A good catch of endangered toothfish far outweighs later fines

The vessel, the Viarsa, is believed to have an illegal haul of the rare Patagonian toothfish - a sought-after delicacy also known as the "white gold" of the Southern Ocean.

The long-line trawler was first seen inside Australia's fishing zone about 4,000 kilometres (2,500 miles) south-west off the coast 10 days ago and repeatedly ignored radio orders to stop.

The pursuit is continuing. We will not be giving up Australian fisheries spokesman

It is reported to be fleeing westwards at high speed in a mountainous, freezing ocean dotted with icebergs.

Demand for toothfish is driven largely by Japan and the United States - where it is called Chilean sea bass - and sells for about $24 per kilo on the black market.

Australia's fisheries patrol ship, Southern Supporter, has been chasing the Viarsa since 7 August.

"The pursuit is continuing. We will not be giving up," said a spokesman for Australia's Fisheries Ministry.

Poised to help

South Africa's deputy director-general of environment, Horst Kleinschmidt, told Australian radio its helicopter-equipped Antarctic supply ship, the MV Agulhas, could assist in the operation.

"If there are two vessels it would find it presumably extremely difficult to escape or go further," he said.

"The captain on the Viarsa would be told that an action was imminent and that either through siding up to the vessel, or through a helicopter, officials will mount it."

Mr Kleinschmidt warned the ship's crew faced criminal charges and extradition issues in many other countries if they resisted arrest.

Britain has also been alerted, according to officials, because it operates navy and fisheries patrol vessels off the Falkland Islands.

Prized catch

The Patagonian toothfish lives mainly in Antarctic waters and can reach more than two metres in length.

It lives for up to 50 years and does not breed until it is at least 10 years old.

The Australian Government warned in 1998 that the continuation of pirate fishing at present levels would mean the Toothfish could become commercially extinct within two or three years.

Conservationists warned in 2001 illegal, unreported and unregulated catches were running at four times the level scientists had thought.