From particles to individuals:: modelling the early stages of anchovy (Engraulis capensis/encrasicolus) in the southern Benguela

Several individual-based models (IBMs) have recently been developed to improve understanding of factors impacting on recruitment variability of anchovy (Engraulis capensis/encrasicolus) in the southern Benguela. These IBMs have focused on early life history stages ( eggs through to post-larvae) as it is thought that variations in anchovy recruitment strength are primarily driven by biological and/or physical factors impacting on these stages. The pelagic zone of the Benguela system constitutes an ideal system for studying the coupling between biological and physical processes; in the IBMs this coupling is obtained by releasing particles endowed with biological properties in the virtual currents resulting from the output of a hydrodynamic model of the southwestern coast of South Africa. The particles are tracked through virtual time and space and their final locations are assessed in terms of previously defined criteria deemed to promote successful recruitment. The aim of this paper is to provide a synthesis of the results of IBMs of the early stages of anchovy in the southern Benguela constructed to date. Emphasis is placed on the methodological aspects of these studies and on the sequential link of several simulation experiments of increasing complexity. In addition to improving understanding, such an approach allows for effective interplay between modelling experiments and surveys or laboratory experiments. Details of individual IBM experiments and their results have been published elsewhere.