31/08/2026
Understanding the Recent Sardine Mortalities Along South Africa’s Coast
Researchers from the Institute for Coastal and Marine Research (CMR), at Nelson Mandela University are contributing to ongoing scientific investigations into the significant numbers of sardines observed floating offshore and washing ashore along sections of South Africa’s coastline.
CMR's Professor Mike Roberts, NRF South African Research Chair in Ocean Sciences and Food Security, together with PhD student Savannah Andersen and Dr Patrick Vianello, is assisting Dr Janet Coetzee of the Department of Forestry, Fisheries and the Environment (DFFE), who is coordinating the scientific response to the event.
Sardine mortalities have been observed from Elands Bay on the West Coast to Algoa Bay, with investigations continuing to better understand the apparent eastward movement of affected fish.
What do scientists know so far?
🧬 A viral infection has been identified
Analyses of collected samples indicate that the sardine mortalities are associated with infection by a herpes virus, which affects the gills and makes it difficult for fish to obtain sufficient oxygen from the water.
🌊 Environmental conditions are being investigated
Satellite analyses of sea surface temperature and ocean colour data have not revealed any striking environmental anomalies that would clearly explain the outbreak. Analyses have also found no evidence of toxins associated with harmful algal blooms in examined gill samples.
🔬 The origin of the outbreak remains under investigation
Researchers are continuing to investigate how the virus may have been introduced and what factors may have contributed to this unusual mortality event.
🐟 Further investigations are underway
Sardines are still being observed along parts of the southern KwaZulu-Natal coast, and additional samples are currently being analysed.
As investigations continue, CMR researchers remain committed to supporting collaborative scientific efforts to better understand this unusual marine event.
Further official communication on the matter will be provided by the DFFE as the investigation progresses.
