A raft of whio, or blue ducks, discovered on rocks above a stream in the Route Burn last weekend. PHOTOS: DOC, HARLEY LAWSON

Monitoring of blue duck or whio in Mt Aspiring and Fiordland rivers has found many populations managed to survive the recent heavy rains and floods.

Department of Conservation contractor Paul Van Klink and his conservation dog Hoki surveyed the Route Burn last weekend and found six adults and 10 juvenile birds, which was on a par with previous years, he said.

Whio are one of only four duck species in the world which live all year round on fast-flowing rivers.

Doc contractor Paul Van Klink follows his conservation dog Hoki to a rock crevice where whio were found.

They nested on riverbanks and were at high risk of attack by stoats and rats but floods could also be quite devastating, Mr Van Klink said.

"If the ducklings are big enough, the parents can take them higher up to a side creek, but real heavy water can wash away nests and even kill adults."

Mr Van Klink said it was not known what would be the impact on whio of more frequent and heavy rain events because of climate change but Doc rangers had observed whio feeding from water ponding beside a track.

Whio beside a stream in the Route Burn.

He said intensive predator trapping and 1080 aerial bait drops had also helped populations survive and thrive.

Mr Van Klink this week gave a Doc-sponsored talk on whio and his search dog Hoki, who is retiring at the end of this season.