Abstract
Seasonal succession and vertical distribution of zooplankton in the central region of Lake Ozenuma were studied during icefree seasons in 1987 and 1988. Rotifers were more abundant in density than cladocerans. Copepods were rare. The most dominant species were Polyarthra trigla in Rotifera and Bosmina longirostris in Cladocera. In biomass, however, cladocerans usually surpassed rotifers, and the cladoceran Holopedium gibberum took the highest percentage of the total zooplankton biomass. Some zooplankton species were found commonly throughout the study period, whereas others appeared irregularly. It seems that, in recent years, rotifers have become more abundant in the lake.
