The effect of stocking densities on growth performance and biochemical indices in new hybrid of Leuciscus aspius ♀ × Rutilus frisii ♂

Abstract

To determine the influence of density on the hybrid of Leuciscus aspius ♀ × Rutilus frisii ♂, fish performance was evaluated at densities of 2, 4, 6, 8 and 10 kg m–3 for a 56-day period. Fish (60.41 ± 0.04 g; mean ± SEM) were maintained in 15 circular concrete tanks under natural photoperiod and were fed with a commercial diet (40% protein and 18% fat) three times a day. Growth performance was assessed at the end of the experiment by measuring the length and weight of all fish. Hematological and biochemical parameters were analyzed following blood sampling at day 0, 7, 28 and 56 of the experiment. At the end of the experiment, body weight, specific growth rate and feed intake at 10 kg m–3 were significantly greater (72.55 ± 0.81 g) than 2 kg m–3 (67.58 ± 1.33 g). Hematocrit, hemoglobin, erythrocytes, mean corpuscular volume and mean corpuscular hemoglobin indicated significant changes among different densities and sampling times. Leukocytes, lymphocytes, neutrophils and monocytes variations were statistically significant at different sampling times; however, they were not affected by experimental densities. Plasma cortisol concentrations showed a significant elevation over time at 4 and 8 kg m–3. Plasma glucose and lactate increased significantly on day 28 and then decreased. Plasma cholesterol decreased at 10 kg m–3 from day 7 to day 56 and it was higher at 10 kg m–3 compared with 8 kg m–3 at day 7. Improved growth performance by increasing the density and changes in blood parameters among different densities revealed that the density of 10 kg m–3 or probably more can be applied for rearing Leuciscus aspius ♀ × Rutilus frisii ♂ hybrid to achieve an optimal production under commercial culture conditions.