Fish kills in NSW 2019-2020

Report received of a fish kill in Lake Wyangan affecting several species of native fish including: Bony Bream (100,000s), Golden Perch, Murray Cod and Silver Perch. There were also large numbers of smaller bodied native fish including Carp Gudgeon, Australian Smelt and Unspecked Hardyhead. Staff attended the scene the following day and confirmed initial reports.

There was very limited data on the water quality in the lake prior to the fish kill. An investigation into the cause of the event was led by the Environmental Protection Authority (EPA) in collaboration with DPI Fisheries, and this found no conclusive evidence as to a single cause for the fish kill; however analysis of water samples was able to rule out localised pollution or pesticide input.

The independent analysis commissioned by NSW DPI suggested that the most likely cause of the fish deaths was the disturbance of sulfidic sediments from inflows into the lake on the day prior to the fish kill. The report contains recommendations that will assist with the future management of Lake Wyangan.

View more information, including the report by Rivers and Wetlands (PDF, 1293.24 KB), into the cause of the fish kill.

Report of up to 100,000 dead Bony Herring with approximately 30 dead Murray Cod and 45-50 dead Golden Perch.

Report coincided with the arrival of flow into the lake. Suspected cause was destratification of the upstream section of the lake, leading to initial poor water quality including a reduction in Dissolved Oxygen.

Report of several large 9dead Murray Cod.

Cause was episodic rainfall events that caused short and sharp flow in the river. This can cause a rapid reduction in dissolved oxygen levels due to large volumes of organic material entering the river system.

Report of 10 to 100 dead fish including Golden Perch and Murray Cod.

Cause was episodic rainfall events that caused short and sharp flow in the river. This can cause a rapid reduction in dissolved oxygen levels due to large volumes of organic material entering the river system.

Report of approximately 40 dead Bony Bream in the Macquarie River above the 20A Regulator.

Cause was episodic rainfall events that caused short and sharp flow in the river. This can cause a rapid reduction in dissolved oxygen levels due to large volumes of organic material entering the river system.

Report of thousands of dead Bonny Herring.

Report coincided with the arrival of flow into the Barwon-Darling River. Suspected cause was destratification of the upstream section of the Louth Weir Pool, leading to initial poor water quality including a reduction in Dissolved Oxygen.

Report of thousands of dead Carp.

Cause was episodic rainfall events that caused short and sharp flow into Burrendong Dam. This can cause a rapid reduction in dissolved oxygen levels due to large volumes of organic material entering the river system.

Report of thousands of dead Bony Herring and low numbers of dead Golden and SIlver Perch.

Report coincided with the arrival of flow into the Barwon-Darling River. Suspected cause was destratification of the upstream section of the Brewarrina Weir Pool, leading to initial poor water quality including a reduction in Dissolved Oxygen.

Report of approximately more than 100 dead fish including Murray Cod and Eel-Tailed Catfish.

Cause was episodic rainfall events that caused short and sharp flow in the river. This can cause a rapid reduction in dissolved oxygen levels due to large volumes of organic material entering the river system.

Report of hundreds of dead Bony Bream in the Mehi River.

Likely cause was episodic rainfall events that caused short and sharp flow in the river. This can cause a rapid reduction in dissolved oxygen levels due to large volumes of organic material entering the river system.

Reports of hundreds of dead fish species included Murray Cod, Golden Perch, Silver Perch and Carp.

Cause was episodic rainfall events that caused short and sharp flow in the river. This can cause a rapid reduction in dissolved oxygen levels due to large volumes of organic material entering the river system.

Reports of hundreds of dead fish on the Mooki, species included Golden Perch, Murray Cod, Eel-Tailed Catfish, Bony Bream and Carp.

Cause was episodic rainfall events that caused short and sharp flow in the river. This can cause a rapid reduction in dissolved oxygen levels due to large volumes of organic material entering the river system.

Report of approximately 100 dead fish including Murray Cod and Eel-Tailed Catfish.

Cause was episodic rainfall events that caused short and sharp flow in the river. This can cause a rapid reduction in dissolved oxygen levels due to large volumes of organic material entering the river system.

Report of hundreds of dead fish, including Murray Cod, Golden Perch and Carp.

