Multiple fish kills in the Richmond River estuary, including Wardell yesterday, are the result of low oxygen levels in the water following the recent flooding say Rous County Council (RCC).
‘Down at North Creek in Ballina and there were dead fish everywhere on Monday along the high tide line,’ said Chair of the RCC, Ballina councillor Kieth Williams.
‘During the 2008 fish kill, North Creek was habitable and provided safe haven for many fish. However, it doesn’t look like that’s going to happen this time.’
Water running off these low-lying area of the floodplain is low in oxygen, forming what is commonly known as Blackwater. As the flood mitigation authority RCC have been monitoring water quality after recent flooding in these areas of the floodplain.
‘Blackwater is created from plant matter breaking down or rotting in floodwater,’ said Andrew Logan planning manager at RCC.
‘Blackwater contains little or no oxygen, is dark in colour and has an unpleasant smell.’
The organic matter in Blackwater can consume large amounts of dissolved oxygen. When Blackwater enters rivers and creeks in large volumes, it can be harmful to fish and other aquatic life.
‘Council has confirmed that dissolved oxygen levels are now critically low in parts of the estuary’ said Mr Logan. ‘A dissolved oxygen level of 1.5mg/L was recorded yesterday at Woodburn and 1.1mg/L at Wardell in the main river channel.’
Multiple fish kills have taken place within the estuary including North Creek last weekend, and Wardell yesterday.
According to RCC the blackwater conditions are expected to continue until floodwaters leave the lowest lying areas and normal tidal flows resume. However, the speed at which this takes place this will depend on weather conditions in the coming weeks.
Community members are encouraged to report any fish deaths or observations through to DPI at the Fishers Watch phoneline on 1800 043 536.
Rous County Council is working closely with the Department of Primary Industries and Ballina Shire Council to monitor the event.
‘Many Ballina Shire residents have already observed the negative impact this event is having on fish and aquatic life in the lower estuary areas of the Richmond River.,’ said Mr Logan.
‘Ballina Shire Council will continue to monitor local foreshores and beaches to ensure public safety. Residents are encouraged to contact Ballina Shire Council on 1300 864 444 if they are concerned about a particular public area, which may require cleaning up.’