Agriculture, Forestry and Fisheries Minister Michihiko Kano wore a pained expression Friday as he announced Japan would halt its Antarctic whaling mission due to repeated harassment by the Sea Shepherd Conservation Society, but insisted the government had no other options.

Kano said the decision was very difficult, but the government had to make it to ensure crew members' safety. However, people involved in the country's research whaling voiced concern, with one saying, "We want the government to stand undaunted."

At a press conference, Kano said sternly: "To ensure the safety of crew members, we were forced to halt our research whaling. I hope the whaling fleet will return to Japan safely.

"[Repeated harassment by Sea Shepherd] threatens the lives of the crew members and the assets of the state. Its obstruction can never be tolerated," he said.

Since research whaling has been partly financed by sales of whale meat, future whaling activities are expected to face financial difficulty, Kano said.

"Apparently, our whaling fleet's location was tracked via satellite. We have no choice [but to halt the mission] for safety's sake," a senior fisheries ministry official said.

Meanwhile, people involved in research whaling displayed mixed reactions following the government's announcement.

Yoshinori Shoji, 49, who makes his living from whale hunting at Wada Fishing Port in Minami-Boso, Chiba Prefecture, was angry.

"The [Sea Shepherd's] obstructive behavior is illegal. I'm completely mortified by the government's decision to return the fleet. If such a thing is allowed, there's no need for the International Whaling Commission," Shoji said.

However, he also expressed understanding of the government's decision.

"I can understand how dangerous the Sea Shepherd's harassment is for Japan's crew members. So I can't say the decision was weak."

Representatives of the Ishinomaki municipal government in Miyagi Prefecture, home to a whaling station, had similar reactions.

"Many Ishinomaki citizens have joined the research whaling fleet," a municipal official said. "If the safety of those citizens cannot be protected from [Sea Shepherd's] obstructions, [the research whaling] must be halted."

"To prevent future obstruction, I want the government to resolutely implement strict measures," he said.

According to the Institute of Cetacean Research, the current method of whaling research is now in its sixth season, conducted every year in the Antarctic Ocean since 2005.

During the first season, the fleet caught nearly the planned number of whales, including 853 Antarctic minke whales. But from the second season, the catch has remained at about 60 per cent to 70 per cent of initial targets, due mainly to harassment by Sea Shepherd.

"If the catch declines greatly following the halt, the credibility of the research data could be significantly harmed," an official of the institute said.

According to the fisheries ministry, Japan also has conducted research whaling in the northwest Pacific Ocean, and conducted whaling on a small scale in waters off Japan's coasts.

Whales caught in the past have been refrigerated, so the whale meat supply will not be immediately affected by the stoppage, the ministry said.

However, some restaurants serving whale meat have expressed concern.

"We serve whale meat dishes with pride, to pass on Japanese food culture to the next generation. I'm worried the halt [of whaling] will prevent us from passing on this part of our culture," said Yachiyo Ichihara, 61, who runs a whale meat restaurant in Minami-Boso.

History of sabotage by Sea Shepherd

Sea Shepherd was established in 1977 by Canadian Paul Watson, who was a member of the environmental organization Greenpeace.

Sea Shepherd's aim is to protect marine species, and its members are sometimes branded as "eco-terrorists" because of the extreme nature of their activities, and their willingness to use violent methods to achieve their goal.

Sea Shepherd has sabotaged Japan's research whaling in the Antarctic Ocean on and off since 2005, injuring at least eight crew members on board Japanese vessels.

Their acts of sabotage have become increasingly aggressive over the years. In January 2010, Sea Shepherd's small high-speed boat Ady Gil rammed into the Japanese research vessel Shonan Maru No. 2. In February that year, the former captain of the Ady Gil was detained for breaking into the Japanese vessel, and was arrested by the Japan Coast Guard the following month on suspicion of trespassing.

The JCG also obtained an arrest warrant for Watson on suspicion of directing the former captain to sabotage research whaling.