New Evidence Emerges in Sardine Mortality Investigation 

Laboratory sequencing has confirmed that pilchard herpesvirus (PHV) genetic material is present in sampled sardines. This is the first time this has been detected in South Africa. 

This news has resulted in the Department of Forestry, Fisheries and the Environment (DFFE) convening an urgent briefing with small pelagic fishing industry stakeholders with a view to establishing a task team to formulate a high-level coordinated response plan for PHV-associated sardine mortality in South African waters.

Through a coordinated inter-agency effort, the Department is expanding disease surveillance along the West, South and East coasts, while further disease, pathology and environmental investigations continue. The Department’s routine October/ November hydroacoustic biomass survey will be the first opportunity to assess the possible effect on the sardine population.

The role of the pilchard herpesvirus (PHV) in the recent sardine mortality remains under investigation. PHV was detected in both dead sardines and, at lower levels, in some apparently healthy sardine collected from the West Coast. This suggests that the presence of the virus alone may not be sufficient to cause mass mortality.

Scientists are therefore also investigating whether an environmental stressor, such as harmful algae, low oxygen or unusual oceanographic conditions, may have triggered or intensified the event. This remains a hypothesis requiring further evidence.

Tests for toxins in sardines collected off Saldanha Bay, the Cape Canyon and Gansbaai, together with an apparently healthy comparison sample from St Helena Bay, found none of the paralytic toxins associated with a harmful algal bloom in Saldanha Bay. Two other algal toxins, domoic acid and yessotoxin, were detected at low levels, with the highest levels found in the apparently healthy comparison sample. No other toxins included in the screening were detected.

These findings suggest that the toxins tested for were unlikely to have been the primary cause of the sardine deaths. However, they do not entirely rule out harmful algae or environmental conditions as factors that may have placed additional stress on the fish.

PHV has previously been associated with two large-scale sardine mortality events in Australasia during the 1990s. However, the virus was subsequently detected in apparently healthy Australian populations without causing continuous mortality.

There is no evidence that PHV infects people or other animals and the finding alone does not indicate that healthy sardines caught commercially or canned products are unsafe. Nor does it currently justify a general suspension of fishing or canning. 

According to the Department the biotoxin results are reassuring, although they do not constitute a general clearance of all commercial catches. Monitoring and normal food-safety controls should therefore continue.

Dead or dying fish should not be collected or consumed, nor should they be fed to pets.

The Department says it will provide further information as results become available.