Assessment of the South African sardine resource using data from 1984-2015: Results at the joint posterior mode for the single stock hypothesis

Abstract

The assessment of the South African sardine resource has been revised and updated using data available up to November 2015. Two primary hypotheses regarding the sardine stock structure have been agreed for investigation. The first considers sardine distributed off the west and south coasts of South Africa to form a single homogeneous “stock” (or “population”). The second considers the sardine to consist of a western stock and southern stock with some mixing between the two. While there is growing evidence supporting the existence of sub-population structure amongst sardine distributed off the west and south coasts of South Africa (e.g. Coetzee et al. 2008, van der Lingen et al. 2009, 2015, van der Lingen 2011, Weston et al. 2015), the single stock hypothesis continues to be modelled as it allows for easy comparison to past assessments and, in particular, to past risk statistics and previous Operational Management Procedures. It also reflects a limiting case of the mixing model as the extent of mixing becomes very large. This document presents results at the joint posterior mode for the single stock hypothesis only

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