18/08/2026
Update! A Virus, Low Oxygen, or Something Else? The Mystery Behind South Africa’s Sardine Die-Off is still a mystery.
The Department of Forestry, Fisheries and the Environment (DFFE) has confirmed the presence of Pilchard Herpesvirus (PHV) genetic material in sardines collected during the recent mortality event along South Africa’s coastline.
While this may seem like the obvious cause, the picture is more complicated. PHV was detected in both dead sardines and, at lower levels, in some apparently healthy fish. Scientists are therefore investigating whether environmental stressors such as low oxygen levels, harmful algal blooms, or unusual oceanographic conditions may have triggered or intensified the event.
Interestingly, this is the first time PHV has been recorded in South African sardines. Similar mortality events were linked to the virus in Australia during the 1990s, but the virus has also been detected in healthy sardine populations without causing widespread mortality.
Why does this matter?
Sardines are one of the most important species in our oceans. Often referred to as a “forage fish,” they transfer energy from plankton to larger predators and are a critical food source for dolphins, seabirds, sharks, seals, tuna, and whales.
DFFE has expanded disease surveillance around the country and investigations are ongoing. Understanding what caused this mortality event will help scientists better understand the health and resilience of South Africa’s marine ecosystems.
