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Environment Protection Authority

Natural causes likely responsible for fish kill in Ramsgate

Media release: 30 May 2016

Final tests have found that a recent fish kill in Ramsgate likely occurred because of an infrequent, but natural process of inversion which caused low dissolved oxygen levels in the water. These results come after tests found water taken from the Tonbridge Reserve (known as Scarborough Ponds) was not toxic and contained no contaminants.

Inversion occurs when strong winds, rapid temperature change or a large volume of cold water causes a pond to turn over. The upper layer of water is replaced by the lower layer of oxygen-deficient water. Usually this turnover of water also stirs up the fine, bottom layer of sediment which continues to deoxygenate the water. This deoxygenated and disturbed water is known to result in fish kills, similar to that experienced recently in Ramsgate.

In this instance, it’s likely the inversion was caused by broad temperature shifts between day and night, coupled with a large tidal cycle bringing in cold, salty water into the ponds.

Greg Sheehy, Acting Director of Metropolitan Branch, thanked Rockdale City Council, NSW Department of Primary Industries and the community for their cooperation.  

“Throughout this investigation we received some great information from local residents through our Environment Line,” Mr Sheehy continued.

“If you have concerns about the environment, you can call the Environment Line 24 hours a day, 7 days a week on 131 555. You can also find the answers to many frequently asked questions at our website by visiting www.epa.nsw.gov.au/AskEnvironmentLine.”  

Contact: EPA Public Affairs

Page last updated: 30 May 2016