ANCHORAGE, JULY 14 -- An oil spill in Alaska's Cook Inlet has contaminated part of a major salmon catch, forcing an emergency shutdown of the area's $50 million seafood harvest.

The state Department of Fish and Game ordered a temporary halt to fishing early today in a 20-mile stretch of inlet waters after a Kenai Peninsula processing plant discovered at least 1,500 pounds of red salmon tainted by a July 2 tanker spill of an estimated 125,000 gallons of Prudhoe Bay crude.

Ken Tarbox, a state fish and game biologist who helps manage the harvest, said the area could reopen later this week if the oil can be kept out of the fishing zones. "We're in the process of assessing the situation," he said. "We're certainly not panicking."

The contaminated fish are a fraction of the 1.6 million red salmon harvested to date from the July salmon run. But keeping the oil off the fish has proved increasingly difficult in recent days. "Oil has been spotted in all the major fishing areas, at different times and in different quantities," Tarbox said.

The spill has dampened the fishermen's prospects for what had been forecast as a bumper harvest. It floats in many of the same tidal rips where salmon, which swim near the surface, also congregate. Once nets get fouled with oil they must be retired until thoroughly scrubbed.

For more than a decade, the oil industry has been planning for a major crude oil spill in Alaska's salmon-rich coastal waters. But when it finally occurred, Cook Inlet response crews were unable to contain the spread of viscous crude. The oil leaked from the tanker Glacier Bay, a Standard Oil Co.-chartered ship, registered in Wilmington, Del., that apparently struck a rock while she was several miles offshore awaiting a berth to unload oil at a Kenai Peninsula refinery.

"There's a lot of anger and frustration and resentment," said Frank Mullen, a Cook Inlet salmon fishermen. "They {fisherman} just can't believe this happened."

Coast Guard officials first estimated the spill at no more than 16,000 gallons, then revised that estimate to 125,000 gallons. By Coast Guard standards, that is a major spill. For the past 12 days, the oil has hung in narrow, tarry slicks, some more than 10 miles long, and occasionally washed up on beaches on both sides of the inlet.

"Cook Inlet has to be one of the hardest places to clean up an oil spill that I can think of," said Paul O'Brien, the state Department of Environmental Conservation's oil spill program manager. "People . . . think that maybe man has the ultimate hand in these things. But the state of the art . . . when you encounter a Cook Inlet, it is really pushed to the maximum."

Under federal law, the company or companies responsible for a spill must be given first chance at directing that effort. The initial cleanup effort was organized by St. Louis-based Trinidad Shipping, owner of the tanker, and a regional oil industry cooperative formed to deal with spills.

That effort was hampered by faulty predictions about the oil's behavior in the churning Cook Inlet waters. Initially, some experts thought the oil would quickly be dissipated by the inlet's powerful tides and strong currents. Instead, heavy oil pooled in the slicks, which have moved about with the tides and occasionally washed up on the beaches. Ineffective cleanup equipment also has been a major problem.

Last week the Coast Guard, dissatisfied with industry efforts, took control of the cleanup.

The accident has occurred as red, silver and chum salmon migrate up Cook Inlet on their way to spawn in freshwater streams and lakes. About 600 fishermen harvest the fish from drift boats that trail long green-meshed nets from the stern. Another 100 fishermen are based on the beach and use nets strung out close to the shore.