Australia is deploying an armed surveillance ship to deter fish poachers in the Southern Ocean, mainly to help protect valuable stocks of Patagonian toothfish. Conservationists say it is being hunted to near-extinction. But regulating trade in the fish is proving to be difficult, despite international agreements to limit catches.

The toothfish is known as the "white gold" of the Southern Ocean. Its flaky flesh is a delicacy in Japan and the United States, where strong demand has fueled an illegal trade in the fish.

Legal fishing is restricted, with boats allowed to take only a certain amount of fish.

Criminal gangs control the illegal trade, and there are suspicions many poachers operate with the corrupt support of government officials in several countries.

Australia, one of the largest legal harvesters of Patagonian toothfish, has been among the most determined governments in cracking down on the pirates.

The Fisheries Minister Ian Macdonald says a unified international response is the only way to combat rogue fishermen.

"We will be able to work more cooperatively with the British and the South Africans, New Zealanders, and together I think we can form some sort of a Southern Ocean coalition that jointly will embark upon a major attack on this illegal fishing problem and all of the consequences that follow from illegal fishing," he said.

Late last year, Australia captured a Uruguayan ship suspected of poaching toothfish after a dramatic three-week pursuit across the Southern Ocean. The case has prompted Australia to deploy a heavily armed patrol boat in the region.

This conservation battle, however, goes beyond concerns over the Patagonian toothfish. The Southern Ocean, which surrounds Antarctica, is a vast sea rich with fish, marine mammals and seabirds.

As part of the diet of the sperm whale and the elephant seal, the toothfish plays an important role in the Antarctic's marine ecosystem.

Matt Jacobs from Sydney Aquarium says the entire food chain is so interdependent that the loss of one link could be a disaster.

"Like, if you take out an apex predator like the great white shark, you'll end up with a larger seal population, which could in turn mean less fish," he explained. "You know, professional fishermen then get affected as well as everyone else."

There is destruction both below the surface of the ocean and above it.

An estimated 100,000 seabirds breeding on sub-Antarctic islands are killed every year by the long-line hooks used by illegal fishing trawlers.

Nicola Beynon of the Humane Society International says some bird species - particularly albatrosses and petrels - are slowly being wiped out.

"The reason they're going extinct is because of illegal poaching in toothfish," said Ms. Beynon. "The poachers use a method called long-line fishing and that involves setting lines that are kilometers long and they're baited with hooks and the seabirds are attracted to the baited hooks and when the lines are set and then they sink, the seabirds drown."

Some scientists say we know more about the surface of Mars than about the depths of the cold, turbulent Southern Ocean.

Dr. Adele Pile from the University of Sydney says there is still time to stop the plundering of the ocean.

"It is probably the last chance for us to get it right," she said. "The Southern Ocean is really important in regulating globally things like our climate. We do have, I think, an obligation to be the custodians of one of our last great resources on the planet."

Environmental crime in the Southern Ocean shows little sign of abating. Dozens of pirate ships are reported to be stalking the lucrative fish. Despite signs that stocks are dwindling, the Patagonian toothfish has not been placed on international lists of endangered species. Conservationists say efforts to get it listed have so far failed.