A principal concern with implementing marine protected areas (MPAs) is the displacement of fishing effort from closed areas, which may result in new and unexpected consequences for both fisheries and the ecosystem. Understanding such outcomes is critical in the Southern Ocean, where MPAs are actively being discussed for achieving a range of protection and sustainable use objectives. Here, we evaluated two MPA scenarios and associated displacements of the Antarctic krill fishery in the Scotia Sea by quantifying their potential to affect risks of depleting krill-dependent predators and costs to the fishery. We employed both a static assessment (based on the design of each MPA scenario and the distributions of krill fishing and krill-dependent predators) and a dynamic risk assessment (based on a minimally realistic, spatially explicit ecosystem model), and considered three alternative redistributions of displaced catches. We found that neither MPA scenario increased the risks of depleting krill predators when closed areas included ca. 80% of predator foraging distributions, but differences between the scenarios suggest ways to improve protection of seals and penguins in the Scotia Sea. Both scenarios could increase total fishery yields, but this benefit came with costs. Realized catches were smaller proportions of overall catch limits, and there was a greater likelihood that low krill densities would cause the fishery to suspend operations. The three alternatives for redistributing displaced fishing had little effect on risks to predators, but evenly redistributing displaced fishing among open areas could be more costly for the fishery than permitting vessels to self-sort among the same areas. Collectively, our results suggest a well-designed MPA in the Scotia Sea may protect krill-dependent predators, preclude requirements for further spatial management of fishing outside its boundaries, and substitute for spatially explicit catch limits in the Antarctic krill fishery.