**AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** NON-TECHNICAL PROJECT SUMMARYTHE UNITED STATES IS THE TOP PRODUCER OF HYBRID STRIPED BASS (HSB) IN THE WORLD. FISHMEAL HAS TRADITIONALLY BEEN USED AS THE MAJOR PROTEIN FEEDSTUFF IN HSB DIETS, BUT THIS APPROACH IS NOT SUSTAINABLE IN AQUACULTURE DUE TO THE INCREASINGLY LIMITED SOURCES AND HIGH COSTS OF FISHMEAL. THUS, THERE HAS BEEN GROWING INTEREST IN USING PLANT PROTEINS (MAINLY SOYBEAN MEAL) TO REPLACE FISHMEAL IN AQUAFOODS, BUT SUCCESS HAS BEEN VARIABLE. WE FOUND THAT GLYCINE (THE MOST ABUNDANT AMINO ACID IN THE BODY OF FISH AND FISHMEAL) IS RELATIVELY LOW IN PLANT PROTEINS. BASED ON RESULTS OF OUR PRELIMINARY STUDY, WE HYPOTHESIZE THAT DIETARY GLYCINE PLAYS AN IMPORTANT ROLE IN HSB GROWTH BY MAXIMIZING PROTEIN SYNTHESIS, ANTI-OXIDATIVE CAPACITY, AND CREATINE (MUSCLE BUILDER) PRODUCTION IN THEIR TISSUES. WE WILL TEST THIS HYPOTHESIS BY PURSUING THREE SPECIFIC OBJECTIVES TO DETERMINE: (1) TISSUE-SPECIFIC GLYCINE- AND CREATINE-SYNTHETIC PATHWAYS IN HSB; (2) ROLES OF GLUTATHIONE (THE MOST ABUNDANT LOW-MOLECULAR WEIGHT ANTI-OXIDANT) AND CREATINE IN MEDIATING THE EFFECT OF DIETARY GLYCINE TO IMPROVE GROWTH, ANTI-OXIDATIVE RESPONSES, INTESTINAL INTEGRITY, METABOLIC HEALTH, AND IMMUNITY IN HSB; AND (3) ROLES OF THE TARGET OF RAPAMYCIN (TOR; THE MASTER REGULATOR OF PROTEIN SYNTHESIS) AND AUTOPHAGY/PROTEASOMES (INTRACELLULAR MACHINERIES FOR PROTEIN DEGRADATION) IN MEDIATING THE EFFECT OF DIETARY GLYCINE TO PROMOTE PROTEIN SYNTHESIS AND INHIBIT PROTEOLYSIS IN TISSUES OF HSB. WE EXPECT THAT: (1) IN CONTRAST TO LAND MAMMALS, SKELETAL MUSCLE IS THE MAJOR SITE FOR CREATINE SYNTHESIS FROM GLYCINE IN HSB; (2) GLYCINE ACTIVATES THE TOR CELL SIGNALING PATHWAY TO PROMOTE PROTEIN SYNTHESIS IN SKELETAL MUSCLE, WHILE REDUCING INTRAMUSCULAR PROTEIN BREAKDOWN VIA THE AUTOPHAGY/PROTEASOMES PATHWAYS, TO PROMOTE MUSCLE GROWTH; AND (3) SUPPLEMENTING 2% GLYCINE TO SOYBEAN MEAL (58%)-BASED DIETS CAN REPLACE 45% FISHMEAL IN HSB DIETS. OUR FINDINGS WILL HAVE A SIGNIFICANT IMPACT ON U.S. AQUACULTURE BY GENERATING NEW FUNDAMENTAL KNOWLEDGE ABOUT THE CRUCIAL ROLE OF GLYCINE IN IMPROVING THE GROWTH OF HSB AND PROVIDING A NEW NUTRITIONAL METHOD FOR THE USE OF GLYCINE TO SUBSTANTIALLY REDUCE THE INCLUSION LEVEL OF FISHMEAL IN SOYBEAN MEAL-BASED DIETS FOR THE FISH.