On a hillside overlooking the Japanese coastal village of Katsumoto on the island of Iki, American environmentalist Dexter Cate, 36, peered through binoculars at a stage set for slaughter. Below, in a shallow harbor, local fishermen had strung nets trapping hundreds of dolphins, soon to be ground into fertilizer and hog feed. "Those fishermen were there merely to do a job," says Cate. "They didn't consider it murder, but I did. I knew I had to do something."

So on a stormy night last February, Cate kissed his wife, Suzie, and year-old son, Banyan, and paddled into the bay in his inflatable kayak. "I untied three nets where they were fastened to the shore," he recalls. "The last one was too tight, and I had to cut the knot." Still, his night's work wasn't finished. Frightened and disoriented, many of the dolphins thrashed aimlessly in the now bloodied waters, unable to find their way to the sea. "I climbed into the water and tried to direct them out," Cate recalls. "I stayed on the island all night putting beached dolphins back in the water."

By morning, Cate estimates, he had freed between 200 and 300 dolphins. Then the fishermen returned to their nets. "They were angry, but not abusive," he remembers. "They understood, finally, that I had acted from a moral position. They just didn't understand that position." Neither did a Japanese court following his arrest. Cate spent three months in jail during trial proceedings. Recently he was found guilty of forcibly obstructing business, given a suspended six-month sentence and deported to his Hilo, Hawaii home.

Cate grew up in landlocked Kingman, Ariz., but was fascinated by sea creatures. On the wall next to his bunk bed he drew pictures of whales—"only whales," he recalls. Both his parents were teachers, and at 16 he moved with his family to Guam. Captivated by the island's beauty, Cate later studied anthropology and marine zoology at the University of Hawaii. After graduation he taught science and mathematics for two years as a Peace Corpsman in Sierra Leone, then returned to Hawaii to continue his teaching. "In 1978," he says, "I retired to devote the rest of my life to protecting the environment." (He is now a salaried field agent for Cleveland Amory's Fund for Animals.)

That same year Cate visited Japan and witnessed the destruction of more than 1,300 dolphins on the Izu Peninsula. Determined to prevent further killing, he and his wife toured Japan's west coast by bicycle, talking with fishermen and union leaders. The dolphins were being butchered, the Cates learned, because the local catch of yellowtail had declined alarmingly and the seagoing mammals were blamed. Convinced that pollution and over-fishing were the real reasons for the decline (one scientist's study has since revealed no yellowtail in dolphins' stomachs), Cate decided to return to Japan last winter. To his dismay, he learned that the killing was now officially encouraged: The government had placed an $80 bounty on dolphins. It was then that he turned to civil disobedience.

Defended without fee by a Japanese lawyer and visited almost daily by Suzie and Banyan, Cate says he was treated well by his jailers. "All my mail had to go through the censors," he says, "and they read all the letters of support I received. After a time even some of the guards became openly sympathetic." Though some of his Japanese friends on Iki feel he betrayed them, Cate believes his much-publicized jailing helped raise the nation's consciousness. "It's very important," he says, "that people recognize the true issue is not fisherman vs. dolphin nor America vs. Japan. The issue is how we relate to our environment. We are exploiting our land and our resources. Unless we change our ways, we can kiss our grandchildren goodbye."