Fish brim-full of mice getting hooked out of NSW river

For every cloud there's a silver lining, and the state's anglers may have found one for the ongoing mouse plague wreaking havoc on crops across New South Wales.

In the Macquarie River, the Murray cod are the biggest they've been for years, gorging on mice and getting fat.

Agronomist Mick Harris, from Narromine in the NSW Central West, said he had never seen Murray cod so fat this time of year.

READ MORE: Fears mouse plague 'napalm' could kill native fish

"It's not just the mouse plague," he said.

"The (Macquarie) river is in really good condition after a few down years, and there's lots of shrimp in it at the moment. But the mice are a factor."

Mr Harris said a friend of his had caught a cod in the Macquarie in recent days only to find several mice inside its gullet.

READ MORE: Mouse plague plotted from Queensland to NSW-Victoria border

Dubbo fisherman Aaron Graham has also been pulling up fish full of mice.

"I haven't seen the cod this healthy in years," he said.

Photos Mr Graham snapped showed fish so full of mice they were visible down its mouth.

READ MORE: 'The snakes will follow': Ominous sequel to mouse plague

But the situation could turn sickly if the use of secondary poison bromadiolone is approved by the Australian Pesticides and Veterinary Medicines Authority.

The NSW government has petitioned the federal authority to allow the use of the bait, which is currently banned outdoors.

But others have warned that the use of the poison would pose a risk to native animals that feed on mice - including the Murray cod.

Mr Harris said he didn't think there was any "real benefit" to using bromadiolone as opposed to the currently permitted poison, zinc phosphate.

Mice poisoned with bromadiolone were likely to seek water, he said, and if eaten by Murray cod, could kill them in turn.