Bushfires are an extreme weather event that present a threat to the natural environment and this extends to our native fish populations during and also many years thereafter.
During a bushfire, water temperatures can reach lethal levels, causing localised fish kill events, particularly in small water bodies, e.g creeks and pools.
For fish that survive the bushfire, loss of vegetation and large amounts of ash on the ground present additional risks.
The lack of vegetation allows rainfall over recently burned areas to wash ash and sediment into waterways. This creates murky water and sudden drops in dissolved oxygen which causes fish to suffocate or be very stressed. Bushfire ash is made up of organic material that supports rapid bacterial growth that quickly uses up oxygen in the water. These risks can persist until sufficient regrowth of trees, shrubs and ground cover prevents ash and sediment entering the water.
Loss of trees, shrubs, and ground cover along a riverbank can cause rivers to heat up and increase runoff and sediment entering waterways. Along with the loss of vegetation, is the loss of insects which are a common food for many fish. Lack of food and habitat can have lasting impacts on the recovery of native fish populations.
Native species have evolved to survive severe short-term weather events such as bushfires, however they have a long road back to recovery. The NSW Government is planning the restocking of rivers impacted by drought and bushfires along with ongoing efforts to restore river health and habitat.
If you live in an area that has been affected by the bushfires, keep an eye on your local waterways and report any fish kills to the Fishers Watch Phoneline on 1800 043 536.
For more information on bushfire impacts on waterways, have a read on The Conversation.