Fisheries development of Lake Tana, Ethiopia, urgently requires the identification of its unknown units of fish stock. A diversity of large barbs (up to 80 cm SL), lumped into one species Barbus intermedius and contributing over 35% of the annual catch, consists of at least thirteen distinct morphotypes (Nagelkerke et al., 1994), possibly species. Their abilities and limitations in food selection and feeding can be predicted from structural specializations following functional morphological methods. Using ecomorphology, a spectrum of ecotypes ranging from detritivores to piscivores is predicted. Such hypotheses may be tested by analysing these fishes' intestinal contents. From knowledge of available food organisms and the trophic segregation thus found among barbs and sympatric species, a preliminary food web has been constructed. This food web, together with quantitative studies on population dynamics and energy flow, provides a biological framework for rational fisheries management aiming at sustainable production and protection of biodiversity.