2021 January: Dead fish, yabbies, aquatic life (Cohuna, Vic). Pesticide: Acrolein

Fish, yabbies and aquatic life dead after ‘toxic’ herbicide treatment in irrigation channel


Mal Johnson isn’t happy. The Cohuna farmer has spent the past few days cleaning up dead fish and plants from an irrigation channel on his property near Cohuna in northern Victoria.

“I walked up onto the channel bank, looked into the water and there was just a foot-wide stream of fish, all dead,” Mr Johnson said.

The Torrumbarry Irrigation Channel was injected this week with the toxic herbicide Acrolein to get rid of weeds that are blocking up the system that provides water to more than 100 farming properties in the region.

“I’ve walked up here several times in the last few days, and I go home and say why? Why does this keep on happening to our environment? It’s just not fair,” Mr Johnson said.

Murray Goulburn Water (MGW) notified irrigators about the herbicide treatment and told them not to use water from the channels for 72 hours afterwards.

Water full of dead fish is meant to be safe

But three days later, Mr Johnson is still removing dead fish from the water.

“This channel is meant to be safe to use today,” he said.

But he’s concerned that the dead fish and plants in the water may cause botulism in cattle.

GMW assistant manager Tim Nitschke said the water was safe for use.

“I’m extremely confident that it is safe,” he said.

“There have been many, many studies done on this product. We’ve also done multiple and extensive water quality testing programs to demonstrate that,” he said.

Mr Nitschke said fish kills were to be expected during the herbicide treatment, but there was no alternative.

Outdated herbicide kills endangered species, ecologist says

“Acroelin is our last resort,” he said.

“We don’t use it as our ‘go-to’ product, but it’s something we use when we have no other options.”

But ecologist Damien Cook said Acrolein is an outdated herbicide from the 1960s and is killing endangered species like the growling grass frog.

“It was once described as the most common species of frog — now there’s only one population that we know of in the area,” Mr Cook said.

“One of the reasons it’s declined is herbicide use, and chemicals in the environment.

“The frog has gone from being one of the most common species to now being endangered.”

Mr Cook said although the Torrumbarry Channel was an artificially constructed irrigation network, the channels remained an important habitat for aquatic life along the Murray-Darling Basin.

Weeds blocking irrigation channel

But Kerang farmer Geoff Kendell said the weeds are causing headaches along the channels and need to be removed.

“Goulburn Murray Water will ring us up and say ‘What’s wrong? You’re supposed to be having 20 megalitres coming out of the channel, and you’re only getting three out,'” he said.

“It’s the weed that’s causing the problem.”

But Mr Kendell said Goulburn Murray Water should have taken a proactive approach, rather than a reactive one.

“They should have dried the channels and the creeks out in winter and allowed the frost to kill most of the weeds,” he said.

Mr Nitschke said that idea was under consideration.

“GMW is definitely looking at de-watering our network more regularly,” he said.

“There are losses associated with that, but we’re trying to find that right balance — making sure we still provide irrigation water to our farmers so that they can produce food and fibre.”