ROCKLAND — F.J. O’Hara and Sons Inc., a mainstay of the fishing industry in Maine for 40 years, on Monday admitted violations of federal antitrust laws and the filing of false information connected with government contracts.

Attorneys for the fishing company issued a press release and copies of two suits filed Monday by the government against O’Hara in U.S. District Court at Philadelphia and Portland.

The maximum penalties for the crimes could mean fines of $500,000 and imprisonment for up to eight years for president Francis J. O’Hara, and fines ranging from up to $1.5 million against the corporation.

The case against O’Hara had been investigated for the past two years by the government. It involved charges that O’Hara engaged with other companies to suppress competition in the awarding of seafood contracts by the Department of Defense, and that the company improperly certified that U.S.-landed fish were used for certain government contracts on which Canadian fish actually were used.

The government’s antitrust case alleged that beginning as early as 1981 and continuing to September 1989, O’Hara and “others known and unknown” to the government engaged in a combination and conspiracy to restrain, suppress and eliminate competition for the award of seafood contracts, “by rigging bids submitted for such contracts.”

A spokesman for the company said that when subpoenas were issued last fall, O’Hara agreed to cooperate fully with the government in its investigation, and both the company and O’Hara had agreed to plead guilty to the offenses without any promise of what the punishment would be.

In a prepared statement, O’Hara said, “I accept full responsibility for the company’s involvement in this situation. My intention was to try and keep the company going and protect the jobs in an increasingly adverse business environment. But that’s not an excuse for what happened, and I’m sorry that it did.”

O’Hara closed down the fish processing and government contracting operations in April. The company continued to maintain its fishing fleet, landing catches in Gloucester, Mass., Portland and other ports. During recent weeks the company purchased the vacant National Sea Products property in Rockland amid speculation that it would be converted for a commercial use other than the fish business.

According to an O’Hara attorney, the maximum penalty possible against O’Hara personally on the antitrust charge would be up to three years in prison and $250,000 in fines. The fine also could be based on twice the amount the government lost because of the antitrust activity. The corporation could be fined up to $1 million, or twice the government’s loss.

As for certifying on government contracts that the fish being sold to the Department of Defense had been caught, landed and processed in the United States, O’Hara could be imprisoned for up to five years and fined up to $250,000. The corporation would face a maximum fine of $500,000, or twice the government’s loss. According to government charges O’Hara was selling the government fish caught in Canada.

The spokesman said the situation had developed because of pressure on the U.S. fishing industry when domestic fish stocks decreased greatly in the mid-1980s. After the failure of the U.S.-Canadian fishing treaty negotiations in 1978, and the U.S. loss in 1984 of the fishing boundary dispute with Canada in the World Court, areas available to U.S. fishermen were greatly reduced.