Abstract: Six isonitrogenous and isolipidic diets with increasing digestible starch levels (5.93%,8.71%,11.96%,15.11%,18.16%,21.74%) were formulated to determine suitable level of digestible starch in diets for largemouth bass (Micropterus salmoides),based on growth performance,body composition,serum glucose and non-specific immunological index.Each diet was randomly assigned to triplicate tanks,in each of which 35 fish with an average initial weight of (28.36±0.10) g were stocked.Fish were fed to apparent satiation twice daily (8:00 and 16:00) for 48 days.At the end of feeding test,the lowest survival rate was showed with fish fed a diet containing 21.74% dietary digestible starch (DDS) (P<0.05).Final body weight,specific growth rate and feed intake occurred to a significant declining tendency with DDS levels being higher than 8.71% (P<0.05).Feed efficiency and protein efficiency ratio,however,were the highest with fish fed 11.96% DDS (P<0.05).With an increasing DDS level,apparent digestibility coefficients (ADCs) of dietary lipid and starch were found to be lower (P<0.05),but ADCs of dietary protein showed no significant differences (P>0.05).Meanwhile,in the whole body,muscle,viscera and liver of test fish,protein concentrations significantly decreased,but lipid concentrations became the highest in fish fed the diet containing up to 8.71% DDS,and then declined (P<0.05).With a DDS level increasing,hepatosomatic index,viscerosomatic index,liver glycogen content,activities of serum alanine aminotransferase and aspartate aminotransferase significantly increased,but hemoglobin content gradually declined (P<0.05).In fish fed diets containing higher than 11.96% DDS,serum glucose concentrations constantly increased from 3 to 12 h postprandial,and a continuous hyperglycaemia was observed.The highest serum protein content and complement activity (CH50) were found with fish fed the diet with 8.71% DDS (P<0.05),whereas activities of serum lysozyme and respiratory burst of head kidney leukocytes occurred to fish fed the diet with 11.96% DDS (P<0.05).Based on broken-line regression analysis of specific growth rate and protein efficiency ratio against DDS levels,the suitable inclusion levels of digestible starch in the diet for largemouth bass were 9.22% and 10.05%,respectively.It can be concluded from this study that largemouth bass have a limited ability to utilize DDS efficiently.