This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: The tide came in last week carrying thousands of dead sardines onto South Africa's south coast, and by dawn, stretches of Gqeberha's shoreline were flecked with silver. Along Hobie and Pollock beaches, bewildered residents watched as waves deposited more fish on the sand, fueling fears that a virus linked to devastating sardine die-offs overseas may be at work.
"It was a heartbreaking sight," local environmental group Algoa Bay Conservation said. Calls soon flooded marine scientists' offices. "We received numerous calls," Nadine Strydom, a professor in the zoology department at Nelson Mandela University, told AFP.
Most of the fish were sardines and pilchards, she said, adding that the true scale of the mortality could be far greater than what washed ashore. "What we see on the beach is only a fraction, as some could be lying on the seabed," she said. The mass stranding came just weeks after a similar die-off along South Africa's Western Cape coast, hundreds of kilometers away.
The wash-up has intensified concerns that pilchard herpesvirus, or PHV, a disease that devastated sardine populations in Australia and New Zealand in the 1990s, may be spreading through South African waters. The Department of Forestry, Fisheries and the Environment (DFFE) said on Sunday that a link between the Gqeberha and Western Cape events was considered likely, although it still required confirmation. "PHV remains the leading explanation for the Western Cape mortality event," the department said, adding that other causes and environmental factors would also be investigated.
The virus was first confirmed in South African waters in July after sardines collected off Saldanha Bay, Cape Canyon, Elands Bay and Gansbaai tested positive, DFFE said. Genetic sequencing showed more than 99% similarity to the strain associated with the Australian outbreak. "This is the first time it has happened in South African history," Strydom said.
PHV genetic material was found in both dead and apparently healthy sardines collected off Saldanha Bay, with the highest viral levels recorded in dead fish. But the finding does not prove that PHV caused the deaths, DFFE spokesperson Zolile Nqayi said. Scientists are examining whether the virus is the primary cause or is infecting fish already weakened by environmental stress.
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