Integrated culture of white leg shrimp (Litopenaeus vannamei) with different densities of Nile tilapia (Oreochromis niloticus) in recirculation system

Recirculation water system in shrimp culture with objective of decline waste materials of culture media and decreasing the disease is one of strategy which helping the shrimp production. In this investigation, effects of different densities of Nile tilapia (Oreochromis niloticus) culture with white leg shrimp (Litopenaeus vannamei ) on growth, nutrients conversion rate (nitrogen and phosphor) of shrimp biomass and production economy in recirculation system were studied. Economical efficiency obtained according to final harvested biomass (shrimp and tilapia), the price and other costs for each treatment. Experiments were done in tanks with 6 treatments including: Culture shrimp with exchanged water (T1), culture shrimp with recirculated water system (T2) and integrated culture of shrimp with different densities of tilapia (T3- 0.01, T4- 0.025, T5- 0.05 and T6- 0.075 shrimp- tilapia ratio). The density of shrimp in all treatments was constant about 40/m2. Shrimps were fed with commercial food pellet for 8 weeks. Tilapia was not fed during 7 weeks of experiment. Growth rate and total production of shrimp in T2 compared to that of T5 and T6 and results showed significant differences. No significant differences were detected with other treatments. Growth rate in T3 significantly increased compared to other treatments. Nitrogen conversion rate of biomass (tilapia and shrimp) in all treatments except T1 statistically demonstrated an increasing rate as the tilapia-shrimp ratio was increased. Phosphor conversion ratio of biomass (tilapia and shrimp) showed an increment in T3, T4, T5 and T6 and was significantly different with T1 and T2. Production economy in T2 followed by T4 was significantly increased compared with other treatments. The lowest economical efficiency obtained in T5 and T6 and the highest found in T2. The results of present study suggest that in integrated culture system (tilapia-shrimp), increasing tilapia densities may have a direct significance effect on phosphor conversion rate improvement and an inverse effect on nitrogen conversion and shrimp growth rates. Regarding to studied parameters, decreasing the tilapia- shrimp ratio (0.01 and 0.025) increased nitrogen conversion rate with no decrease in shrimp growth rate