On the day oyster season traditionally begins in Maryland, Paul Coleman was catching crabs instead, and working on his boat engine on Kent Island.

"All my life I've been oystering," Coleman, 71, said last week. "Thirty years ago here, the oysters grew out of the water. We caught us 100 bushels in one day about 30 years ago. Now I bet there ain't 20 bushels in the whole place. Twenty years from now, there's liable to be nobody oystering."

Maryland's oyster industry, which once supplied about half the nation's oysters, is in trouble. Harvests have plummeted to record lows, and pollution and overharvesting are ravaging what's left. In addition, a deadly oyster disease this year has wiped out unprecedented proportions of an already depleted supply, and more than 90 percent of the state's oyster grounds are infected.

Experts have stopped short of pronouncing the death of oystering, for which Maryland was once famous, but they admit that despite the state's efforts to save the industry, the overharvesting and pollution that are killing it continue. The mysterious disease will never completely go away, scientists said, and it will be years before enough disease-resistant oysters can be bred to make a significant difference.

Once, the Chesapeake Bay teemed with oysters. Fortunes were made on them. Railroads were built to haul them out to market, and towns grew on top of their discarded shells. At the turn of the century, about 28,000 oystermen worked Maryland's waters and harvested more than 10 million bushels of oysters a year.

Now, about 1,600 oystermen harvest a total of less than 1 million bushels annually.

"The outlook for harvest in 1988-89, 1989-90, and future years is grim," a recent report by the state Department of Natural Resources stated. "The extent of mortality of . . . oysters due to disease is alarming."

The dwindling harvests have resulted in higher prices for oysters, making them more expensive in restaurants and forcing businesses to order them from other parts of the country. Because of the increase in price, the negative effect on the state economy has not yet been significant, officials said, but the oystermen, once the subject of Maryland lore, are disappearing.

Maryland watermen traditionally view state officials as interfering know-nothings, and automatically reject their warnings and predictions. But for once, many are in agreement on the industry's dire fate, and that the disease called MSX is a calamitous problem.

"They are right this time, for the first time ever, I think," said Rob Joiner, a waterman from Rock Hall, an upper Eastern Shore fishing town, who has seen the results of MSX while dredging for clams during the summer. "MSX, it's taken over. It's killed close to all the oysters down the bay."

As much as 90 percent of oysters in some of Maryland's most profitable oystering areas have been killed by the fast-spreading parasitic MSX. The disease has not been found to affect humans.

Among the dead and dying oysters are the unusually large number of young oysters, called "spat," which were born in 1985, and would have been ready for harvest this year and next, and had promised to inject new life into the industry.

The state has asked watermen to keep clamming and crabbing into the fall and leave the oysters alone. Opening day of the oyster season was pushed back from Sept. 15 to Oct. 1. But Joiner and most other watermen interviewed said they had to catch the oysters quickly, to get what they can before disease or other watermen claim them all.

"I believe all of them will be gone in two or three weeks," said Ashley Elbourn, another waterman from Rock Hall. "Then you may get a day or two when you catch a few, but it will peter down so you don't get nothing."

Scientists have so far been unable to discover ways of preventing MSX, or even determining the origin of the parasite that causes the disease. They do know that once it infects an area, it never goes away, although it is more virulent in dry years such as this one when water salinity is above normal. And they also know that it can wipe out a state's oyster industry.

When MSX hit the Delaware Bay in the late 1950s, harvests plummeted and never recovered. "We can't make projections for the Chesapeake Bay," said George Krantz, director of Maryland's shellfish laboratory near Cambridge. "We can only look at what happened in Delaware Bay. They went from 5 million {bushels} a year harvest to under 200,000, and have stayed under 300,000 ever since. It's quite possible the same thing could happen here."

State officials say they have little choice but to try to encourage oystermen to work water that has so far been uninfected, to attempt to breed selectively disease-resistant oysters in the laboratory, and to hope that MSX abates and evolution quickly produces disease-resistant oysters.

