With a determination as flinty as the rocks this Yankee fishing town has clung to for more than two centuries, the citizens of Gloucester are mobilizing to cope with an invasion by the Unification Church.

Within the past two months, the religious conglomerate headed by controversial Korean evangelist Sun Myung Moon has spent nearly $2 million for real estate in this town of 27,000 people. That is in addition to the church's purchase here two years ago of a seafood processing plant, a 14-room house in a choice residential area and four acres near the waterfront which the church plans to develop for a maritime academy.

Today, a unit of the Moon conglomerate used one of the new purchases, a waterfront restaurant with valuable docking facilities, to launch a "World Tuna Fishing Tournament."

Despite the $100,000 prize money for the tournament, many Gloucester residents believe that the $100 entrance fee collected from each of about 100 participants and the requirement that all bluefin tuna caught must be sold to the Moon fish processing enterprise will result in a tidy profit. Bluefin tuna, which brings from $1.80 to $2.20 a pound here, sells for up to $14 a pound in Japan where the Moon enterprises have sales outlets. f

Besides, 20 or 25 percent of the entrants are Unification Church members and there are strong suspicions among townspeople that the $100,000 in prize money will stay in the Unification family.

"I believe it's rigged," Councilman Louis Sinagra told an emotional town meeting Saturday night on the eve of the tournament. "I predict that the Moonies will make a profit and win the tournament."

Almost every Gloucester fisherman has boycotted the Moonies' tuna tourney.

Concern over the Unification church in Gloucester began two years ago when the church-related business, International Oceanic Enterprises, bought the Gloucester Lobster Co. and renamed it International Seafood. But the Moonies' purchase two months ago of the 30-room Cardinal Cushing Villa, a Tudor-style mansion which had been given to the Roman Catholic Church 40 years ago by a town patriarch, and of a restaurant brought local emotions to a peak.

What particularly irked residents was the perceived deception involved in the villa transaction. The structure and 11 acres, part of it on the waterfront, was sold by the Roman Catholic Daughters of Mary of the Immaculate Conception, who had been using it for a retirement home, to a New Hampshire businessman, Myron Block. Block, who could not be reached for comment, reportedly told Gloucester citizens there was not truth in the widespread rumor that he was buying it for the Unification Church. The next day he sold it to the Unification Church for $1.1 million -- $127.600 more than he paid for it.

There is no evidence that the sisters or Cardinal Humberto Medieros of the Boston archdiocese, which originally received the estate, knew the house was destined for the Moonies. But some in this heavily Catholic town are affronted that Medieros has refused to confer with town officials about the sale.

"My basic complaint is the deception, the use of fronts," said Kathy Hurlbert. "If the Jehovah's Witnesses come to your door, they say they're Jehovah's Witnesses."

Aiden Barry, New England regional director of the Unification Church, defended the transaction. Because of "prejudice" against the church in Gloucester, he said, the property was not sold directly to the Unification Church. It was not deception, he added, it was merely "a secret transaction."

When only a few days later, Uniworld Sea Enterprises, a New York-based affiliate of the church, paid $650,000 for Bob's Clam Shack, a bankrupt rstaurant with valuable docking space, the normally phlegmatic Gloucester temperament erupted.

A figure of Moon was hanged in effigy in the harbour. The City Council passed a fiery but muddily worded resolution that likened the Unification Church to Jim Jones and his Guyana suicide cult and asked town-people not to trade with International Seafood. The resolution was later rescinded on advice of the city attorney.

There was so much harassment at the villa that the Moonies encircled the place with an eight-foot chain link fence and posted armed guards.

A neighbor of the villa, Paul Picone, who shares part of a high stone wall that surrounds the property, found bullet holes in his car and endures continued harassment from passersby who confuse his property with that of the Moonies. Picone now carries a gun to ward off trespassers, most of them youths.

On the other side of Gloucester harbor, just off East Main Street, the Clam Shack is an easier target for vandalism -- broken windows and almost nightly bottle smashings in its spacious parking lot.

"It's the kids," complained an off-duty Gloucester policemen, who has been hired by the new owners of the Clam Shack, renamed the New One restaurant, to patrol the place. "They [the kids] have got nothing to do.

They go out and get a few beers and then it starts."

Gloucester is a Yankee town that has little use for extremes of any kind. It is a quiet working man's town with its own way of life. The 18,000 or so summer people who come here each year are expected to accommodate themselves to the town -- not the other way around.

For the tourist who finds nourishment from breathtaking vistas of the white-capped blue Atlantic crashing on craggy rocks, from eating seafood fresh and well cooked, and prowling the yard sales that line its streets, Gloucester is heaven. But those who quest after amusement arcades and gift shops displaying pornographic coffee mugs and replicas of great art done on seashells must look elsewhere.

Most people here confess they know little about the Unification Church. But based on the experiences in recent months they perceive a number of threats:

That having used less than straightforward tactics to secure the Cardianl Cushing Villa, the church leaders may not be trustworthy in other areas.

That Unification Church-related fish processing businesses, staffed by the low-cost labor of devoted church members and funded by massive church capital, could operate at such a low overhead that they would ultimately bankrupt commercial plants and thereby gain control of Gloucester's lifeline, the fishing industry.

That the Unification Church will seek to lure Gloucester youth into the cult.

That the church, through its more than 100 organizations and fronts throughout the world is buying up more Gloucester real estate with an eye on eventual control of the town.

Although regional director Barry pledged that the Unification Church will not seek to evangelize in Gloucester, there is still considerable concern here. Hurlbert, the mother of three, believes Gloucester citizens are too complacent about dangers of "brainwashing" often associated with cults such as the Unification Church. "We don't warn our children about cults," she said. "We warn them: 'Don't go with a lonely man with a lollipop in the car,' but not about cults."

Hurlbert and a number of other citizens, most of them also housewives, have formed the Coalition for a Free Gloucester to inform the community about the Moonies.

On Saturday night, a handful of citizens picketed the New One restaurant as fishermen arrived for final instructions on the tuna tournament. Numerous passing motorists honked and gave the thumbs-up sign of approval.

A small group of onlookers, clustered on the white steps of a neat green frame house across the street, broke out cans of beer and shouted encouragement. Later, after the pickets had gone, the group remained, enjoying the evening warmth and warning away would-be patrons of the restaurant's carryout section.

"They're Moonies," they shouted as tourist drove into the parking lot. "You don't want to eat Moonie food." Some of the tourist drove off to find other facilities.

Antinette Corkery, a Gloucester schol teacher and self-described "liberal," reflected the conflict many people here feel about the Unification Church. "They have a right to exist," she said. "But I really get upset because I don't see them doing anything for the community, some charity. But I can't work against them. We are Christians and we are supposed to love our neighbors."

A lobsterman, short and powerfully built, who declined to give his name, had a darker view of possible domination by the church of the fishing industry. h"No, they won't take over. If it comes to that, they'll get burned down, if they don't get shot first."