With five Soviet ships and cruising gray whales as escorts, seven jubilant anti-whaling demonstrators were handed over in U.S. waters and began steaming toward Nome, Alaska, after being released from the Soviet Union, where they had landed without permission to photograph a whaling station.

The protesters' return, at 11:03 p.m. Bering Daylight Time Friday (5:03 a.m. EDT today) came as the International Whaling Commission, meeting in Brighton, Britain, announced that it is slashing commercial hunting quotas by more than 18 percent and has won Peru's support for a ban by 1986, weakening the opposition from major whaling nations.

The new annual catch quota for eight species of whales will be 10,160. Five years ago, the estimated catch was 60,000.

Environmentalists hailed both the Soviets' and the whaling commission's actions. "We are absolutely delighted. More than another 2,000 whales have been saved," said John Frizel, executive director of Greenpeace International. "But we will continue campaigning against whaling until there is no more to campaign against."

The seven whaling protesters, who were held in military barracks after Soviet authorities detained them late Monday following their raid on a Siberian whale processing plant, boarded the Greenpeace trawler Rainbow Warrior from a Soviet merchant vessel at a rendezvous point across the international dateline. A warship and three other Soviet vessels waited in the background in the calm Bering Sea under a well-lit Arctic summer sky. "Gray whales spurted round the hand-over point," a Greenpeace spokesman said.

"I'm glad you're back," said Betty Jo Jackson, as she hugged her son Patrick Herron, 32, of Seattle, during the emotion-packed reunion. "I'm glad you're not hurt."

"I think we made some friends, and that's what we went over there for," said Dave Rhinehart, 27, of Albany, Ore., adding that he felt the activists had made a good impression on their Russian captors. "The Russians treated us very well," agreed Barbara Higgins, 25, of Philadelphia, another detainee.

"The attention we've received because of the high-speed chase at sea and the people being taken captive has been beyond our greatest expectations," said Patrick Moore, Greenpeace Canada director.

After the seven climbed aboard the Rainbow Warrior, skipper Peter Willcox told them that because of what they did, the Soviet Union has admitted privately that it had been feeding whale meat to mink, a violation of international accords, at the Bering Sea whaling station of Lorino, where they were seized.

However, Ivan Nikonorov, the Soviet delegate to the International Whaling Commission in Britain, said that he doubts the authenticity of film that Greenpeace said shows that the whaling station was processing whale meat to feed to minks.

Chief Mate Jim Henry, 33, of Orrs Island, Maine, and Higgins said that the biggest problem during their detention was boredom. The Soviets gave them a chess game and a Rubik's Cube, but there was little other entertainment.

The six arrested at the whaling camp were Rinehart; Higgins; Herron; U.S. Greenpeace director Chris Cook, 35, of Washington, D.C.; cameraman Ron Precious, 36, of Vancouver, British Columbia, and Nancy Foote, 35, of Washington D.C. Henry was picked up off the coast from an inflatable boat.

They said that they were seized by armed soldiers at the whaling station. At one point, they were led to believe they might spend from one to three years in prison, Henry said.

They also said that after their arrest they were flown by helicopter to a military base, back to Lorino for interrogation, then again to the base, where they spent most of the week.

Nome Mayor Leo Rasmussen, who was deputized as a U.S. State Department representative, was taken to the Soviet merchant ship Fedor Matisen, where he met with Soviet officials for about an hour. He said that he signed release papers and accepted a formal protest from the Soviets.

The whaling commission's action in Britain today brings it nearer to its goal of a ban on commercial whaling by 1986. Japan, which kills more whales than any other nation, the Soviet Union and Norway together account for 90 percent of the commercial whale catches.

The commission has no legal power to force whaling nations to comply with its decisions. After Peru agreed to halt whaling, Norwegian delegate Per Tresselt said that his country will continue whaling "as long as it is biologically justified."

The Soviet and Japanese delegates expressed concern about the future of the commission. But conservationists voiced confidence that Japan will comply rather than face a threatened embargo on fish exports.

Alaskan Eskimos, under the category of aboriginal hunting, will be allowed by the commission to catch 43 bowhead whales during 1983-85.