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    Trends of Antarctic fur seal population at SSSI No. 32, Livingston Island, South Shetlands, Antarctica

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    Document Number:
    WG-EMM-99/16
    Author(s):
    R. Hucke-Gaete, D. Torres, A. Aguayo, J. Acevedo and V. Vallejos (Chile)
    Agenda Item(s)
    Abstract

    We update in this paper the previously reported model for the Antarctic fur seal Arctocephalus gazella population breeding at Cape Shirreff and San Telmo Islets (SSSI No.32), Livingston Island, South Shetland, Antarctica. We also discuss the current reliability of the model and related population parameters to an environmental index (the Southern Ocean Oscillation Index - SOI).
    Two fur seal censuses were developed at Cape Shirreff during 1998/99, but we could not census the San Telmo Islets. In this regard, we had to model the population at the latter site, in order to have a complete estimate of the population. From this, we estimated an overall increase of 17% in the total population, including in this figure a 10% increase in pup production in the SSSI No.32.
    Current population estimates are reaching modelled values of the carrying capacity of the environment (K). This might not be correct due to the restrictions of the simple model used, and the weighted effect of the continuos data set during these last 8 years, and the scattered historical data.
    Further evidence that the breeding population of A. gazella is affected by the El Niño Southern Oscillation phenomena might be given by the intrinsic rate of population growth (r) when compared with Southern Oscillation Index (SOI) values.
    The intrinsic rate of increase of a population of top predators, in this case A. gazella, can probably predict large scale environmental phenomena if the population is under a monitoring programme, and may have an interesting effect on resources management policies.

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