South Georgia and the South Sandwich Islands, located about 2,500 miles north of Antarctica, play an important role in the Antarctic ecosystem. These islands support one of the most diverse aggregations of seabirds and marine mammals on Earth, including 25% of the world’s gentoo penguins.
However, a new study shows that this population of gentoo penguins could be under threat. The research found that over certain periods of the year, the penguins forage for food, such as krill, in the same areas where an industrial krill fishery operates—an overlap that could carry negative consequences for the birds. The research was led by the British Antarctic Survey and published Jan. 13 in the peer-reviewed scientific journal Diversity and Distributions; it was funded in part by the Pew Bertarelli Ocean Legacy Project.
In 2018, the Government of South Georgia and the South Sandwich Islands sought to review the efficacy of the 1 million-square-kilometer marine protected area (MPA) surrounding the islands and answer the question: “Do existing fisheries pose a threat to populations of predators, such as penguins, by directly competing for their food, such as krill?”
Scientists traveled to South Georgia for the study and equipped 16 gentoo penguins with satellite tracking devices that recorded their movements over a period of up to 76 days. The data showed where and when the penguins foraged within no-take zones of the MPA, which stretched 12 nautical miles from land, and within commercial fishing grounds for krill, which extend beyond these zones.
The tracking data showed that the gentoo penguins spent almost half their time foraging for food such as krill beyond that 12-mile no-fishing zone around South Georgia and demonstrated the potential for penguin colonies to overlap with international fishing fleets in their search for krill. The penguins’ ability to meet their nutritional needs is already stressed by climate change: Inconsistent Antarctic temperatures are affecting krill abundance, which carries a direct impact for krill predators such as penguins.
The study began in 2018, and as a direct result of its initial findings, the local government extended the no-take zone around South Georgia in December 2018 from 12 nautical miles to 16.2 nautical miles—expanding protection for gentoo penguins and other predators by approximately 1,900 square miles.
Now that the full analysis has been completed, the scientists note that to fully protect the gentoo foraging areas observed, the no-take zone would need to be extended to 34 miles from shore—marked by the 400-meter depth contour line on the map. This depth represents the edge of the continental shelf, beyond which gentoos rarely feed as ocean depths increase significantly. Scientists suggest that, if the government declines to pursue that option, officials consider periodic and temporary expansions of closed areas in the years that krill are scarce to enhance the protection of penguin foraging areas. This so-called flexible closure management framework should be preceded by additional research.
This study showed how satellite tagging of ocean predators such as penguins can be used to inform evidence-backed expansions of fully protected areas and reduce the risk of competition for prey between wildlife and commercial fishing operators. The Pew Bertarelli Ocean Legacy, as part of the Great British Oceans coalition, remains committed to fully protecting the waters surrounding the South Sandwich Islands.
Johnny Briggs is a senior officer and Katie Gray is a senior associate working on the Pew Bertarelli Ocean Legacy Project’s efforts in the U.K., based in London.