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Authorities investigate significant fish kill after once-in-50-year Victorian flooding

By Daniel Miles, Tuesday October 13, 2020 - 11:31 EDT
ABC licensed image
Thousands of fish have been found dead in the Glenelg River in south-west Victoria after recent flooding. - ABC licensed

Thousands of fish have died in south-west Victorian rivers, and water authorities say there is nothing that can be done to save them.

Victoria's shipwreck coast was inundated with rain last week, with .

The region's rivers bore the brunt of the floodwater, with river heights in

Groundwater has since subsided, with an official flood warning in the town yesterday downgraded to alert level.

However the flow-on effects from the floods are being felt in rivers right across the region.

Nothing can be done

Fishermen and recreational boaters began noticing changes to rivers on Sunday.

Normally clear rivers and estuaries have turned brown, with sleek and winding rivers expanding and bursting their banks.

Fishermen in Nelson, near the Victorian–South Australian border, began noticing dead fish washing up on the banks of the Glenelg River.

The Glenelg Hopkins Catchment Management Authority (CMA), which manages the waterway, said it was investigating the situation.

"Reports are of black bream, estuary perch, mulloway, mullet, small-bodied fish, and crustaceans dying," a CMA spokesperson said.

"We do not have a firm estimate of the numbers of fish.

"Social media posts indicate that it could be in the thousands and we have staff on the scene inspecting the estuary to gain a better understanding of the extent of the issue."

The authority was also asking for members of the public to provide them with any photos they had.

"Unfortunately, there are no remedial actions that can be undertaken," the spokesperson said.

Flooding most likely to blame

The Victorian Fisheries Authority (VFA) and the Glenelg Hopkins CMA are investigating what role recent floods have played in the fish kill.

Both groups pointed to falling oxygenation levels as the most likely cause of the fish kill.

"Our officers attended to find several hundred fish of multiple species had washed up, likely caused by low dissolved oxygen levels after recent heavy rain," a VFA spokesperson said.

Fish deaths can occur after heavy rain events, due to the de-oxygenation of water that flows downstream.

It is understood that oxygen level tests show the event was likely to have occurred naturally due to inflows of fresh water.

"As flows from upstream push the poor quality water out to sea, dissolved oxygen levels are expected to improve," the Glenelg Hopkins CMA spokesperson said.

"We are unsure how long this will take at the moment."

The Environment Protection Authority is also working with the VFA to investigate and monitor the situation.


© ABC 2020

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