The quasi-judicial US International Trade Commission (ITC) ruled after a one-year probe that Thailand, India, China, Vietnam, Brazil and Ecuador were dumping shrimp at unfair prices.
But the commission left open the possibility of reviewing the cases of Thailand and India if their shrimp industries had been hit by the deadly tsunami that ravaged through the coast of 11 Indian Ocean nations last week.
The ITC ruling paves the way for the Department of Commerce to order tariffs expected to average 17 percent on frozen shrimp imported from the six countries.
"They (members of the commission) made affirmative determinations with respect to certain non-canned warmwater shrimp and prawns from all six countries, finding that an industry in the United States is materially injured by reason of imports of these products," the ITC said in a statement.
Frozen shrimp accounts for nearly all of US imports.
The Commerce Department had earlier imposed import duties for Ecuador at 2.35-4.48 percent, 5.02-13.42 percent for India, 5.79-6.82 percent for Thailand, 9.69-67.80 percent for Brazil, 27.89 to 112.81 percent for China and 4.13 to 25.76 percent for Vietnam.
The ITC said it would "collect information and invite submissions on whether the tsunami's impact" on industries in India and Thailand warranted a so-called "changed circumstances review."
The provision allows the commission "to address situations in which changed circumstances warrant review of an injury determination that has culminated in the issuance of an antidumping order."
Thailand, the largest exporter of shrimp to the United States, had already filed a complaint to the World Trade Organization, saying the duties violated trade rules.
US imports nearly 90 percent of its shrimp, the number one seafood consumed in the world's richest country.
The domestic shrimp industry blames a 32 percent drop in the price of imported shrimp over the past three years for wrecking profit and causing a drastic decline in the US harvest of shrimp.
But importers contend that the US industry, which relies on catching shrimp in the wild, simply cannot compete with the low-cost, farm-raised shrimp shipped from the countries targeted in the dumping case.
The Southern Shrimp Alliance, grouping US shrimpers from southern states of North Carolina, South Carolina, Georgia, Florida, Alabama, Mississippi, Louisiana and Texas, hailed the ITC decision Thursday.
The "unfair" pricing practices of the six countries had caused thousands of job losses and hundreds of business closures and led to loss of 4.4 billion dollars of US economic activity, it said.
"The trade actions provide shrimpers and communities throughout the southeast with hope that the offsetting duties will prevent further market distortions and will allow shrimpers to get back to business supplying consumers with safe and delicious American wild-caught shrimp," said Deborah Long, a spokeswoman for the alliance.
But the Consuming Industries Trade Action Coalition/American Seafood Distributors Association (CITAC/ASDA) Shrimp Task Force criticized the decision.
"The ITC's decision helps no one, but instead causes havoc in the market, may raise prices for consumers and hurts thousands of Americans who work in the shrimp consuming sector," said task force chief Wally Stevens.
"Families across this country have been able to enjoy shrimp dinners in their homes and at restaurants at record levels. These duties will do nothing to make the domestic shrimpers more competitive," he said.