China has sent an armada of sophisticated and highly subsidised fishing boats into the South Pacific, including waters north of New Zealand, in a bid to kill off domestic fleets and seize control of the longline tuna fishery, a key fishing industry conference has heard.

Fiji Tuna Boat Owners Association head Russell Dunham told the Auckland forum that no one will talk about what Beijing is doing and nor will they say anything to China.

"It is the same with the Fiji government, same with Pacific governments, same with the New Zealand government; no one is game to say anything."

Figures from the Forum Fisheries Agency obtained by Fairfax Media show this year there had been a 125 per cent jump in the size of the China South Pacific tuna fleet, with many of them just built.

The agency says there are 241 China-flagged vessels approved to fish, ahead of Taiwan with 221.

Dunham said South Pacific boats could not compete against the Chinese.

"I think they have agenda, an agenda to control the whole Pacific longline industry. Once we die out maybe they will not have subsidies."

Dunham said the Chinese did not care about the economics of albacore tuna fishing at this stage. Each Chinese boat received US$300,000-$400,000 (NZ$370,000-$490,000) a year from the state, irrespective of whether they fished.

New boats were built virtually for free and Chinese boats received an additional subsidy if they sent their catch to China for processing.

Making matters even worse, if a Fiji-flagged boat sent a tuna to China it would attract a 25 per cent duty. The same tuna caught in the same place by a Chinese boat would enter duty free.

"Something has to be done about subsidised fleets," Dunham said.

"They don't live in the real world and they don't care about cost and they don't care about quality."

The Chinese are catching poorer quality fish and sending it into the same markets as tuna caught by Pacific states to undercut it.

"It is a difficult thing to face up to the might of the foreign fleets," he told the conference sponsored by the government's Pacific Co-operation Foundation and the Pacific Islands Tuna Industry Association.

High seas tuna access is controlled by the multinational Western and Central Pacific Fisheries Commission and Dunham says they will ultimately determine quotas by catch histories.

If the Chinese can show they have had more boats fishing for tuna, they will be entitled to the greatest number of quotas.

"That is what they want, total control," he said.

"Some one has to tell china to be a responsible fishing nation."

Longlining is a technique using a line with 3000 baited hooks on it. It can be controversial because of the risk of by-catch, particularly turtles, sea birds and sharks.

Chinese longliners seldom attempt to sell fresh fish, preferring super-freezing which returns a much lower price on tuna markets.

Tuna can also be caught by purse seine boats using large nets but the Chinese did not appear to be interested in this technique.