The joint operation between Dubbo's Inland Waterways Ozfish program and NSW Department of Primary Industries and Fisheries helped rescue fish that were more than 20 years old and 100 centimetres in length.

Mr Hansen said it felt good to do such important work.

"As tired as we are at the moment, to be involved in the rescue was honestly a once in a lifetime experience," he said.

"But, It is so bittersweet.

"As sad as it is to see the river in such a terrible state, it's still great to know such a dedicated group of people were willing to take significant time out of their lives, annual leave or leave without pay, and cared enough to support the relocation."

Mr Hansen said experts from the NSW DPI Fisheries helped the crew assemble equipment that was critical to the mass fish rescue.

The expert angler said operations like this could be the way forward to reducing fish kills.

"The volunteers were up to their elbows in mud, doing 13 hour days, and the whole time they had expert NSW DPI fisheries staff right beside them in the field leading the way," he said.

"It was like nothing I've ever seen.

"It's great to know we have breeding fish tucked away safely for the future, with the remnant population staring down the barrel of a scorching summer, with many unfortunately predicted to perish."

The operation used techniques like electrofishing to capture and move a significant number of native fish which were subsequently resettled into a refuge to survive the harsh weather conditions forecast for this summer.

Mr Hansen said the operation was possible due to the enormous amount of volunteer hours worked.

"There were more than 1090 volunteer hours involved and more than 12,000 kilometres driven by the people who often shuttled fish more than 100 kilometres in a single run," he said.

"By anyone's measurement that was a massive effort.

"Without our local habitat unit, Samantha Davis and her team, this operation would not have been possible."

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