In an attempt to better understand and characterize the variability in the female reproduction of individual Thai-Chitralada strains of Nile tilapia, Oreochromis niloticus (L.), tagged mature females (n 5 68) from a single population were monitored in a hapa-in-pond system over a 12-month experimental period. Spawn female À1 , eggs female À1 day À1 , eggs kg female À1 day À1 , day spawn À1 and weight (g) at ¢rst spawning of individual females were determined from the regular weekly sampling of weight (g) and eggs per spawn. For analysis, the females were grouped into two, high spawning (HSF) and low spawning frequency (LSF) classes based on their spawning frequency (SF) record. Moreover, nested under these two classes were two groups each based on growth rate, i.e., high frequency^large size (HL), high frequency^small size (HS), low frequencyl arge size (LL) and low frequency^small size (LS). There was no di¡erence in eggs spawn À1 among all females. The HSF group produced 68% and 361% more eggs female À1 day À1 than the population mean and LSF group respectively. Eggs female À1 day À1 and spawn female À1 remained high in the HSF group and low in the LSF group throughout the 12-month experimental period. This suggests that individual female spawning activity is consistent within a population in a common environment. The inter-spawn interval increased with age in all four groups, and day spawn À1 was shorter by 130% in HSF females compared with day spawn À1 in LSF. The HSF group also spawned more successively ( ! 3), while the LSF group of females had fewer successive spawns ( 2). Body weight (g) had no in£uence on the number of eggs produced. The study indicates that separating frequently spawning females could be used as an important strategy to improve commercial seed production of Nile tilapia. HSF, high spawning frequency group; LSF, low spawning frequency group; HL, high spawning frequency^large size; HS, high spawning frequency^small size; LL, low spawning frequency^large size; LS, low spawning frequency^small size; E, eggs spawn À1 ; SF, spawn female À1 ; EFD, eggs female À1 day À1 ; EKD, eggs kg female À1 day À1 ; ISI, inter-spawn interval; WS, weight at ¢rst spawning; AS, age at ¢rst spawning; FW, ¢nal body weight; WG, weight gain.