This study presents an assessment of the establishment success of smallmouth yellowfish, Labeobarbus aeneus (Burchell 1822), in the Great Fish River (GFRI), where they were introduced by the Orange-Fish River interbasin water transfer scheme and in the Glen Melville Reservoir (GMR), where the species was subsequently introduced from the GFRI. Edge Analysis of asteriscii validated an annual deposition rate of one growth increment per year and sampled fish were aged at between 0 and 10 years old. Combined sex length-at-age (L_t) was described by L_t = 650(l - e^{-066(t 4.22)}) mm FL for GMR and L_t = 498(l - e^{-0.23(t -0.373)}) mm FL for GFRI. Natural mortality rate was estimated at 0.56/yr in GFRI and 0.96/yr in GMR. Condition factor was significantly higher in the GFRI than in GMR. In comparison with other populations, the GFRI population had reproductive and growth traits that were similar to those in its natural riverine range. Reproductive assessment showed ripe male and female fish in October to December in the GFRI, while in the GMR, ripe male fish but few ripe female fish were recorded. This was attributed to the lack of spawning cues in the reservoir. As a result, L. aeneus were considered established in the GFRI, but were not established and likely dependent on introductions in the GMR.