Cause was episodic rainfall events that caused short and sharp flow in the river. This can cause a rapid reduction in dissolved oxygen levels due to large volumes of organic material entering the river system.

Report of hundreds of dead Mullet, Bream and Spangled Perch.

Suspected cause is very low levels of dissolved oxygen in the lakes, likely caused by the significant growth of aquatic vegetation such as Duckweed.

Report of hundreds of dead Beam, Mullet, Luderick and Eels.

Suspected cause is related to water quality impacts from ICOLL opening. General water quality fish kills can occur when fish and other aquatic organisms are exposed to sudden changes in the water quality.

Report of  10 to 50 dead Mullet.

Suspected cause was the bacterial infection known as Red Spot which is often displayed in fish that have been exposed to low quality water.

Report of hundreds of dead Sea Mullet.

Cause of the fish kill unknown.

Report of less than 10 dead fish, including Bream, Flathead, Mullet and Luderick.

Reduction in dissolved oxygen (DO) levels caused by a significant rainfall/flooding event, followed by hot weather, leading to discharge of large volumes of critically low DO water entering the waterway via creeks and drains.

Report of 100 dead fish including Gambusia, Catfish and Eels.

Reduction in dissolved oxygen (DO) levels caused by significant rainfall/flooding event on floodplain, followed by hot weather, leading to discharge of large volumes of critically low DO water entering the waterway via creeks and drains.

Report of hundreds of dead Bream and Mullet.

Reduction in dissolved oxygen (DO) levels caused by significant rainfall/flooding event on floodplain, followed by hot weather, leading to discharge of large volumes of critically low DO water entering the waterway via creeks and drains.

Report of dead sea urchins.

Suspected cause is extreme low tides with freshwater inundated in the area that stressed stationary animals and eventually washed them onshore.

Report of approximately 30 dead fish including Eel-tailed Catfish.

Reduction in dissolved oxygen (DO) levels caused by significant rainfall/flooding event on floodplain, followed by hot weather, leading large volumes of critically low DO water entering the Lagoon.

Report of 10-100 dead fish including Mullet.

Reduction in dissolved oxygen (DO) levels caused by significant rainfall/flooding event on floodplain, followed by hot weather, leading to discharge of large volumes of critically low DO water entering the waterway via creeks and drains.

Report of thousands of dead fish including Sea Mullet, Dusky Flathead, Luderick, Bass, Sand Whiting and Yellowfin Bream.

Reduction in dissolved oxygen (DO) levels caused by significant rainfall/flooding event on floodplain, followed by hot weather, leading to discharge of large volumes of critically low DO water entering the waterway via creeks and drains.

Report of 10-100 dead fish including Bream, Mullet and Eels.

Reduction in dissolved oxygen (DO) levels caused by significant rainfall/flooding event on floodplain, followed by hot weather, leading to discharge of large volumes of critically low DO water entering the waterway via creeks and drains.

Report of hundreds of dead fish including Sea Mullet, Freshwater Mullet, Fork Tail Catfish, Herring, Bass and Estuary Perch.

Reduction in dissolved oxygen (DO) levels caused by significant rainfall/flooding event on floodplain, followed by hot weather, leading to discharge of large volumes of critically low DO water entering the waterway via creeks and drains.

Report of thousands of dead fish including Bream, Flathead, Mullet, Eel, Garfish and Leatherjacket.

Reduction in dissolved oxygen (DO) levels caused by significant rainfall, followed by hot weather, leading to discharge of large volumes of critically low DO water entering the lake.

Report of hundreds of dead fishing including Bream, Flathead, Garfish, Whiting, Mullet, Herring ranging from 10cm to 40cm.

Reduction in dissolved oxygen (DO) levels caused by significant rainfall/flooding event on floodplain, followed by hot weather, leading to discharge of large volumes of critically low DO water entering the waterway via creeks and drains.

Report of thousands of dead mullet deposited into Nulama Pond, Taree following receding floodwaters.

Reduction in dissolved oxygen (DO) levels caused by significant rainfall/flooding event on floodplain, followed by hot weather, leading to discharge of large volumes of critically low DO water entering the waterway via creeks and drains.

Reports of thousands of dead fish including mullet and eels.

