A statistical framework for fitting of a population dynamics model to a range of fishery and survey data. It is designed to accommodate both age and size composition samples from a fishery, and multiple stock subareas. Selectivity can be modelled as age specific only, size specific in the observations only, or size specific with the ability to capture the major effect of size-specific survivorship. The overall model contains sub-components that simulate the dynamics of the stock and fisheries, derive expected values for the various observed data, and quantify the magnitude of difference between observed and expected data to allow a ‘best fit’ model to be selected as the basis for management advice.