Environmental DNA testing of the creek in May showed it was home to giant kokopu, longfin eel, redfin bully, and other native species, Otokia Creek and Marsh Habitat Trust secretary Matthew York said.
Mr York took samples for the test as part of the Environmental Protection Authority’s Wai Tuwhera o te Taiao community science programme.
The trust has raised concerns about a proposed landfill in the Brighton area that could affect the creek’s headwaters.
What the testing showed was that the creek was "actually tidying itself up", Mr York said.
The whole of Brighton was on a septic tank system when he was a child, but moved to a reticulated sewerage system about 40 years ago, he said.
The creek then started showing signs of improvement from about the mid-1990s, he said.
Now, despite a lifetime playing in and along the creek, Mr York only learned there was redfin bully present when the results of the test came back last month.
And yet he said he knew of other species in the creek that had not been detected in the sample he sent to Wilderlab in Wellington about five weeks ago.
"Further up, I know there are freshwater crayfish in the creek," Mr York said.
But the snapshot provided through the environmental DNA testing did not show the species, he believed, because the sampling he did was during a low-flow period.
And the freshwater crayfish were found much further, about 4km, up the creek.
The testing did find giant and banded kokopu, shortfin and longfin eel, and redfin bully.
The samples also returned evidence of bellbird, freshwater bivalves, snails and mudsnails.
Testing confirmed the presence of exotic species, including pests, and a strong marker for human DNA in the water as well.
Nevertheless, the results demonstrated the ecological value of the area.
"The older generation probably remember it far worse than I do, but the idea that it’s a little, dead, muddy ditch is totally incorrect," Mr York said.
The trust engaged Wildland Consultants ecologist Kelvin Lloyd to prepare a five-year biodiversity plan to inform its restoration work, he said.
In a submission to the Dunedin City Council’s 10-year plan process under way, trust chairman Simon Laing said the trust remained deeply concerned about the lack of clear steps the council would take to reduce waste and the impact of its proposed landfill site on the creek.
