Colloquially referred to as a hypoxic blackwater event, the deaths are a direct result of flooding.
The Edward Wakool Angling Association and its members have said while some mitigation processes are in place, more deaths are inevitable.
Well known local angler Ian Fisher said despite flushes into the system, he is expecting a repeat of 2016.
During the 2016 flood, fish and crayfish were dying in large quantities behind his business on Davidson St, and in other parts of the river.
“One of the good things this time around is that they have opened the Edward Escape, which seems to be mitigating some of the impacts of blackwater,” Mr Fisher said.
“We’ve already had reports of fish deaths at Conargo and in the Yanco.
“I have been taking dissolved oxygen levels myself, and they have been dropping.
“I went out on Sunday and the DO was 6.5 at the escape and 4.3 in the main part of the river.
“It’s when it gets under two we have a real problem.”
At the time of going to print yesterday, the DO level in the Edward River at Deniliqun was 1.6.
“We have a slight improvement on 2016 with the fish refuges, but there’s not much that can be done to prevent these deaths - this is a naturally occurring event,” Mr Fisher said.
“We just ask that people report any death of fish or crayfish in distress to the authorities.”
The NSW Department of Primary Industries (DPI) Fisheries has already launched a rescue and relocation operation to save Murray crayfish impacted by poor water quality.
Their efforts are particularly focussed on the Murray River at Echuca and Swan Hill, but also other parts of the Murray, Barwon-Darling, Murrumbidgee, Edward-Wakool and Lachlan catchments.
DPI Fisheries deputy director general Sean Sloan said the rescued crayfish will be transported to Narrandera Fisheries Centre for safekeeping until conditions improve and they can be returned to the river.
Fishers and community members are encouraged to report any fish deaths or observations through the Fishers Watch phoneline on 1800 043 536.
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