APC conservation biologist Melody Serena said there have been a number of sightings of platypuses in regional waterways and recent surveys by the APC at Campbells Creek found that numbers had nearly doubled since 2001.

"Although platypus have declined in some places, they have remained common in others," Dr Serena said. "As far as we're aware, there is no reason to believe they are on the brink of extinction.

"As part of a survey last year, we captured seven animals compared to 2001 when we only captured four. So the numbers can go up as well as down. Last spring we (also) had a very reliable report of 30 platypus seen along two kilometres of Goulburn River near Alexandra."

UNSW Centre for Ecosystem Science Gilad Bino said action was needed to ensure the platypus didn't disappear from Australian waterways.

"There is an urgent need for a national risk assessment for the platypus to assess its conservation status, evaluate risks and impacts, and prioritise management in order to minimise any risk of extinction," Dr Bino said.

Dr Serena said the Campaspe and Loddon rivers provide important habitats for platypuses.

"Fortunately, there has been a lot of work done by a lot of people to improve platypus habitats," she said. "People have done a fantastic job and the animals are responding."