AUGUSTA, Maine — Federal officials announced Monday that they plan to add all Atlantic salmon populations in the Penobscot, Kennebec and Androscoggin rivers to the Endangered Species List.

The decision significantly expands the previous “endangered” designation for Gulf of Maine salmon from eight smaller Maine rivers and the lower stretches of the Penobscot and Kennebec to the entire watersheds of the state’s three largest rivers. Salmon reared at two federal fish hatcheries will also be protected when the designation takes effect, likely some time next month.

Although widely expected, the decision was nonetheless strongly criticized by state officials, who had urged the federal agencies to adopt the somewhat less restrictive “threatened” designation.

“This federal action ignores Maine’s strong track record in species management and our need for a flexible approach which will enable us to use all our tools to work with stakeholders to manage Atlantic salmon,” Gov. John Baldacci said in a statement Monday afternoon. “The extreme approach chosen by the federal government hamstrings the state’s ability to use creative conservation efforts that have been successful in the past.”

While the previous designation affected primarily smaller rivers in rural Down East Maine, the expansion announced Monday encompasses salmon in Maine’s three largest and most heavily developed rivers.

Federal officials acknowledged Monday that the designation will affect hydropower facilities and other industries located throughout the three watersheds but pledged to work with the state and businesses to minimize those impacts.

In some cases, dams will be required to build new or improved fish ladders or traps to allow the salmon to pass upstream unharmed. Current conservation efforts, including a proposal to remove two Penobscot River dams and bypass a third, were taken into consideration. But federal officials believe more protections are needed.

“Our goal and our responsibility under the law is to help the Atlantic salmon recover from the brink of extinction,” said Marvin Moriarty, acting deputy director for the U.S. Fish and Wildlife Service. “The state of Maine is a long-term partner of ours and we will continue to work with them closely.”

Although an endangered designation prohibits any “take” of salmon — including killing, catching or inadvertently capturing the fish — Moriarty said recreational fishing for other species in the Penobscot and its tributaries should not be affected.

The National Oceanic and Atmospheric Administration and USFWS plan to issue a special permit to the state that would shield recreational anglers from any penalties should they accidentally hook a salmon while fishing for other species. Maine’s recent tradition of allowing catch-and-release fishing for Atlantic salmon for a few weeks on the Penobscot is in all likelihood over, however.

The Penobscot is home to the nation’s last sizeable spawning run of adult Atlantic salmon. But the roughly 1,000 adults that return, on average, each year is a fraction of the number that biologists say is needed for salmon to survive on their own. And the vast majority of the sea-run salmon that return can be traced to the Green Lake and Craig Brook salmon hatcheries run by USFWS.

“The goal of the Endangered Species Act is to have natural, self-sustaining populations,” said Mary Colligan, protected resources director with NOAA’s northeast fisheries service.