Nobody told the men to start their engines this morning.Nobody had to. By 5 a.m., they were three dozen deep around G. L. Fairbank's general store. It was time to oyster - and time to catch up.

As Maryland's oyster season began at sunrise this morning, so, too, did the efforts of the state's 5,000 licensed watermen to make up for the devastating effects of last winter.

Hard, biting cold froze Chesapeake Bay solid for six weeks last January and February. Nowhere was the ice as thick, or the effects as profound as in this small Eastern Shore town of 650.

Although a hardly few but holes in the ice and tried to catch oysters that way, the great majority of the oystermen in Talbot County, where the catch is traditionally Maryland's most bountiful, simply sat home.

Delmas Haddaway was one of the sitters, so it was little surprise that, this morning, he was one of the most anxious to begin.

He had his 39-footer, the Island Star, under way before 6 a.m. White it is illegal to take oysters before sunrise, Haddaway wanted 40 early-bird minutes to look for the best place to "park."

He found it above a sandbar called Shell Hill, near Poplar Island, about four miles northwest of here. When dawn officially broke at about 6:40, Haddaway and his two young assistants immediately began to "tong" oysters from the bottom, using the massive scissor-like objects that most oystermen use to pull, up their catch.

Haddaway, 67, has been tonging these waters - indeed, he has been tonging the very oyster bar where he sat this morning - for 55 years. So he asked the forgiveness of a companion; after all that experience, he said, he stil judges how good a season is going to be by the presence of a rainbow.

And there one was, arcing to the west, as high and nearly as broad as the Bay Bridge. "Just look at that," said Haddaway. "You know, they say, 'A rainbow in the morning, you better take warning.' But I've got it figured just the other way."

When Haddaway figures, watermen listen. For he is not only the oldest and most experienced hand tisll working the waters off Tilghman, but he has the reputation of being one of the best oystermen on the whole bay.

The reputation stems, of course, from being able to collect oysters. And that is hard to do without first finding them. The man they call "Mr. Delmas" finds them using a kind of radar even he cannot explain.

He told a fellow tonger this morning about a promising oyster bar "just opposite those trees near Poplar Island." The man nodded, apparently in understanding. But as soon as the 6 a.m. chase was on, he simply followed the Island Star. There was quickly enough for both boats.

Haddaway claims he is now retired - "Just out here for the pastime is all." So he keeps his well-weathered face amidships away from the heavy work, merely culling through what is heaped on board by his grandson Randy, 24, and Dennis Jones, 25.

Hand tongers like Jones and the Haddaways use wooden implements 22 feet long, with cages mounted on one end. The tonger is dipped into the water until it hits bottom. Then two handles are worked back and forth across the chest, rapidly, like a man trying to ward off a bad chill. In a few seconds, by feel, the tonger can tell he has a full load. He raises the cage, drops the oysters into the boat and plunges in again.

The process goes on about seven hours a day, seven days a week. This season, oyster prices are expected to average between $6 and $7 per bushel. For the Island Star crew, that will mean about $100 a day for Randy Haddaway and Dennis Jones. Delmas Haddaway will take only $10 a day because he will lose his right to Social Security payments if he earns more than $3,000 a year.

The three men's oystering habits are circumscribed by the dictates of the seven-month season, which starts in September - for hand tongers - partially because the crab catch the other state of their livelihood, is beginning to dwindle at that time.

The actual date of Sept. 15, state officials concede, is somewhat arbitrary - all maritime seasons, for oysters, crabs, or other types of seafood begin either on the 1st, 15th or 30th of their opening month.

It seems as if the portents are nothing but good for oystermen here this season.

Not only does the Farmer's Almanac promise a milder winter than last year, but, for the first year since tropical storm Agnes devasteted the oystering industry in 1972, changing the habitat of the very young oysters and drastically altering the environment salinity of the water - a crucial element of the oyster habitat. The sources predicted last month that this year's catch should be the best since 1972-73, barring unforeseen circumstances.

But neither good news nor bad news surprises Delmas Haddaway.

"After all these years," he insisted this morning, as he poked at shells with a tonging hammer, "I still don't know nothing about oysters. I don't believe it's storms or pollution or anything. Nature just takes care of things."

Stills, he acknowledged that "it's a hard life. A lot of time you get thoughts in your head" about another line of work, he said.

His young companions think it's a hard life in other ways. They work seven days a week year round, seven months oystering, the rest of the year crabbing. And they are used to being exhausted. "Oysters may be good for your love life," said Jones, "but tonging sure ain't good for it."