Mass fish kill in NSW Northern Rivers following Tropical Cyclone Alfred
By Cathy Adams
ABC North Coast
Topic:Fish
13m ago13 minutes agoTue 18 Mar 2025 at 2:28am
Dead fish washed up on the banks of the Richmond River at Ballina.
Fish are dying due to poor water quality in rivers across the Northern Rivers region after Cyclone Alfred. (Supplied: OzFish)
In short:
NSW Department of Primary Industries has confirmed fish kills are occurring in waterways from Ballina to Crescent Head.
It says low oxygen levels in the water have occurred after recent floods.
What's next?
Authorities are preparing for similar fish kill events throughout the Clarence and Tweed rivers.
Thousands of fish and other aquatic animals have washed ashore across the NSW Northern Rivers, as floodwaters surge through the catchment triggering a fish kill.
Professional fisherman John Joblin first noticed something was wrong when he caught the distinctive smell of blackwater in the Richmond River at Wardell, upriver from Ballina.
"You can just smell the stench from the dead water coming down the river," he said.
"We have noticed about 100 dead fish in the Ballina boat harbour, and there are baby school prawns, rock prawns, and little baby white shrimp just floating on top of the water, gasping."
A man in a grey shirt sitting in front of a river with a big concrete bridge behind.
John Joblin says the recent floods have reduced water quality in the Richmond River. (ABC North Coast: Emma Rennie)
A NSW Department of Primary Industries (DPI) spokesperson confirmed fish kills are occurring in waterways from Ballina to Crescent Head.
Authorities are also bracing for similar events in the Clarence and Tweed rivers.
The spokesperson said thousands of dead fish have been identified in the Bungawalbin and Sandy Creek area, as well as throughout the mid and lower Richmond River.
At Evans Head, hundreds of fish deaths have been reported, including bream, prawns and mud crabs and many more observed in a stressed condition**.**
Low oxygen levels
The DPI spokesperson says the cause of the fish deaths is low oxygen levels in the water.
According to the NSW government, organic material washes into the river during floods and its decay consumes oxygen from the water.
If the oxygen drops to very low levels, this can cause "hypoxic" water which can be stressful for native fish and lead to fish kills.
An adult hand shows the size of a dead fish that washed up on the banks of the Richmond River at Ballina.
Mature flathead are among the fish dying in the blackwater event. (Supplied: OzFish)
Not-for-profit organisation OzFish Unlimited chief executive Cassie Price said there was almost no oxygen in the water at Richmond River after the flooding.
"We've seen oxygen go from what would normally be about 5mg per litre, and that's what fish like, right down to nil," she said.
"We were getting measurements of 0.4mg of oxygen per litre yesterday.
"So, there really is no oxygen in that waterway at the moment."
Ms Price says it is devastating to the waterway's inhabitants.
"All of our marine life that are living in this lower estuary will really be suffering," she said.
"If you're on the river today, you'll probably see dead mud crabs and mud crabs trying to get out of the water, and prawns washing up, and eels too."
Cautiously optimistic
Mr Joblin is aware of how damaging black water can be to the marine life in the river.
However, he is cautiously optimistic it won't be as bad as a similar fish kill in 2001, when flooding caused one of the largest fish kills in the state's history.
A NSW Department of Primary Industries report said the economic impact of that event was severe.
"These impacts particularly lost revenue from cancelled visits by tourists, affected bait and tackle stores in particular and other businesses such as motels, caravan parks, service stations, seafood outlets, fishermen's co-operatives, boat hire and maintenance businesses," the report noted.
A dead fish floating on the surface of the water in the Richmond River at Ballina.
Dead fish are floating in the Richmond River at Ballina. (Supplied: OzFish)
Meanwhile, Ms Price said to help maintain a stronger fish population, fishers should always release mature female fish if caught.
She said returning the functionality of wetlands was key to preventing fish kills in the future.
"We have beautiful floodplain wetlands, like the Tuckean Swamp, and the management of those is something in the long term that we can improve to make sure the frequency of these fish kill events aren't happening as much as they are now."
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Posted13m ago13 minutes agoTue 18 Mar 2025 at 2:28am
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