Niushan Lake (114°32' E, 30°19' N),situated in Hubei Province of China is a shallow macrophyte lake in the middle reachesof the Changjiang (Yangtse) River with a total surface a.ea of 40 km².Age growth and reproduction of Rhodeus ocellatus from the lake were studied during April to June 1999.Annuli on scales were clear and could be used as valid indicators of age.The population of the bitterling comprised only one age group and the maximum of life span for both sexes may be less than 2 years.The sex ratio of males tofemales was 1.59:1 (n=332) with significant difference from 1:1 (X²test,X_c² 16.94 P<0.01) The relation-ship between total length n=(TL, mm) and body weight n=(W, g) for sexes was expressed by the equation lnW=-11.945+3.163 lnTL (n=238,r=0.98,P〈 0.0001).Slope of the equation was significantly greater than 3 (P〈 0.01).This may suggest an allometiic growth. The bitterling were multiple spawners reaching maturity in the second year.During spawning,both sexes exhibited secondary sexualcharacters.Minimum size was 26 mm in total length and 0.216 g in weight for males and 32 mm and 0.393 g for females.Mature eggs were cucurbit-like form with mean size of 3.31 mm long (n=23,SD=0.14).Fecundity per female averaged 61 eggs (n=46,SD=18) with a range of from28 to 119.In addition to that, There wassignificantly correlation of fecundity (F,eggs) to total length (TL,mm) or body weight n=(W,g)(p〈 0.0001),and the relationships were expressed by the equations F=26.1+83.2 W (n=52 r=0.73) F=4.78 10^-3 TL^2.537 (n=52 r=0.78).