As reports of dead minke whales in the Southern Ocean circulate, the battle over Japanese whaling heats up in turbulent waters.

Video shot by an aircraft operated by the anti-whaling group Sea Shepherd Conservation Society and widely shared online appears to show three minke whales loaded onto the Nisshin Maru, a large whaling ship.

Sea Shepherd says a fourth whale was also seen being cut on the ship's deck.

The video, and Sea Shepherd's allegations, have caused an international stir.

New Zealand's government has condemned what it calls "pointless and offensive" whaling while disputing Sea Shepherd's claims that the Japanese fleet has been operating in New Zealand's territorial waters, in the Ross Sea in Antarctica.

The captain of Sea Shepherd's ship the Steve Irwin, Siddharth Chakravarty, told the media on Tuesday that the activists have since driven off the Japanese fleet from chasing whales in the Southern Ocean.

"We're returning back to the ice edge to stand guard," he said. "Should the whaling ships return again we'll be there to drive them out again from the sanctuary."

Chakravarty is referring to the Southern Ocean Whale Sanctuary, a 31-million-square-mile area around Antarctica that is officially off-limits to commercial whaling as part of a 1986 moratorium to which Japan is a signatory.

Due to what critics call a "loophole," countries are technically allowed to hunt a certain number of whales there for "scientific purposes."

The Japanese government says the minke whales are collected for that purpose.

Sea Shepherd disputes that, saying in a statement that the Japanese boats were operating within the sanctuary "in contravention of the 1986 global moratorium on commercial whaling under the guise of scientific research."

Whaling's Complicated Legal Status

The legal status of whaling is more intricate than the finest scrimshaw of Melville's day.

The signatories to the moratorium, known as the International Whaling Commission, together form a voluntary international body whose member nations agreed not to commercially hunt medium and large whales, including minke whales (smaller whales and dolphins are exempt and are still widely hunted).

In June, Australia and New Zealand sued Japan before the International Court of Justice in The Hague, asking the court to withdraw all permits for future whale hunts from the Japanese fleet. Arguments were held over the summer, and a decision is expected in the next few months.

During the proceedings, Australia and New Zealand dismissed Japan's claims that it was whaling for scientific purposes. The countries alleged that Japan was motivated by the opportunity to sell whale meat, which is legal in Japanese shops and restaurants.

"You don't kill 935 whales in a year to conduct scientific research. You don't even need to kill one whale to conduct scientific research," Bill Campbell, Australia's presenter at the court, told the 16-judge panel.

He was referring to Japan receiving permits last year to kill up to 935 Antarctic minkes, 50 fin whales, and 50 humpbacks.

Leah R. Gerber, a professor of marine biology at Arizona State University, told National Geographic that despite strong interest in ending the scientific whaling exemption from Australia, New Zealand, the U.S., and other members of the International Whaling Commission, the delegates have not been able to obtain a three-fourths majority to make the change.

Japan has convinced enough small island nations to vote its way by plying them with international aid, she said.

But even if the court does rule against Japan, "Japan is still going to find a way to whale," said Gerber, who has written extensively on whales and whaling.

"They will continue commercial whaling based on a sense of needing to plant a stake on marine resources," she says, "which are very important to their culture."

Japan's Ongoing Support of Whaling

Japan's support for whaling is not about economics, Gerber agues.

Because the market for whale meat in Japan is quite weak, and because the costs of operating a fleet, providing international aid to other International Whaling Commission nations, and paying for public relations efforts are high, whaling actually loses Japan money, she says.

A report released last February by the advocacy group International Fund for Animal Welfare (IFAW) estimated that whaling has cost Japanese taxpayers $378 million since 1987.

"It's a very small fraction of the society who have any interest in consuming whales," says Gerber.

Efforts to improve the market by putting whale meat in school lunches have drawn criticism from parents, some of whom have complained that the flesh can be relatively high in toxic mercury. In 2011, the Japanese government tried to unload some of its stockpile of whale meat in a public auction, but only a quarter of it found a buyer.

