Laboratory sequencing has confirmed the presence of pilchard herpesvirus (PHV) genetic material in sampled sardines, as investigations continue into the cause of recent sardine mortalities along South Africa’s West Coast.
In a statement issued on Friday, the Department of Forestry, Fisheries and the Environment (DFFE) said PHV was detected in both dead sardines and, at lower levels, in some apparently healthy sardines collected from the West Coast.
The department said the findings suggest 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,” the department said.
The department noted that tests for toxins in sardines collected off Saldanha Bay, the Cape Canyon and Gansbaai, as well as 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.”
Task team
The department has convened an urgent briefing with small pelagic fishing industry stakeholders and will establish a task team comprising the department, the fishing industry and other relevant stakeholders.
The task team will urgently formulate a high-level, coordinated response plan to address 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,” it said.
The department said PHV has not previously been reported in South African sardines, and the virus was associated with two large-scale sardine mortality events in Australasia during the 1990s.
However, the virus was subsequently detected in apparently healthy Australian sardine populations without causing continuous mortality. PHV is a virus associated with sardines, also known as pilchards, and there is no evidence that it infects people or other animals.
No general fishing suspension
The department said the detection of PHV alone does not indicate that healthy sardines caught commercially or canned sardine products are unsafe.
“The finding does not currently justify a general suspension of fishing or canning. The biotoxin results are also reassuring, although they do not constitute a general clearance of all commercial catches.
“Monitoring and normal food-safety controls should therefore continue. Members of the public should not collect or consume dead or dying fish. They should also not feed dead or dying fish to pets,” it said.
READ | Sardine deaths ease as investigation continues
The DFFE said it will provide further information as additional results from the ongoing investigations become available. – SAnews.gov.za
