Effects of Stocking Density on growth parameters and some biochemical factors of blood serum in rainbow trout larvae (Oncorhynchus mykiss Walbaum, 1792)

A experiment was carried out to evaluate the effect of four levels of stocking density (30, 45, 60 and 75 fish/m3) on growth parameters and biochemical factors of blood serum of Oncorhynchus mykiss larvae with average mean weight 0.235±0.08 g were stocked in 12 fiberglass tank (10 L) was studied for a period of 45 days. At the end of the experiment, were observed no significant differences between growth parameters and feed efficiency among treatments (p>0.05). However, Analysis of biochemical factors of serum blood showed significant difference between treatments (p<0.05). The highest amount of blood serum of total protein (7.40±0.10), ALT (23.00±1.00) and ALP (243.00±8.18) activity enzymes, amylase (23.66±1.52), lipase (111.00±6.55) and calcium (15.66±0.05), as well as the lowest amount of cortisol (36.00±1.73) and albumin (10.76±0.11) was observed in treatment containing maximum stocking density level at 75 fish larva per m3 (p<0.05). Also, the highest amount of glucose (139.00±5.56) was observed in treatment at 60 fish larva per m3 and the highest AST activity enzyme (7.33±0.57) was observed in two treatment at 30 and 45 fish larva per m3 (p<0.05). Finally, according to the results, an increase in stocking density of O. mykiss larvae cannot be affected the efficiency of fish farming. But, this increasing density had significant effect on immune factors and stressors.