Staying hidden behind sea ice and large waves, sailors aboard a navy patrol boat from New Zealand sneaked up on three suspected poaching ships, then took photos and video of the fishermen hauling in prized fish in banned nets from the ocean near Antarctica. Seemingly caught red-handed, the crews of the rusting vessels just kept on fishing.

Authorities say this month’s high-seas confrontations, and the detailed evidence collected, mark a first in Antarctic waters, where regulators have long suspected poaching activities but have found them difficult to police in an area that’s roughly the size of the continental United States.

It is a huge illegal business. Each of the ships could hold more than $1m worth of Antarctic toothfish, marketed in North America as Chilean sea bass.

The three ships were encountered between 6 and 13 January, near Commonwealth Bay and about 110 kilometres (70 miles) from the Antarctic coast. Each quickly hoisted a flag proclaiming it to be a fishing vessel from Equatorial Guinea, said Lt. Cmdr. Graham MacLean, the patrol boat’s commanding officer. When the navy demanded to board to check documentation, each of the three captains flatly refused, he said.

MacLean said he decided the 5-meter (16-foot) swells made it too dangerous to board the ships using force, so the fishermen slipped away, carrying with them hundreds of Antarctic toothfish. The fish can grow to over two meters (6-foot-6) in length, weigh up to 120 kilograms (265 pounds) and sell for thousands of dollars apiece.

New Zealand hopes the confrontations will mark a turning point in the pursuit of poachers. It has sent an alert to 190 countries through Interpol, a move it hopes will make it difficult for the three crews to unload their catches. And it’s trying to exert diplomatic pressure on nations it suspects could be harboring poachers.

“It’s the start of a lengthy process to try to stamp out such insidious activity,” said Murray McCully, New Zealand’s foreign minister.

Records show the three ships — the Kunlun, the Songhua and the Yongding — have repeatedly changed their names, country of registration, and ownership details in an apparent attempt to stay one step ahead of the law.

According to the Interpol summary, the three ships are ostensibly owned by shell companies in Central America, under listings that reveal nothing about the “true beneficial owners” of the vessels.

The Kunlun has been called the Black Moon, the Galaxy and the Dorita, among other names, and has been registered in North Korea, Sierra Leone, Tanzania, Panama, Indonesia and Equatorial Guinea. Despite the fishermen’s use of Equatorial Guinean flags this month, McCully said the central African nation’s foreign minister has told him the ships are not currently registered there.

The dozens of crew aboard the three ships point to the scale of the operation. Each ship ranges in length from 48 to 62 meters (157 to 203 feet) with the heaviest, the Songhua, weighing more than 1,100 tons.

Back in 2008, when the Songhua was named the Paloma V, an investigation linked that ship to a Spanish company, Vidal Armadores. In 2010, the company was fined €150,000 for participating in illegal fishing activities with the Paloma V near Antarctica.

McCully said he believes the Spanish company is currently involved with the three ships: “Everything we have seen points to Vidal Armadores continuing to control and manage this illegal activity.”

The foreign ministry, however, refuses to disclose any evidence linking the company, saying it is part of an active investigation.

Carlos Perez-Bouzada, a lawyer who has represented one of the owners of Vidal Armadores, said that while the company has previous fines and convictions from years ago, it’s now focusing on sectors such as renewable energy. He said the company no longer owns fishing boats and, as far as he’s aware, has no current connection with the three ships found near Antarctica.

“Unfortunately, every time there is a case of illegal fishing, it’s linked to Vidal Armadores,” he said.

Spain’s Ministry of Agriculture, Food and Environment said in a statement it has requested more information from New Zealand and will initiate proceedings under national and European legislation if any Spanish citizens are found to be involved.

With highly-valued fish in remote locations, the Southern Ocean around the Antarctic is believed to be a hotbed of illegal fishing. Poaching of the Antarctic toothfish is making it difficult for scientists to understand the impact fishing is having on the species, said Andrea Kavanagh, director of Antarctic and Southern Ocean conservation for The Pew Charitable Trusts.

“It’s not just hurting the stocks. It’s making the study of them invalid,” Kavanagh said.

Illegal fishing for toothfish hurts other species in the region as well, said Andrew Wright, executive secretary of the Commission for the Conservation of Antarctic Marine Living Resources, which oversees international fishing in the region. He said poachers use nets up to 25 kilometers (15.5 miles) long and often abandon them, allowing the equipment to needlessly kill other fish for years afterward.

The commission lists on its website 17 ships it suspects have fished illegally around Antarctica, a place some describe as the last unspoiled environment on the planet.

Some in New Zealand have criticised the navy for not getting more aggressive with the suspects on the high seas, perhaps by firing a warning shot from the patrol boat’s cannon or using its machine guns to forcibly board the ships.

But Lt. Cmdr. MacLean said those comments are ill-informed, and that he’s proud of his crew for collecting abundant evidence. Now it’s up to the international community, he said, to keep the poachers from selling their fish, and to bring their financial backers to justice.