The? study? investigated? dietary? effects? of replacing? fish? meal? (FM)? with Clostridium? autoethanogenum powder (CAP) on growth, flesh quality and metabolomics of largemouth bass (Micropterus salmoides). The control diet contained 350 g/kg FM, and then dietary FM was decreased to 300 g/kg, 250 g/kg, 200 g/kg, 150 g/kg and 100 g/kg by CAP inclusion, respectively (FM-30, FM-25, FM-20, FM-15, FM-10). Then, the six diets were fed to largemouth bass with initial body weight of 110 g for 56 days. The high CAP inclusion (FM-10) decreased specific growth rate, flesh collagen, flesh hardness and increased feed conversion ratio (P < 0.05), but no significant difference was found in feed intake among all the groups. FM-25 and FM-10 groups presented higher flavoring amino acids contents and better performance in sensory evaluation than the control group (P < 0.05), and FM-10 group also showed better values in electronic tongue evaluation. The differential metabolites in FM-25 and FM- 10 groups were found to be involved in lipid, amino acid and protein metabolism. In conclusion, in a basal diet containing 350 g/kg FM, 150 g/kg dietary FM could be successfully replaced by CAP, while higher FM substitution decreased the flesh collagen content and flesh hardness of largemouth bass.? ?