DEAD ZONE: Thousands of dead fish wash up on Gqeberha beaches — authorities investigate

Thousands of fish have washed up dead along Gqeberha’s beaches, with sardines making up most of the deaths. Scientists are investigating whether pilchard herpesvirus, an algal bloom or sudden ocean temperature changes are to blame, while experts warn the die-off could affect marine life and the fishing industry.

Thousands of fish, mostly sardines, have washed up dead along Gqeberha’s beaches, prompting warnings not to touch or eat them as scientists investigate whether a virus, algal bloom or sudden ocean temperature shift is to blame.

Nelson Mandela Bay University Professor of Ichthyology Nadine Strydom said they strongly suspect the mortality is related to the pilchard herpesvirus (PHV) discovered in the Western Cape earlier this month.

“The [virus] has spread in the pilchard population, even though other species have been affected, but in small numbers. What we are seeing on the beaches is actually a small number compared to what lies on the ocean floor.”

Strydom said the sardine deaths would have major and far-reaching implications for the small-scale fishing industry.

“Penguins and other marine life will start starving. The government needs to start preparing and adjusting how [many] pilchards can be harvested to save the industry.”

Strydom said South Africa was experiencing what happened in Australia in the 1990s, when two large-scale mortality events were recorded in sardines due to PHV.

She said the virus was later detected in apparently healthy Australian sardine populations without causing continuous mortality.

“It took years for their marine ecosystem to recover; obviously the virus is still in their pilchard population because immunity has improved and they live with it. There’s no curing the virus, they have to live it out.”

Strydom said South Africa had been importing sardines from South America for several years and that increased shipping traffic in the Cape could provide a route for the virus to spread.

Strydom said ships would collect seawater from an area, and discharge it when they were close to a port elsewhere, “but international shipping laws dictate that the water is not to be released [inside] a certain distance, but this is not policed so they end up breaking the law”.

While tests have yet to determine the cause of the Gqeberha die-off, Wildlife and Environment Society of SA (Wessa) Eastern Cape chair Gary Koekemoer said there were three possible explanations.

“The majority of the fish are sardines, but there are also other fish; it seems it’s a huge die-off all the way from Pollock Beach, behind Something Good to Kings Beach. We think it’s a mixture of the virus that was detected in Cape Town on the West Coast, a sudden change in temperature or an algal bloom,” said Koekemoer.

“We had a massive amount of cold water recently for the last two weeks, and it could be that there’s warm water that has come into the system. Nothing has changed on the beach, but out in the current. But it’s likely the virus in combination with temperature change. Our other concern is that penguins and others live off the sardines, so it will impact them in time.”