Lake Malawi contains a pelagic ecosystem which is based on a deep euphotic zone (up to 60 m) and medium primary production (0.7 g C m super(-2) day super(-1)). A trophic box model has been implemented based mainly on investigations conducted from 1977 to 1981. The grazer chain in the pelagic system is dominated by one major pathway: via crustacean zooplankton to a larvae of the lake fly, Chaoborus edulis. Nearly all the primary production is estimated to pass through this pathway. Minor pathways pass through planktivorous fish of which the most important are the cyprinid Rastrineobola sardella and a group of haplochromine cichlid species (Cichlidae). The top predators constitute a small group of species which feed on fish as well as on Chaoborus larvae. The majority of the Chaoborus production is exported from the lake.