Effect of salinity stress on the growth rate, biochemical parameters and cortisol level of the blood in Sistan's loach Schizothorax zarudnyi (Nikolskii, 1897)

Continuous droughts, decline of water-wellquality and their salinity increaseare the future bottlenecks in the culture of Sistan’s loach (Schizithorax zarudnyi). This fishes an endemic species in Sistan region. Effects of different degrees of salinity stress (1, 3, 6, 9 and 12 ppt) on the growth rate; some of bloodbiochemical parameters (such as glucose, sodium, potassium, calcium and total protein) and cortisol hormone level inthis species wereevaluated in order to obtain the appropriate conditions for growth and culture. For this purpose, 255 individualswith total length of 14.49±0.387 cm and mean weight of 24.89±1.41 g were cultured for 30 days.Thegrowth rate was determined atday (D)1, D15 and D30 and the levels of cortisol andbiochemical parameters of the blood were measuredat the end of the experimentalperiod. The growth rate decreased withsalinity increase compared to the control treatment (1 ppt salinity) in that growth rate was negative in treatments with3, 6 and specially 9 and 12 ppt salinitiesbut no mortalities were observed in all treatments. The levels of cortisol hormone and glucose increased with salinity increases. The highest and lowest levels of cortisol and glucose were observed for the treatmentwith12 pptsalinity and control treatment, respectively (p