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    The commercial fishery and pygoscelid penguins at three breeding sites in the Bransfield Strait, Subarea 48.1

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    Document Number:
    WG-EMM-2021/19 Rev. 1
    Author(s):
    A. Lowther, H. Ahonen, C. Cárdenas, W. Jouanneau, B. Krafft, L. Krüger, A. Makkhado, A. Narvestad and C. Oosthuizen
    Submitted By:
    Dr Andrew Lowther (Norway)
    Approved By:
    Dr Bjørn Krafft (Norway)
    Abstract

    We present initial findings from a multi-site, multi-species ecological study of pygoscelis penguins in the Bransfield Strait through the austral summer 2018-2019. Using high resolution GPS movement data in conjunction with C1 Catch and Effort data for the Antarctic krill fishery, we identify the home range distribution of chinstrap, gentoo and Adélie penguins at Baily Head (Deception Island), Harmony Point (Nelson Island) and Kopaitic Islands and estimate the amount of direct competition with the fishery over time. We further integrate information on humpback whale (Megaptera novaeangliae) abundance and distribution in the Bransfield Strait collected during the 2019-2020 summer in the same area, to provide an estimate of the potential competitive implications that recovering whale populations may have on constrained, breeding pygoscelid penguins. During the period in which these data were collected, there was no competitive overlap with the fishery during the brood-crèche phase, only 107 tonnes of krill caught during incubation within the foraging ranges of all three species, and a total of ~10,000 tonnes of krill fished in areas occupied by chinstrap penguins during brood-crèche over the preceding thirty years. We summarise the amount of krill fishing conducted during the penguin breeding season at the Subarea 48.1 scale, which has never exceeded 35% of the trigger level and most seasons were under 10%. We also highlight that in the past 10 years the fishery has begun to increase fishing efforts throughout March, resulting in increased spatiotemporal segregation with breeding pygoscelid penguins. Population abundance of chinstrap penguins at Deception and Nelson Islands have declined precipitously over the preceding three decades, and while the marginal levels of direct competition with the fishery cannot be ruled out, it is prudent to actively consider other mechanisms that are contributing to the decline of this species throughout the western Antarctic Peninsula. The movement data of penguins from the three colonies (when considered alongside other species that are not constrained by offspring provisioning) also suggests a structuring of foraging habitat within the Bransfield Strait, that may be linked to hydrographic variability driven by larger scale climactic processes such as the Amundsen Sea Low and its interactions with the El Niño Southern Oscillation and the Southern Annular Mode. As our data represent foraging behaviour of breeding penguins from three sites across the Bransfield Strait which are under no direct competitive pressure from the Antarctic krill fishery, they are amenable for use when comparing similar data to be collected off the western coastline of the South Orkney Islands over the coming two years.

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