Significance Elucidating the mechanisms that regulate animal populations is a fundamental goal in ecology and is increasingly important at a time of unprecedented anthropogenic disturbance to ecosystems. Here, we present direct evidence of a phenomenon known as “Ashmole’s halo”: a zone of prey depletion that is hypothesized to form around aggregations of central-place foraging predators and is believed to be the principal mechanism regulating populations of many colonially breeding animals. In effect, Ashmole’s halo constitutes rare, visible evidence of the food limitation that naturally limits many predator populations and can be exacerbated by human impacts such as fisheries. Therefore, the large extent of the resource footprint we demonstrate has important implications for conservation of marine food webs at ecologically relevant scales.