This article is more than 6 years old

This article is more than 6 years old

Japan's whaling fleet is on its way to the Southern Ocean, where it hopes to kill almost 1,000 whales this winter as the world awaits a ruling on Australia's landmark legal attempt to ban the controversial hunts.

Two whaling vessels and a surveillance ship left the south-western port of Shimonoseki at the weekend and are expected to link up with the fleet's factory ship, the Nisshin Maru, Kyodo News reported.

As the fleet began its long journey to the Antarctic to slaughter up to 935 minke whales and 50 fin whales in waters that Australia considers a sanctuary for the mammals, campaigners called on Canberra to send a customs vessel to observe the whalers.

Sea Shepherd, a marine conservation group that has clashed with Japanese whalers in the icy seas of the Antarctic for the past several years, said it was time for the coalition government to honour its pledge to put pressure on the fleet.

Bob Brown, a former Greens leader who now chairs Sea Shepherd's Australian chapter, said the environment minister, Greg Hunt, had promised in May to send a customs ship to monitor the fleet's activities.

"We need to hear from the prime minister [Tony Abbott] that that promise to the Australian people will be kept," Brown told ABC.

Sea Shepherd activists, who will set sail from Melbourne and Hobart to pursue the fleet in about a week's time, claim their campaign has saved hundreds of whales in recent years.

Last winter, Japan's fleet returned to port with just 103 whales, its lowest ever haul, and blamed Sea Shepherd for using dangerous tactics to sabotage the hunt.

Japan is permitted to kill almost 1,000 whales in the region every year for what it describes as "scientific research".

Critics say the hunts are a de facto return to commercial whaling, which was banned by the International Whaling Commission [IWC] in 1986.

A clause in the IWC moratorium allows meat from the research hunts to be processed and sold legally in Japanese restaurants and markets, although the public's appetite for whale meat has declined sharply .

The biggest challenge yet to Japan's whaling programme could come within weeks, when the Iinternational court of justice (ICJ) in The Hague is expected to rule on Australia's case against Japan.

Australia hopes the verdict will come by the end of the year, possibly in time to force the fleet back to port well ahead of its scheduled return next March.