Water quality in irrigation channels stoked with nile tilapia (Oreochromis niloticus)

To evaluate water quality in an integrated cultivation system of agriculture and fishculture, physical, chemical and biological parameters of the water of irrigation channels stocked with nile tilapia (Oreochromis niloticus) in the density 10; 20 and 30 fish/m(3), were determined. The experiment was realized in tertiary irrigation channels of DITALPI/DNOCS, sectioned with screens, stocked with fish weghing 30 +/- 3 g in average, and the water monitored at 8; 14; 21; 29, 35; 43; 50; 58 and 78 days after the start of the experiment. The results of the analysis ranged from 29 to 30.9 degrees C for water temperature; from 41 to 78 cm for transparency;: from 19.5 to 28.7 m L-1 or total alkalinity; pH: 6.6 to 7.9; hardness: 26 to 66 mg L-1; dissolved oxygen: 4.3 to 6.9 m L-1; electrical conductivity: 0.059 to 0.150 mS cm(-1); carbonic gas: 3.4 to 5.3 mg L-1; nitrite: 1.93 to 3.36 mg L-1; ortophosphate: 0.00 to 0.07 mg L-1 and chlorophyll alpha: 0.00 to 3.36 mu g L-1. The results indicated that raising tilapia in the channels, for the tested densities, didn't alter in a negative way the quality of the water for irrigation. In conclusion, there is the possibility of integrating the fish farming with the irrigated agriculture, maximizing the use of water resources.