Abstract: 【Objective】Understand the current state of plankton resources in the Juyan lake as well as the water nutritional status and the productivity of Hypophthalmichthys molitrix and Aristichthys nobilis.【Methods】The plankton resources in Juyan lake were investigated from November 2020 to September 2021 following the Technical Specification for Freshwater Plankton Investigation（SC/T 9402—2010）. The productivity of Hypophthalmichthys molitrix and Aristichthys nobilis in Juyan lake was evaluated based on the plankton biomass.【Results】In the Juyan lake,there are 63 phytoplankton species belonging to six phyla. The majority are 29 species of Bacillariophyta,21 species of Chlorophyta and 6 species of Cyanophyta. The average density is 163 900 ind/L,and the average biomass is 0.52 mg/L. The community structure is dominated by 16 major species,including Symedra sp.,Navicula sp.,and Ankistrodesmus falcatus. There are 22 zooplankton species,including 16 Rotifera species and 6 Cladocera species,with an average density of 87.30 ind/L,and average biomass of 0.61 mg/L. The community structure is dominated by 17 prominent species,including Brachionus sp.,Asplanchna sp. and Cyclops strennus. The yield of Hypophthalmichthys molitrix and Aristichthys nobilis is estimated to be 33.04-38.12 t based on the plankton biomass in the lake.【Conclusion】 According to the biomass of plankton in Juyan lake,it was oligotrophic. However,the plankton population pattern revealed that Juyan lake was eutrophic. The predicted productivity of Hypophthalmichthys molitrix and Aristichthys nobilis in Juyan lake is substantially higher than the actual quantity,indicating that the plankton in the Juyan lake is underutilized and has significant potential.

Key words: Juyan lake, Plankton, Dominant species, Hypophthalmichthys molitrix, Aristichthys nobilis, Fish productivity