NEW YORK, OCT. 15 -- The Justice Department asked a federal judge here today to approve a takeover of the Fulton Fish Market, charging that it is "dominated" by organized-crime figures who extort money from the merchants and drivers doing business there.

The Fulton Fish Market, a tourist attraction and bustling landmark on the lower Manhattan waterfront, is a center of the East Coast's wholesale fresh seafood industry.

In a civil racketeering suit, the government charged that the fish market, a local union and members of the Genovese crime family have engaged in offenses ranging from theft of fish to loan-sharking and gambling.

Rudolph W. Giuliani, the U.S. attorney in Manhattan, told reporters that "millions and millions of dollars" are involved in the extortion schemes, which he said have inflated the price of fish by as much as 20 percent.

Prosecutors did not explain why they took the unusual step of filing a civil suit under the Racketeering Influenced and Corrupt Organizations (RICO) law before seeking criminal charges for the felonies alleged in the complaint. Assistant U.S. Attorney Randy Mastro said only that future criminal charges are possible.

The move reflects the government's increased use of civil RICO proceedings against the mob, including a suit here in August that sought to seize three hotels, a taxi service and other assets from the Bonnano crime family.

U.S. District Court Judge Lee P. Gagliardi set an Oct. 26 hearing on the government's request to name an administrator to take over affairs of the Fulton Fish Market Employers Association. The government also has asked that a trustee take control of Local 359 of the United Seafood Workers and its pension and welfare funds.

Al Zack, spokesman for the 700-member local's parent union, the United Food and Commercial Workers, expressed "a very serious objection" to "the government taking over democratic institutions" though a civil suit.

Mastro said legitimate retailers have been victims of extortion in various forms, such as being forced to pay excessive fees to park at the market and to have fish loaded or unloaded from trucks. Mobsters have told reluctant businessmen that their fish will be stolen, their cars damaged or work stoppages orchestrated if they do not comply, prosecutors said.

"There are threats of violence against people who do not make extortionate payments," Mastro said. "The purpose of the suit is to clean up the market as a whole so the racketeering and corruption will cease."

The lawsuit named two Genovese associates, both former officers of Local 359. They are Carmine and Peter Romano, who were convicted of criminal RICO charges in 1981 in connection with their activities at the fish market. The suit charged that a third brother, Vincent Romano, secretly controls the union.