Since ex-Tropical Cyclone Alfred tore through the Northern Rivers, there have been reports of thousands of fish dying in our waterways.

The NSW Government responded to the fish death events this week the fish deaths are the result of a series of Hypoxic water events, which occur when floodplain vegetation dies, and organic material is washed into waterways during flooding.

As this organic material breaks down in the water, it depletes the levels of dissolved oxygen. Without sufficient levels of dissolved oxygen, fish and other aquatic organisms struggle to breathe, and in some cases, this causes them to die.

Water can appear dark brown or black as the organic matter decays due to the release of dissolved carbon compounds, including tannins.

The EPA and DPIRD are working with local councils to manage clean-up actions in key locations where fish deaths have been reported.

As part of flood debris clean-up in waterways, the EPA has engaged specialist clean-up contractors to assist with the collection of dead fish from accessible riverbanks in urban areas during their search for large and hazardous flood debris.

This week, clean up contractors have been deployed in the Tweed, Clarence and Manning Rivers. Next week, clean up contractors will commence work in the Richmond River.

Community members are encouraged to report any fish deaths or water quality concerns to the Fishers Watch phoneline on 1800 043 536.