A study on bacteria population dynamics in the cultural period and fish productivity in Tuerjishan reservoir was carried out.The results showed that the amount of bacteria was 0 26×10 6～18 63×10 6 cells/ml,peaked in the period from August to October,The bacteria population in the water body with macrophyte grow was notably larger than that in the water body without macrophyte grow.There were not significant correlation between bacteria numbers and plankton biomass、COD、NH + 4 N and PO 3 4 P...