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    AERIAL SURVEYS OF WEDDELL SEALS DURING 2007-08, WITH NOTES ON THE HISTORY OF AERIAL CENSUSES IN THE ROSS SEA AND RECOMMENDATIONS FOR CONTINUED COUNT EFFORT

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    Document Number:
    WG-EMM-08/23
    Author(s):
    D. Siniff and D. Ainley (USA)
    Agenda Item(s)
    Abstract

    Weddell seals (Leptonychotes weddellii) have proved to be an important predator of Antarctic toothfish (Dissostichus mawsoni), and currently there is no ecosystem monitoring program (CEMP) in place under CCAMLR with respect to the Ross Sea toothfish fishery. In a previous paper submitted to EMM in 2007 (WG-EMM 07/13), we described procedures whereby aerial photography could be used to monitor Weddell seals along the Victoria Land coast. That area would be important to monitor changes in distribution and abundance, as seals from all the colonies along that coast likely forage in CCAMLR SSRUs 88.1H and 88.1J (WG-EMM 06/29). Herein, we compare air with ground counts made in Erebus Bay, McMurdo Sound, in November 2007, and summarize historical results of aerial surveys made along the coast of Victoria Land. The high correspondence between air and ground counts shows that aerial photography can successfully be used to document changes in distribution and abundance of Weddell seals. Ground counts of Erebus Bay colonies made annually, 1974-2007, demonstrate the sensitivity of count data to environmental variability and the variance that could be expected over a time when the Ross Sea system was without influence from industrial fishing. On the basis of this and the previous paper, a Weddell seals monitoring program can now be put into effect under CEMP, begun with a one-time survey to identify all important haul out locations and the ones that best lend themselves to aerial surveillance.

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