THE Glenelg Hopkins Catchment Management Authority (GHCMA) is aware of a fish death event in the upper Wannon River.

Blackwater and low dissolved oxygen levels in the waterways are causing stress or death of native fish in several locations.

These events are usually associated with large rain events and water sitting on the floodplains for extended periods.

GHCMA Waterways executive manager, Chris Solum, said the event was challenging but not unexpected considering recent flooding and weather conditions.

“Water quality levels, such as dissolved oxygen in the waterway is very low due to high levels of organic matter that has been washed into the Wannon River,” he said.

“Combined with warm weather, this can cause oxygen levels in the water to drop. This can harm or cause the death of aquatic species such as fish and crayfish.”

Mr Solum said Glenelg Hopkins CMA staff have been on-site to monitor rivers for water quality issues to find the extent of the hypoxic blackwater.

“Low levels of dissolved oxygen have been recorded at several locations between a 40 kilometre stretch of the upper Wannon River including the Cavendish area where dead fish and yabbies have been witnessed,” he said.

The scale of the rain events that occurred in late October means water quality will not improve quickly as water will take time to flow off the flood plains.

Any fish death event in Victoria should be reported to the Environment Protection Authority on 1300 372 842.