Reduction in dissolved oxygen (DO) levels caused by significant rainfall/flooding event on floodplain, followed by hot weather, leading to discharge of large volumes of critically low DO water entering the waterway via creeks and drains.

Reports of 10-100 dead fish at creek mouth including small estuary fish and long finned eels.

Cause unknown.

Reports of hundreds of dead Mullet.

Reduction in dissolved oxygen (DO) levels caused by significant rainfall/flooding event on floodplain, followed by hot weather, leading to discharge of large volumes of critically low DO water entering the waterway via creeks and drains.

Reports of hundreds of thousands of dead fish in an ongoing event including Mullet, Bream, Estuary Perch and other small estuary fish and prawns.

Reduction in dissolved oxygen (DO) levels caused by significant rainfall/flooding event on floodplain, followed by hot weather, leading to discharge of large volumes of critically low DO water entering the waterway via creeks and drains.

Report of approximately 10 dead Mullet.

Reduction in dissolved oxygen (DO) levels caused by significant rainfall/flooding event on floodplain, followed by hot weather, leading to discharge of large volumes of critically low DO water entering the waterway via creeks and drains.

Reports of thousands of dead fish including Bream, Leather jacket and Trumpeter.

Cause unknown.

Report of thousands of dead fish including Mangrove Jack, Sand Whiting, Bream, Mudcrabs  and numerous small baitfish.

Reduction in dissolved oxygen (DO) levels caused by significant rainfall/flooding event on floodplain, followed by hot weather, leading to discharge of large volumes of critically low DO water entering the waterway via creeks and drains.

Report of approximately 10 dead fish including Mullet and Flathead and Prawns.

Reduction in dissolved oxygen (DO) levels caused by significant rainfall/flooding event on floodplain, followed by hot weather, leading to discharge of large volumes of critically low DO water entering the waterway via creeks and drains. This system is an ICOLL that has opened to the sea facilitating a drawdown of surrounding floodwaters.

Report of hundreds of dead fish including Flounder, Anglerfish, Blue Swimmer Crabs and Kingfish.

Reduction in dissolved oxygen levels due to large volumes of organic debris, sediment and bushfire ash being washed into local waterways following large rainfall events.

Report of 10-100 fish including Bream, Mullet, Whiting and Black Fish.

Reduction in dissolved oxygen levels due to large volumes of organic debris, sediment and bushfire ash being washed into local waterways following large rainfall events.

Report of hundreds of dead Mullet.

Reduction in dissolved oxygen (DO) levels caused by significant rainfall/flooding event on floodplain, followed by hot weather, leading to discharge of large volumes of critically low DO water entering the waterway via creeks and drains.

Report of hundreds of dead toad fish.

Reduction in dissolved oxygen levels due to large volumes of organic debris, sediment and bushfire ash being washed into local waterways following large rainfall events.

Report of thousands of dead Sea Urchins, Abalone and Mixed Shellfish.

Significant rainfall events occurred over a short period of time creating a high run-off that affected organisms at the shore experiencing the king low tide.

Report of thousands of dead fish including Garfish, Mullet, Blackfish, Silver Biddy, Flathead, Bream and Whiting.

Recent rainfall events have caused flooding of the backswamp system resulting in deoxygenated and low pH water, killing fish upstream and downstream of the gates.

Report of thousands of dead fish including Yellowfin Bream, Mullet, Longtail Eels and Flathead.

Stressed fish observed gasping at the water surface indicating low dissolved oxygen levels present. Cause was episodic rainfall events that caused short and sharp flow. This can cause a rapid reduction in dissolved oxygen levels due to large volumes of organic material entering the river system.

Report of approximately 150 to 200 dead fish including Mullet and Perch.

Likely cause being low dissolved oxygen within an isolated pool receiving minimal inflows.

Report of hundreds of dead fish including Eels, Yellow Eye Mullet, Sea Mullet, Gudgeons, Tandnas Catfish.

Cause was episodic rainfall events that caused short and sharp flow in the river. This can cause a rapid reduction in dissolved oxygen levels due to large volumes of organic material entering the river system.

Report of 10 to 100 dead Mullet.

Cause was episodic rainfall events that caused short and sharp flow in the river. This can cause a rapid reduction in dissolved oxygen levels due to large volumes of organic material entering the river system.

Report of hundreds of dead Mullet.

