Alternative hypotheses of two mixing stocks of South African sardine: initial testing

Abstract

A new assessment of sardine based on data from 1984 to 2014 is planned to commence in a few months’ time. This assessment will eventually form the operating model which will be used to project the sardine population forward in time under alternative future catch scenarios – i.e. it will be used in the development of the next OMP to likely be finalised in 2016. In preparation for this assessment, some initial potential alternative two mixing stock hypotheses are considered using the previous assessment based on data from 1984 to 2011 (de Moor and Butterworth In Review) which has been used in the development of OMP-14. These tests would hopefully highlight any hypotheses that could have a substantial influence on model results and those which might not, and thus aid in prioritisation of future research. This document is a first stage of this process, firstly outlining the alternative hypotheses currently considered plausible, and then refitting the previous assessment at the joint posterior mode for some of these hypotheses.