Comparison of growth, nonspecific immunity systems and stress of Oncorhynchus mykiss in concrete agricultural water storage ponds (octagonal, round and rectangular) in the Sistan region

The present study was conducted to compare the growth, nonspecific immunity systems and stress of Oncorhynchus mykiss in three concrete agricultural water storage ponds, consisted rectangular (Treatment 1), round (Treatment 2), and octagonal (Treatment 3) shapes in a trout farm. Density of 20 fish/m3 (3 repetitions) and water flow D.B of 2.5 lit/sec, were run for each experimental unite and fish cultured for 5 months. According to the results, higher dissolved oxygen and reduction in sludge and NH3 production recorded in water in treatment 3 compared to other treatments (p≤0.05). The highest and lowest final individual weight measured in treatment 3 (434.21±22.16 g) and treatment 1 (349.41±18.91 g), respectively (p≤0.05). The values of RBC, hemoglobin, hematocrit, MCV, MCH and MCHC were not significantly different among treatments (p≥0.05). The highest and lowest levels of stress indicators (glucose and cortisol) and nonspecific immune systems of fish (number and differential percentage of WBC, plasma complement activity, immunoglobulin, total protein and serum lysozyme) belonged to treatments 1 and 3, respectively (p≤0.05). The results showed that, treatment 3 has better self-purification status than the other treatments, and has a positive and significant effect on growth, nonspecific immune systems and stress in rainbow trout. Therefore, using rectangular shape of pond for culture of trout can be promoted among the farmers of Sistan region in the direction of resistance economy and more economical production.