ANNAPOLIS, AUG. 20 -- An interstate commission that monitors the health standards of seafood has threatened to declare Maryland in violation of sanitary shellfishing practices, a move that could lead several states to impose embargoes on Maryland clams and oysters.

The move could have a disastrous effect on Maryland's multimillion-dollar seafood industry, which is already suffering from health-related clam embargoes imposed this month by Maine and Massachusetts. The industry has been further buffeted by the prospects of its worst-ever oyster season expected this winter.

State officials said today they disagree with the complaints of the Interstate Shellfish Sanitation Conference, but are rushing to satisfy them for fear of the economic consequences.

The ISSC, following a vote on the issue last month, notified state officials last week that Maryland violates accepted standards by allowing shellfishing close to marinas where pollutants may be present and by not routinely closing down several Chesapeake Bay shellfishing areas with relatively high bacteria levels after heavy rains, a time when bacteria are more prevalent. The ISSC, comprising representatives of 23 shellfish-producing states, said it would notify states that Maryland is in violation unless the problems are corrected by Sept. 15.

The ISSC has no power to impose embargoes, but many states have laws that forbid shellfish from states that do not meet ISSC guidelines. ISSC officials said today that many without those laws would probably also impose embargoes.

"It could have some serious consequences," said Ray Feldman, a spokesman for the Maryland Department of the Environment. "This has not been a banner year for our watermen. They've had more than their share of hard times and problems . . . . Anything we can do to protect that industry and to protect the reputation of Maryland, we're going to do.

"I can't discuss specific points, but we're going to work with them and we're going to try to get the outstanding issues resolved and try to comply with what they want to do," Feldman added.

ISSC Vice Chairman Ken Moore said today that monitoring had shown bacteria levels that were slightly higher than permitted in several small, isolated areas. "Their nonconforming with guidelines does not necessarily mean that the product is of a lesser quality," Moore said. "It means that the potential exists that it could very easily be of a lesser quality. Public health protection is based on potential."

Massachusetts, citing high bacteria levels that are believed caused by improper food-handling, banned imports of soft-shell clams from four major Maryland seafood dealers, while Maine banned imports of clams this week from three areas in the upper Chesapeake. Health officials in both states said several samples of Maryland clams had been tested with bacteria counts more than 70 times as high as ISSC standards.

Massachusetts health officials said this week that they expect to embargo clams from several additional Maryland seafood dealers in the next few days. Health officials in Massachusetts, one of the largest markets for Maryland clams, said no illnesses have been reported because of infected clams but noted that the most likely sickness would cause stomach and intestinal problems that few people would bother to report.

Health officials in both states agreed the problem is probably caused by poor refrigeration and made worse by hot weather. Maryland health and fisheries specialists have been encouraging clammers to rush their catch to shore more quickly than normal, and are asking truckers and dealers to make sure their refrigeration systems are working properly.

"There's been some improvement," said Betty Harden, chief of the Maryland Department of Health and Mental Hygiene's food control division. "But whether it's improved to the point where New England is going to see the effects of it, I don't know. It doesn't appear that it has yet."

Officials in Massachusetts, Maryland and Maine denied allegations by some watermen and seafood dealers that the embargoes are a form of economic warfare designed to keep Maryland clams out of New England. Massachusetts authorities noted they have banned clamming within their own waters off Cape Cod for the last two weeks because of high bacteria counts caused by heavy rain.

Larry Simns, a clammer who is president of the Maryland Watermen's Association, said most clammers were catching their legal limit of 15 bushels a day before the embargoes began, but have now cut back to about half that. Clam prices had already been low because clams have been plentiful this year. Now, with a reduced catch caused by the embargoes, Simns said, "we're not even making expenses. We're not breaking even."

Many clammers switch to catching oysters when oyster season begins Sept. 15. But state fisheries specialists are predicting the worst oyster season of the century. Not only is pollution causing poor oyster production -- annual harvests have fallen from 3.5 million bushels 20 years ago to just under 1 million last year -- but an oyster disease called MSX has been killing large numbers of Maryland oysters this summer.

The Maryland Department of Natural Resources had predicted a harvest of about 900,000 bushels this year, according to shellfish division chief Bill Outten, but is now expecting a harvest nearer 600,000 bushels. "It's going to have a pretty severe impact," he said.

"It seems like all the problems are bunching up on us," Simns added. "I think this is probably going to be one of the worst years that we've ever been through. A lot of people count on paying their bills and getting money for the wintertime with oysters . . . . If there's anybody out there who can find something else to do, there going to do it."