Another Chinese tuna vessel has been found in breach of multiple rules, after being boarded by the Royal New Zealand Navy off Fiji.

Working alongside the Kiwis is a group of Fijians, who say the training they've received will help them prepare for the threat of illegal vessels, known as blue boats, which have been plundering the South Pacific of valuable marine life.

After boarding the Chinese long-liner on the high seas it was quickly established it had been flouting the rules by chucking its rubbish over the side.

"You're obviously putting marine life at risk," Sub-Lieutenant Julian Grimmett, told crew. "Also, it's a violation of our Maritime Pollution Act, which forbids the disposal of plastics at sea."

The rusty tuna boat also wasn't clearly displaying its registration on the side of the vessel.

"The call signs, the vessel name - they need to repaint the whole thing," says Fiji fisheries officer Torika Keteca.

So far the crew from the Navy boat, Hawea, have boarded and inspected more than 300 vessels and issued more than 54 infringement notices.

The presence of the Hawea is also helping Fiji prepare for the possible arrival of unregistered Vietnamese blue boats, which have already been caught stealing huge quantities fish off the Solomon Islands and New Caledonia.

"It could be a developing threat for the southwest Pacific and certainly something New Zealand and Fiji are interested in," says Lieutenant Dave Luhrs.

From firearms training to navigation, the joint expedition is the first of its kind in the South Pacific.

"The training goes both ways. We are seeing quality training in terms of operating in an offshore context within a reef environment, for instance."

There's no shortage of work here, and the Kiwis will continue to keep watch on these waters for another three months.

Newshub.