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Assessment of the South African anchovy resource using data from 1984 – 2014: base case results at the posterior mode

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posted on 2022-03-25, 12:28 authored by Carryn de MoorCarryn de Moor, Doug ButterworthDoug Butterworth
The operating model (OM) for the South African anchovy resource has been updated from that used to develop OMP 14 given three more years of data. The model has been altered from previous assessments to now fit directly to length frequency data, removing the earlier need for estimates of proportions of anchovy-at-age 1 during the annual November hydroacoustic survey. A Beverton Holt stock recruitment relationship is used for the base case. Time-invariant natural mortality is assumed to be 1.2year-1 for both juvenile and adult natural mortality as before. The resource abundance is estimated to be above the historical (1984-2013) average, with a total biomass of 4.2 million tons in November 2014. Recruitment reflects three major peaks over the past 20 years, although the lowest points in these fluctuations were still large, being similar to the maximum recruitment prior to 2000.

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Department of Mathematics and Applied Mathematics, University of Cape Town