Responses of Antarctic pack-ice seals to environmental change and increasing krill fishing

The compound effects of changing habitats, ecosystem interactions, and fishing practices have implications for the management of Antarctic krill and conservation of its predators. For Antarctic pack-ice seals, an important group of krill predators, we estimate the 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 based upon predictions from declines in sea ice cover. More than 3 million crabeater seals consumed over 12 million tonnes of krill each year. This was approximately 17% of the krill standing stock. The highest densities of pack ice seals where found in the WAP, including in its small-scale fishery management areas, where apparently suitable seal habitat has declined by 21–28% over a 30 year period, where krill density is likely to have declined, and fishing has increased. The highest seal density was found in the Marguerite Bay area which is a source of krill for the Antarctic Peninsula and elsewhere. Significant sea-ice loss since 1979 has already occurred, leading to open water and possible expansion for the fishery in the future. These factors may combine to potentially reduce food for pack ice seals. Therefore, high uncertainty in krill and seal stock trends and in their environmental drivers call for a precautionary management of the krill fishery, in the absence of survey data to support management based on specific conservation objectives for pack-ice seals.

► The highest known density of Antarctic pack-ice seals is in the Antarctic Peninsula.
► Crabeater seals could consume approximately 17% of Antarctic krill in the region.
► Their apparent suitable sea-ice habitat has significantly declined over 30 years.
► Ice loss, a krill decline and increased fishing could potentially reduce seal food.
► Data uncertainty requires a high level of precaution in krill fishery management.