Among the Lake Tana large barbs of about 10 cm SL only representatives of the ' acute ' morphotype can be distinguished, in the size range 10-20 cm SL ' bigmouth big eye ' can be identified also. As for the rest, very few individuals can be confidently affiliated with a particular morphotype most of them looking like ' intermedius '. Even within the range of 20-30 cm SL some individuals are still difficult to identify. Principal component analysis of cranial characters revealed discrete groups of morphotypes. Differences in both external and cranial characters of the morphotypes result from divergence which is most pronounced when fish are 4-5 years old and 20-25 cm SL. This divergence cannot be related exclusively with differences in the growth rates of individuals representing different morphotypes. Differences in food composition between the morphotypes probably increase in parallel with their morphological divergence. Differences between the morphotypes in the lateral line (ll) and the gill rakers (Sb) counts were revealed using ANOVA. Comparison of the Lake Tana Barbus complex of forms with that previously known from Lake Lanao (Philippines) suggests that in both lakes the different forms arose sympatrically but that sympatric speciation in Lake Lanao has advanced further than in Lake Tana. 1996 The Fisheries Society of the British Isles

In the Lake Tana barbs the PCA of skull measurements reveals "ontogenetic channels" within which individual ontogenetic trajectories are located. Some individuals seem to acquire states of characters specific for a certain morphotype quite late when they are 20-25 cm SL and 3-5 years old. Morphologically different sympatric forms of large barbs are also found in the Didessa (Blue Nile basin), Genale (Wabi Shebeli basin), and Gibe (Omo basin) rivers. In all the three rivers barbs resembling certain morphotypes of the Lake Tana barbs occur. Most probably, allopatric bigmouthed forms originated independently from sympatric forms which have no conspicuous specific traits and that their similarity results from homoplasies.

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