EFFECTS OF ADDITION OF PENGBA Osteobrama belangeri AT DIFFERENT DENSITIES ON GROWTH PERFORMANCE, YIELD AND FEED UTILIZATION OF SEMI-INTENSIVE CULTURE OF PABDA Ompok bimaculatus IN CEMENT TANKS

A three month grow-out trail in outdoor cement tanks (5m x 4m x 1m) were conducted to evaluate impact of incorporating pengba (Osteobrama belangeri,15.2 ± 0.52 g) at different stocking densities into pabda (Ompok bimaculatus) grow out system (2.74 ± 0.13 g; stocking density 3 m^-2) on their individual growth performances, net fish yield and feed utilization. Monoculture of pabda served as control (T1) and while five (5) stocking densities of pengba were employed viz. 0.2 m^-2 (T2), 0.4 m^-2(T3), 0.6 m^-2(T4), 0.8 m^-2(T5), 1.0 m^-2 (T6) in polyculture with pabda. Two diets of 35% protein diet (equivalent to 2-5% pabda biomass; application time: 5-6 p.m.) and 25% protein diet (equivalent to 4-1% pengba biomass; application time: 10 a.m.) were employed. No significant differences (p>0.05) in final individual mean weight and biomass of pabda, except between T6 (12.4 g & 744.2 g) and T3 (16.1 g & 967.4 g) were evident. Further, T1 and T3 exhibited significantly high specific growth rate (SGR) and daily growth index (DGI) of pabda in comparison to rest other treatments. On other hand, no significant differences in final mean weight, DGI and SGR of pengba were evident among T2-T6. Notably, final combined fish biomass (pengba+pabda) were significantly high (p<0.05) for T3-T6 in comparison to those for T1 and T2. Increase in final combined fish biomass for T6 was ca. 2-fold (200%) while that for T5 was 1.8 -fold (180%) over that of T1. Further, significantly improved overall feed utilization as reflected by low (p<0.05) apparent protein efficiency ratio and high apparent protein efficiency ratio was evident for T1 in comparison to T2, T5 & T6. Results indicated that adoption of polyculture of pengba with pabda has potential of significantly increasing the net fish yield over monoculture of pabda.