Ecological Systems and Devices Annotation << Back Dimensional Structure of Cyanobacteria (Anabaena spiroides) as a Characteristic of Zooplankton Food Base Gerasimova T.N., Sadchikov A.P Cyanobacteria in a high-trophicity pond start developing in early summer; Anabaena spiroides is dominating among them. In the early June, at a biomass of 1.5 mg/L, the edible fraction with a size <50 μm accounted for 48% of its composition. At a biomass of 15.9 mg/L, the edible fraction accounted for 29% of its biomass, and the proportion of conventionally edible (50–100 μm) fraction reached 45 % of A. spiroides population. In the early July, at the biomass of A. spiroides of 14.8 mg/L, the proportion of A. spiroides <50 μm in size was 12 % of this value. In the late July, at A. spiroides biomass of 0.9–5.7 mg/L, the proportion of the edible fraction was 36–54 %. In August, A. spiroides biomass dropped to 0.7 mg/L, and the proportion of its edible fraction (<50 μm) was 22 % of its biomass. Keywords: cyanobacteria, dimensional structure of cyanobacteria, plankton-eating fi shes, zooplankton, trophic press of fi shes on zooplankton. DOI: 10.25791/esip.11.2023.1414 Pp. 57-62.