NSW DPI to investigate fish kills at Menindee

These Murray cod were pulled from the Darling after one of the recent fish kills. NSW DPI says their otiliths will be extracted to see how old they were and help improve their future management.

THE NSW Department of Primary Industries (DPI) and WaterNSW are investigating a large fish kill at Menindee in Western NSW.

In recent weeks fish kills have occurred in the Namoi River below Keepit Dam, the Lachlan River at Wyangala Dam and also in the the Darling River at Menindee in a separate event in December.

DPI Senior Fisheries Manager, Anthony Townsend, said fisheries officers have visited the affected area downstream of Menindee today and are investigating the incident.

“The ongoing drought conditions across western NSW have resulted in fish kills in a number of waterways recently and today our fisheries officers have confirmed a major fish kill event in the Darling River at Menindee affecting hundreds of thousands of fish, including golden perch, Murray cod and bony herring,” Mr Townsend said.

“After a very hot period, a sharp cool change hit the Menindee region over the weekend, with large temperature drops experienced.

“This sudden drop in temperature may have disrupted an existing algal bloom at Menindee, killing the algae and resulting in the depletion of dissolved oxygen.”

The incident follows an earlier fish kill in December, after intense rainfall events following hot weather, which disrupted algal blooms resulting in low dissolved oxygen levels conditions that exacerbated water quality for already stressed fish.

During the December event investigations by District Fisheries Officers from DPI revealed over 10,000 fish mortalities along a 40 km stretch of the Darling River, including numerous Murray cod, golden perch and silver perch, and native bony herring.

Mr Townsend said preliminary investigations by DPI into the current fish kill event suggest that hundreds of thousands of native fish have been impacted in the same stretch of waterway and further downstream.

“As a result of this incident, DPI will take this opportunity to learn more about our native fish to help improve their future management,” Mr Townsend said.

“Our fisheries experts are extracting otoliths (or the ear bone) from some of the Murray cod killed during the event to improve our knowledge of the species.

“Otoliths allow us to work out how old a fish is and can be used to help establish age and length/weight relationships, as well as potentially unearth other secrets including where the fish was born and spent its life through microchemistry work.

“All of this new knowledge will help improve how we manage waterways and the fishery across the entire Murray-Darling Basin to help protect and improve native fish populations when conditions improve.

“Fisheries staff would like to thank local anglers and residents who have provided information.

“The current low flows and warming temperatures are likely to pose an ongoing threat to native fish throughout the summer.”

WaterNSW is continuing to monitor water quality throughout the dams and river systems.

Adrian Langdon, WaterNSW executive manager of systems operations said regional NSW is experiencing intense drought conditions, with the state’s Central West, Far West and North West regions the worst affected.

“Algal alerts have been in place for several weeks in the Menindee region and linked to this, low dissolved oxygen levels are likely to occur within slow flowing or no flow sections of the river,” Mr Langdon said.

“It is almost certain these impacts will persist and possibly increase further as summer proceeds if we don’t receive significant rainfall to generate replenishment flows.”

Community members are encouraged not to be alarmed and to report any similar incidents or observations through the Fishers Watch hotline on 1800 043 536.

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