Keywords: Polyculture, daily weight gain, survival rate, net fish yield

Growth performance of sahar (Tor putitora) and Nile tilapia (Oreochromis niloticus ) in monoculture and polyculture was evaluated using out door concrete tanks (4.9 m × 4.9 m × 1.75 m ) at Institute of Agriculture and Animal Science (IAAS), Rampur, Chitwan from 19 April to 27 September 2003 for 161 days. The experiment was conduced in a completely randomized design (CRD) with three treatments, each replicated thrice. The treatments were: Sahar monoculture (TI); Nile tilapia monoculture (T2), and sahar and Nile tilapia polycultue (T3) with stocking density of 1 fish/m² for T1 and 2 fish/m² for T3. The stocking ratio of sahar and Nile tilapia was 1:1 in polyculture (T3). Sahar fingerlings (25.0± 1.7 to 26.0 ± 0.2 g) and mixed -sex Nile tilapia fingerlings (22.1 ± 0.5 to 22.8 ±1.2 g) were stocked in the respective tanks on 19th April 2003. The feed, containing 35 percent crude protein was supplied at the rate of 3% of total body weight of fish per day. Mean daily weight gain, mean final weight, survival rate, and net fish yield were mainly evaluated. The results showed that the mean daily weight gain of sahar was similar in monoculture (0.32 ± 0.04 g) and polyculture (0.32 ± 0.02 g) conditions ( P > 0.05). Likewise, the mean survival rate (%) of sahar in monoculture (92 ± 8.0) was also similar ( P > 0.05) to polyculture (92 ± 8.0). However, the mean daily weight gain of tilapia was higher in polyculture (1.15 ± 0.07 g) than in the monoculture (0.83 ± 0.14 g), but was not significantly different ( P > 0.05). In the case of Nile tilapia, the mean survival rate (%) was higher in polyculture (100) than monoculture (97 ± 2.8), but was not significantly different ( P > 0.05). On the other hand, net fish yield (g/m2/d) was the highest in the case of sahar + Nile tilapia polyculture (1.6 ± 0.2 ), intermediate in Nile tilapia monoculture ( 0.8 ± 0.1), and the lowest in sahar monoculture ( 0.3 ± 0.0). The recruits per tank was also significantly ( P < 0.05) higher (1745 ± 256) in Nile tilapia monoculture compared to that in sahar + Nile tilapia polyculture (2.7 ± 0). On the other hand, mean size of recruit of Nile tilapia was significantly higher ( P < 0.05) in sahar + Nile tilapia polyculture (34.4 ± 11.2) than in Nile tilapia monoculture (3.8 ± 0.30). Thus, the result of this study demonstrated that there is a potentiality of cultivation of sahar and Nile tilapia in polycultue systems. The result also showed that sahar is more suitable in polyculture with Nile tilapia for controlling tilapia recruitment.