Passive transportation of pelagic system components in the southern Benguela area

Abstract

A current-closure system for pelagic species between the Agulhas Bank and St Helena Bay in the southern Benguela system is proposed, in particular for the anchovy Engraulis capensis. It is shown that current speeds for the most part exceed swimming speeds and that the species depends for its survival on passive transportation from spawning to nursery grounds and, in all likelihood, back to the spawning grounds. Such matters as active migration, navigation and orientation are briefly discussed as alternative or modifying influences on passive transport. A simple numerical procedure is used to study the initial conditions required for larvae to be able to enter the nursery grounds in St Helena Bay on a hypothetical current field by way of illustrating the possible effects of passive transport.