The sudden mass "spawning events" of the European species introduced more than 100 years ago have alarmed some farmers in the NSW Riverina and spurred an irrigation group to call for urgent action.

While farmers closer to the Hume Dam have not reported major problems, further out west graziers are concerned about water for livestock being contaminated when the masses die, and fish bodies clogging irrigation pumps.

Irrigators have released shocking footage of creeks brimming with carp, raising fears of an impending ecological disaster.

NSW Irrigators' Council chief executive officer Claire Miller said the impact of carp on habitat and water quality "is one of the greatest ecological threats to native fish recovery and healthy rivers in the Basin".

"The number of carp spawning is jaw-dropping," Ms Miller said. "It looks like the water is bubbling."

"We call on the authorities to act promptly.

"Carp control is essential to avoid these floods leaving a lasting legacy of ecological degradation for years to come thanks to carp in plague proportions."

Moulamein irrigator Jeremy Morton, who released footage of a drain on his NSW Riverina property throbbing with spawning carp, said it was the biggest proliferation in 50 years.

He said as well as being hazardous for water supplies for livestock, they also competed with native fish for food sources.

"They tend to follow the water when it floods, so this is happening on people's properties - the flooding has brought perfect conditions," Mr Morton said.

"From a farming point of view, the numbers are enormous, so when they die, you get water quality issues for livestock

"For those that are pumping water, they block all the pumps up. The bigger issue is the environmental damage."

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Future Fisheries Veterinary Service director Matt Landos described carp as a "premium surviving fish" taking advantage of poor quality water.

"Carp are in fact a superlative animal in terms of their biological ability to survive," Dr Landos said.

Unlike native species, carp thrive in heavily contaminated and changed environments like the toxic waters caused by polluted runoffs in the Murray Darling.

"If you put a carp in a tank and you put a native fish like a golden perch or silver perch in a tank and you lower the oxygen level down, the native fish will die first," Dr Landos said.

Therefore, the reportedly large number of carp seen in the flooded region are less reflective of a "plague" and more of "normal aquatic productivity".

"What you're now seeing is the consequence of poor land management and poor water management," he said.

"That's why you're seeing the carp - they're the last man standing in a polluted river."