The senators, in a letter to acting Commerce Secretary Rebecca Blank, urged her to enforce an antidumping order against frozen fillets from Vietnam. Senators from Alabama, Arkansas and Louisiana also signed the letter.
The senators say the Commerce Department's inaction has resulted in a surge in the volume of low-priced imports.
Cochran and Wicker say those imports are direct competition with catfish. They say American companies deserve a level playing field.
The letter says Vietnamese imports have tripled since 2008 and now account for more than 75 percent of the U.S. market.