YOKOHAMA, Japan (AP) _ A band played and streamers stretched from ship to shore Tuesday as Japanese whalers began the voyage that will end their 400-year-old industry unless a rule protecting whales is changed.

The 23,000-ton Nisshin Maru No. 3, Japan's last mother ship for whalers, steamed out of Yokohama Port for six months in the Antarctic. Streamers of yellow, green, purple and red paper linked well-wishers on shore to the ship's 231 crew members as the brass band played marches.

Four smaller vessels with 20-man crews are to follow on Thursday. They will catch 1,941 minke whales that the men of the Nisshin Maru will turn into 582 tons of whale oil and 9,317 tons of meat, Japan Whaling Association spokesman Kunio Arai said.

Shortly before the mother ship sailed under overcast skies, Capt. Yasushi Iso told the crewmen and their guests that the break after the 1986-87 season will be ''like a rest period. ... These are not the last whales. We will be able to go whaling again.''

The International Whaling Commission declared a moratorium on whaling in 1982. Japan, the Soviet Union and Norway objected and continued to hunt the huge mammals.

This year, Japan agreed to withdraw its objections to the commission's order after concluding an agreement with the United States. Under it, the Japanese will stop commercial whaling by next year and the United States will not reduce the fish catch the Japanese are allowed in American coastal waters.

Norway has said it will stop catching minke whales after the 1987 season, except for a small number as part of a scientific program.

The moratorium is to be reviewed in 1990.

According to the International Whaling Commission, whales are in danger of extinction unless commercial killing stops. Japan disagrees and cites international scientific surveys.

''A conservative estimate is that there are 250,000 to 300,000 minke whales,'' said Arai, spokesman for the Japanese whalers. ''We think that's more than before.''

Japan says a ban on whaling would put many people out of work, even though the size of the industry has declined steadily. Whale meat was a major source of protein for the Japanese in the lean years after World War II, but today it is a delicacy.

The $77.42 million whaling industry, still the world's largest, employs 1,200 people. Arai said that compares with about 15,000 in the 1960s, when annual catches of 20,000 whales - 10 times this year's anticipated catch - were common.

Ten years ago, the country's three whaling firms merged into the Nihon Kyodo Hogei Co. Officials said two of the three mother ships were scrapped in 1978.

Arai said most whalers used to make their first trip when they were about 16, but there is no longer room for recruits. He estimated the average age of the Nisshin Maru crew at 45.

''As they do their work, they think of how there's no future, so today's spirit is not happy,'' he said.

Haruo Hitaka, sailing for the 30th time as a whale processor, works for an ice cream company in Kobe the rest of the year. He said he followed his father into whaling ''because I thought it would be profitable. Each year I would tell myself, 'Just one more year,' but somehow I kept coming back.''

Yojiro Hirai, one of the ship's seven cooks and also a second-generation whaler, said he expects to be shipping again next year, despite the ban, probably on a scientific whaling trip.

Crew members stood at attention during the departure ceremony, some with tears in their eyes.

Fukujiro Kikuchi, a member of Parliament, told them: ''Ships have been our tradition for a long time. We have to develop a strategy for whaling and look toward a review in 1990 (of the IWC ban). ... From my heart, I wish that your trip is safe, peaceful and properous.''