U.S. Senators from Alabama, Arkansas, Louisiana and Mississippi have urged the Obama administration to enforce U.S. trade laws and protect American catfish growers from an increasing flood of low-cost Asian imports.

In their letter (read here) to acting Commerce Secretary Rebecca Blank, eight senators called on the administration to use "all available tools to prevent unfair imports" and provide American producers with a "level playing field" on which to compete.

The letter was signed by Alabama Sen. Jeff Sessions, Alabama Sen. Richard Shelby, Arkansas Sen. Mark Pryor, Arkansas Sen. John Boozman, Louisiana Sen. Mary Landrieu, Louisiana Sen. Mark Vitter, Mississippi Sen. Thad Cochran and Mississippi Sen. Roger Wicker.

Vietnamese imports of catfish-like species (often sold as catfish in restaurants) have tripled since 2008 and now account for more than75 percent of the U.S. market.

The Senators wrote that our farmers' dramatic loss of market share "correlates directly with the change in the Commerce Department's approach in the antidumping case and the resulting flood of low-priced Vietnamese imports."

Since an anti-dumping case was filed against imported Vietnamese fillets in 2007, the USDA found the market share maintained by U.S. catfish producers has dropped from 80 percent to 20 percent.

Here's what that means for U.S. Farm-Raised Catfish producers:

• In 2007, U.S. catfish farming covered almost 164,000 water acres; by January 2013, acreage totaled only 83,020 water acres.

• In 2007, U.S. catfish processors sold about 104 million pounds of frozen fillets; by 2012 that number had dwindled to just over 67 million pounds.

"Unfortunately, these imports are impacting the most vulnerable members of our society.  Many catfish processors, which can be the largest employers in their community, operate in regions suffering from poverty and unemployment rates well above the national average," the Senators wrote.