Experiments were conducted to assess the effects of African catfish (C. gariepinus) as a predator control interaction for unwanted tilapia offspring in a polyculture system and bamboo poles as substrate for periphyton development, on growth performance and production of the mono-sex , mixed -sex Nile tilapia (O. niloticus)and common carp (C. carpio) in semi-intensive polyculture pond system over a period of 150 days supplemented with wheat bran. Control and three treatments were tested using twelive 200 m2 earthen ponds randomly applied as follow:
Control : ponds stocked with 400 mixed sex Nile tilapia (1:1) + 200 common carp+100 catfish (without treatment).
(T1): ponds stocked with 400 male Nile tilapia+200 common carp+100 catfish +fertilization, supplementary feed and bamboo poles.
(T2): ponds stocked with 400 mixed sex Nile tilapia (1:1)+200 common carp+ fertilization , supplementary feed and bamboo poles .
(T3):ponds stocked with 400 mixed sex Nile tilapia+200 common carp+100 catfish+ fertilization , supplementary feed and bamboo poles
Fish were fed a wheat bran diet ration of 3% of body weight per day. Statistical analyses of the three replicates of control, T1, T2 and T3 indicated that growth performance and production were significantly higher for treatment (T1) in which male tilapia and catfish were stocked. Mixed-sex Tilapia production in polyculture without African catfish was significantly lower than the culture systems with either all male tilapia or mixed sex tilapia with catfish . The mean gross fish yield (kg/200m2) varied from 120.7 kg/pond for (control), 348.5 kg/ pond for (T1) , 208.8 kg /pond for (T2), and 301.1 kg/pond for (T3) . The study indicated that bamboo poles as substrate for periphyton , fertilization, supplementary feed and African catfish were a superior alternative to improve fish production under pond conditions. Water quality parameters variation in mean values were within acceptable ranges for fish culture. It could be concluded that T1 was the best in term of growth performance and economic evaluation .