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    Characterising the preferred at-sea habitats used by chinstrap penguins and the fishery for Antarctic krill: slow-flowing, nearshore waters over shallow bathymetry

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    Numéro du document:
    WG-EMM-17/34
    Auteur(s):
    P.N. Trathan, V. Warwick-Evans, J. Hinke, E.F. Young, A.P.B. Carneiro, M.P. Dias, K. Kovacs, O.R. Godø and M. Santos
    Soumis par:
    Marta Söffker (Union européenne)
    Approuvé par:
    Doro Forck (Secrétariat de la CCAMLR)
    Résumé

    We show that the preferred habitat models developed by Warwick-Evans et al. (2017) for chinstrap penguins breeding at the South Orkney Islands, can be modified to predict the at-sea distribution of chinstraps breeding at the South Shetland Islands, based on the distance from the colony, and the bearing to the shelf edge, adjusting for the at-sea density of Pygoscelis penguins from other colonies. The models performed well, even when using lower resolution tracking data. Cross validations between colonies and between regions indicated that our models perform better if local tracking data were available. Nevertheless, we conclude that these models can, with some confidence, be extrapolated to predict the foraging locations of animals during the breeding season from untracked colonies, even in different regions and across different archipelagos.

    Based on mean summer (January to March) near-surface (averaged over 50 m to 150 m) oceanographic flows derived from a high resolution oceanographic model developed using NEMO, we report that chinstrap penguins prefer habitats with slow-flowing, nearshore waters over shallow bathymetry, but that they also sometimes move towards the edge of the continental shelf where the faster-flowing waters of the Coastal Current or fronts of the Antarctic Circumpolar Current exist. The preferred habitats are also locations preferentially used by the commercial krill fishery. Cross-shelf submarine canyons occur near to a number of preferred krill fishing locations, suggesting that these canyons potentially play an important role in krill transport onto the shelf. In the relatively slow-moving shelf waters krill depletion is probably more likely and krill replenishment less likely. Our results suggest that better understanding of krill retention and depletion in areas used by natural predators and the krill fishery are needed, and that  management strategies for the fishery should include assessment of how krill movement can satisfy the demands of both predators and the fishery across a range of spatial and temporal scales.

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