The reproductive biology of the endemic â€˜largeâ€™ Barbus (renamed Labeobarbus) species was studied fromrnDecember 2003 to November 2004 in Dirma and Megech affluent rivers of Lake Tana. Fish and otherrnenvironmental parameters were sampled monthly from November to June, bimonthly in July and weeklyrnfrom August to October at the river mouths. Similarly, the spawning migration to upstream reaches ofrnthese rivers was monitored weekly in the peak breeding season (August to October) using 6, 8, 10, 12rnstretched mesh size multi-filament and multi-mesh monofilament gillnets, fykes, local basket traps andrnhook-and-line fishing gears. Samples of fish caught were identified, measured, weighed, dissected andrnsexed. Changes in mean gonado-somatic index, Fultonâ€™s condition factor and relative abundance of eachrnparticular Labeobarbus species were analyzed seasonally. Peak spawning generally occurred from Augustrnto October. Six species (L. brevicephalus, L. intermedius, L. megastoma, L. tsanensis, L. truttiformis and L.rnsurkis) formed aggregation in the river mouths. The first species to congregate was L. megastoma,rnfollowed by L. tsanensis and L. truttiformis and the final were L. brevicephalus and L. surkis. Macrospatialrnsegregation among these species between the two river mouths did not occur, however, except L.rnintermedius, temporal segregation was apparent in the river mouths in the spawning season. All thesernspecies, except L. surkis, that congregate in the river mouths ascend to upstream reaches of the rivers.rnThis spawning run showed sequential patterns of segregation among the migrating Labeobarbus species. L.rntruttiformis and L. tsanensis were the first to migrate up rivers and L. megastoma just run next to them,rnhowever, L. brevicephalus was the last in the sequence of migration. Excluding the running (egg shedding)rnindividuals, mean absolute fecundity and egg diameter of L. truttiformis, 4563 eggs and 1.99 mm,rnrespectively, were higher than L. brevicephalus (2421 eggs and 1.97 mm) but their relative fecundityrnremained the same. The relationships of absolute fecundity with fork length, body weight, and gonadrnweight were curvilinear. Length-weight relationships were curvilinear and in agreement with the cube law.rnBased on the results obtained in this study and previous investigations in other affluent rivers, the LakernTana Labeobarbus spawning strategies are hypothetically categorized into three: (1) obligate riverinernspawners (L. brevicephalus, L. tsanensis, L.truttiformis), (2) generalists (spawning in the rivers and inrnLake Tana) (L. acutirostris, L. intermedius, L. macrophtalmus, L. megastoma, and L. platydorsus), and (3)rnlacustrine spawners (L. crassibarbis, L. dainellii, L. gorgorensis, L. gorguari, L. longissimus, L. nedgia,rnand L. surkis). Generalists and lacustrine spawners most probably spawn in the littoral and adjacentrnfloodplains of Fogera and Dembea; however, their actual breeding ground should be investigated tornimplement sound management options. To sustain the riverine Labeobarbus spawners, closing the gillnetrnfishery from August to October in the rivers and river mouths is believed to be necessary.rnKeywords: endemic, fecundity, Labeobarbus, Lake Tana, reproduction, spawning migration