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Antarctic researchers want New Zealand to forfeit a $20 million fishing haul to save what they say is the world's last pristine ocean.

Ross Sea ecologists David Ainley and Peter Wilson, both veteran Antarctic penguin researchers, have been touring the country asking people to back efforts to end deep-sea fishing there.

The pair have set their sights on the lucrative international trade in Antarctic toothfish - a tightly controlled fishery which earns New Zealand between $20 million and $30 million a year.

Quotas set by the 25-country Commission for the Conservation of Antarctic Marine Living Resources allow up to half the original spawning stock to be removed in the long term, according to a summary on the National Institute of Water and Atmospheric Research website.

Dr Ainley and a union of other researchers fear fishing in the Ross Sea - led by New Zealand - will cost them their last chance to study an ocean that is still largely untouched by pollution and over-fishing.

He has been touring under the banner of the newly formed New Zealand branch of the Last Ocean Trust, a United States lobby group for which he is science director.

With him was New Zealand wildlife film-maker Peter Young, who has been making a documentary about the Ross Sea.

Dr Ainley said the sea was the closest thing left to an untouched ocean. "It's like Eden - or the closest we've got in a marine setting."

The Antarctic and Southern Coalition of conservation groups has described the Ross Sea as a "living laboratory" of wildlife to rival the Galapagos Islands.

Dr Ainley said it was one of the few places where large numbers of predators at the top of the food chain survived and where scientists could watch hunters such as whales, toothfish and penguins interact.

Fishing came late there because of the extreme cold, difficult and dangerous conditions and long distance to North American markets.

But as northern fisheries have become more depleted, the Ross Sea fishery has become more crowded.

The huge, slow-breeding toothfish are caught and frozen on the spot to be sold at premium prices to expensive restaurants, many of them in the United States, as Chilean sea bass. They are seldom available in this country.

Dr Wilson said the New Zealand fishing fleet was "very responsible" and always co-operated with the scientific observers they must carry under commission rules.

"Unfortunately they are not the only fleet down there," he said.

In May, an illegal gillnet 130km long was found near Antarctica (not in the Ross Sea) bulging with 29 tonnes of toothfish.

A 2007 Niwa report noted little was known about the effects of fishing on the Ross Sea ecosystem, though scientists were working to understand it.

Niwa said toothfish were both prey and predator, and reducing their numbers could affect the food chain in both directions.

Because there are no sharks so far south, toothfish have taken over their role as deep-sea predators.

They can live to be 40 years old, are more than 1.5m long and live as deep as 2km.

Trevor Hughes, head of the Antarctic policy unit at the Ministry of Foreign Affairs and Trade, said New Zealand was watching marine protected areas in the Ross Sea.

It had hosted an international workshop this year, which would help earmark areas for protection.