Abstract: Based on materials of 48 samples collected in Sept.—Oct. of 1983 in the northern and southern fishing grounds, this paper studies and eompares the spatial distribution of dominant species of zooplankton in the two fishing grounds. The index of aggregated intensity has been used in the study. In the northern fishing ground, dominant species of zooplankton are less abundant in number and are concentratively distributed with high aggregated intensity.In the southern fishing ground,they are on the contrary. The location and characters of high plankton biomass areas in the northern fishing ground are coinoided with those of mackerel and sead central fishing ground. In the southern fishing ground, the scope of central ground is less concentrated as in the northern fishing ground, and it needs to be expanded in the exploitation of the mackerel and scad seined grounds in autumn in the southern fishing ground.