Since 1950 several exploited fish stocks in the Benguela ecosystem have undergone major changes in distribution and abundance, which cannot be ascribed solely to fishing. In the southern Benguela the changes are related to interannual variability of oceanic sea-surface temperature, which to some extent reflects the leakage of Agulhas Current water into the Southeast Atlantic. In the northern Benguela fish populations have responded to both changes in the local environment and large-scale processes in the tropical Atlantic. As a general rule, the environment appears to have favoured either epipelagic species or groundfish species, but not both simultaneously.