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Dead fish choking reserve
27/12/2006 11:05 - (SA)
Cape Town - The Rietvlei Wetland Reserve has been closed after thousands of dead fish washed up on its banks, said the City of Cape Town on Wednesday.
Spokesperson Dalton Gibbs said: "More than 10 tons of fish are estimated to have washed up along the 3km banks of the wetland water."
Test results are expected on Thursday from the city's scientific services.
Dalton said: "The reserve is used for recreational purposes and poses no threat to drinking water in the surrounding Table View and Flamingo Vlei residential areas."
Indications are that the freshwater and estuarine fish died from a combination of factors.
Being dumped at Visserhok
High nutrient levels coupled with recent calm conditions and high temperatures had resulted in high bacterial activity which had depleted oxygen in the water.
Officials from the city's disaster risk management and nature conservation had removed four tons of the fish.
Species that washed up included flat-head mullet, harder and carp.
The dead fish are being taken to the Visserhok landfill site.
The reserve's deep-water lake had no outflow to the sea for most of the year, said Gibbs.
Run-off from the Diep River catchment area and storm water, carrying excess nutrients, from residential areas had flowed into the wetland for the past 30 years.
Bacteria in the water broke down nutrients, but used oxygen to do so.
"Large quantities of nutrients and high temperatures have depleted oxygen levels in the water," said Gibbs. "As a result, the gill-breathing organisms suffer from the lack of oxygen."
Volunteers are needed for the clean-up, said Gibbs. They can contact the city's disaster management centre on 021 597 5000.
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