Combined acoustic (12 and 120 kHz) and trawling (RMT-2 and Bongo net) surveys in offshore waters of the Prince Edward Archipelago revealed diurnal vertical migration of major prey species (the euphausiid Euphausia vallentini and the myctophid fish Krefftichthys andersson~) of landbased predators. Migration was from 200-400 m in the day to near-surface levels at night and was linked to feeding periodicity. Consistently high winds result in drift of surface waters (down to 10-20 m) and advection of prey over the shelf Within the seasonal limits of the investigation (autumn), an estimated 3200 t of zooplankton and 310 t of myctophid fish were carried over the shelf every 24 h. Predators in the archipelago consume ca 900 t of crustaceans and 1700 t of fish d' Thus, advection could supply sufficient crustaceans to the shelf area for the needs of the land-based predators, but is inadequate to support myctophid-feeding piscivores. Once over the shelf, prey attempting to migrate downwards ~vould be trapped by bottom topography and vulnerable to predation. The fit between estimates of advect~on and consumption of different prey types is supported by observed prey densities and predator behaviour Prey density in shelf and oceanic waters was similar at night, but decreased dramatically over, and downstream of, the shelf in the day. Rockhopper and Macaroni penguins are the most important crustacean predators and feed mainly over the shelf, with foraging ranges of about 30 and 100 km respectively. In contrast, King penguins account for >70 O/o of the fish consumed in the area and forage in deep waters, having an average foraging range of 300 km. This spatial segregation of the main predators is consistent with the availability of their prey.