According to a poll commissioned by IFAW in 2011, nearly 90 percent of Japanese adults had not bought whale meat in the previous 12 months. More than 50 percent of Japanese said they had no opinion on their country's whaling program, while 26.8 percent said they supported it and 18.5 percent were opposed to it.

So why does Japan still officially support whaling?

The Japan Whaling Association says on its website that minke whales in the Antarctic need "marine management" through scientific whaling and that the International Whaling Commission has enough regulations in place to allow sustainable harvest.

"Asking Japan to abandon this part of its culture would compare to Australians being asked to stop eating meat pies, Americans being asked to stop eating hamburgers, and the English being asked to go without fish and chips," the site says. "Attitudes toward animals are a part of national cultures. No nations should try to impose their attitudes on others."

Gerber says polls show that Japanese young people are generally opposed to whaling, but that it remains a matter of "national pride" to some of those from older generations. "When these older people move out of positions of power and more enlightened people take over and start to negotiate, things will change," she says.

In an academic paper published in 2009 in the journal Japanese Studies, Japanese studies professor Midori Kagawa-Fox wrote that "reasons put forward by the [Japanese] government, such as the maintenance of its culture and the utilization of the whale resource, have not convinced Western nations of its legitimacy."

Kagawa-Fox, who grew up in Japan and teaches at the University of Adelaide in Australia, wrote that "commercial whaling [is] less about maintaining traditions than about providing opportunities to the vested interests of the Japanese 'Whaling Iron Triangle,'" which she identifies as "bureaucrats, politicians, and big business."

In 2001, Japan's then-commissioner of whaling, Masayuki Komatsu, embodied what some have described as a cultural defiance of the whaling taboo when he referred to minke whales as "cockroaches of the sea" in an interview in Australia.

In a later interview, he said what he meant was that "cockroach is plenty in its number and also reproduction is very rapid and big..."

Bold Activist Tactics

As anti-whaling nations have attempted to end the practice, battles between whalers and activists have become a regular occurrence in the Southern Ocean, where up to 1,000 minke whales are killed annually.

In spring 2010, this reporter toured the Steve Irwin and met with Sea Shepherd crew, including the group's colorful founder, Paul Watson, who is well known for his turns on the reality TV show Animal Wars on Animal Planet and for his role as one of the earliest members of Greenpeace.

"Hanging banners and taking pictures isn't going to save the whales, but kicking a-- is," Watson said then.

He founded Sea Shepherd in 1977, after he was voted off the board of Greenpeace.

Sea Shepherd has offices in Washington State and in Australia, and has been sending boats to confront whalers for more than 30 years, in ways that have attracted a lot of attention and a fair amount of criticism.

Sea Shepherd activists routinely position themselves between harpoons and marine mammals. They blast whaling vessels with water cannons, throw flash grenades, and try to cut ensnared animals free.

They have also thrown acid on captured whale carcasses, to make them less sellable.

The activists have been known to "scuttle" whaling ships in port by sinking them, and to ram whalers on the seas. The group claims that, despite decades of such tactics, they have not caused any human injuries, which they attribute to strict discipline and rules of engagement.

Still, whalers and various nations have often fought back.

Arrest warrants have been issued for Sea Shepherd leadership from Japan, Norway, and Costa Rica, with varying degrees of success.

New Zealander Pete Bethune, a Sea Shepherd captain, got two years in prison in Japan for the disputed sinking of the Ady Gil, a Sea Shepherd vessel that collided with a Japanese whaling vessel in January 2010 (each side blames the other as the aggressor). After a lengthy legal battle, the sentence was suspended after he had served five months.

In New York in spring 2010, Watson said he didn't mind that some people call him a "terrorist." "We represent the whales, tuna, and other creatures of the sea," he said. "If people support us, fine. If people disagree, then tough."