Blackwater is the likely cause of a fish kill that has occurred in the Richmond River, at Ballina following ex-cyclone Alfred.
OzFish, Australia say they have multiple messages overnight of ‘thousands of fish gasping for air, or washing up dead, following the recent cyclone and flooding’.
OzFish CEO Cassie Price said ‘blackwater’ is the likely cause.
‘Blackwater is caused by flooding washing organic material into waterways. This strips oxygen from the water as it decomposes, suffocating fish and other aquatic wildlife,’ she explained.
Photos provided to Ozfish show dead flathead, bream, whiting, prawns and other marine life washed up on shore, and videos show dying fish gasping on the shoreline. OzFish have also received reports of mud crabs and eels walking out of the water to escape smothering.
Ms Price said OzFish volunteers are out testing and monitoring water quality.
‘The results aren’t good. Healthy water should have at least 5mg of oxygen per litre. Fish experience distress when it falls below 4mg per litre, and start to die at 2mg a litre. In Richmond River(March 16, 2025), the dissolved oxygen levels are almost nil, sitting at 0.4 mg a litre.’
Urgent action needed
Ms Price said she fears that this could repeat earlier large-scale fish kills and decimate the resilience of local fisheries.
‘Urgent action must be taken to prevent further fish kills, and build resilience into our waterways,’ she said.
Ms Price said restoring local swamplands that border the Richmond River would reduce the severity of the black water events, and fish kills.
‘Healthy swamp bordering rivers acts as a sieve, or a filter, that reduces the blackwater from entering the waterway.’
‘Restoring the Tuckean Nature Reserve to a more natural hydrological regime would mean that much of the swamp would process the flood water, so that significantly less blackwater enters the lower Richmond River after events like this.’
Get involved
She encouraged the public to record any dead fish they discover and share the information with the charity.
‘The community can capture a lot of information in a lot of places, very quickly, which is we’re calling for assistance.’
‘Record a pin drop or geo reference of your location, estimate the number of fish, take note of any key species you can identify, and take photos and videos. Send it through to us at [email protected].’
‘This data will give us an evidence base that can assist in navigating the approvals pathways to restore areas of known blackwater production, like the Tuckean Swamp.’
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