suspects… but nature is dynamic and as humans we want one simple answer to blame the orcas on the disappearance of the great white but I think there might be a little bit more at play here.

Leigh de-Necker, Marine biologist, aquarist and commercial diver – Two Oceans Aquarium

It could be environmental factors, from a temperature or climate point of view or it could be fishing related.

Leigh de-Necker, Marine biologist, aquarist and commercial diver – Two Oceans Aquarium

On top of that, there’s extensive shark fishing happening in False Bay and all along our coastline, which could be removing important prey species for the great whites so they have to move to.

Leigh de-Necker, Marine biologist, aquarist and commercial diver – Two Oceans Aquarium