Morphometric relations, diet composition and ontogenetic dietary shift of Labeobarbus intermedius (Rppell, 1836) in Lake Tana gulf of Gorgora, Ethiopia

Morphometric relations, feeding habits and dietary shifts of Labeobarbus intermedius in Lake Tana at gulf of Gorgora were studied during the dry season. A total of 250 fish ranging from 13.2 to 43.8 cm total length (TL) and 73.4 to 742.8 g total weight (TW) were randomly sampled from the lake. The data generated from both morphometric parameters were analyzed using SPSS (Version 20) and expressed using least square regression, and stomach content analysis was based on frequency of occurrence and volumetric contributions. The relation between TL and standard length (SL) was linear (SL = 0.802 TL - 0.164) and the relation between TL and TW as well as fork length (FL) and TW was curvilinear and significant (TW = 0.014 TL2.9; TW = 0.029 FL2.8). The results of gut content analysis revealed that about 4.4% of the sampled fish guts were empty and the remaining non empty. Detritus were the most important food item that dominates the bulk by accounting 43.12% of the total volume of the diet. Other important food items in the diet composition of the fish included insects, phytoplankton and gastropods which constituted 17.89, 14.57 and 12.02% to the bulk, respectively. The remaining groups of food items that included zooplankton, macrophyte and nematode were recorded as foods of minor importance in the diet of the fish. The result revealed that there was no visible dietary shift in the diet of L. intermedius in the lake. In conclusion, L. intermedius in Lake Tana shows an isometric growth and was found to be omnivorous in its feeding habit.   Key words: Detritus, frequency of occurrence, isometric, Labeobarbus intermedius, omnivorous, volumetric composition.