Rivers of Hope – crayfish lead the campaign for healthy waterways

ANU biologists are helping crayfish lead the campaign for fresher waterways along the west of Canberra. 

Biologist Dr Chris Fulton and Masters student Mae Noble have spent time snorkelling in the Goobarragandra River, in the high country west of Canberra, hoping to catch a glimpse of the Murray Crayfish.

Six years ago, this was an idyllic stream of clear water gurgling over boulders, surrounded by shady trees. However, when Dr Fulton and Mae Noble arrived the trees were gone and only a muddy creek remained. Huge floods in 2012 had devastated the Goobarragandra, eroding the banks and choking it with silt.

As the pair began searching for the iconic crayfish with its distinctive white claws, their fears were confirmed. The population had plunged by 95 per cent. “The ecosystem was sitting on the edge and the 2012 flood was the catastrophic event that pushed it over the cliff,” explains Fulton.

 Although floods like the one in 2012 only happen once or twice a century, clearing of vegetation on the stream’s edge had left the Goobarragandra vulnerable when flooding came.
“Without the vegetation on the banks, the floods scour the banks. The sand and soil that should be held in place gets ripped away and deposited into the stream. The sunlight hits the stream and warms it up and it loses dissolved oxygen, which the crayfish are very sensitive to. The trees would have dropped twigs and leaves and insects which are food for all kinds of species, from bacteria up. So when you remove them it’s a triple jeopardy going on,” says Fulton.
It’s not just crayfish that have suffered. Fulton lists many species throughout the river system that are now in heavy decline, such as the two-spine blackfish, the silver perch and the Macquarie perch.