Fish kills

With drought conditions expected to continue over the coming months it is likely more fish kills will occur without significant rainfall to generate replenishment flows.

Report similar incidents

Community members are encouraged to report any similar incidents or observations: Fishers Watch Phoneline on 1800 043 536.

Identified fish kills in 2019 due to environmental conditions

Location and date kill observed

Cause and extent

Murray Darling Catchments

Darling River, Menindee (28 Jan)

Affecting approximately 30km of the Darling River from Weir 32 to Menindee main weir and upstream.

Darling River, Menindee (6 Jan)

Affecting approximately 45 km of the Darling River below the Menindee Main Weir including Menindee township

  • Both are suspected to be caused by very low dissolved oxygen levels   triggered by sudden drops in temperature that disrupted existing algal blooms   with mixing of  low dissolved oxygen   water through the water column

Hundreds of thousands of fish affected of a range of species on both occasions. Fish affected include significant numbers of Bony Herring (Bream), Golden and Silver Perch, Murray Cod and Carp.

Glenarbon Weir (Dumaresq River) (12 Mar)

Cause suspected to be very low dissolved oxygen and high turbidity.

200-300 dead fish were observed ranging in size. A number of species were affected including Murray Cod, Golden Perch and Freshwater Catfish. Carp was the dominant species affected.

Lake Inverell and downstream pool (Macintyre River) (18, 21, 22 and 30 Jan)

Suspected cause is low dissolved oxygen and deteriorating water quality

One Murray Cod confirmed dead on 18 Jan, and further reports of fish deaths along a 500m section of the lake on the morning of Jan 21.

Thousands of small fish observed on 21 Jan including Gudgeon spp, Murray Cod, Golden Perch, Freshwater Catfish, Carp and shrimp.

Further fish kills occurred in the Lake and upstream and downstream on Jan 22.

Up to 100 dead fish were reported from an isolated pool immediately downstream of Lake Inverell on 30 Jan. Species included Golden Perch, Murray Cod, Eel-tailed Catfish and Carp.

Lake Keepit (Namoi River) (9, 22, 24 and 30 Jan)

  • Low dissolved oxygen as lake level dropped and hot weather.
  • Hundreds of Murray Cod and Golden Perch affected.

Barwon River, 40km from Walgett (26 Mar)

Drying pools, low dissolved oxygen, poor water quality

Hundreds of fish, mainly Golden Perch and Murray Cod.

Bourke (Darling River) (24 Apr)

  • Drop in temperature and rainfall/inflow.

Hundreds of Bony Bream affected

Lake Burrendong (Macquarie River) foreshore (12 Jan)

  • Recent localised storm activity that produced a flow event that   contributed organic debris into the lake resulting in a sudden reduction in   dissolved oxygen levels when the organic debris started to decompose.
  • Over one thousand fish observed namely Carp and Redfin Perch with small   numbers of native fish

Lower Macquarie River, Downstream Marebone Weir, Oxley Station (5 Jan)

Suspect cause: high temperatures, low flows, resulting in low dissolved oxygen & heat stress

Small numbers of Golden Perch (10-20) and 1 Murray Cod.

Lower Murrumbidgee from Hay to Balranald (Late Dec, 9 and Redbank Weir 31 Jan)

Suspected cause is very low dissolved oxygen levels triggered by a sudden drop in temperature that mixed low dissolved oxygen water through the water column.

Small numbers of dead fish (<10) observed in Redbank Weir before Christmas 2018 and in the Balranald Weir Pool on 9 Jan.

  • Thousands of fish observed on 31 Jan including Murray Cod, Golden   Perch, Silver Perch, Bony Herring (Bream) and Carp.

Coppabella Creek (Murray River) (28 Feb)

  • Drying creek

Hundreds of Southern Pygmy Perch. 50 live fish were rescued and relocated by DPI Fisheries

Thredbo River (25 Jan)

Cause is suspected to be high water temperatures as dissolved oxygen levels were within normal ranges (6.9mg/L) and no other factors were observed/reported.

Approximately 20 Trout (Rainbow and Brown Trout) reported dead.

Billabong Creek (Murray River) (20 Jan)

Suspected cause is low dissolved oxygen and water stratification

Less than 50 fish observed dead including Golden Perch and Murray Cod.

