Ash from the summer bushfires coupled with highly acidic waterways caused by heavy rainfall could lead to some of the worst fish kills seen throughout NSW, experts say.
The NSW Department of Primary Industries recorded 31 significant fish kills in coastal catchments in February, mostly caused by low oxygen levels due to organic material runoff.
William Glamore, principal research fellow at the UNSW Water Research Laboratory, says unhealthy waterways are getting worse particularly along the NSW coastline.
Climate change is a key factor and the decline has been exacerbated by recent natural disasters.
Dr Glamore says decades of over-drainage has created acidic waters rich in toxic heavy metals but low in oxygen, leading to a high number of fish deaths including other marine species such as oysters and prawns.
“We expect the ash will also remove oxygen from the water, so if there is already a lot of oxygen coming out, we’re now seeing the ash taking anything that might have been left in there,” Dr Glamore told AAP.
He believes NSW’s recent drought has likely generated the worst acid-producing conditions ever experienced in the state, which has exacerbated fish kills.
“We certainly have seen the numbers be greater than we expected them to be.”
Restoring surrounding landscapes through revegetation is a major factor for protecting NSW waterways and is supported by the state government’s marine estate management strategy, the academic added.
“We need to encourage the state to get behind their own strategy and further support it with some funding.”
Dr Glamore says “there is a lot of talk but very little action” from the federal government in this space.