Modelling dominance shifts of anchovy and sardine with a frame-based approach : sensitivity to the underlying sardine population dynamics

Includes bibliographical references.It has been shown that sardine and anchovy populations in the southern Benguela have alternated dominance during the past 50 years, and a frame based model that explores the usefulness of frames within a marine ecosystem by modelling sardine/anchovy dominance shifts in the southern Benguela has been developed in a previous study. The existing model contains a sardine population sub-model without age structure and the inclusion of age-structure allows age-related dynamics to be incorporated in the model design. In this mini-dissertation, an age-structured sardine population is implemented in the frame based model by using the sardine assessment model from the joint sardine/anchovy Operational Management Procedure, OMP-02. Methods for incorporating biological processes - such as the hypothesised school trap phenomena - that were present in the existing frame based model into the OMP-02 equations are developed, critically analysed and tested