A sudden decline in water quality is the likely cause of the mass fish death at the Umhlali River mouth last week, according to independent test results.

KwaDukuza municipality (KDM) spokesperson Bridget Shange confirmed high levels of organic pollution and ammonia were found in a sample taken last Thursday, February 12. High water temperatures and low oxygen levels were also cited in the results, which came from a South African National Accreditation System affiliated laboratory.

Elevated levels of organic pollution means there was a high nutrient load entering the river – this could be caused by runoff containing sewage, fertilisers, decaying plant matter or other waste – which, combined with the high temperature, resulted in oxygen deprivation for the fish.

Ammonia is a chemical that often comes from sewage and waste, which is also poisonous to marine life in high levels.

“The combination of these factors can place severe stress on marine life and may result in fish mortality,” said Shange.

“Importantly, bacterial levels (E. coli) were found to be within acceptable recreational water quality limits at the time of sampling.”

The test came after thousands of fish and other marine animals washed up dead in the estuary area last Thursday morning.

A separate, unrelated mass death of about 150 fish happened at the Chaka’s Cove tidal pool last Friday.

The tidal pool incident was attributed to high water temperatures and a lack of seawater replenishment because of unusually calm sea conditions. The pool was reopened to bathing earlier today.

Shange said further tests taken on Tuesday, February 17, confirmed the water at the Umhlali River mouth posed no risk to beachgoers and the area has also since been reopened.

“The municipality will continue to monitor water quality and work closely with relevant environmental authorities,” she said.

“Further updates will be communicated should additional information become available.”

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