BUCKSPORT, Maine — State fishery officials have decided to permanently close 7 square miles of the lower Penobscot River to lobster and crab harvesting.

The Department of Marine Resources closed the area in February, citing concerns about elevated mercury levels found in lobsters along that section of river. The source of the mercury, the level of which is little more than what is found in canned white tuna, has been traced to the defunct HoltraChem plant in Orrington.

Officials have said the closure is a precautionary measure and that the mercury found in the lobster upriver from Jellison Point in Stockton Springs could pose a health threat to certain people or if someone ate a lot of it over a period of time.

The closure was enacted in February by emergency rule, which lasts for only 90 days. The decision to make the closure permanent, or until the state decides it is no longer needed, went into effect Wednesday.

The closed area is considered to be fairly small and is fished by maybe a dozen fishermen, industry officials have estimated. There are about 6,000 licensed lobstermen in Maine who spread their traps out over 14,000 square miles of ocean along the coast.

“We understand it is very small,” Jeff Nichols, DMR spokesman, said Friday about the amount of lobster that traditionally has been harvested in the closure area. Most people who have fished in the area, he added, hold recreational lobster licenses that do not permit them to sell their catch.

Maine’s signature seafood industry is the largest lobster fishery in the country and by far the largest commercial fishery in the state. In 2013, nearly 126 million pounds of lobster with a record total dockside value of $364 million was caught by Maine fishermen.

Nichols said the closure in February was enacted through emergency rule-making in order to make it take effect immediately. He said the department intended at the time to eventually make the closure permanent so it could last for at least two years.

By making the closure permanent, he said, the department can continue to monitor the area year-round to see whether contamination levels change. The department plans to revisit the closure in 2016 to see if any change in the closure status may be warranted.

Mallinckrodt LLC, which ran the riverfront chemical plant from 1967 to 1982, was in court recently in connection with its dispute with the Department of Environmental Protection about cleanup of mercury pollution at the site. Information about the mercury-tainted lobsters came from a scientific study ordered by U.S. District Court in Bangor.

At a public hearing in March in Bucksport, there was criticism of how the situation came to be and how it has been handled, but no one spoke in opposition to banning lobster and crab fishing in the lower river for the long term.

Sheila and Mike Dassatt, a Belfast couple active with the Downeast Lobstermen’s Association, said Friday that the indefinite closure of the lower river does not come as a surprise.

The closure will have an impact on the small number of fishermen who set traps in that area during the summer, Sheila Dassatt said, but it will help send a message to consumers that Maine lobster is harvested sustainably and safe to eat.

“If it will protect the entire Maine fishery, then it’s a small sacrifice,” she said.

Mike Dassatt said that not only does he fish in the upper Penobscot Bay, near where the closure has gone into effect, but he helped ferry scientists around the area on his boat when they were testing for mercury levels.

He said fishermen may not be happy with the situation, but there is broad support in the fishing community for a long-term, limited acreage closure downriver from the old chemical plant.

“I think a lot of fishermen agree it’s a good thing to do,” Mike Dassatt said.

But many fishermen think something else should be done, too, he added. The contaminated soils and sediments should not be left indefinitely to continue leaching pollution into the river, he said.

“Those responsible are going to have to step up and clean it up,” Mike Dassatt said.

Bill Trotter

A news reporter in coastal Maine for more than 20 years, Bill Trotter writes about how the Atlantic Ocean and the state's iconic coastline help to shape the lives of coastal Maine residents and visitors....