This could be a plausible explanation for the increasingly glaring absence of sharks near the South African coast.
The presence of orcas, superpredators nicknamed "killer whales", is undoubtedly at the origin of the disappearance of the great white shark in certain areas off Cape Town, according to a South African government report published on Tuesday.
Present in South Africa, white sharks have disappeared from some of its coasts in recent years, some attributing the phenomenon to shark hunting, others to the use of drifting nets or even to overfishing.
At least six sharks killed by orcas
But another hypothesis emerges from studies carried out by a team of nine national and international experts appointed in March by the government, which launched an ambitious program to protect sharks, several of which are threatened or endangered.
"There is evidence of a causal link with the appearance of a group of orcas that hunt white sharks," according to the report.
In 2017, the remains of five white sharks killed by orcas were found in Gaansbai, in the southwest of the country.
Another, similarly killed, was found on the beach this year, and there could be many more, marine biology researcher Alison Kock, who is on the panel, demonstrated during the presentation of the report. experts.
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"Each time this was followed by an immediate drop in the number of white sharks" in the region, presumably fleeing the predator, she observed, adding that similar cases have been seen in the United States offshore. from California (West).
"We do not have all the answers", however, concluded the specialist, recommending further research.
Improving the fight against illegal fishing
Shark fishing is a historical sector in South Africa and tourism derives significant income from activities linked to the presence of sharks.
To fight against the disappearance of sharks in the country, the report also recommends improving the fight against illegal fishing and better practices in the tourism sector.
Experts identify some 1,250 species of sharks, many of which are already protected.
In South Africa, "14% of shark species are threatened," said Environment Minister Barbara Creecy during the presentation
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Each year, 100 million sharks are killed in the world's seas.
A number of captures twice as high as that which would maintain their population at its current level, according to wildlife protection NGOs.