Wildlife in and around the Makotuku Stream seems to have fared well after the September 27 diesel spill that contaminated the water.
Department of Conservation staff conducted a walk-through survey of the upper reaches of the stream shortly after news of the spill broke and found that creatures there were coping.
An estimated 15,000 litres of diesel spilled down Mt Ruapehu and into the stream when a pipe disconnected from a tank on the Turoa skifield. The contamination has meant Raetihi's town water supply has been turned off since October 2.
Dave Conley, partnership ranger at DoC's Tongariro office, said a team conducted a walk-through survey of the Makotuku Stream on October 5. While it was early days, initial observations were encouraging.
"Our concern was particularly in regard to any whio which may live on the Makotuku," he said.
"Clearly diesel was still present in the stream, with vapour present and visible slicks or sheens on slower sections of the river.
"However, we didn't observe any obvious impacts on the fish, insects or birds on the river. Invertebrates were present and alive, including mayfly nymphs and caddis fly larvae, although in very low numbers."
He said only one whio, or blue duck, was encountered by the team and appeared to be in good health as it was observed to be active and capable of flight.
"Given their ability to fly, we suspect any resident whio would most likely fly off to unpolluted water and only return once the pollution has dissipated."
Mr Conley said there may have been impacts on the stream staff were unable to observe and that further surveys would be required to assess longer term impacts.
"At this stage things look as good as could be expected. From here on the department will continue to monitor the situation, but our immediate involvement is scaling back."
He said the department's role during the spill had largely been one of supporting both Horizons Regional Council and Ruapehu District Council in mitigating the effects of the spill.
"The department has offered advice and support where we can ... and has been supporting them in any way we have been able, with labour and other help."