Effects of rearing density on physicochemical properties of water, growth parameters, survival, and body composition of Caspian kutum (Rutilus frisii)

Proper storage density affects the growth and rearing of fish. This experiment was carried out to investigate the effects of rearing densities on the growth and carcass composition of Caspian kutum (Rutilus frisii) fry and physicochemical factors of farming water. Fish were examined in five rearing densities (5, 10, 15, 20, and 25 fish/60 L of water) with three replications, and fed based on 8% of body weight for 56 days. Kutum fry underwent biometry after being anesthetized and weighed at the onset and completion of the experiment. There were significant differences in growth parameters (final weight, body weight gain, daily growth rate, specific growth rate, feed conversion ratio, and condition factor) at different densities (P < 0.05). There were also significant differences in the values ​​of turbidity, ammonia, nitrate, hardness, pH, protein, fat, and water magnesium (P < 0.05). No significant differences were observed for Kutum dry weight, moisture, temperature, oxygen, electrical conductivity, TDS, alkalinity, calcium, and sodium contents of skin and fillets at different densities (P > 0.05). To reduce the current cost of fish farming, a density of 166 Caspian fry is recommended for stocking in 1.0 m3 of a concrete pond.