Getahun, Abebe(PhD)Dejen, Eshete (PhD)Geremew, Akewake2018-06-142023-11-082018-06-142023-11-082007-08http://etd.aau.edu.et/handle/123456789/846Taxonomic revision, relative abundance, reproductive biology, length-weight relation, condition factor and aspects of feeding of Lake Tana Garra species were studied from 2187 fish collected during January to December, 2006. Morphological, psychometric and mesmeric characters were used to revise the taxonomy of the three already described species (G. tana, G. dembecha and G. regressus) and one different form of Garra (small mouth, sm). Cluster and principal component analyses using 23 external and 14 skull bone morphometric measurements revealed that G. tana and G. regressus are separate dissimilar species from others. G. dembecha and G. sm showed some similarities, though the few meristic and morphological features were important to differentiate them. The % IRI (Index of Relative Importance) indicated that G. tana is abundant in the pelagic sites whereas G. sm is abundant in the littoral, and sub littoral sites having the rest of Garra species less abundant. Gonad-somatic index (GSI) and % frequency of ripe females were used to determine main breeding season. The main breeding time of G. regresses (April-October), G. tana (March-July) and G. December (May-July) was coincident with the rainy season of the area. G. sm was found to breed intensively during the dry season (November-March). G. tana is capable of breeding throughout the year, whereas G. December breeds only for three months. Extended breeding times were observed in G. sm and G. regresses. Significant differences were observed between the species for both sexes in the mean size at maturity, except for G. sm and G. December. Absolute fecundity was found to be related rectilinear with standard length and linearly with body and gonad weight for G.sm Regress and G. tana. The range of absolute fecundity was (538.9-2968), (606-3397), (1215-1229) and (580.8-1800) for G. tana, G. sm, G. dembecha and G. regressus, respectively. The average relative fecundity was 63.3, 77.1, 102.7, and 55.5 for G. dembecha, G. sm, G. tana and G. regressus, respectively. Both relative and absolute fecundity were statistically different (P< 0.001) between the species. Egg size frequency distribution revealed that G. regresses was found to be multiple spawner, while G. December; G. tana and G. sm were single spanners. Except for G. December and G. regresses (Chi-square, P< 0.05), the sex ratio in the total catch was not different from 1:1 for the other two species. The relationship between standard length and total weight was curvilinear for all the species, and isometric growth was assumed for all. A significant seasonal fluctuation (P< 0.0001) was observed in the condition of all Garra species. The better condition of these fishes during late dry and pre-rainy seasons was attributed to the increase in temperature and availability of food. Microscopic examination of gut contents of G. sm, G. tana and G. December indicated that green, blue-green, diatoms and zooplanktons that are detrimental in their origin were dominant. Key words and phrases: Condition factor, Food items, Garra, Lake Tana, Length-weight relation,Relative abundance, Reproductive biology, and Taxonomic revision.enCondition factor; Food items; Garra; Lake Tana, Length-weight relation; Relative abundance; Reproductive biology; and Taxonomic revision.Thesis