Population dynamics in cladoceran zooplankton in the presence and absence of fishes

Abstract

The pattern of annual changes in zooplankton composition and abundance was investigated in Lake Mikoajskie [Poland] and in a small, artificial pond. Changes in the cladoceran abundance in the lake do not accord with the competitive exclusion principle, which appears to occur in the pond. In the lake, though not in the pond, fish predation on zooplankton seems to weaken interspecific competition sufficiently to allow related cladocerans to achieve their highest levels of abundance simultaneously.