Water tests … dead fish in Sir Joseph Banks Park.MASSES of dead fish, including carp, mullet and eels, washed up dead in pools next to Botany Bay on Tuesday, possibly because of a blue-green algal bloom.
The cause is yet to be determined though, and the recent downpour has not been ruled out as a factor, with millions of litres of rainwater flowing down storm drains towards the ocean.
Ponds in Sir Joseph Banks Park, adjacent to Sydney Airport, were littered with hundreds of dead fish.
”The EPA is investigating this fish kill in conjunction with Botany Bay Council,” a spokeswoman for the NSW Environment Protection Authority said.
”The dead fish have been removed and water and fish samples have been taken by council for further analysis.”
The council said it was made aware of potential algae problems in the wetland system last year, and agreed in November to spend $137,000 cleaning up the waterway.
”[The] council is now undertaking further sampling which will test water up to 1.5 metres deep,” the Botany Bay mayor, Ben Keneally, said. ”This will determine if the cause of the fish kill is blue-green algae as originally thought, or another factor.”
Most mass fish kills take place because of low dissolved oxygen levels in water, which stops fish from breathing properly.
This can be caused by floods of muddy water entering rivers or lakes, or algal blooms that soak up oxygen.
According to the Department of Primary Industries, direct water pollution by chemicals or other substances caused about 8 per cent of reported fish kills in NSW in the past 30 years, but it says that proportion seems to be higher in Sydney.
The number of reported fish kills seems to have risen sharply since 2000. In the past month, large-scale kills have been recorded near Menindee in western NSW and at Jervis Bay.
It is unclear how aquatic life around Sydney will fare after the recent heatwave followed by heavy rain.
A senior environmental assessments engineer with the Department of Primary Industries, Marcel Green, said the city’s fish might even benefit from the rain.
”The nature of fish kills is almost impossible to predict because they occur at all sorts of times and conditions,” Mr Green said. ”It is usually a sudden change in conditions that can bring them on, but in the Sydney region I’m hoping it will bring a lot of fresh water in and flush through the system.”
The original release of this article first appeared on the website of Shanghai Night Net.