River fix a must for platypuses
Long-term work to reverse degradation dating back to European settlement looms as the only way of re-establishing a platypus population in the upper reaches of the Wimmera River.
Even then the prospect might be difficult, considering platypuses are notoriously sensitive.
That’s a general assessment of a waterway officer based on data that suggests the monotremes are in the grip of localised ‘functional’ extinction north-east of Ararat.
Wimmera Catchment Management Authority project and planning officer Greg Fletcher said research based on animal DNA in water samples had all but confirmed fears.
“EDNA sampling results, based on cells animals shed into the water, have gone a long way to confirm suspicions that the Wimmera River’s upper catchment no longer has a self-sustaining population of platypuses,” he said.
“The information tells us there is a critical a lack of genetic diversity.
“This, combined with the absence of any definitive sightings and captures, leads us to an obvious conclusion.
“That’s not to say there is not an odd individual there, but if they are, they are very sparsely populated and there is probably not enough genetic diversity for the species to repopulate the area.”
Isolated population
Mr Fletcher said the circumstance differed to Mackenzie River, to the north-west and on the other side of the Grampians, where researchers were seeing evidence of platypus-population recruitment.
“In that circumstance there remains a small and isolated but self-sustaining population,” he said.
Mr Fletcher said the reality was for any translocation or repopulation of platypus to the Wimmera River’s upper catchment to be successful, the river had to first be ‘fixed’.
“These animals are also very tricky to breed in captivity and it would be pointless putting them there anyway if they had no way of surviving. We need to ensure there is habitat for them,” he said.
“We’re talking about decades of riparian damage and hillside clearing that has led to waterway sedimentation and ultimately what we’re seeing today.
“It can’t be fixed overnight, but in saying that, that’s what we’re attempting to do in partnership with communities.
“It is times like this that what we’re doing in trying to understand and mitigate environment waterway issues, that everything becomes obvious.”
EnviroDNA, in partnership with Project Platypus Landcare network, collected samples at 35 river sites during the studies.
Data has also revealed a serious decline in other river species in the area, including ‘bioindicating’ freshwater blackfish.