AN EXPERIMENTAL-STUDY OF PISCIVORE PLANKTIVORE INTERACTIONS - POPULATION AND COMMUNITY RESPONSES TO PREDATION

The population dynamics and behavior of an assemblage of fishes in a small bog lake were studied in a succession of whole-lake manipulations of piscivores. Total prey fish biomass declined after the addition of northern pike (Esox lucius). This decline was the result of emigration by cyprinid prey and consumption by northern pike. The emigration response of the cyprinids was dependent on cyprinid density. At high prey fish biomass, a significant portion of the loss in biomass was the result of emigration; this was not the case at low prey fish biomass. The prey fish community shifted from small-bodied soft-rayed species prior to the introduction of northern pike to species with spines or deep bodies after predator stocking. The community response was analyzed at four levels of numerical resolution: absolute, relative, and ranked abundance and presence-absence of prey species. High numerical resolution captured the dynamic short-term population responses to predation and suggests unstable community structure.