The management of Antarctic krill and conservation of its predators requires understanding about the compound effects of changing habitats, ecosystem interactions, and fishing practices. For Antarctic pack-ice seals, a main group of krill predators, we report the spatial density and krill consumption in the West Antarctic Peninsula (WAP)-western Weddell Sea area, the main fishery region; and we consider long-term changes in suitable pack-ice habitat, increased fishing pressure and potential krill declines consequent on climate change. We find that the WAP has the highest known density of pack-ice seals and in the entire area, over 3 million crabeater seals can consume over 12 million tonnes of krill, approximately 17% of the krill standing stock; this highlights their extreme trophic pressure and dependence on krill. High seal densities where found in the small-scale fishery management areas of the WAP, where suitable seal habitat has declined between 21 and 28% over a 30 year period; krill density has potentially declined, and fishing has increased rapidly. The highest seal density was found in the Marguerite Bay area, a critical source of krill for the Antarctic Peninsula and elsewhere. This area has the highest seal impact on an already highly variable krill biomass, sea-ice loss of 66% has already occurred, and it could be an area of expansion for the fishery in the future. Uncertainty in krill and seal stock trends and in their environmental drivers calls for a precautionary management approach, in the absence of data to support a management based on specific conservation objectives for pack-ice seals.