Marine Predator Movements in Winter and Their Impact on Fisheries Management

Jim Crocker
19th May, 2024

Marine Predator Movements in Winter and Their Impact on Fisheries Management

Image Source: Natural Science News, 2024

Key Findings

  • The British Antarctic Survey studied krill-dependent predators around South Georgia during the winters of 2010 and 2011
  • Higher numbers of krill predators, especially Antarctic fur seals, were observed in 2011, a "good" krill year, compared to 2010, a "poor" krill year
  • Significant overlap was found between fur seals and the krill fishery in the northeast, indicating potential competition for resources
The sub-Antarctic island of South Georgia is a crucial habitat for numerous marine species, particularly those dependent on Antarctic krill (Euphausia superba). These krill are a vital food source for many seabirds and marine mammals. The surrounding waters also support a commercial krill fishery, which operates exclusively in winter. The British Antarctic Survey conducted at-sea surveys during the winters of 2010 and 2011 to assess the abundance and distribution of krill-dependent predators, providing valuable insights into the ecosystem’s response to krill harvesting activities[1]. The study aimed to fill a gap in existing monitoring efforts, which primarily focus on land-breeding animals during the austral summer, whereas the krill fishery operates in winter. The surveys revealed significant variations in predator numbers between the two years, correlating with the availability of krill. In 2011, a "good" krill year, higher numbers of krill predators were observed, especially Antarctic fur seals (Arctocephalus gazella) across the northern shelf. This finding aligns with previous research indicating that the diet of Antarctic fur seals at South Georgia is dominated by krill, and their foraging trips are influenced by the need to provision their pups during the breeding season[2]. The spatial overlap between fur seals and the krill fishery was primarily within the northeast hotspot, suggesting potential competition. This echoes earlier studies that modeled the winter distribution of female fur seals and found that their habitat overlapped with krill harvesting areas, albeit in small, localized regions[2]. The 2010 survey, representing a "poor" krill year, showed fewer krill-dependent predators, highlighting the variability in ecosystem dynamics. Cetaceans were observed in both years but in lower numbers compared to recent studies. Gentoo penguins (Pygoscelis papua) were the most frequently observed penguin species, showing an inshore distribution with minimal overlap with the krill fishery. Diving-petrels (Pelecanoides spp.) were the most abundant flying seabirds, particularly in early winter 2010. This research provides essential baseline data on the winter distribution of South Georgia’s predators, which is crucial for effective ecosystem management. The findings underscore the importance of continuous monitoring to detect changes in predator populations and their spatial distribution in response to krill harvesting. Such data can inform management strategies to mitigate potential conflicts between the fishery and krill-dependent predators. The study also complements previous research on the spatial management of South Georgia and the South Sandwich Islands (SGSSI). The SGSSI Maritime Zone is designated as an IUCN Category VI reserve, with specific areas identified as IUCN Category I reserves, allowing for multiple-use zones and temporal closures to protect the ecosystem[3]. By providing detailed information on predator distribution during winter, the study supports the development of management measures that consider both pelagic and benthic domains, ensuring the sustainability of the krill fishery and the conservation of marine biodiversity. In summary, the British Antarctic Survey’s at-sea surveys from 2010 and 2011 offer critical insights into the winter distribution of krill-dependent predators around South Georgia. These findings highlight the need for ongoing monitoring and adaptive management to balance commercial fishing activities with the conservation of key marine species.

EnvironmentEcologyMarine Biology

References

Main Study

1) At-sea distribution of marine predators around South Georgia during austral winter, with implications for fisheries management

Published 18th May, 2024

https://doi.org/10.1007/s00300-024-03257-6

Related Studies

2) Wintertime overlaps between female Antarctic fur seals (Arctocephalus gazella) and the krill fishery at South Georgia, South Atlantic.

https://doi.org/10.1371/journal.pone.0248071

3) The South Georgia and the South Sandwich Islands MPA: protecting a biodiverse oceanic island chain situated in the flow of the antarctic circumpolar current.

https://doi.org/10.1016/B978-0-12-800214-8.00002-5


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