**AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** FISH LIVE IN WATER AND ARE CONSTANTLY CHALLENGED BY HARMFUL MICROORGANISMS IN THE ENVIRONMENT. THE SURFACE TISSUES (MUCOSA) OF THE INTESTINE SERVE AS THE NATURAL BARRIER TO DEFEND THE AQUATIC ANIMALS AGAINST THE INVASION OF THE HARMFUL MICROORGANISMS. THUS, THE ABILITY OF THE GUT TO RESIST THE INFECTIOUS AGENTS OUTSIDE THE BODY IS CRUCIAL FOR THE HEALTH AND SURVIVAL OF THE FISH, INCLUDING HYBRID STRIPED BASS (HSB). BASED ON RESULTS OF OUR PRELIMINARY STUDY, WE HYPOTHESIZE THAT DIETARY GLUTAMATE PLAYS AN IMPORTANT ROLE IN THE DEVELOPMENT OF THE INTESTINAL IMMUNE SYSTEM IN HSB. WE WILL TEST THIS HYPOTHESIS BY PURSUING THREE SPECIFIC OBJECTIVES TO DETERMINE: (1) DEVELOPMENTAL CHANGES IN THE UTILIZATION OF GLUTAMATE BY IMMUNE CELLS IN THE INTESTINAL MUCOSA OF HSB TO GENERATE FUNCTIONAL (INCLUDING ANTI-INFECTIOUS) MOLECULES; (2) EFFECTS OF DIETARY GLUTAMATE ON IMPROVING THE INTESTINAL MUCOSAL IMMUNE SYSTEM IN HSB; AND (3) A ROLE OF GLUTATHIONE IN MEDIATING EFFECTS OF DIETARY GLUTAMATE ON THE INTESTINAL IMMUNE SYSTEM IN HSB. WE EXPECT GLUTAMATE TO INCREASE THE PRODUCTION OF ANTI-INFECTIOUS AND ANTI-OXIDATIVE MOLECULES BY IMMUNE CELLS IN THE INTESTINAL MUCOSA OF HBS. OUR FINDINGS WILL HAVE A SIGNIFICANT IMPACT ON U.S. AQUACULTURE BY GENERATING NEW FUNDAMENTAL KNOWLEDGE ABOUT GLUTAMATE IN IMPROVING INTESTINAL MUCOSAL HEALTH AND SURVIVAL OF HSB AND PROVIDING A NEW NUTRITIONAL METHOD FOR THE USE OF GLUTAMATE AS AN ADJUVANT IN VACCINE DEVELOPMENT FOR THE FISH.