On the 9th of February, it was reported that an estimate of 4000 fishes were found dead along the shores of Sydney’s Parramatta River including species of flathead, whiting, herring, puffer fish, bream, and prawns along with litter. The tragic fish death was said to occur along the river from Rhodes all the way to Rydalmere which has prompted an investigation from the NSW Environment Protection Authority (EPA). On the 3rd of February, a similar incident occurred at Haslams Creek in Sydney Olympic Park (SOP) which is a tributary of the Parramatta River at Homebush Bay where thousands of fishes and prawns were found floating in the creek. Initial speculation was that legacy contamination from the remediated and managed SOP site or other local sites was to blame however, investigations proved otherwise.
Authorities believe the massive fish kill in the Parramatta River were not caused by chemical pollution but were more likely to be by natural causes. Natural causes such as low oxygen and high-water temperature are said to be the main cause of the fish death. Observations by EPA officers indicate that the low oxygen levels in the river on both occasions were caused by the recent high intensity storms that washed organic matter from the city into the waterways. Also, the elevated water temperatures may have caused the organic matter to rapidly decay using up the dissolved oxygen in the water as opposed to during the cooler months.
Stuart Khan, the director of the graduate school of engineering at the University of New South Wales, said the stormwater runoff could have been easily managed to avoid such disasters. Khan stated that if the city was designed to have more permeable surfaces like grasses, soils, or pervious pavements, stormwater runoffs would be minimized by infiltrating into the soils first, thereby reducing the amount of urban contaminants into the rivers.