Twenty "stressed" Murray Cod have embarked on a 590-kilometre road trip from the lower Darling River near Menindee in the state's far west in a bid to keep them alive and help future breeding stocks.

The Department of Primary Industries said the fish were removed from a pool immediately downstream of Weir 32 near Menindee where releases of water will stop this week to conserve drinking water for residents.

A Murray Cod being relocated by a DPI fisheries staff member at Menindee on the lower Darling River on Thursday. Credit:Graeme McCrabb

Hundreds of thousands of fish have died in the Darling River at Menindee recently in what NSW Primary Industries Minister Niall Blair described as "an environmental disaster".

DPI said the fish were going to the Narrandera Fisheries Centre "where it is hoped they will regain health for future breeding and restocking purposes that will directly benefit the native fish community of the lower Darling River".