Shrimp exports from Vietnam and China are to be hit with anti-dumping duties in the US of up to 112%, the US Commerce Department has said.
Shrimpers are facing falling prices
In a preliminary ruling, it agreed with the opinion of the US shrimp industry that both nations were exporting shrimps to the US below market prices.
Vietnamese firms now face duties of up to 93%, with the Chinese up to 112%.
Both countries have said their shrimp industries are simply more efficient than rival producers in the US.
Vietnam will be particularly hit by the tariffs, as shrimp is the nation's third biggest export item, and the industry employs two million people.
The Commerce Department's judgement follows an anti-dumping petition made by US shrimp organisation Southern Shrimp Alliance last December, which said that cheap imports had cut the value of the US shrimp harvest to $550m in 2002 from $1.25bn in 2000.
Although the tariffs were not as high as the trade body had requested (up to 200%), Southern Shrimp Alliance President Eddie Gordon praised
the decisions as "a critical step on the road to recovery for tens of thousands of fishermen, farmers and processors devastated by the
massive volume of dumped Chinese and Vietnamese shrimp."
Mr Gordon added that the US industry "is fighting for survival and on the brink of extinction from the tidal wave of dumped foreign shrimp,"
which are now wildly farmed compared to the mainly wild-caught shrimp in the US.
Asian seafood farmers, meanwhile, accuse the US of blatant protectionism.
Last year Vietnam lost a bitterly fought campaign against a similar tariffs move by US catfish producers.
Officials at the Commerce Department have yet to give their judgement on four other countries named in the initial Southern Shrimp Alliance complaint - Thailand, India, Brazil and Ecuador.
For these the Commerce Department has said it will make a preliminary ruling by the end of July.
Analysts say the duties against China and Vietnam are likely to be enforced because the two countries are classified as "non-market economy" by the US.
By contrast they say it is much less certain whether the other four countries will be found against, as the US officially sees them as market economies.