Likely cause being low dissolved oxygen within an isolated pool receiving minimal inflows.

Report of approximately 10-100 dead fish including Silver Mullet and Yellow-Finned Bream.

Investigated by EPA. Water testing revealed slightly elevated ammonia levels, this may indicate sewage overflow. Further testing was unable to confirm and levels have since returned to normal range.

Report of less than ten dead Mullet.

Likely cause is critically low dissolved oxygen related to low water levels in dam and excessive algae and aquatic weed growth from high nutrient levels.

Small event with approximately five fish affected.

Likely cause is temperature and critically low dissolved oxygen levels caused from low water level in creek and hot weather.

Report of hundreds to thousands of dead fish including Bass, Eels, Common Carp and Long Neck Turtles.

Likely cause is temperature, low – no water in lagoon and critically low dissolved oxygen.

Report of approximately a thousand dead fish. Species included Murray Cod, Golden Perch and Silver Perch.

Cause is episodic rainfall events that caused short and sharp flow in the river. This caused a rapid reduction in dissolved oxygen levels due to organic material runoff.

50 dead fish including Murray Cod, Golden Perch and Common Carp.

Cause is episodic rainfall events that caused short and sharp flow in the river. This caused a rapid reduction in dissolved oxygen levels due to organic material runoff.

Report of 10 to 100 dead Carp.

Likely cause being low dissolved oxygen within an isolated pool receiving minimal inflows.

Report of thousands of dead fish including Murray Cod, Golden Perch, Silver Perch, Bony Bream, Common Carp and Shrimp.

Cause is episodic rainfall events that caused short and sharp flow in the river. This caused a rapid reduction in dissolved oxygen levels due to organic material runoff.

Report of 30 to 40 dead fish with Murray Cod and Eel-tailed Catfish affected.

Cause was episodic rainfall events that caused short and sharp flow in the river. This caused a rapid reduction in dissolved oxygen levels due to organic material runoff.

Barwon River, Brewarrina (Jan 30)

Report of approximately a thousand dead fish. Reported species affected were Bony Bream and Murray Cod.

Cause was no inflows and drying refuge pools due to drought conditions.

Report of hundreds of dead Carp.

Cause was episodic rainfall events that caused short and sharp flow in the river. This caused a rapid reduction in dissolved oxygen levels due to organic material runoff.

Approximately 50 dead fish were reported as dead. Species affected were Murray Cod and Carp.

Likely cause is episodic rainfall events that caused short and sharp flow in the river. This caused a rapid reduction in dissolved oxygen levels due to organic material runoff.

Small fish kill affecting under 10 fish - including Golden Perch and Murray Cod.

Likely cause is episodic rainfall events that caused short and sharp flow in the river. This caused a rapid reduction in dissolved oxygen levels due to organic material runoff.

Small scale fish kill (estimate 50+) affecting Murray Cod and Golden Perch mainly (as well as lots of Carp), but Murray Crayfish also identified (no images).

Likely cause poor water quality caused by localised runoff over bushfire affected parts of the catchment.

Hundreds of fish reported dead after a rainfall event. Species affected included Murray Cod, Golden Perch and Common Carp.

Cause is episodic rainfall events that caused short and sharp flow in the river. This caused a rapid reduction in dissolved oxygen levels due to organic material runoff.

Report of thousands of dead fish affecting multiple species including Murray Cod, Golden Perch, Silver Perch, Bony Bream, Common Carp and Shrimp.

Flow had ceased in the Macquarie River in September 2019. A rainfall in the upstream sub-catchments of Bell & Little Rivers had resulted in an unregulated flow reaching Warren. The flow hitting the dry river bed mobilised thick plumes of silt and picking up significant volumes of organic debris in the river bed. This caused a rapid reduction in dissolved oxygen levels due to organic material runoff.

Report of a fish death affecting approximately 200 fish, mostly Carp and Redfin with some Murray Cod, Golden Perch and Black Fish.

Likely cause is a rainfall event that has caused short and sharp flow in the river. This has caused a rapid reduction in dissolved oxygen levels due to organic material runoff including ash and sediment from local bushfires.

Estimated that thousands of fish in varying sizes ranges have been impacted. Species affected included Murray Cod, Golden Perch and Freshwater Catfish, as well as Carp and Shrimp.

