Fish kills in NSW

What are fish kills?

Fish kills are defined as a sudden mass mortality of wild fish.

Fish kills can occur at any time although data indicates fish kills are more likely to occur in summer or following sudden changes in temperature.

Recent reports of fish kills are included in the table below and we will update the table as we receive reports.

Some of the key causes of fish kills are outlined in the information below.

Blackwater

Blackwater occurs naturally over time when leaf litter and woody debris build up on the floodplain and then get washed into the river system during a flood. It’s an important part of the aquatic food web as it provides food for insects which feed fish, frogs and other aquatic wildlife.

When there is a prolonged dry period, the leaf litter and organic matter on the floodplain builds up until the next flood event. This can result in a significant amount of organic matter returning to the river with any big flushes of water after prolonged drought, making blackwater events more likely.

Hypoxic blackwater

When there is a lot of organic material washed into the river, its rapid decay can consume dissolved oxygen from the water. If dissolved oxygen drops to very low levels, this can cause ‘hypoxic’ water which can be stressful for native fish and can lead to fish kills.

More information on blackwater can be found on the MDBA website and in this factsheet by DPIE Environment, Energy and Science (NSW DPIE EES).

To notify the department of potential blackwater events email waterqualitydata@dpie.nsw.gov.au or to report a fish kill, contact the Fishers Watch Phoneline on 1800 043 536.

Bushfire impacts on native fish

Find information on the impacts of bushfires on native fish.

Stratification?

Stratification is when the surface of the water heats up more than the deeper water. That warmer layer tends to be warm and well-oxygenated compared to the deeper water that is colder and oxygen-depleted.

Thermal stratification

De-stratification ("Turn over")

Simple things you can do

• Be on the lookout for any changes in water quality - i.e. changes to the colour or odour of your local waterway and report them to us via the Fishers Watch Phoneline on 1800 043 536.
• Contact us on the phoneline if you observe any dead fish or fish starting to gasp at the water surfaces.

Investigating and reporting

• Protocol for investigating and reporting fish kills

Vertessy Report Recommendations – Fish Deaths

• March 2023 Progress Update

2023 Fish deaths in the LDBR: summary of available Fisheries data

• July Report

Lower Darling-Baaka Recovery Reach Fish Community Monitoring report (August 2023)

• The primary objective of the Lower Darling-Baaka Recovery Reach research was to evaluate the status of the fish community in the LDBR following the 2018 – 19 fish kills and track the trajectory of the fish community, including in Menindee Town Weir Pool and the LDBR downstream of Weir 32.
• Varied responses were observed in species abundances in the study reaches, attributed to the various life-history traits and reproductive strategies of native fish.
  • The abundance of some native fish species in the LDBR has declined (in comparison to data collected since 2019) following the fish deaths events of early 2023.
  • Murray Cod and Golden Perch abundance has declined in comparison to previous data collected since 2019.
  • There were consecutive years of Murray Cod spawning in the LDBR between 2020-2021 on the back of water for the environment delivery.
  • Carp were the most abundant species caught during the 2023 sampling.
• The results presented a fish community in continued stress. This is despite earlier demonstrated recovery of native fish from 2020-2022, driven by natural flows and deliveries of water for the environment to the LDBR.
• Sustained and holistic management actions are needed for native fish protection and recovery, with continued monitoring guiding and tracking the effectiveness of these actions in the region.
• With appropriate flow regimes, native fish communities will gradually recover, although catastrophic events such as fish kills related to lack of flow or hypoxic blackwater will hinder, and potentially undermine this recovery. Being long-lived, recovery of local populations of Murray Cod, Golden Perch and Silver Perch will take time.

Lower Darling-Baaka Recovery Reach Fish Community Monitoring report (August 2023)

Recent fish death events

Updated: 12 April 2024, 3.32pm

Below are the fish kills that were investigated and confirmed by NSW DPI Fisheries.

There is a current risk of widespread fish kills across parts of NSW. There may be other fish death events that have not been reported directly to DPI Fisheries. To report fish deaths please contact 1800 043 536. This page will be updated as needed to maintain currency.

1 July 2023 - 30 June 2024