North Queensland recreational fishermen say a new report released shows net-free zones are helping to replenish legal fish stocks.

The St Helens to Cape Hillsborough net-free zone pre and post-declaration surveys suggested fish caught and released since the net-free zones were introduced were bigger than those caught before the zones.

The report is a joint partnership between Reef Catchments, Mackay Recreational Fishers Alliance and hundreds of volunteers, while Info Fish collated the data.

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More than 2,000 hours were invested into the collection of data between October 2015 and April this year, surveying net-free zones from St Helen's to Cape Hillsborough, in the tropical north.

The information recorded during that time indicated that the percentage of legal caught barramundi had increased by 23 per cent, and some fish were over one-metre long.

Mackay Recreational Fishers Alliance team leader, Lance Murray, said monitoring was only in the early phases but the results were encouraging.

"What it means in theory is the amount of legal fish caught compared to 2015 — which was 32 per cent of all the fish caught — in April this year it was 63.1 per cent," he said.

He believed the net-free zones, which were introduced in November 2015, have allowed fish to live longer and grow much bigger.

"Before the net-free zone was implemented there was no barramundi caught [but] in the post net free data, there were 28 of the barramundi which were a metre and there were two at 1.2 metres," Mr Murray said.

All of the fish were released.

Commercial fishers not convinced

However, Mackay commercial fish David Caracciolo hit back at the report.

He questioned the timing and reliability of the data.

"Everyone knows that from February through to June is the fishing season for barramundi, grunter, coastal fish and all fish; prawns, mud crabs," Mr Caracciolo.

"There is no way you can compare those sets of figures because that time of year in October, November our guys do not even fish the coastal areas for barramundi and grunter or that type of stuff.

"They are out fishing for different species because coastal fish are not around at that time of year."

As far as the size of the barramundi were concerned, Mr Caracciolo said his fishermen had caught big fish in the past.

"We have always caught big barramundi in that area at certain times of the year ... the big barramundi move out in the deep on the headlands at certain times," he said.

"We have caught large barramundi ... eight to 15-kilo fish all the time in the Cape Hillsborough [and] Seaforth area for the last years."