Freshwater plankton communities are regulated by a variety of factors, among which nutrients and predators are two of the most important. Increases in limiting nutrients such as phosphorus and nitrogen can stimulate production and biomass of phytoplankton (Schindler 1978), which in turn can stimulate production and biomass of herbivorous zooplankton. Predators such as fish can influence plankton communities through selective predation on large zooplankton species (Zaret 1980; Northcote 1988). Because large zooplankton species have relatively high grazing rates (per individual) on phytoplankton and graze on a wider range of food particles (Burns 1969), size-selective predation on large zooplankton can also have a substantial influence on phytoplankton (Carpenter and Kitchell 1988; Vanni et al. 1990a).