Effect of reused water on growth index and survival rate of the Rainbow trout (Oncorhynchus mykiss)

This research was carried out to determine water reuse effects on growth indices of rainbow trout. For this reason 4 groups including: Control (with use of 100% fresh water), Test 1(rearing with use of 30% recycled water (with physical filtration and 10% fresh water), Test 2 (using of 10% recycled water (with physical filtration and 30% fresh water), Test 3(using of 100% recycled water) was done. Fish stock of each groups were done with 62 fish in each square meter and average (±SD) weight (15±1.5). The Growth index, SGR, CF, FCR, SR between different groups in each month was calculated and determined. In this research comparing the average of monthly growth increasment between different groups indicated that significant decrease of growth in test groups with control group as well as groups 1 and 2 with 3 groups. There were no significant differences in this factor between groups 1 and 2. FCR, SR and MR showed a significant difference between different groups. These results showed with increasing the replacement of water in rainbow trout culture ponds with recycled water cased significant decrease in SR and CF and significant increase in MR and finally decrease in production and density per unit area.