Only two years ago, New Englanders were thumbing their noses at Maryland clams, and Bill Baxter joked that he was considering a career change, although he had been clamming on the Chesapeake for nearly 30 years.

Baxter was part owner of two of the 11 Maryland seafood distributors embargoed in 1987 and 1988, when health officials in Maine, Massachusetts and New Hampshire found high levels of bacteria in some batches of Maryland's soft-shell clams. In 1988 Massachusetts threatened to ban all Maryland clams unless the problem was corrected.

Today, however, Baxter and other watermen on the Eastern Shore say they can't catch enough to meet demand, and they're earning $20 more a bushel than last year.

The difference, many say, is a two-pronged state regulation requiring clammers to cool their catch on the clam boats and then to pass their haul through state-run check stations, which monitor the temperature of the shellfish.

Since the regulation went into effect last year, no clam companies in Maryland have been embargoed because of high bacterial counts.

"The icing program is the only thing that's keeping us in business," said Baxter, part owner of the Chesapeake Clam Co. in Stevensville.

Maryland is the only clam-producing state that mandated immediate cooling of shellfish. Such regulations are needed during summer months because the Chesapeake Bay is the southernmost region where soft-shell clams are harvested commercially, said biologist Keith Lockwood, who oversees the monitoring program for the Maryland Department of Natural Resources.

"In the old days, the clams would sit in the hot sun for hours out on the clam boat, then maybe on the back of a pickup truck. That's an ideal breeding ground for bacteria," said Lockwood. "By the time some guy got his clams three days later in Massachusetts, half of them might be dead."

The 13 check stations along the shore are operated primarily by college students during the summer. This fall retired and handicapped people are taking over as the students return to school, said Eric May, coordinator of fish health and disease programs for the department. The monitoring program runs from Memorial Day to the end of October.

If cooled to the proper temperature, bushels of clams are labeled with a green tag, which accompanies the shellfish to market.

"The green tag tells the owners of restaurants and wholesalers from Maryland to Canada that these clams have been put on ice immediately after capture," said Lockwood. "Without that green tag, the clams are not marketable."

Maryland is the nation's top producer of soft-shell clams, and in 1988, the most recent year for which figures are available, the state sold 4.2 million pounds bringing in $8.8 million.

Maryland ships about 90 percent of its catch to the Northeast; more than half of the clams eaten in Maine come from Maryland, and officials there say the new regulations have made a difference.

"The product that we've tested for the most part has come in exceeding standards," said Hal Winters, director of marine development for the Maine Department of Marine Resources. "It definitely is an improvement."

About 60 percent of the clams landed in Maryland pass through six monitoring stations around Kent Island, 10 miles east of Annapolis.

This summer Kristy Hassell, a senior psychology major at Salisbury State University, and Micah Clough, a sophomore at Sts. Peter and Paul High School in Easton, mannned the station at W.H. Harris Seafood Co. in Grasonville, one of the busiest around Kent Island. About 20 boats pass through each day.

This was Hassel's second summer as a clam checker. "I'm an outdoors kind of person, and this is a great summer job for me," she said.

Most of the program's 18 clam checkers work from 9 a.m. to 3 p.m. Monday through Saturday. They are paid about $5 an hour.

When the boats pull into the station, clammers unload their ice- and clam-laden bushels, and the checkers measure the clams' temperatures and issue green tags to all properly cooled bushels.

Stations are busiest from 1 to 3 p.m. By state law, clammers must stop harvesting by 1 p.m. They then have two hours to get to a monitoring station.

Not everyone is thrilled with the extra bother and expense of keeping their clam boats stocked with ice.

Baxter said he'll spend $3,000 for ice alone this year, and he has invested an additional $800 in a fiberglass freezer for his boat. "It really hurts in your pocket," he said.

David and Pat Lee, a husband and wife team who have been clamming together for eight years, estimate they spend $15 a day for ice.

And some dealers, like Bill Harris of Harris Seafood on Kent Island, say they never had a problem with bacteria before the program.

But all agree that immediate icing of clams seems to be effective, and most echo the sentiments of David Lee. "It's a lot more hassle," he said, "but as long as it keeps us working, it's worth it."

The Maryland Department of Natural Resources is aware of the watermen's complaints.

"We're looking for alternatives to the expense of ice that are easier to employ and equally as effective," said May. "We have companion studies underway to examine the effectiveness of salt to reduce levels of bacteria, and we're looking at how salt and ice collectively might reduce bacteria levels."

"We have a program here that works," said May. "Now the question is whether we can make it better."