A Japanese whaling ship left port for Antarctic waters for the annual hunt of the giant sea mammals, Greenpeace said, forecasting this year's whaling operation may be curtailed "considerably."
The factory ship Nisshin Maru left the western port of Innoshima Thursday "later in the season than in the past," said the environmental activist group.
"Every year, after departing from its home port, Nisshin Maru joins other ships offshore without stopping by at another port, and then they form a fleet to jointly head for Antarctic waters," a Greenpeace spokesman said.
Japan kills hundreds of whales a year in Antarctic waters by using a loophole in the 1986 moratorium on commercial whaling that allows the sea mammals to be hunted for "lethal research."
But the group said Japan's whaling operations in Antarctic waters are expected to shrink "due to a decline in demand for whale meat and deterioration of fund raising."
"The possibility of Nisshin Maru's early return is high," the group said in a statement. "It is anticipated that the number of whale catches will decline considerably."
A Japan fisheries agency spokesman refused to confirm the departure due to "security reasons."
Anti-whaling nations led by Australia and New Zealand and environmental groups have attacked Japan for its annual hunting expeditions, criticising them as cruel and unnecessary.
Japan, which says whaling is part of its culture, makes no secret of the fact that whale meat ends up on dinner tables.
Militant activists, especially the Sea Shepherd Conservation Society, have harassed whalers in recent years, moving their ships and inflatable boats between the harpoon vessels and the sea mammals.
On Wednesday, Sea Shepherd members said they had launched a new "Godzilla" speedboat to chase Japanese harpooners hunting the giant mammals in Antarctic waters.
The newest vessel "Gojira," as the giant monster Godzilla is known in Japan, has replaced its futuristic Ady Gil craft, which was destroyed in a high-seas clash with whalers.
A New Zealand inquiry found both vessels were at fault over the incident, which occurred as Sea Shepherd boats harassed Japanese harpooners and resulted in the Ady Gil sinking.
Australia strongly opposes Japan's whaling and has started action against Tokyo in the International Court of Justice over its continued slaughter of the animals.