The results of a study on the variation in morphology and biochemistry of four populations of blunt snout bream from three lakes and one branch along the middle and lower reach of Changjiang River are presented. Discriminant analysis indicated that,overall,there was a significant difference among populations (p0.001),thus the fish could be identified as to their original water body with an accuracy of average 65.7%. The truss network morphometric analysis enhanced the discrimination among populations significantly. The mean proportion of polymorphism was 13.3—20.0%. The average heterozygosity was 0.0549—0.0851. The Nei genetic distance was 0—0. 0219.