The mass fish kill the boots navigable in the byron region
When too much plant material enters the waterways, the bacteria that decompose the material consume most of the dissolved oxygen available, producing swampy “black water” that smells of sewage and suffocates the mass water animals.
Reports of fish dead from tweed to Crescent Head started last Monday, said Cassie Price, CEO of Fish Habitat Charity Ozfish.
“Healthy water should have at least five milligrams of oxygen per liter,” said Price. “The fish experience anguish when it goes down below four milligrams per liter and starts to die for two milligrams per liter.”
Last week readings found levels up to 0.4 milligrams and some monitoring had returned with zero oxygen levels. Price said that the killing fish usually last 3-4 days, but this event has been eliminated unusually.
“At the beginning of last week we were talking about tens of thousands of fish. We are now talking about hundreds of thousands.”
Price said that Ozfish is monitoring another pulse of fatal black water from the under-the-skate of Bungowalbin, south-west of Balline, who is moving towards areas already affected. “If something remains to die for, the following week will happen,” he said.
The mass of mass fish have become common in the region after the conversion of the wetlands nearby in artificially drained agricultural fields, said Professor Damien Maher, a hydrobiogenic specialist of the Southern Cross University of Lismore. The main killings of fish affected floods in 2008, 2017 and 2022.
Joshua McPherson of the Lismore Council helps to clean up the killing of the fish in Balline.Credit: Danielle Smith
Part of the problem is a vast drainage network carved through the tucke marsh, which is located 25 kilometers upstream from Balline.
The 6000 hectare area was once one of the largest Australian wetlands and known anecdotally like the “southern Kakadu,” said Maher.
But over the decades the wetlands were drained and the plants tolerant of floods were replaced by crops, sugar cane and grazing grass.
“As soon as those plants are underwater, they begin to die, break down and consume oxygen,” said Maher, who studied the killing of the fish in the area for years.
The Tuckea swamp is located 25 kilometers from Balline and is a source of black water after floods.Credit: Priority study of the Alluvial Plain of Richmond, Unsw
The drainage system means that the water in black water impoverished of oxygen quickly rushes into the main waterways such as the Richmond river, unleashing the killing of fish. The possible solutions include the removal of the exhausts and the restoration of the wetlands.
“Firm it is possible to keep the water on the alluvial plain and allow that it slowly released into the river over time, which reduces the impact in terms of killing of fish,” Main said.
“But it is a complicated question in terms of social, political and economic pressures. We have people who earn a living from agriculture on the alluvial plain. It is not as simple as filling the discharges.”
Ozfish is looking for the best way to manage and restore wetlands.
More fish deaths could reach the end of this week.Credit: Danielle Smith
“The healthy swamp on the border with the rivers acts as a sieve, or a filter, which reduces the black water that enters the navigable street,” said Price.
In the meantime, the premises continue to help clean up the fish batteries in decomposition while the stink of black waters and the yeasts decay in homes through the drainage tubes.
The operator of the Council of Lismore Joshua McPherson headed to Balline during the weekend to help. He said that the Council staff and residents enamelled four tons of fish on Saturday morning.
“And they weren’t all of them. There were a lot on the bank, a lot in water.”
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