TOKYO, Japan — Several years after they began pursuing whalers through the perilous waters of the Antarctic, environmental activists had cause for celebration last week with Japan’s decision to recall its fleet, weeks before its annual hunt was due to end.

Two days after it suspended whaling activities, citing harassment from the marine conservation group Sea Shepherd, Japan’s government ordered the fleet to return home Feb. 18 with its lowest ever catch.

While it insists the decision was made purely for safety reasons, there is speculation that this could be the last year Japan ventures south to conduct the “lethal research” it says is necessary to study whale populations ahead of a possible return to sustainable commercial whaling.

The International Whaling Commission banned commercial whaling in 1986, but for the past 23 years Japan has used a clause in the moratorium that allows it to kill a certain number every year for research.

The meat — a delicacy often eaten raw, deep-fried or in a hotpot — is sold on the domestic market, but poor demand at home could mean the heavily subsidized industry’s days are numbered. The whaling program costs Japan as much as $60 million a year, with 85 percent of funding coming from sales of meat from the research hunts.

Japan’s agriculture minister, Michihiko Kano, told a news conference: "It has become difficult to secure the fleet's safety. We have no choice but to cut short our research. It's regrettable that such obstructions have taken place. We will have to find ways to prevent this kind of harassment.”

Kano was unable to say if the hunt would resume next season; only that the ministry would “examine” the issue before deciding.

Sea Shepherd’s founder, Paul Watson, described the withdrawal of the fleet’s four ships and 180 crewmembers as a “very happy day for people everywhere who love whales and our oceans.”

He said the move was the culmination of an aggressive international campaign that began seven years ago.

“I have a crew of 88 very happy people from 23 nations, including Japan, and they are absolutely thrilled that the whalers are heading home and the Southern Ocean whale sanctuary is indeed a real sanctuary,” he said from the Steve Irwin, one of three Sea Shepherd boats in the Antarctic.

“This a great victory for the whales.”

Sea Shepherd claimed it had pursued the Nisshin Maru for more than 3,200 kilometers this winter, and prevented the fleet from killing any whales since Feb. 9. The group estimated the fleet had caught only 30-100 minke whales, while Japanese officials said the catch was about 170, still only about one-fifth the intended quota this year of 945.

The ministry could not say when the fleet would return. It left Japan on Dec. 2, arriving in the whaling grounds at the end of last year, and was supposed to have stayed there until mid-March before arriving home in April.

Sea Shepherd has been involved in a series of skirmishes with whalers in the Southern Ocean in recent years. Its tactics include targeting the decks of whaling vessels with butyric acid and distracting crews with infrared beams and flares.

The Japanese government describes the group as a terrorist organization and has shown a willingness to pursue its members through the courts. Last summer, Peter Bethune, a Sea Shepherd activist from New Zealand, was given a two-year suspended prison sentence after he climbed aboard a whaling ship, the Shonan Maru 2, to protest the sinking of his high-tech powerboat, the Ady Gil, after a collision with the Japanese vessel.

But there may be more to Japan’s surprise decision to recall the fleet than concern for the whaling fleet’s safety. The hunts have soured relations with Australia, a major trading partner with whom Tokyo hopes to conclude a new free trade agreement.

Last year, Australia filed a complaint against Japan at the international court of justice in The Hague in an attempt to put a permanent end to its expeditions to the Southern Ocean. A decision is expected in 2013 at the earliest.

"I'm glad this season is over and Australia doesn't believe there should ever be another whaling season again," Australia’s environment minister, Tony Burke, said in a statement Friday.

While many Japanese bristle at what they regard as Western interference in a culinary tradition stretching back centuries, domestic demand for whale meat has plummeted since its heyday as a much-needed source of protein in the postwar years.

Despite special promotions and programs to serve the dish as part of school lunches, the Japanese eat the equivalent of only four slices of sashimi a year, according to one estimate. As of December, industrial freezers across the country housed 5,093 tons of whale meat, according to the fisheries agency.

While Sea Shepherd has engaged in whale wars on the high seas, Greenpeace has attempted to shift public opinion by exposing waste and criminality in the whaling industry.

Last September, Greenpeace Japan members Junichi Sato and Toru Suzuki each received a one-year suspended sentence after they intercepted a parcel of whale meat they said had been stolen by crewmembers who intended to sell it on the black market.

Sato, who is now the group’s executive director, said last week’s announcement should be followed by a permanent end to whaling. “The historic announcement confirms what we all know: that Japan’s whaling serves no purpose whatsoever and that the fleet has no business in the Southern Ocean whale sanctuary,” he said.

“All the whaling program has produced is a stockpile of thousands of tons of frozen whale meat, the waste of billions of Japanese taxpayers’ yen, and a culture of corruption and scandal.

“An early return of the whaling fleet is not enough. Japan’s whaling ships should never leave port again.”