Abstract: By using dark and light bottle dissolved oxygen method, the fishery primary productivity in the south part and the experimental enclosure of Dianshan Lake was measured monthly from October 2008 to September 2009. Based on the measurement in the south part, the potential productivity and reasonable stocking amount of silver carp and bighead carp in the experimental enclosure were estimated, and the correlations of the primary productivity with the water temperature,transparency, nutrients, and chlorophyll-a were discussed. The nutrient removal effect of stocking silver carp and bighead carp was also discussed. In the south part of the Lake, the daily gross primary productivity (P_G) was 4.02 g O₂·m^-2 on average, with the maximum in August and the minimum in January, the net primary productivity (P_N) was 1.99 g O₂·m^-2, and the yearly P_N/P_G ratio was averaged 52%. The 0-0.5 m water layer contributed most to the primary productivity, with its contribution occupied 32.3% and 32.2% of the total in the south part and the experimental enclosure, respectively. The primary productivity was positively correlated with water temperature and transparency, but not significantly correlated with other physical and chemical factors. The yearly production of phytoplankton in the Lake was 28.18×10.4 t. If the stocking ratio of silver carp  to bighead carp was 3∶1, the potential productivity of silver carp and bighead carp would be 1621.58 t and 1216.18 t, and their reasonable stocking amount was 16.94 t·km^-2 and 6.35 t·km^-2, respectively. Based on these estimations, the total nitrogen and total phosphorus absorbed by the 2837.76 t fish would be 85.50 t and 7.63 t, and the nitrogen and phosphorus concentrations in the water body of Dianshan Lake would be decreased by 0.67 mg·L^-1 and 0.06 mg·L^-1, respectively.

Key words: Qinling Mountains, Sharp tooth oak, Clustering analysis, PCA