The Commerce Department said the duties would range up to 67.80 percent for Brazil, 6.08 to 9.35 percent for Ecuador, 3.56 to 27.49 percent for India and 5.56 to 10.25 percent for Thailand.

The agency said a preliminary probe indicated imports from the four countries were sold "at less than fair value," opening the door to punitive tariffs.

It was the second action on shrimp in the past month after duties were imposed on shrimp from China and Vietnam.

A separate investigation was used for the other four countries because they are considered market-based economies, unlike China and Vietnam.

The duties may be adjusted, but will be collected until a final ruling by the quasi-judicial International Trade Commission next January.

A group representing the US shrimp producers that filed the petition welcomed the decision but said the preliminary tariffs may be too low.

US shrimp producers argue that their wild-caught shrimp cannot compete with farm-raised shrimp from the other countries.

"We commend the Department of Commerce for imposing antidumping duties, but feel that in certain instances the duties underestimate the seriousness of the violations," said Southern Shrimp Alliance President Eddie Gordon.

"Today's findings confirm that unfair trade has allowed importers to slash import prices 41 percent since 2000 while flooding the US market with a 71 percent increase in imports. This is not the result of efficient production, but unfair competition."

But a trade group representing grocers, restaurants, processors and distributors called the duties an unneeded "tax" on US consumers.

"These four countries are not dumping shrimp in the US. They are efficiently producing a high-quality product, and the US industry has failed to compete effectively with these imports," said Wally Stevens, chairman of the Shrimp Task Force.

"This is a case of the current administration imposing a new food tax on millions of Americans that will do nothing to help the shrimp industry except line the pockets of a few shrimpers. It's a classic case of unnecessary, undeserved and unwise protectionism."

The fact that the preliminary duties were lower than what the US industry sought "is convincing evidence that imports are not the cause of domestic shrimpers' problems," said Stevens.

"Attempting to shut out competition by imposing a food tax won't make the US industry's problems go away."

Thailand last week pleaded with US trade authorities not to impose tariffs, claiming the move could devastate thousands of Thai shrimp farmers and workers in food processing plants as well as raise prices for US consumers, according to reports in Bangkok.

The US decision, in a further blow to some producers, found "critical circumstances" exist on imports from one Indian producer, meaning duties can be imposed 90 days retroactively. The agency said there was insufficient evidence to impose retroactive duties on Thai shrimp.

The duties affect some 956 million dollars in imports from Thailand; 398 million dollars from India; 206 million from India and 97 million from Brazil.