Likely cause is episodic rainfall events that caused short and sharp flow in the river. This caused a rapid reduction in dissolved oxygen levels due to organic material runoff.

Reports of 10-100 dead fish including Murray Cod and Carp.

Likely cause is a rainfall event that has caused short and sharp flow in the river. This has caused a rapid reduction in dissolved oxygen levels due to organic material runoff including ash and sediment from local bushfires.

Reports of hundreds of dead fish including Murray Cod, Common Carp and Murray Crayfish seen to be leaving the water. Fish noticed to be gasping at the surface.

Likely cause is a rainfall event that has caused short and sharp flow in the river. This has caused a rapid reduction in dissolved oxygen levels due to organic material runoff including ash and sediment.

Report of 10-100 dead fish including Mullet and Australian Bass.

Most likely cause is recent rainfall washing organic material into the river, resulting in poor water quality and very low oxygen levels.

Report of six dead Murray Cod near Wentworth.

Likely cause is low dissolved oxygen within an isolated pool receiving minimal inflows due to drought conditions.

Estimated that thousands of fish in varying sizes ranges have been impacted. Species affected included Murray Cod, Golden Perch and Freshwater Catfish as well as Carp and Shrimp.

Likely cause is a rainfall event that has caused short and sharp flow in the river. This has caused a rapid reduction in dissolved oxygen levels due to organic material runoff.

Impacts are still being seen as the flow moves downstream below Warren Weir. Flow had ceased due to operational aspects to conserve critical human needs, and as the water has flowed over the dry river bed small scale fish kills are being observed as a result of poor water quality.

Limited knowledge of a fish kill event with exact numbers unconfirmed.

Small fish kill affected four fish including Bass and Mullet.

Recent rainfall washed organic material into the river, resulting in poor water quality and very low oxygen levels for native fish.

Report of hundreds of dead fish including Mullet, Perch, Freshwater Turtles and Herring.

A rainfall event has caused short and sharp flow in the river. This has caused a rapid reduction in dissolved oxygen levels due to organic material runoff including ash and sediment from local bushfires.

Report of 10-100 dead fish affecting mainly Sea Mullet.

Cause was low dissolved oxygen within an isolated pool receiving minimal inflows.

Approximately 50-100 European Carp affected.

Suspected cause is a blue/green algal bloom amidst low inflows and low dissolved oxygen levels.

Reported fish kill affecting 10-100 Eels.

Recent rainfall washed organic material into the river, resulting in poor water quality and very low oxygen levels for native fish.

Report of approximately a hundred dead Whiting and Bream confined to a 75m area.

Likely caused by low oxygen and water levels and high salinity.

Approximately 20 dead Australian Bass and one Long Finned-Eel noted.

A rainfall event has caused short and sharp flow in the river. This has caused a rapid reduction in dissolved oxygen levels due to organic material runoff including ash and sediment from local bushfires.  This is an active fireground and Fisheries staff have been unable to gain access to the area and will be monitoring the area as access becomes available.

Report of tens of thousands dead fish, predominantly Mullet, Bass, Catfish, Bullrout, Shrimp and Crayfish.

Likely cause being low dissolved oxygen within an isolated pool receiving minimal inflows.

Report of a fish kill affecting several hundred fish including Mullet, Bream, Luderick, Herring, Garfish, Flathead and Prawns.

Likely cause being low dissolved oxygen within an isolated pool receiving minimal inflows.

Limited information about a fish kill event affecting Carp.

The cause of the event is unknown.

Reports of hundreds of dead fish including Carp, Bass and Catfish.

Ongoing currently being investigated by EPA.

Report of approximately 25 fish affected including Eastern Freshwater Cod, Freshwater Mullet, Bass and an Eel.

Most likely cause is recent rainfall washing organic material into the river, resulting in poor water quality and very low oxygen levels.

Reports of 10-100 dead fish including Freshwater Mullet, Australian Bass and Bullrout.

Most likely cause is recent rainfall washing organic material into the river, resulting in poor water quality and very low oxygen levels.

Approximately 15 Mullet and many smaller Mullet observed gasping for air.

Likely cause being low dissolved oxygen within an isolated pool receiving minimal inflows due to drought conditions.