Optimization of rainbow trout production through the use of wastewater in earth ponds (Case study: Bafgh city, Yazd province)

This study was carried out in a brackish water earth farm in Bafgh, to use wastewater of earth ponds in order to increase production in rainbow trout earth farms. It was performed in 2 treatments with 2 replications. For this purpose, four 0.5ha earth ponds (two of those with 30 m3 round cement ponds at the end and others without cement ponds) were made. The wastewater of culture earth ponds flew in cement ponds through pumping and gravity. The cement ponds aerated with splash aerator during nights. The average initial weight of fish for stocking in all ponds was 25 g and the density of stocking was one and 70 fish per square in earth pond and cement pond, respectively. During about 120 days’ culture period, water temperature and salinity were 14±4 °c and 12.8±1 g/l, respectively. The results of some chemical factors measuring in cement ponds indicated that none of them was critical during the culture period. There were significant differences among treatments on some growth factors (p<0/05). According to The results, through reusing of earth ponds wastewater, yield quantity and production income increased up to 31% and 41%, respectively.