ABSTRACT. The trophic position isotope spectrum is a stable-isotope-based method with which to analyse food web interactions and quantify the relative magnitude of dietary pathways. The approach was developed and tested for anchovy in the Southern Benguela using b' " determinations of the protein fraction. The results confirm recent findings that anchovy in the Southern Benguela are largely zooplanktivorous and refute the traditional Ryther hypothesis that large pelagic fish populations in upwelling areas are supported mainly by direct feeding on phytoplankton.

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