The discovery of dead sardines and pilchards washing up along Gqeberha’s beaches has raised fresh concern about a suspected fish virus that may be spreading through South African waters.
Along Hobie and Pollock beaches, residents watched as waves deposited more fish on the sand, adding to fears that pilchard herpesvirus, or PHV, could be linked to a series of devastating sardine die-offs.
“It was a heartbreaking sight,” local environmental group Algoa Bay Conservation said.
The latest mass stranding came just weeks after a similar mortality event along the Western Cape coast, hundreds of kilometres away.
Calls soon flooded marine scientists’ offices as residents tried to understand why so many fish had washed ashore.
“We received numerous calls,” said Professor Nadine Strydom of Nelson Mandela University’s zoology department.
Strydom said most of the fish were sardines and pilchards, but warned that the number found on the beaches might not reflect the true scale of the deaths.
“What we see on the beach is only a fraction, as some could be lying on the seabed,” she said.
The Department of Forestry, Fisheries and the Environment said 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.
Virus Detected In South African Waters
PHV was first confirmed in South African waters in July after sardines collected off Saldanha Bay, Cape Canyon, Elands Bay and Gansbaai tested positive.
Genetic sequencing showed more than 99% similarity to the strain associated with a major Australian outbreak.
“This is the first time it has happened in South African history,” Strydom said.
The virus has previously been linked to mass sardine mortality events in Australia and New Zealand during the 1990s. It can cause inflammation and thickening of the fish’s gills, affecting their ability to take in oxygen.
However, the detection of PHV does not yet prove that it caused the South African deaths.
PHV genetic material was found in both dead and apparently healthy sardines collected off the West Coast. The highest viral levels were recorded in dead fish, while lower and varied levels were found in some living sardines.
DFFE spokesperson Zolile Nqayi said the finding had to be interpreted carefully as scientists continued to examine the evidence.
Researchers are investigating whether PHV is the primary cause of the mortality or whether the virus is infecting fish that had already been weakened by environmental stress.
Possible contributing factors include low sardine stocks, oxygen-depleted water, harmful algal blooms, unusually cold sea temperatures and changes in water quality.
Government testing found no evidence of paralytic shellfish toxins. Only low levels of other marine toxins were detected, suggesting that algal poisoning was unlikely to be the main cause of the deaths.
No Known Risk To Human Health
The virus poses no known risk to human health, according to the environmental authorities.
Its detection also does not mean that healthy sardines caught commercially or canned sardine products are unsafe to eat.
The warning comes as investigators work to establish whether the deaths are part of one connected event stretching along the South African coastline.
Sardine strandings have also been reported along Namibia’s coastline, widening the area under investigation.
An intergovernmental task team is coordinating surveillance, testing, the disposal of dead fish and assessments of the impact on sardine stocks.
The Small Pelagic Scientific Working Group is due to meet to consider whether additional management measures are needed.
For now, the full scale of the mortality remains uncertain. A clearer picture may emerge later in the year when DFFE conducts its annual hydroacoustic survey of sardine stocks.
Fears For Penguins And Marine Life
Scientists and conservation groups say the impact could extend far beyond the sardines themselves.
Sardines are a crucial part of the marine food chain and are prey for dolphins, seals, seabirds and the critically endangered African penguin.
Algoa Bay is home to one of the world’s most important African penguin colonies. Conservationists fear that the loss of sardines could intensify pressure on penguins that are already struggling to find enough food.
“The implications ‘are huge’ as lots of fish have died and this can affect the environment,” Strydom said.
Ronelle Friend, an environmental chemist with Algoa Bay Conservation, said the situation could make existing pressures on penguins worse.
“Already because of the uncontrolled fishing, penguins are struggling to get food and now with this virus killing sardines it's going to be worse,” she said.
The concern is that a large reduction in sardine numbers could affect the wider marine ecosystem, particularly in areas where predators depend heavily on small pelagic fish for food.
Craig Smith, a senior technical specialist at WWF South Africa, said the organisation was working with government and industry representatives on the response.
“We are deeply concerned,” Smith said. “In Australia the virus wiped out 70 percent of the stock. We fear this may be the first wave, with the possibility of a more deadly second wave.”
The Australian experience has added urgency to the South African investigation, although scientists have not yet confirmed that the same scale of mortality will occur locally.
Koeberg Cooling System Affected
The dead fish have already caused disruption beyond the fishing and conservation sectors.
At Koeberg nuclear power station near Cape Town, dead sardines clogged a cooling-water intake basin, forcing the national electricity utility to halve the power output of one of its two units.
The incident highlighted how a marine mortality event can affect critical infrastructure when large quantities of fish are carried into coastal water-intake systems.
Officials are monitoring the situation as further fish deaths and strandings are reported.
Fishing communities are also watching closely. Veteran Durban fisherman Bonny Adams said this year’s sardine run had already been quieter than usual.
“Now, with this virus, we don't know what to expect. We are worried indeed,” he said.
The sardine run is an important seasonal event for fishing communities, tourism operators and marine predators. Any prolonged decline in sardine stocks could affect livelihoods as well as the species that depend on the fish.
Investigation Continues
The authorities have not yet confirmed that PHV is solely responsible for the deaths.
Scientists must still determine whether the virus caused the mortality, acted alongside environmental stress or spread through fish populations already weakened by changing ocean conditions.
The presence of PHV in apparently healthy fish is also being examined as part of the wider investigation.
The results of further laboratory testing, coastal surveillance and the annual stock survey are expected to provide more information about the condition of South Africa’s sardine population.
In the meantime, the intergovernmental task team will continue monitoring the coastline, collecting samples and coordinating the removal of dead fish.
For residents who watched the sardines wash ashore, the immediate concern is visible. For scientists, the larger question is what the deaths may reveal about the health of the marine environment and the future of one of South Africa’s most important small fish stocks.
