As part of the process of updating the assessment of the South African sardine resource, a model of a sardine two mixing-stock hypothesis has been developed. This hypothesis postulates a “west” stock distributed west of Cape Agulhas and a “south” stock distributed south-east of Cape Agulhas, with movement from the “west” to the “south” stock in November as recruits age to 1 year olds. de Moor and Butterworth (2012a, 2013) presented some initial results for a two mixing-stock model. Work on modelling this hypothesis has continued to try to ascertain in which areas the model may be over-parameterised and which “unimportant” parameters can be fixed at constant values without unduly influencing key results. Further testing of model assumptions has also been undertaken. In this document further results for the model of a two sardine mixing-stock hypothesis are presented and a base case operating model is proposed.