Menindee Main Weir has become the scene of a mass fish kill as the consequences of the major flood event seen in that region continues to cause problems.
Locals are pointing out this fish kill situation is nothing like the more serious 2019 and 2020 episodes which saw mass die offs due to low water and oxygen levels, with more than one resident telling us this time around was, “a storm in a teacup”.
The problem is down to the large number of carp that have found their way into the system following the deluge of water earlier this year. The number of carp has led to low oxygen levels in the water.
Professor Richard Kingsford, Director of the Centre for Ecosystem Science at the University of New South Wales, told us, “the carp numbers have really exploded and when there’s lots of areas for them to get into, they’re just very good at doing that and it may be that oxygen levels are dropping a bit and obviously, if they haven’t got oxygen in the water, they’ll die.
“All of those little carp have hatched out of this big flood and are now spreading out wherever possible, and they are stopping there at the weir so you just get them stacking there,” Professor Kingsford.”
There is also the issue of water quality.
“If they die in the water, they’re obviously going to decompose and there’ll be lots of bacteria and that’s happening. It is likely you’ll get a spike in those sorts of bacteria in that system as well,” Prof Kingsford said.
Local wildlife photographer Geoff Looney doesn’t think it is too much of a big deal – he’s one of those calling it a “a bit of a storm in a teacup.’
“It is just that they have turned the flow off. Just stopping the water dead like they did is probably why it is happened,” Mr Looney told the Barrier Truth.
WaterNSW told us they had increased monitoring at Menindee Lakes in recent months to track water quality impacts due to prolonged flooding in the region.
“The work is part of a multi-agency government initiative to monitor the impacts of regional flooding, which typically results in reduced oxygen levels as floodplain water flows back into the river channel.
“Recent results indicate that while dissolved oxygen levels have fallen at key monitoring points within the lakes, the area of most concern at this stage is Lake Wetherell in the vicinity of the main weir,” a WaterNSW spokesperson said.
A NSW Department of Primary Industries (DPI) spokesperson told us, “we have received reports of fish death events within the Lower Darling-Baaka, including below Menindee Main Weir. It is estimated that thousands of fish, predominantly Carp and Bony Herring have been affected, with smaller numbers of Murray Cod and Yabbies also impacted.
“Fish deaths are likely related to low dissolved oxygen levels as flood waters recede. High levels of nutrients draining back into the river channel in recent weeks has impacted water quality throughout the system including in the upper Menindee Lakes.
“The current hot weather in the region is also exacerbating the risk of low oxygen levels within the Menindee Lakes.
“DPI are working with water management agencies to consider options to improve the quality of water released downstream of the Menindee Lakes System. DPI will continue to work with NSW and Commonwealth agencies to monitor the water quality and conditions.”
