Orcas blamed for disappearance of South Africa's great white sharks

Study by a government-appointed team of experts suggests killer whales could be the culprits

Tourists go shark cage diving with a great white shark in South Africa. Alamy (file images)

A large bull Orca surfacing, Monterey, California, Pacific Ocean. Alamy

Tourists dive in a shark cage as they wait to see a great white shark during a diving tour in the waters of Gansbaai in the Western Cape, South Africa. AFP Photo

Orcas swim in the waters of the Reisafjorden fjord region, near the Norwegian northern city of Tromso in the Arctic Circle. AFP

An orca breaches in view of Mount Baker in the San Juan Islands. AP Photo

A shark diving cage is lowered into the water in Gansbaai, South Africa. Getty Images

Killer whales are suspected to be responsible for the disappearance of great white sharks from Cape Town's waters over the past few years, according to a report published by the South African government on Tuesday.

The vanishing of great whites from the coastal sites False Bay and Gansbaai was previously blamed on illegal hunting and overfishing, among other causes.

But the results of a study by a government-appointed team of nine local and international experts suggest that orcas could be responsible, after a pair of killer whales was first sighted in the area in 2015.

The researchers said they "found some evidence for a causative link between the appearances of a pod of orcas that specialised on preying on white sharks".

The number of great whites in the area is not known, but spotters initially reported a steep population decline in 2017 – then an extended absence.

The remains of five great white sharks killed by orcas were discovered in the Gansbaai area in 2017.

Another shark killed in a similar fashion was found on a beach this year, and there could be many more, a marine biologist and one of the researchers, Alison Kock, said during the report presentation.

"Each and every time that this happened, there was an immediate drop and gap in white shark sightings," Ms Kock said, conceding that "we still don't have all the answers".

Great white sharks are a big tourist attraction in South Africa – they are viewed from boats or from cages lowered into the water.