A high-level scientific panel has again urged the Government to ban set netting and conventional trawling across the entirety of the critically endangered Maui dolphin's habitat.

The call from the Scientific Committee of the International Whaling Commission (IWC) proved the fifth year in a row that the 120-member panel has pushed for action to save the world's smallest and rarest marine dolphin from extinction.

To help protect the species - now limited to a population estimated at between 57 and 65 - the Government has closed more than 1700 and 6200 sq km of water off the North Island's west coast to trawl net fishing and set netting.

More than $2 million has also been budgeted for research to aid a full review of a threat management plan for the dolphins, due to be completed next year, that would assess those measures already in place, risk of fishing-related threats and whether extra measures were needed.

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But the IWC committee again reasserted that the existing management measures fell short of what was required to prevent the dolphins' extinction.

Its report urged the New Zealand government to protect Maui dolphins across their whole habitat, from Maunganui Bluff in Northland to Whanganui, offshore to 20 nautical miles and inside harbours.

The committee agreed that longlines were a potential alternative to reduce risk from the set nets and trawling currently associated with bycatch of Maui dolphin and that this should be investigated.

"It recognises that Government support is required to develop and implement such alternatives and assess any associated impacts on target catch or other marine species," the committee stated.

It further noted that no new management action regarding the Maui dolphin has been enacted since 2013.

"It therefore concludes, as it has repeatedly in the past, that existing management measures in relation to bycatch mitigation fall short of what has been recommended previously and expresses continued grave concern over the status of this small, severely depleted subspecies."

The committee reiterated that the death of just one individual as a result of human actions would significantly raise the risk of extinction for the diminutive dolphins.

According to new research presented by Otago University researchers Professor Liz Slooten and Professor Steve Dawson, gill nets were prohibited in just 14 percent of the dolphins' habitat, while trawling is excluded from a mere five percent.

The researchers estimated that two to four Maui dolphins perish in fishing nets each year, causing continued overall decline.

David Tong of WWF-New Zealand, which recently commissioned a report estimating a shift to safer fishing practices in the habitat would cost the industry between $40 million and $65 million, said the committee's conclusions were clear.

"Maui dolphins can be saved from extinction if our government ends set netting and conventional trawling across their whole known habitat and supports affected people and communities to move to kinds of fishing that are safe for dolphins."

One of the reasons the IWC is worried about the fate of Maui dolphins are the baiji or Chinese river dolphin and the vaquita, a Mexican porpoise.

The baiji declined from some 400 individuals in the 1980s to around 13 in 1999 and was declared extinct in 2006.

More recently, vaquita numbers declined from 60 to just 30 individuals in the past 12 months.

The call follows recently-announced moves by major companies Sanford and Moana New Zealand to shift away from the practices.

They aim to have no catching rights leased to coastal set netters out to 100m depth north of New Plymouth from next October, and no conventional trawling within 100m depth in the Maui dolphin habitat after 2022.