The effects of piscivores upon zooplanktivore behaviour anddistribution and the impact of zooplanktivores on the abundance anddistribution of zooplankton are well documented. However, thepotential indirect effect of piscivores reducing the predationpressure upon grazing zooplankton through behavioural changes ofzooplanktivores has received little attention, even though this maybe an important mechanism in enhancing the stability of submergedmacrophytes in shallow lakes. Preliminary observations from anunreplicated large-scale field enclosure experiment and areplicated pond experiment suggest that this mechanism is plausiblewith the set of piscivores (pike Esox lucius and perch Perca fluviatilis) and the zooplanktivores (0+ roach Rutilusrutilus and perch) common in temperate Europe. The presence ofpiscivores typically changed the habitat use and the activity levelof zooplanktivores and the presence of zooplanktivores typicallychanged the habitat selection of cladoceran zooplankton. In thecase of piscivore/zooplanktivore interactions, the risk ofpredation was enough to generate clear responses even where thelosses to predation were low. However, only in the enclosureexperiment was an indirect impact of the presence of piscivores,enabling Daphnia spp. to utilise open water in the presenceof a high density of zooplanktivorous fish observed. Whether themagnitude and direction of the effect of piscivores is sufficientto benefit zooplankton may depend on the functional group (capableof foraging within structured habitats) of the predator (bothpiscivore and zooplanktivore), absolute and relative densities ofpredator and prey and predator dietary choice.