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The fauna of Lake George is dominated by herbivores, in particular the fish Tilapia nilotica and Haplochromis nigripinnis , and the cyclopoid copepod Thermocyclops hyalinus . Digestion, and the assimilation of carbon from algae, by these herbivores were studied in detail. It was found that, contrary to previous observations reported in the literature, both fish and zooplankton were able to digest and assimilate blue-green algae. The diurnal feeding patterns of the herbivores were examined, and methods devised for assessing, in terms of carbon, the daily ingestion of algae. Hence, using biomass data, the total amount grazed by the herbivores was calculated. Estimates of carbon requirements at other trophic levels were made, as was an assessment of the required level of net production by the algae for comparison with figures for standing crop and net algal production measured by other means. Food selection by secondary and tertiary producers is discussed, and in several species age correlated changes in selectivity were examined. Both the major herbivorous species of fish adopt phytoplankton feeding after a period of carnivorous or omnivorous feeding as fry. Thermocyclops hyalinus is herbivorous all its life, but the size of particle taken changes with age. There are more species of carnivorous than herbivorous fish and these exploit a wider variety of food sources; the few species studied also show changes in food preference with age.

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Lake George, a shallow equatorial lake, supports a Haplochromis species-flock of 17 species. Of the five species that dominate the species-flock, two feed mainly on benthic and midwater dipteran larvae, one is a piscivore, one exploits microcrustacea and another the abundant blue-green phytoplankton population. There is little stenophagy in this group.There is a seasonal variation in the total gill-net catch of the three dominant Haplochromis of the sandy shoal habitat, with high catches in the wet season and low catches in the dry. Similar fluctuations are known to occur in the commercial catches of Surotherodon niloticus. No seasonal changes were observed in the proportions of the individual species making up this community and the individuals breed all the year round.A combination of ecologically unspecialized species, resulting in an efficient exploitation and stability of the ecosystem may account for the observed high fish biomass and the high numbers of individuals. Taking into account the effect of the monotony of the environmental conditions, the physical continuty of the available habitat types and the relatively short time that the lake has been in existence, coupled with the apparent lack of rigid ecological requirements by the individual members of the Haplochrornis group, it is suggested that this species-flock may still be at an early stage in its evolutionary develoment.