Another two boats, including the 7,575-tonne "Nisshin Maru" mother ship, are set to leave from different ports on Saturday, while a final ship leaves on July 14.

Tokyo maintains that eating whale, regarded as a gourmet delicacy, is an important part of its cultural heritage despite protests by environmentalists determined to prevent the slaughter of the intelligent mammals - many of them endangered.

Many argue that Japan's "scientific" research whaling, which began in 1987, is commercial whaling in disguise. Japan abandoned commercial whaling in 1986 in line with an IWC moratorium.

This year's hunt has faced especially fierce protests because it includes the 12-to 17-metre pointed-snout sei whale that has not been hunted by Japan since 1978 and is listed as in danger.

"Sei whales are much larger than other whales, such as the minkes, and eat more fish," said Takanori Nagatomo, an official at the Fisheries Agency's Whaling Division.

"It is impossible to know their impact on the marine environment without knowing how much, and what, they eat."

Japanese officials blame whales for falling fish catches, saying the mammoth mammals consume such vast amounts of fish that they have contributed to a drop in fish landings by half, to six million tonnes, in the last 20 years.

MORE WHALES

This hunting season, Japan proposes to take 150 minkes in the North Pacific, 50 more than last season. It plans to take 50 sei whales, 50 Bryde's whales and 10 sperm whales in the North Pacific in addition to some 400 Antarctic minkes.

Japan, like fellow whaler Norway, believes that endangered species should be protected but argues that others, such as the minke, are in no danger of dying out.

"The sei whale is not endangered," Nagatomo said, reflecting government arguments that the arguments of environmentalists are based on obsolete data. "Fifty whales is just a small fraction of the population."

Motoji Nagasawa, a whale campaigner at Greenpeace Japan, termed the hunt "extremely regrettable".

"Even though they call it 'research whaling', it's really commercial whaling," he said. "And they have to expand it in order to keep the prices for whale meat down."

The IWC routinely criticises Japan's whaling programme, but protracted feuding at this year's meeting, the result of a heated power struggle between conservationists and those wanting to end a ban on commercial whaling, prevented discussion of the issue.

Among the most contentious points was the decision not to renew hunting permits for bowhead whales for native peoples in the United States and Russia for the first time in the IWC's 56-year history.

CONTENTIOUS ISSUE

The U.S. State Department, and many delegates, singled out Japan for criticism, saying it blocked renewal of the permits to press its own demand that it be allowed to hunt 50 minke whales.

Japan in turn accused the United States of hypocrisy on the issue, since Tokyo maintains that bowheads are endangered.

This week, U.S. Ambassador to Japan Howard Baker told Kyodo news agency that Japan had withdrawn its opposition to a U.S.-Russian bid to get the quotas renewed, and this would pave the way for resolving this issue at a special IWC meeting later this year.

The Fisheries Agency's Nagatomo said more talks were needed.