South Africa’s Great White Shark population: Imploding, or fleeing Orcas?
A group of marine biologists are challenging the findings of a recent study suggesting that South Africa’s White Shark population has not decreased, but simply redistributed eastwards to flee predation by Orcas.
Lester Kiewit speaks to Marine Biologist Dr Enrico Gennari of the Oceans Research Institute and the Department of Ichthyology and Fisheries Science at Rhodes University.
Gennari led a rebuttal of a recent study which suggested that the dramatic decline in South Africa's Great White Shark population is caused by predation by Orcas.
He challenges the findings which suggest that South Africa's Great White Sharks have not decreased, but moved east to flee Orcas.
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Are South Africa’s White Sharks Simply Relocating? Uncertainty remains for white sharks in #SouthAfrica, as population stability and redistribution cannot be concluded. https://t.co/3rklQA3aIo @EnricoGennari2 @Matias_Braccini @AndreottiSara @ApexSharks #sharks #marinebiology
— Dr. Neil Hammerschlag (@DrNeilHammer) March 6, 2024
In September 2023, the article “Decline or Shifting Distribution? A First Regional Trend Assessment For White Sharks in South Africa” was published in the open-access journal Ecological Indicators.
This was followed by two articles in the popular media – one in Nature titled “Orcas Blamed for Missing Great White Sharks” and another in The Conversation Africa titled “South Africa’s Great White Sharks are Changing Locations – They Need to be Monitored for Beach Safety and Conservation”.
In a rebuttal article published in the same journal recently, titled “Uncertainty Remains for White Sharks in South Africa, as Population Stability and Redistribution Cannot be Concluded, by Bowlby et al (2023)”, the group of concerned marine biologists highlight several issues with the methods and inferences made in the study mentioned above. They argue that the data do not support the theory of population stability or redistribution of South Africa’s White Sharks.
Gennari argues that Orcas are not the sole reason for the "decline" in Great White Shark populations in South Africa.
"There's something we are not factoring into the issue of White Sharks. Yes, the Orcas have an impact. However, the decline we see in False Bay and Gansbaai started two years before the first appearance of those Orcas so, again, there is something we have not really factored yet into the conservation of White Sharks in South Africa."
- Dr Enrico Gennari, Marine Biologist - Oceans Research Institute
Gennari argues that illegal fishing is partly to blame for the population collapse of White Sharks in South Africa and that 'there is something we can do about it'.
"It comes down to numbers and how many sharks are hunted and killed yearly by humans. These are things we can do something about to better manage South African fisheries to conserve Great White Sharks in South Africa."
- Dr Enrico Gennari, Marine Biologist - Oceans Research Institute
Gennari calls for the following interventions:
1) Better fisheries policies with permit implementations for specific kinds of fishing.
2) Using technology such as drones instead of barrier nets to spot Great White Sharks.