A Pacific fisheries meeting is being urged to consider a ban on vessels transferring their catch to other ships at sea, saying it encourages illegal fishing.
The Western and Central Pacific Fisheries Commission (WFPFC) meeting on fish stock protection will be asked to change regulation to curb illegal fishing.
"Transferring catch from one boat to another at sea - known as transshipment - is only legal in certain circumstances and the WCPFC has to be informed before and after it takes place. However, we know the practice is being used in many circumstances to hide illegal catches," said Lagi Toribau, Greenpeace Australia Pacific's oceans campaigner.
"Transshipment at sea must be banned for tuna longliner vessels, as is already the case for purse seiners. All vessels should be required to to offload their catch in the ports of Pacific countries."
The environmentalist group also wants the 'high seas' closed to all fishing.
"There are vessels that are 'high seas only vessels'. These don't have a license to fish in any of the Pacific country waters, have different sets of rules that apply to them, and are more prone to fish illegally away from the watchful eyes of Pacific authorities," Mr Toribau said.
"There should be procedures giving countries more freedom to act on illegal vessels fishing in the high seas areas that border their Exclusive Economic Zones."
The call comes after the Taiwanese-flagged Shuen De Ching No. 888 was busted in the high seas off the waters of Papua New Guinea with illegally caught tuna and shark fins on board.
"The Shuen De Ching No. 888 case highlights the gaps and loopholes in the WCPFC's regulatory systems and shows it is failing in its own objective to eliminate pirate fishing," Mr Toribau said.
He added: "In order to truly clamp down on this practice, we require collective, Pacific-wide regulation to stamp out this practice."