Coastal Catchments

Belongil Creek (Byron Bay) (1 Mar)

The suspected cause of the kill is very low levels of dissolved oxygen associated with high levels of suspended sediment in the water which drained into the creek following the opening of Belongil Creek to the ocean on 26/2.

Hundreds to thousands of fish were observed including mullet, whiting, bream, flathead, mangrove jack, trevally, milk fish, luderick, puffer fish and bullrout.

Old Grevillia, Kyogle, Richmond River (23 Jan, & 9 Feb)

The cause is suspected to be low dissolved oxygen levels due to minimal river flows at the site and high temperatures.

Approximately 70 fish (mostly Mullet).

Corindi River and Pipeclay Creek, Coffs Harbour area (27-28 Jan)

Cause is suspected to be very low levels of dissolved oxygen, shallow water levels and high temperatures

Hundreds of Bully Mullet and small numbers of Mangrove Jack observed dead at these locations.

Fiddamans Creek, Emerald Beach (north of Coffs Harbour) (18-20 Apr)

Initial investigations found low dissolved oxygen levels.

Estimates of over a thousand sea mullet and over a hundred bream.

Lake Cathie / Innes near Port Macquarie (8 Jan, 26 Feb)

  • 8 Jan - Deaths suspected to be caused by low levels of dissolved   oxygen from high water temperatures and low lake water levels with no   flushing.
  • Hundreds of fish reported including Bream, Tarwhine and Whiting

26 Feb – Low dissolved oxygen.

Thousands of dead mullet, herring and bream

Crowdy Head Harbour (Mid North Coast) (19 Jan)

The cause was marine algae that washed into the harbour and subsequent low dissolved oxygen caused by the decomposing algae. The kill is likely to be a result of changing currents and tides causing significant amounts of the algae to be washed into Crowdy Head Harbour and trapping fish before they could escape.

The major species was Ceramium along with a diatom species. Ceramium can bloom in summer due to elevated nutrients associated with cold upwellings that naturally occur due to do the activities of the East Australian Current and North East winds.

Approximately 25 fish were recorded dead, including Herring and Moses Perch. All fish were less than 15cm in length. Small numbers of deceased marine worms were also observed.

Bellambi Lagoon (north of Wollongong) (approx. 15 Jan)

The cause is estimated to be rainfall during 9-12 January resulting in a natural opening of the entrance of the lagoon. Local residents report a significant lowering of the lagoon water level following the opening which may have stranded some fish.

17 mullet and 1 shortfin eel were observed dead on 21 Jan with the deaths estimated to have occurred between 5-7 days prior.

Meringo Lake, near Moruya  (13 Mar)

Suspected to be the result of lower water levels in the lake, high water temperatures and low dissolved oxygen from decaying algal material growing on exposed shoreline.

Hundreds of fish including juvenile bream, gudgeons, mullet, eel and king prawn.

Ornamental Lake, Haslems Creek, Newington (Georges River Catchment) (10 Jan)

Suspect cause: Dramatic rise and fall in temperature (39˚ to 18.2˚ overnight)

Approximately 85 Sea Mullet

Wallagoot Lake (south of Tathra) (11 Feb)

Low dissolved oxygen levels and low lake levels.

Thousands of large Snapper and Six-spined Leatherjackets

If you want to report a fish kill, please ring the Fishers Watch hotline on 1800 043 536 or refer to the fish kill investigating and reporting protocol for more details.

Water quality can have a range of impacts on fish. The impacts can be acute, resulting in fish kills, or chronic, impacting on breeding, growth and development.

A fish kill is defined as "any sudden and unexpected mass mortality of wild or cultured fish".

Fish kills are often very visible events, which cause considerable interest and concern to the public and the media because they're often perceived to be the result of pollution or contamination of waters. In fact, there are many and varied causes of fish kills, and a large proportion are due to natural events.

The range of causes of fish kills in NSW is shown below. In just under half the fish kill events, the cause is not known. Where it is known the majority of cases are caused by one of three most common causes:

  • low dissolved oxygen
  • pesticide / chemical pollution
  • sewerage discharge or other pollution.

Causes of fish kills in NSW

A chart showing the various causes of fish kills