"It takes about three years for an oyster to reach market size," Krantz said. "If the disease went totally away this year, it would take at least {three years} to recover, and that's assuming you have enough brood stock around to create a new population . . . . It would be five to seven years for a complete recovery. And then, of course, if harvesting is permitted while the rebuilding process is occurring, it may take even longer."

Oysters have always been an important part of the state's economy and culture. Until the early 1980s, oysters were more valuable than blue crabs, finfish or any other Maryland seafood. The small white oyster boats and large sailing skipjacks became recognizable Maryland symbols, while oyster towns like Crisfield became tourist attractions.

In recent years, Maryland's annual oyster crop has sold for about $16 million, but state officials estimate that the shellfish produce enough business for packing houses and restaurants to be worth three times that amount. (Seafood production, worth about $40 million annually, according to 1983 figures, ranks behind the state's $1 billion agriculture business and $8 billion manufacturing industry.)

Even if MSX abated, Maryland would probably still face the serious overharvesting problems confronting it before the disease struck. The state is trying to limit harvesting by imposing daily catch limits and by forcing oystermen to use antiquated and inefficient methods. The only modern method allowed is scuba diving, but divers are allowed to catch far fewer oysters than those using traditional methods. Mechanical dredging is allowed only from sailboats -- the old wooden skipjacks that form the last fleet of working sailboats in the country.

The vast majority of oysters are still caught with hand tongs, a technology used by American Indians before white settlers arrived on the Chesapeake. The oysterman stands on the edge of his boat, lowers a long scissors-like apparatus into the water, scrapes together a pile of oysters and hauls them hand-over-hand to the surface. A variation called the patent tong is lowered by ropes to reach oysters in water too deep to reach with hand tongs.

But despite the dramatic decline in oyster harvests, Maryland officials say oystermen are still extracting more oysters from the bay than the bay can support.

The average oysterman last year caught less than the legal daily limit, the recent Department of Natural Resources (DNR) report noted, showing that "the daily catch limit is no longer an effective conservation measure."

In addition, rising oyster prices have encouraged watermen to spend the extra time it now takes to catch fewer oysters.

Between 1975 and last year, the waterman's average daily oyster catch fell from more than 16 bushels a day to almost five bushels, but the average price he received went from less than $5 a bushel to more than $16.

When adjustments for inflation are made, the average oysterman now makes about the same amount of money -- just under $10,000 -- as he made in 1975.

Whether prices will rise enough this year to make up for a paltry harvest remains to be seen. While many state officials hope the prices will allow watermen to stay in business, the DNR report stated that a large price increase "encourages overharvest of the resource to the detriment of future stock."

State officials say they are not considering closing down the oyster industry to give the oysters time to recover from overharvesting and disease.

They say the large number of young oysters born in 1985 -- despite the pollution and overharvesting -- show that the oysters can reproduce, although the young were killed by disease. They also argue that it is best to let the watermen catch the oysters before they are infected with disease.

"The oysters are still going to die, so in a sense, it's better utilization of oysters to let them use {them} at the present time," Krantz said. "Closing the industry wouldn't do anything. The disease situation is going to take its economic toll, and the industry will end up pretty much closing itself. I think the watermen will begin choosing something else to do."

When MSX crippled the oyster industry in the southern Chesapeake Bay in the early 1960s, many Virginia watermen turned to catching rockfish. Maryland watermen do not have the same option, because fishing for rockfish was banned in 1985 because of overharvesting.

"There are fewer things to switch to," said DNR Secretary Torrey C. Brown. "Everybody used to keep busy by going from shad to rockfish to perch to crabs to oysters to clams to whatever. Now we're short on perch, rockfish is banned, and shad are banned also because there are so few of them. And oysters have a disease. The crabs are doing fine, and thank goodness for that."

Brown said oysters are important to Maryland's history and culture as well as profitable to watermen.

"It would be awful, but we could survive without them," he said. "But we sure don't want that to happen, and we'll do everything humanly possible to prevent it."