WASHINGTON –

Fish stocks off U.S. coasts, restored to health over the past four decades by cooperation among competing interests and careful management, are being threatened anew by warming and increasingly acidic waters, according to a new report and experts who are gathering in Washington for a conference on the future of fisheries.

The report, released Saturday by the Pew Charitable Trusts and the Ocean Conservancy, hails the 1976 Magnuson-Stevens Fishery Conservation and Management Act and subsequent amendments for bringing commercial and recreational fishermen, marine scientists and legislators together to ensure that fish populations would be sustained.

As Congress approaches another reauthorization of the law, the report says that salmon, scallop and other sea life populations have been brought back from the brink of collapse to healthy and sustainable levels, largely through enforced catch limits.

The "domestic harvest, export, distribution, and retailing of seafood in America . . . generates more than $116 billion in sales and employs more than 1 million people," the report says. "Recreational fishing adds nearly $50 billion and more than 327,000 jobs to that total."

Connie Barclay, spokeswoman for the National Oceanic and Atmospheric Administration, said that acting Administrator Sam Rauch has not yet read the report but "we welcome stakeholders' input as we move toward reauthorization of the Magnuson-Stevens Act." NOAA is hosting this week's conference in the U.S. capital.

Yet more complex problems loom, ones that cannot be solved area by area, experts say. "What we need to pay greater attention to is a changing world and a changing climate and what repercussions that will have," said Chris Dorsett, director of the fish conservation and gulf restoration program of the Ocean Conservancy, a nonprofit advocacy group.

Chief among those issues is the increasing temperature of the oceans, said Lee Crockett, head of the Pew trust's U.S. fisheries campaign. North Atlantic waters last summer were the warmest in 159 years of record-keeping, he noted. Off the coast of Maine, lobsters are molting six weeks to two months earlier than normal, and blue crabs, a Mid-Atlantic shellfish, have been found in New England waters as they and other sea life move toward the Earth's poles to escape warmer seas, Crockett said.

The sea today is 30 percent more acidic compared to preindustrial times. Increasing amounts of carbon are lowering the water's hydrogen ion concentration (pH) and causing it to eat away at the protective shells of marine life and the bony structures of coral, Dorsett said.