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Endangered, culturally significant southern pygmy perch back from the brink in Murray River

By Sophie Landau
two men in the wetland waters doing fish monitoring
The southern pygmy perch has returned to the Murray River in numbers not seen since before the Millennium drought.(Supplied: Scotte Wedderburn)

Land and water stakeholders are overjoyed to find a threatened perch species returning to the lower lakes of the Murray River in record numbers.

The southern pygmy perch has been under the microscope since the Millennium drought, when a reduction in flow coming through the river system put the golden, 7-to-8-centimetre fish at risk.

The lake levels became so low that species inhabiting the lakes were stranded with a lack of food, and were preyed upon by pest species.

But in 2008, researchers from Flinders University's molecular ecology lab embarked on a rescue mission to save the southern pygmy perch, along with other threatened species.

"They only had less than 100 fish but they looked at the genetics and matched them up when they were breeding them," said University of Adelaide fish ecologist Scotte Wedderburn.

A small golden fish in water
The southern pygmy perch is an indicator species, showing the health of the wetland ecosystem.(Supplied: Dr Scotte Wedderburn)

"When the drought broke there was a reintroduction," he said.

In March, Dr Wedderburn led surveys to assess the southern pygmy perch population, as part of the Murray-Darling Basin Authority's The Living Murray Program.

He said the threatened species bounced back in numbers not seen in years thanks to environmental watering and unregulated river flows from recent rainfall.

"I think that's all built up to this really good outcome that we've seen this season," Dr Wedderburn said.

A big fish next to a little fish on a tape measure to indicate size.
The native southern pygmy perch is preyed on by pest species like the redfin perch, pictured left.(Supplied: Scotte Wedderburn)

A culturally significant species

The monitoring took place on Ngarrindjeri country around Lake Alexandrina and Lake Albert, in collaboration with the Department for Environment and Water, and the native title body, the Ngarrindjeri Aboriginal Corporation.

Chief executive Tim Hartman said the southern pygmy perch is culturally significant to the Ngarrindjeri people.

two people in the water collecting fish nets
Mr Hartman says land and water management requires "collective solutions and collective outcomes".(Supplied: Adrienne Rumbelow)

"As a First Nations community of Ngarrindjeri we have a responsibility to continue to care for our land and waters at every opportunity. Where we can actually partner and collaborate with various agencies we're always wanting to do that."

Mr Hartman said the endangered perch plays an important role as an indicator species — revealing information about the general health of the wetland ecosystem.

"If we can have conditions which are good for that particular species, that means all the other fish who use the same ecosystem are hopefully able to improve as well," he said.

"By getting freshwater flowing, it not only benefits that particular species but all the other species that utilise that same environment."

Water the 'critical thing'

Department for Environment and Water project officer Water Kirsty Wedge said in the past, only up to 20 individual new fish were found during monitoring.

A small golden fish against a ruler showing its size
Stakeholders are hopeful the endangered fish will continue to thrive with environmental water and rainfall.(Supplied: Adrienne Rumbelow)

But the latest surveys found the pygmy perch population rising by hundreds.

She hopes this trend continues into the future.

"I'd like to say by hundreds again, all underpinned by the need for water," she said

"Water really is the critical thing for these small-bodied fresh-water species."

Ms Wedge said the perch population should thrive if unregulated flows and environmental water continue to be delivered.