The future of Japan's controversial whale hunts hangs in the balance following the start of a landmark legal case that could put a permanent end to the annual slaughter of hundreds of whales in the Antarctic.

Over the next two weeks, 16 judges at the International Court of Justice (ICJ) in The Hague will consider a request by Australia to deny licenses to Japan's whaling fleet, which kills almost 1,000 whales a year in the name of scientific research. The panel of judges, who opened the hearing earlier this week, are expected to rule by the end of the year, possibly before the next whaling season begins in the Southern Ocean.

The decision will be final, since the ICJ does not have an appeals process. And both Japan and Australia have agreed to abide by the decision.

Australia, with the support of New Zealand, this week challenged Japanese claims that its slaughter of up to 935 minke whales, and about 50 fin whales, every winter is vital to learn about the mammals' breeding, migratory, and other habits ahead of a possible return to sustainable commercial whaling.

The International Whaling Commission banned commercial whaling in 1986, but allows Japan to kill whales for scientific research. The meat from the whales is sold legally in Japanese stores and supermarkets – proof, say campaigners, that the hunts are simply a cover for commercial whaling.

"Japan seeks to cloak its ongoing commercial whaling in the lab coat of science," Bill Campbell, Australia's agent to the court, told the judges this week.

He later told journalists: "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."

Japan insists it is abiding by article 8 of the 1946 International Convention for the Regulation of Whaling, which permits the practice "for purposes of scientific research."

"Japan's research programs have been legally conducted for the purposes of scientific research, in accordance with the [convention]," Japan's deputy minister for foreign affairs, Koji Tsuruoka, said outside the courtroom.

"Australia's claim is invalid. Japan's research whaling has been conducted for scientific research in accordance with international law."

On Thursday, Philippe Sands, a lawyer acting for Australia, claimed that years of lethal research by Japan had added nothing to the body of scientific knowledge of whales, other than they eat large quantities of krill.

"What you have before you is not a scientific research program, it is a heap of body parts taken from a large number of dead whales," he told the court. "Japan's objectives are simply there to allow whales to be killed, not to establish a genuine program of science."

Japan says minke populations have recovered sufficiently for the Antarctic hunts to continue.

"There are about 515,000 minke whales in the Antarctic, and Japan's research is taking only about 815 a year," said Noriyuki Shikata, a foreign ministry official who is part of the Japanese delegation. "This is below the reproductive rate and very sustainable."

Japan has killed more than 14,000 whales since the global ban on commercial whaling was introduced in 1986, according to the International Fund for Animal Welfare (IFAW).

"In the court of public opinion, the verdict is already in," says Patrick Ramage, director of IFAW's global whale program. "Commercial whaling, whether conducted openly or under the guise of science is a cruel and outdated practice which produces no science of value."

The Hague hearings are playing out against a backdrop of declining whale meat consumption in Japan and growing frustration with the use of taxpayers' money – 800 million yen a year (about $8 million), according to Greenpeace – to subsidize the Antarctic fleet.

"Whale meat doesn't sell in Japan, and I don't see that changing any time soon," says Nanami Kurasawa of the Dolphin and Whale Action Network, a Tokyo-based pressure group.

According to a recent study by the Nippon Research Group, whale meat consumption has fallen to about 1 percent of its 1960s peak. Current stockpiles of unsold whale meat have increased to nearly 5,000 tons, about four times greater than they were 15 years ago.

"Selling meat on the open market has been a total failure," Mr. Kurasawa says. "If the court rules in Australia's favor, it will be a good opportunity for Japan to stop the Antarctic hunts. It would be the intelligent thing to do."

An IFAW survey conducted in Japan last year found that 26.8 percent of people agreed with the scientific whaling program, while 18.5 percent opposed it. The rest were undecided. The survey found that 88.8 percent of those polled had not bought whale meat in the previous 12 months.

The decline in consumption is reflected in smaller catches. The whaling fleet caught 853 whales in 2005, but only 266 in 2011. Last season, it returned with a record-low haul of 103 whales, blaming harassment by the marine conservation group Sea Shepherd.

Susan Hartland, a Sea Shepherd campaigner in the US, says a defeat for Australia at the ICJ would be "devastating to people worldwide who support the efforts to save the whales, and as more than 90 percent of the planet's great whales have been wiped out, we need to fight hard to protect the remaining ones from the same fate."

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But some experts believe Australia could struggle to convince the court, given the unprecedented nature of the case. "If it was an easy case to make, previous Australian governments would have no doubt explored these options," Don Rothwell, a legal expert at the Australian National University, told the Australian Broadcasting Corporation.

"The arguments that Australia will be making are ones that have never before been litigated or decided before by any international court, let alone the International Court of Justice."