he number of persons arrested in the attempted blockade of the Diablo Canyon nuclear power plant reached nearly 900 today as sheriff's deputies began rounding up protesters still left on remote parts of the plant's property.

The small municipal court here, with only two spare courtrooms available, today began arraigning those arrested in the three-day-old protest. Sgt. Leon Cole of the county sheriff's department said less than half could be arraigned today and Friday and the rest must remain until next week in temporary jails at a college gym and a minimum security men's prison near here.

"It appears to be winding down," said Cole who estimated that only 400 demonstrators remained on the rugged beaches and hills near the plant or at the demonstrators' temporary campground. "We'll try to go out and seek some of the small groups in the hills and get them off," Cole said.

Unlike yesterday, when demonstrators managed to block the plant's main gate and keep construction workers from entering for several hours, sheriff's deputies pushed demonstrators and reporters out of the way whenever buses entered or left. Some demonstrators complained of rough treatment by the deputies and three newsmen, a photographer for the San Francisco Examiner and a camera crew for the Cable News Network, were also arrested in the confusion, bringing the total of media arrests to six.

Members of the Abalone Alliance, the anti-nuclear coalition protesting the potential health hazards from radiation associated with the plant, said, however, that they expect many of their members to rejoin the blockade after they are released from jail.

"I think it's going to last a lot longer than the authorities think it is," said Valerie Endres, 45, a local realtor who was released yesterday after she promised not to risk arrest again. She said she would still provide support to other demonstrators, however.

Robert Blake, famous for his portrayal of an undercover policeman on the television show "Baretta," left a remote section of beach near the plant today so that he could return to Los Angeles for an appearance on the Johnny Carson show. Blake said "a fat sheriff" tried to arrest him for his part in what the demonstrators call the "sea blockade" part of the protest, but he and others waded to an offshore rock and avoided capture. The sheriff shouted at Blake through a megaphone, "I want you in my car, sonny."