A mystery is unfolding along South Africa’s coastline
· The South African
Something strange has been happening along South Africa’s coastline for weeks now, and nobody can say for certain when it’ll stop.
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Reports of dead fish washing ashore started in one province.
Scientists still can’t determine how much of South Africa’s total sardine stock has been lost, and this is the first time pilchard herpesvirus has ever been detected in South African waters.
South Africa sardine mystery: what scientists actually know so far
The Department of Forestry, Fisheries and the Environment (DFFE) confirmed on 14 August that laboratory sequencing detected pilchard herpesvirus (PHV) genetic material in sardines sampled during the Western Cape mortality event.
The virus is highly contagious among sardines. It can damage their gills, which interferes with their ability to breathe.
Importantly, scientists found PHV not only in dead sardines but also, at lower levels, in some apparently healthy fish.
That detail matters…
It suggests the virus alone might not be enough to cause mass mortality on its own.
Scientists are now also investigating environmental stressors that could have triggered or worsened the die-off.
These include harmful algae, low oxygen levels, and unusual ocean conditions.
Die-offs have since expanded rapidly from the West Coast to Cape Town, Tsitsikamma, Algoa Bay and Gqeberha. Authorities have also reported sardine strandings along the Namibian coast.
They have agreed to provide samples for testing too.
South Africa sardine mystery: why it matters for the country’s penguins
Sardines are a primary food source for the critically endangered African penguin, alongside Cape cormorants and Cape gannets. According to Daily Maverick, conservationists in Nelson Mandela Bay are especially concerned about the impact on penguins nesting on St Croix Island.
Numbers there have already collapsed from around 7,000 breeding pairs in 2017 to roughly 700 pairs by 2023.
That concern isn’t hypothetical. According to GroundUp, two similar mass sardine die-offs in Australian waters during the 1990s were also linked to PHV.
Those die-offs coincided with large mortalities in the local Little Penguin population and significantly reduced breeding success in the years that followed.
The African penguin’s current population sits at just under 20,000 mature individuals, with only around 8,750 to 9,900 breeding pairs remaining.
The department has been careful to clarify what isn’t yet confirmed.
A widely circulated figure suggests the mortality represents 1% of the total sardine population.
The department, however, never approved this as an official estimate.
It reportedly came from confidential, preliminary scientific discussions never meant for public release.
There’s also good news for consumers specifically: PHV poses no known risk to human health, and its detection doesn’t mean commercially caught or canned sardines are unsafe to eat.
This is a hectic story precisely because so much remains unknown, and because the species most at risk from it is already hanging on by a thread, hey.
Have you noticed dead fish washing up along your local beach?
Let us know in the comments below, Mzansi…