Impacts of Filter-Feeding Fishes on the Long-Term Changes of Crustacean Zooplankton in a Eutrophic Subtropical Chinese Lake

Abstract

ABSTRACT Long-term changes in the crustacean zooplankton community (calanoid and cyclopoid copepods and cladocerans) were studied in Lake Donghu, a shallow and eutrophic Chinese lake. This lake had been earlier stocked with two pump Alter-feeding fishes, silver carp (Hypopthalmichthys molitrix) and bighead carp (Aristichthys nobilis). During the 1950s and the mid- 1980s, the ratio of copepods to cladocerans was relatively stable but showed a general increase thereafter. From the early-1980s to the 1990s. calanoid/cyclopoid ratios decreased obviously. In the 1990s. Cyclops vicinus, Diaphanosoma brachyurum, and Moina micrura were dominant; the abundance of C. vicinus and M. micrura increased significantly; and D. brachyurum showed a substantial decrease. The study shows that under extremely high pressure of fish predation, the species which could recover rapidly from fish predation would be the most likely to survive and increase their numbers.