Half of Bristol Harbor has been closed to shellfishing for several years due to contamination. So what do you do when you can’t go to the quahogs? Bring the quahogs to you.

For one day last week, 21 shell fishermen were allowed to dig up quahogs from the bottom of Bristol Harbor just off Independence Park. With bacteria levels from runoff in that area of the harbor unacceptably high for Department of Environmental Management standards, the quahogs are not fit for human consumption — at least not yet — so they were given a temporary reprieve from the dinner table. Instead of selling them at market, the shell fishermen delivered the quahogs to another part of the harbor, off Poppasquash Point, where the water is cleaner. There, the filter feeders that constantly push water through their bodies to eat will be able to flush all toxins out of their bodies.

“Instead of waiting for the water to be clean, we’re just moving the clams,” said Dennis Erkan, a marine biologist with DEM who headed up a quahog transplant program in the bay last Thursday. “They will push clean water through their bodies, and they’ll be safe to eat in three weeks.”

They still won’t be eligible for harvesting at that point, however. The DEM transplant program aims to improve the health of the quahogs, while at the same time increasing their population. To give them time to grow and reproduce, DEM is prohibiting fishing until the end of the year.

“We’re trying to do a double benefit,” Mr. Erkan said. “Not only the depuration, but we’re also giving them the chance to spawn. It’ll be beneficial to give them the opportunity to spawn before they’re harvested in December.”

The 21 fishers were able to fill an average of 30 bags, each weighing about 50 pounds, for a total of more than 30,000 pounds of quahogs transplanted to a cleaner part of the bay. With current wholesale prices of about 35 cents per pound for quahogs, according to Andrade’s Catch on Wood Street, the transplant program injected more than $10,000 worth of clams into the clean part of the harbor. That number will multiply as the clams reproduce.

Thursday’s transplant program was the second of the week for DEM, after last Wednesday’s program in Greenwich Bay. All tolled, DEM moved more than 80,000 pounds of quahogs into clean water, a boost to an industry that makes a significant impact on the state’s economy. Last year, more than 100 million pounds of seafood arrived at a local port, with an export value more than $1 billion, according to the DEM. Wild harvest shellfishing supports hundreds of fishers year-round, which feeding thousands of Rhode Island residents and visitors. More than 28 million quahogs were harvested from Narragansett Bay and local coastal waters last year, contributing about $5.5 million to the economy.

The clams transplanted in Bristol last week will be eligible for harvesting in December. Commercial fishers can harvest three bushels ( totaling about 150 pounds) each, three days a week. Recreational quahoggers can bring in a peck a day, about two gallons.