The NSW government is preparing for a "horror summer of fish kills", announcing funding for a native fish rescue and breeding program to help restock waterways once the drought breaks.

Nature Conservation Council spokesman Jack Gough said the problem was the government's own making, after years of water mismanagement.

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"[Agriculture] Minister Adam Marshall deserves credit for taking action to save some fish, but this announcement is the National Party trying to stick a band aid on a gaping, self-inflicted wound," Mr Gough said.

"Successive Nationals Water Ministers have overseen a regime of over-extraction by large irrigation corporations which has undermined the resilience and health of our mighty inland rivers.

"Since coming to power, they have changed water rules to favour large irrigators, refused to acknowledge climate change and pulled millions in funding from the Murray Darling Basin Native Fish Strategy.

"Now they want credit for creating a fish zoo, rather than taking the necessary steps to ensure we have living, functioning river systems."

Earlier this week, Mr Marshall admitted "there's not a lot we can do to prevent" more fish kills this summer.

"But this new program - the largest in the state's history - will see every effort made to save and protect our native fish species and replenish stocks in our rivers and waterways when conditions improve," Mr Marshall said.

Mr Gough said the government had to look at the bigger environmental picture.

"There is a very serious debate going on within the Government right now about changes recommended by the independent Natural Resources Commission to save the Darling River and Premier Berejiklian has a choice to make," he said.

"Will she fix years of mismanagement by accepting sensible recommendations to stop the Darling River being sucked dry, or will she protect the interests of a handful of irrigation corporations at the expense of the community and the environment?"

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