SummaryColonies of Little PenguinsEudyptula minoron Phillip Island, Victoria, have declined in both breeding areas and numbers. This decrease, and recent mortalities, stimulated research to support a‘Penguin Protection Plan’that started in 1985. Aspects of this research and its management implications are reviewed. Historically, land alienation and subdivision reduced colony distribution. Mortalities at sea have been obvious for some time: those of adults usually involved few birds in Port Phillip Bay. Immature birds die off western Victoria (probably regularly, and occasionally in large numbers): these mortalities may be associated with starvation and endoparasites. Breeding periods have shortened in the past 20 years, and hence reduced potential recruitment, and there are increased losses in the pre-breeding age group. Some losses are due to continuing predator activities (mainly fox) but studies suggest that climate changes, reflected in sea temperature, may play a role in population regulation presumably through food availability. Off Phillip Island, Little Penguins take a range of prey, principally small schooling clupeoids, and breeding can be delayed if these are unavailable. Fish sampling showed the changing abundance and patchy distribution of food and the birds' distribution sometimes related to that of prey. Adults use Port Phillip Bay in non-breeding periods and overfishing of main prey species could affect Little Penguins: commercial catches of Pilchards have increased substantially, but they involve larger fish. There is no commercial Pilchard fishery off the Phillip Island colonies. Present land-management practices favour the Little Penguin on Phillip Island but prospects of moderating at-sea factors are small. A better understanding of the Little Penguins' marine ecosystem is required.