Secret trips across Formosa Strait defy barriers between Taiwan and China

The quickest, most direct route from Taiwan to the mainland passes through this offshore island, 73 nautical miles across the strait from Hsinchu in Taiwan.

In the eyes of the Taiwan authorities, who forbid their citizens to visit the mainland, the 11-hour trip by fishing boat to Pingtan is illegal. But a steady trickle of Taiwanese is taking the Pingtan route each year - to visit relatives, to do business, or to sightsee.

''It's not a comfortable trip,'' said a man in his mid-30s who asked to remain anonymous. ''But you don't need a passport or a visa, and you can stay in China as long as you want.

''Hong Kong is less than an hour from Taiwan by air. But to go to the mainland through Hong Kong, I have to get a passport and my stay in China is limited by the visa that I receive for Hong Kong.''

The young man, who said he had been to the mainland several times on business and to visit relatives, said that this time he had received a cable saying his octogenarian grandfather was critically ill. The cable, sent from the inland city where his grandfather lives, reached him via a mutual contact in Hong Kong.

''Actually,'' said a Taiwan-born professor now living in Fuzhou (Foochow), ''we can telephone Taiwan direct. The operator doesn't tell us how she gets the call through - probably, I suppose, through Hong Kong - but I can talk directly with my relatives on Taiwan.''

Thus, in small but significant ways, the barriers that Taiwan has tried to interpose between its citizens and the mainland are being penetrated. Unlike Taipei, Peking welcomes contacts between the mainland and the island it claims as its 30th province.

Peking has long advocated direct trade, transport, and communications with Taiwan. It is the Kuomintang (Chinese nationalist) regime on Taiwan that stubbornly refuses all direct contacts with the government that chased it off the mainland in 1949.

Gray mists enshroud Pingtan and its lovely bays and beaches at this time of year. The tide has to be just right for the naval landing craft that bounces across the choppy channel separating Pingtan from the mainland to roll on and off its cargo of trucks, jeeps, and buses at each end of the 15-minute ride.

''Welcome to the fifth largest island in China,'' said Fang Jingren, deputy director of the Pingtan Reception Center, as we jumped ashore with the tide lapping at our shoes.

He quickly reeled off the other four: Taiwan, Hainan, Chongming (at the mouth of the Yangtze River) and Zhoushan (in Zhejiang Province). Pingtan is a hilly island. The vistas of green slopes and slate-gray sea one sees from the winding road to its chief town remind one of Scotland, as do the granite cottages along the way. Stone is cheaper here than wood - the island was denuded of tree cover, Mr. Fang said, before the Communist victory in 1949.

Fujian Province, of which Pingtan is a part, opened the reception center here in 1981 as one of four places where Taiwan fishermen caught in storms or needing repairs could seek temporary refuge.

Taiwan fishermen fish the coastal waters of Fujian because Taiwan's own inshore waters suffer from industrial pollution, said a burly captain who said he ran a 33-ton vessel from Taiwan. Each fishing voyage takes about 20 days; yellow croaker and hairtail are the principalcatch. The captain said nothing about smuggling, which Fujian and Taiwan officials say they are trying to stop, but which is difficult to control.

Taiwan and mainland fishermen are said to rendezvous in various places along the highly indented coastline and to exchange goods - tape recorders and other electronic goods from Taiwan, Chinese medicinal herbs, wines, and other native products from the mainland.

The captain said this was his second visit to Pingtan. He had heard on the radio that the reception center was open, but at first he was afraid to land in a communist port. When he finally did so, in July last year, he was so hospitably received that he decided to pay another visit.

The captain was himself from Fujian, having been captured by Taiwan navy boats while fishing off Taiwan-held Matsu Island in 1952. On his July visit, he was able to meet a sister who had been only two at the time of his capture.

''Taiwanese or mainlanders, we are all the descendants of Yen and Huang (legendary early emperors of China),'' Mr. Fang said. ''Taiwanese and Fujianese are particularly close because most Taiwanese came from Fujian and speak the same dialect.''

Seven hundred fishing boats and 5,000 people from Taiwan had visited the center since its opening in 1981, Mr. Fang said. Among them were nonfishermen, such as the young man seeking his grandfather, and merchants. Mr. Fang would not discuss smuggling, but legitimate merchants were welcomed, he said, if they had anything to sell that China needed.

Otherwise, they were asked to bring US dollars or other foreign currency with which to pay for the medicinal herbs and other mainland products they desired to buy. One room in the reception center was set aside for commercial negotiations.

Genuine fishermen were allowed to stay at the center free, but merchants were asked to pay six yuan per day for a single room, plus four yuan per day for meals - altogether the equivalent of $5 per day.

A curious Chinese asked the young man seeking his grandfather, ''Aren't you afraid your neighbors will report you when you get back to Taiwan?''

''Well,'' the young man replied, ''our social system is different from yours. I have lived in the same apartment building for 15 years, but I don't know who my neighbors are and they don't know who I am. No one will ever know how long I was away or where I went.''