By Phil Mercer
BBC News, Sydney
Activists intent on disrupting Japan's annual whale hunt have offered a $25,000 reward for information that leads them to the whaling fleet.
Japan says that hunting whales is its sovereign right
The New Zealand military has filmed the hunters harpooning whales in waters south of Australia, but is refusing to give details.
They are concerned activists could use violent tactics against the whalers.
The Japanese crews are on a mission to kill about 850 minke whales and 10 fin whales.
Commercial hunting was outlawed in the 1980s, but Japan has continued its annual cull for what it calls scientific research.
Critics believe that this is simply a tactic to circumvent the regulations, and amounts to commercial whaling in all but name.
A sophisticated and dangerous game of hide-and-seek is being played out in remote waters off Antarctica.
Conservationists aboard three vessels are hoping to track down the whalers in the Antarctic. Activists have threatened to ram the Japanese ships and force them back to port.
Others intend to use small inflatable boats to put themselves between the hunters and their prey.
Finding the fleet in such a vast area is, of course, a gigantic problem.
Campaigners from the group Sea Shepherd have offered a reward for anyone who can help.
But the Japanese are reported to be using satellites to keep one step ahead of their pursuers.
The New Zealand air force filmed the whaling fleet last week, but is refusing to divulge any details of its location because of the threat of confrontation.
New Zealand and Australia both oppose Japan's whaling programme.