Australia will send a government jet to conduct aerial surveillance of the Southern Ocean as an annual showdown brews between Japanese whalers and militant conservationists, the environment minister said Sunday.

Greg Hunt said Canberra would dispatch an Airbus A-319 Customs and Border Protection crew to monitor exchanges between Japan's harpoon fleet and the Sea Shepherd Conservation Society.

"The purpose of the Customs mission will be to record the incidents on the high seas. It will be to ensure there is a presence to make sure that there is no conflict between the parties," Hunt said.

"It will also be to ensure that there is awareness from all parties that the world is watching."

The government had promised to send a ship to tail the clashing groups, but Hunt said he had settled on aerial surveillance as a more effective way of covering the vast area in which the whalers hunt.

"The flexibility and the range of the A319 allows it to operate across a large area at great speed and therefore it can identify any breaches," he said.

"So this is an important asset... it gives us the ability to cover not just one point in the fleet but a variety of points within the whaling fleet."

The aerial mission will run between January and March 2014.

Sea Shepherd activists left Australia for their 10th annual harassment campaign of the Japanese last week as the international community warned against violence from either side.

High-seas clashes between the groups are common and Sea Shepherd, which has sent three ships to the Antarctic this year, regularly pelts the whaling ships with stink bombs, attempts to foul their propellers and manoeuvres vessels between harpoons and whales.

Last year, the environmental group claimed that a Japanese boat had rammed its vessels on multiple occasions -- destroying masts and a radar on the Bob Barker and leaving it without power.

The Japanese claimed their boats had been rammed by the campaigners as tensions in the Southern Ocean soared, two years after a January 2010 collision in which Sea Shepherd's Ady Gil sank.

Their hunt -- conducted under a loophole permitting harpooning for "scientific research" -- netted just 103 minke whales, less than half the tally in the previous year, and no fin whales, with Japanese authorities blaming "unforgivable sabotage" by activists.

Australia, the Netherlands, New Zealand and the United States issued a joint memo Friday "unreservedly condemn(ing) dangerous, reckless or unlawful behaviour by all participants on either side, whether in the Southern Ocean or elsewhere".

"We will deal with unlawful activity in accordance with relevant international and domestic laws," the four anti-whaling nations said.

Australia has taken Japan to the International Court of Justice seeking a ruling that its whaling programme is illegal. A decision is expected in early 2014.