WASHINGTON — Maine salmon farmers scored a major victory Tuesday when the International Trade Commission left intact duties against the largest importers of Chilean salmon.

By a 2-1 vote, the ITC determined that Maine’s $45 million Atlantic salmon industry had been financially injured by Chile’s salmon companies, which, the U.S. Commerce Department says, have been dumping their product on the U.S. economy at below-market prices.

Tuesday’s decision means that the federal government will continue to impose an average duty of 4.54 percent per pound of salmon imported by three Chilean salmon producers, a small tariff by any measure, but still significant to Maine’s industry.

“It has basically saved this industry,” said Michael J. Coursey, who represented Maine’s interests before the ITC.

Maine’s salmon growers contend that more important than the size of the duty is the increased supervision Chilean salmon will face from U.S. Customs. “It’s like knowing your income tax return will be audited every year,” said Coursey, of the Washington law firm of Collier, Shannon, Rill & Scott.

The ITC board members did not release their opinions, so little is known about why they voted the way they did. But the lone dissenting member, Carol T. Crawford, said she thought that Coursey had not proved that Chilean salmon imports had injured the domestic industry.

“Not even close,” Crawford said in a brief interview.

If one more member of the ITC had agreed with Crawford, the duty on Chilean salmon would have disappeared just six months after the Commerce Department imposed it.

In an investigation prompted by complaints from Maine salmon growers, Commerce determined that three Chilean companies were guilty of dumping their product, and imposed a duty of 5.19 percent — which was revised to 4.54 percent earlier this month, due to technical corrections.

The ITC’s job was to determine if the U.S. industry had been hurt by the dumping; otherwise, there was no need for the duty. After a lengthy hearing in early June, ITC members Lynn Bragg and Marcia Miller agreed Tuesday to leave the duty in place.

“We’ve gotten back to a level playing field,” said Joe McGonigle, head of the Coalition for Fair Salmon Trade, a Maine-based group.

But Chile’s salmon industry is still considering its options. Either Chile’s industry can appeal the decision to the U.S. Court of International Trade, or get the government of Chile to sue Commerce and the ITC in the World Trade Organization.

“If [Maine’s salmon farmers] are suffering any problems, it’s not because of us,” said Richard Johnson of the Washington law firm Arnold & Porter, who represented Chile’s interests. Johnson contended that Maine’s industry was suffering from increased competition from Norway, Canada and Chile, but not from price dumping.

He predicted Maine’s salmon industry — which employs 960 workers, mostly in Washington and Hancock counties — would see little benefit from the duty, a prediction McGonigle said was baseless.

“This industry has been cut in half in recent years. Those [salmon] farms went out of business almost exclusively because of Chilean dumping,” he said, noting 11 of 19 salmon farmers in Maine had closed in three years while Chilean imports jumped 75 percent.

Both sides have brought in two of the biggest law firms in Washington on trade issues. Also on Chile’s side was former Senate Majority Leader Bob Dole, who represented the National Restaurant Association and airlines that benefit from buying and transporting the cheap salmon.

Maine’s lawmakers united against Chile’s hired guns. “[The ITC] only makes decisions based on the data and evidence, nothing more,” said Sen. Olympia Snowe. “It’s clear from the evidence that they were overwhelming the markets with sub-standard prices.”

Rep. John Baldacci credited McGonigle for putting together a well-documented case that should stand up on appeal. “I think it’s only going to get stronger. I don’t see it weakening,” he said.

“It’s a victory that was critical to the future of the industry,” said Sen. Susan Collins.

Johnson, Chile’s attorney, said his clients will not be deterred. “They intend to get back to business,” he said.