STOCKTON SPRINGS, Maine — Mercury contamination found in muscle tissue of lobsters at the mouth of the Penobscot River led to the Maine Department of Marine Resources’ decision to close a small area to fishing for at least two years.

“This closure is being taken as a precautionary measure,” Patrick Keliher, commissioner of the department, said in a press release issued late Tuesday.

The 7-square-mile area in upper Penobscot Bay extends from Fort Point in Stockton Springs to Wilson Point in Castine and north into the river. It will be closed to lobster and crab harvesting effective Saturday, Feb. 22.

Department officials emphasized that the area is a tiny fraction of the 14,000 square miles fished in the Gulf of Maine. Not many lobstermen fish there commercially, with just seven or eight boats based in Stockton Springs and a handful on Verona Island. No one is fishing in the area right now, according to the Stockton Springs harbor master.

One fisherman who will need to find new places for his traps later this spring is Darren Shute of Stockton Springs.

“It’s a very unfortunate thing,” he said Wednesday. “I hope that the state’s making the decision on good facts. I certainly do understand that decision. We have to protect the status of the Maine lobster at all costs. We’ve got to make sure we don’t do anything to jeopardize that. It’s unfortunate [the closure] is in the area where I’m fishing.”

The fishing ground that will be closed is downstream from the now-closed HoltraChem factory in Orrington, which produced 23,000 pounds of toxic mercury waste each year between 1967 and 1982. The company manufactured chemicals for papermaking and other industries before the adoption of significant hazardous waste disposal regulations, according to legal documents filed with the Maine Supreme Judicial Court.

Mallinckrodt LLC, the sole former owner of HoltraChem still in business, reports spending tens of millions of dollars over the years removing metallic mercury, mercury sludge and contaminated storage tanks and buildings from the site, according to the documents.

But the company has been locked in legal and regulatory battles for years, and in 2008 the Maine Department of Environment Protection ordered Mallinckrodt to begin removing an estimated 360,000 tons of material buried in five landfills.

The information about the mercury-tainted lobsters came from a scientific study ordered by the U.S. District Court in Bangor. The final report from the Penobscot River Mercury Study Panel, submitted to the court last April, found that 6 to 12 tons of mercury were discharged from HoltraChem into the Penobscot River between 1967 and the early 1970s. Smaller amounts have been released since that time, and at least 9 tons of the metal are still in sediments of the upper and lower Penobscot estuary.

Although much of the mercury is buried beneath a layer of sediments, enough is still present on the surface to reportedly make water concentrations of the heavy metal in some places 10 or 20 times higher than normal. Those high concentrations can be found in the Penobscot River below the Veazie Dam, Mendall Marsh and in the lower Orland River.

“Mercury has also been dispersed into Fort Point Cove, and further south in Penobscot Bay as far as Vinalhaven Island at lower surface concentrations, but still elevated above regional background levels,” the report’s executive summary stated. “There is also concern for humans that consume ducks and eels from the upper Penobscot estuary, and lobster in Fort Point Cove.”

The level of mercury found in the muscle tissue of lobsters in the contaminated area is similar to the amount found in canned white tuna, according to Jeff Nichols, communications director for the Department of Marine Resources. The lobsters in the contaminated area are still safe to eat, but the Maine state toxicologist has advised that sensitive populations, including pregnant women, nursing mothers and children, limit consumption.

The department could have chosen simply to create a consumption advisory for those people, but officials decided against that, said Nichols.

“We chose a more conservative approach,” he said Wednesday. “The closure is No. 1 a health protective measure … second, we want to assure consumer confidence. Maine lobster is iconic. We want consumers to continue to enjoy Maine lobsters with confidence, as they always have.”

The Maine lobster industry last year was worth $340 million, and accounts for 80 percent of lobsters caught in the country.

The closure of the “very small” contaminated area is supported by the Maine Lobstermen’s Association as a precautionary measure, pending a state investigation to more fully understand the potential impact of mercury contamination in the river, according to a response the group issued Wednesday.

“Maine lobster is the best seafood in the world,” Patrice McCarron, executive director of the association, said. “This small closure ensures that consumers can feel confident that Maine lobster is a safe and healthy meal for all to enjoy.”

Maine Marine Patrol will work with harvesters to ensure all gear — if any remains — is removed from the affected area as soon as possible, according to DMR. State agencies will work together over the next two years to conduct seasonal monitoring of mercury levels in marine organisms of commercial and food web significance in and near the closed area, according to Keliher.

“We will decide, after two years, whether or not to reopen the area or to continue the closure,” the commissioner said. “We’re taking very precautious steps to protect this valuable, unique resource.”

The Penobscot River Mercury Study Panel was composed of scientists and professors from Canada, California and New York, with a fish biologist from the University of Manitoba leading the project, according to documents available on the Maine DEP website.

According to the National Institute of Environmental Health Sciences, mercury, also known as quicksilver, is a naturally occurring metal that is toxic to living organisms. Though metallic mercury, an odorless, shiny, silver-white liquid, is commonly used in thermometers, barometers and fluorescent light bulbs, it is also very dangerous.

Mercury can be absorbed into the bloodstream with dire results. Mercury poisoning may include muscle weakness, skin rashes, mental disturbances such as mood swings and memory loss, impairment of speech, hearing and peripheral vision, impairment of movement such as walking or writing and numbness in the hands, feet and sometimes around the mouth.

Shute, the lobsterman, said that he has a lot of questions and few answers about the mercury contamination, and called the presence of the heavy metal in the water a “sad thing.”

“I hope there’s a way to clean it up. If the levels of mercury truly are that high, what does it take? How long does it take?” he asked. “It is unfortunate. It is too bad. It’s going to mean doing things different.”